International Journal of Nanoscience

This work presents template synthesis of ordered arrays of nickel, cobalt and nickel hexacyanoferrates (NiHCF) with several distinct morphologies such as dots, rods, and tubes. Anodic alumina oxide (AAO) with preferred pore diameters and thickness was fabricated by electrochemical anodization of aluminum used as template. Ni and Co nanostructures inside AAO template were prepared by electrodeposition using galvanostatic method. NiHCF nanostructures were prepared by electrochemical oxidation of Ni using cyclic voltametry (CV) in the presence of hexacyanoferrate ions. The morphology, chemical, and functional properties of prepared nanostructures were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray microscopy (EDAX), and electrochemical methods. The electrocatalytic properties of NiHCF nanorod arrays electrode and their potential for the detection of hydrogen peroxide and biosensing application were demonstrated.

Nanowires of Au and Cu were fabricated using a top–down method in which focused ion beam (FIB) milling process has been used. The width of the fabricated nanowires has been kept in the range of 45 to 300 nm and the length in the range of 2–10 μm. In situ electrical measurements of the nanowires were carried out. The resistivities of these wires are found to be higher (five to nine times larger than their bulk values). These results have been understood on the basis of increase in the electron surface scattering due to one-dimensional confinement of the electrons. Also, other effects such as nanogap formation in the range of 40 nm to few hundreds of nanometers, structural changes of the wires, increase of current density with time at constant applied voltage, etc. have been observed during measurements.

We have grown metal catalyst free, straight Si nanowires (NWs) with high aspect ratio of about 130 on Si(100) substrate using radio frequency magnetron sputtering. Thin Si seed layer on thermally oxidized substrate was used for catalyst-free growth. Then Si deposition was done on that substrate using sputtering technique followed by heat treatment at different temperatures (900°C–1100°C). Sample heated at 1000°C results in straight, long, and uniform cylindrical shaped Si NWs with diameter 62–74 nm and length up to 8 μm, whereas sample heated above 1000°C transformed toward nanorods with larger diameter. However, no significant growth of Si NWs took place at 900°C. Sputter deposition technique provides an alternate fabrication route for Si NW synthesis. For comparison, we have also grown Au catalyst assisted Si NWs on Si(100) substrate by similar process. These nanowires also show similar morphology with diameter 48–65 nm and aspect ratio about 165. Growth mechanism and effect of growth temperatures on the structure and morphology of Si NWs are discussed.

Buckypaper is a thin sheet fabricated from the aggregation of carbon nanotubes. The generally accepted method for forming such carbon nanotube (CNT) films involves the use of stable suspension of carbon nanotubes in water. These suspensions can then be membrane-filtered under pressure to yield uniform films. After preparation of a stable solution, it should be membrane-filtrated on the surface of a filter. Usually, the quality of a buckypaper depends on sonication time and power, surfactant type and concentration, filter type, and concentration of carbon nanotube. In order to investigate the surface quality of buckypapers, low-magnification images could give rather useful information about the roughness of surface. Analysis of the 100 × images clearly shows that with increasing the suspension concentration, the smoothness of buckypaper surface will decrease. Therefore, from this viewpoint, decreasing the concentration can enhance the quality of the buckypaper. Surface of the filter also affects on the buckypaper quality. Therefore, for filtration of the suspension, a filter with suitable material, pore sizes, and surface should be used. As the pore sizes of the filter are usually small, the filtration process may be very time-consuming. Since the process is carring out under pressure and also due to the brittle nature of the buckypaper, removal of the buckypaper from the surface of the filter is a very serious and important stage and depends on the filter type, concentration, and type of CNTs. The buckypaper usually can be removed from the filter mechanically. The type of CNTs (MWNT or SWNT) may change the above-mentioned factors.

High-quality multiwall carbon nanotubes (MWNTs) were produced by a simple one-step technique. The production of MWNTs was based on thermal decomposition of the mixture of a liquid phase organic compound and ferrocene. High degree of alignment was noticed by scanning electron microscopy. The aspect ratio of as-synthesized MWNTs was quite high (more than 4500). Transmission electron microscopy analysis showed the presence of the catalytic iron nanorods at various lengths of MWNTs. Raman spectroscopy was used to know the quality of MWNTs. The ratio of intensity of the G-peak to the D-peak was very high which revealed high quality of MWNTs. Magnetotransport studies were carried out at low temperature and a negative MR was noticed.

A systematic study of structural, electronic and vibrational properties of boron- and nitrogen-doped heterofullerenes has been performed. N and B doping lead to the structural deformation, and the dopant has a tendency to occupy a single position in a pentagon and two positions in a hexagon which are not adjacent. B-substitution produces clusters of greater thermodynamic stability than N substitution. The C–N and C–B bond lengths lie in the range of 1.40–1.44 Å and 1.53–1.57 Å for hexagon–hexagon (6, 6) and 1.39–1.46 Å and 1.55–1.60 Å at pentagon–hexagon (5, 6) interfaces, respectively. The Mulliken charge analysis shows a charge transfer of -0.30 to -0.45 electrons from N to C atoms; B atom act as electron acceptors with charge gain ranging between -0.59 to -0.70 electrons. N- and B-doping in fullerene molecules present an interesting way to alter electronic and chemical properties of the _C60 molecule for useful device applications.

SWCNT was synthesized by catalytic thermal CVD using Fe–Mo and Co–Mo bimetallic catalysts supported by MgO. The nanotubes were studied by SEM and HRTEM microscopy, thermogravimetric analysis, and Raman spectroscopy. The chiralities of the tubes were established from their Raman spectra using Kataura plot. The Raman shifts for the Co-catalyzed nanotubes were found to lie in the semiconducting region.

Graphene has been synthesized using thermal decomposition of ethyl alcohol in a medium pressure autoclave. The synthesis was carried out in the presence of strong alkaline solution at a temperature of ~230°C and pressure of 60 bar. The as-synthesized graphene has been characterized using atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). AFM analysis on various graphene sheets shows the presence of monolayer (n = 1) to trilayer (n = 3) graphene sheets with thickness of ~1.168 nm. HRTEM studies confirm the high quality of graphene obtained after purification of as-synthesized product. Use of chemically nonexplosive material for synthesis and reduced reaction time along with the absence of post-pyrolysis process make it a commercially viable process for bulk production of graphene.

In the present work, we report on the magneto-transport properties of graphitic based materials (graphene, few-layer graphene, and bulk graphite) in very high magnetic field. Quantum Hall Effect (QHE) has been studied in graphitic systems in very high pulsed magnetic field (up to B = 57 T) and at low temperature (≤ 4 K). Graphene sample shows well-defined Hall resistance plateaus at filling factors v = 2,6,10, etc. Few-layer graphene systems display clear signatures of standard and unconventional QHE. Magneto-transport studies on bulk highly oriented pyrolytic graphite show a charge density wave transition at strong enough magnetic field as well as Hall coefficient sign reversal.

The capability of graphitic networks to reorganize their structures under irradiation of energetic particles provides the tool for nano-engineering of carbon nanotubes (CNTs). We have studied the effect of 30 keV N⁺ ion irradiation with three different fluences 10¹², 10¹³, and 10¹⁴ ions/cm² on the structural and spectroscopic properties of single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs). Irradiation-induced structural defects and coalescence of the nanotubes are studied using high-resolution transmission electron microscopy (HRTEM). Upon irradiation, some of the radial breathing modes in Raman spectra disappear due to conversion from single-walled to multiwalled structure. We observed a systematic change in intensity of the intermediate frequency mode (IFM) with increasing dose of ion-irradiation and these IFM modes are attributed to structural defects of SWNTs. Dramatic improvement in the intensity ratio G-band to D-band (at ~1335 cm^-1) for ion fluence of 10¹³ ions/cm² indicates improved graphitic structure as a result of reconstruction. Similarly, X-ray Photoelectron spectroscopy studies show improvement in the amount of sp² carbon upon 10¹³ ions/cm²N⁺ ion irradiation dose. At a higher dose (10¹⁴N⁺ions/cm²), vacancy and bent structures having Stone–Wales defects were observed in HRTEM, whereas MWNTs show formation of surface hillock like protrusions leading to formation of fullerene-like structures.

We report the fabrication of highly ordered TiO₂ nanotube arrays employing electrochemical anodization of titanium using an organic electrolyte comprised of water, NH₄F, and ethylene glycol. To achieve the self-ordering regime of TiO₂ nanotube growth and reliable fabrication optimal potential window between 80 and 100 V was determined. We show that anodization voltage can be used not only to control nanotube diameters (70–180 nm) but also to have impact on nanotube growth rate. The anodization voltage and anodization time were used to adjust the length of TiO₂ nanotube (thickness of nanotube layer). TiO₂ nanotube array films and self-supporting layers with thickness from < 5 μm to > 250 μm were routinely fabricated.

Nanocrystalline TiO₂ sample was prepared by high-energy ball mill method. A known quantity of anatase phase-TiO₂ was milled for 83 h in air. The samples were collected at intervals of 5 h of milling. The XRD patterns were recorded for all the samples. The crystal structure changed from anatase phase for bulk material to rutile-rich phase for nanocrystalline material. Nanocrystalline TiO₂, which is a mixture of anatase, rutile, and srilankite phase, was prepared by milling for 60 h. The XRD pattern of unmilled anatase phase of TiO₂ could be refined with I41/amd space group. The crystallite size of the TiO₂ was found to decrease with milling time upto 50 h and then the size of rutile phase increases while the sizes of anatase and srilankite phases remain constant upto 60 h of milling. After 60 h, the sizes of all the phases remain constant. The average crystallite size for rutile phase is found to be 12 nm after 60 h of milling.

In this work, we have investigated the influence of rapid thermal annealing (RTA) on structural and optical properties of ZnO nanorods synthesized by a mechanochemical reaction route using a planetary ball mill for different reaction time durations. Optical properties of as-grown and RTA-annealed samples are studied by UV–visible absorption and photoluminescence (PL), while structural studies are performed using X-ray diffraction line profile analysis and transmission electron microscopy. X-ray diffraction pattern of each sample is accompanied by characteristic wurtzite peaks of zinc oxide and exhibits the decrease in full width half maxima of the peaks after RTA. Williamson–Hall plot of each pattern is done to correlate the effect of strain of as-synthesized and RTA-treated samples. UV–visible absorption spectra show distinct redshift of excitonic absorption peaks with respect to those of as-synthesized samples. Interestingly, in PL spectra, the broad visible emission peaks observed for as-synthesized samples are eliminated completely for annealed samples. However, some of the constituent peaks in the UV–blue region of the PL spectra redshifted due to the grain growth and strain reduction.

Ultralong zinc oxide nanotubes have been synthesized on glass substrate by a simple chemical bath deposition. The nanotubes are hexagonal with the core diameter about ~200 nm. The length of the nanotubes was about 10 μm. No specific alignment of the nanotubes on the glass substrate was observed. The morphology of the nanostructures depends highly on the concentration of zinc acetate solution, duration of mechanical stirring, and temperature during synthesis. Depending upon these experimental conditions nanorods and nanotubes were observed. The material was structurally characterized using grazing incidence X-ray diffraction, showing hexagonal unit cell structure. Transmission electron microscopy results revealed that the walls of the nanotubes are hexagonal. Room temperature photoluminescence spectrum shows a strong violet emission at ~420 nm from the ZnO nanotubes due to transition between zinc interstitial and zinc vacancy level. These results will be very useful in optoelectronic and nanophotonic device applications.

Here we report on the growth and evolution of ZnO nanowires grown from ZnO nanopowder as a source material using a horizontal muffle furnace. The shape evolution has been studied with variation in growth temperature and zinc vapor pressure. The structural analysis on these nanostructures shows c-axis oriented aligned growth. Scanning electron microscopy imaging of these nanostructures revealed the shape evolution from nanowires to nanoribbons and then to nanorods as the growth temperature increases from 650°C to 870°C. At 650°C, only vertical nanowires have been observed and with increase in growth temperature nanowires transform to nanoribbons and then to nanorods at 870°C. And we also observed simultaneous growth of nanorods and nanoribbons under a specific growth condition. We believe that these nanowires and nanorods were formed by vapor–liquid–solid growth mechanism (catalyst-mediated growth), whereas nanoribbons were grown by vapor–solid growth mechanism (without the aid of a metal catalyst). We observed simultaneous occurrence of vapor–liquid–solid and vapor–solid growth mechanisms at a particular growth temperature. These ZnO nanowires exhibit bound exciton related UV emission at ~379 nm, and defect-emission band in the visible region. Possible growth mechanism, shape evolution, and simultaneous growth of two types of one-dimensional ZnO nanostructures under the same growth condition are discussed.

ZnO nanorods grown by hydrothermal technique on glass, Zinc, and Indium tin oxide (ITO) substrates exhibit both open and closed hexagonal structures. On the nanoscale, closed ZnO nanostructures exhibit two types of ion conduction regions as revealed by AC-impedance spectra collected through the tip of an atomic force microscope (AFM). One region has higher impedance values (apparent values of approximately 10⁷ ohms) with two semicircles. Two semicircles are indicative of a ZnO structure composed of bulk and grain boundary conduction. Other regions were found to have impedance values that were two orders of magnitude lower (apparent values of 10⁵ ohms). This indicates that these ZnO films have two conduction pathways. The polyethylene oxide (PEO)–ZnO nanorod composite was made by spin-coating the ZnO rods growing from the ITO substrate with PEO. In the PEO–ZnO composite film, only the AC impedance values of 10⁵ ohms were observed. This is higher than PEO electrolyte without ZnO nanorods. Since regions of higher impedance were not seen in the PEO–ZnO nanorod composites, the polymer electrolyte either dominated the conduction of the system or suppressed the first pathway of higher impedance in the ZnO rods.

A novel one-step method to synthesize large-scale uniform dumbbell-shaped ZnO nanorods is presented here. The structural morphology was investigated by using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy analyses. The prepared dumbbells with diameter of 300 nm and length of 1.5 μm possess hexagonal structure with preferable [001] growth direction. The UV–vis absorption spectra show blueshift for smaller nanoparticles and redshift for bigger dumbbell-shaped ZnO nanorods.

We report here our investigations on dark DC resistivity and optical absorption of chemical bath deposited CdS thin films prepared by chemical bath deposition. Crystallite sizes of about 30 nm are found from XRD using Scherrer formula with an added term for strain broadening. Energy-dispersive X-ray measurement shows correct stoichiometry of Cd and S atomic ratio. The grain size of the as-deposited film determined from both AFM and TEM is found to be ~180 nm. On vacuum annealing, the dark resistivity decreases from ~10⁹ to 10⁶ Ω-cm. Dark resistivity variation of as-deposited and vacuum-annealed films with temperature in the temperature region (95–350 K) reveals that each film exhibits two types of conduction in this temperature region. From the optical absorption study the optical band gap of as-deposited film is found to be ~2.29 eV.

We report microstructural characterization studies, including cross-sectional TEM, carried out on pristine and swift heavy ion irradiated W/Ni multilayers with different bilayer thicknesses. Our results very clearly show a strong thickness dependence of the SHI effect; thinner Ni-layers get severely affected while the thicker ones remain intact. This has been confirmed using a multilayer having composite bilayer thickness. This result appears to indicate toward the possible electron conferment and its implication on the dissipation of electronic excitation in metals.

Gallium phosphide (GaP) samples were irradiated with swift (100 MeV)⁵⁶Fe⁹⁺ ions for various ion fluences varying from 1 × 10¹¹ to 1 × 10¹⁴cm^-2. Atomic force microscopy, Raman scattering, and X-ray diffraction techniques have been used to investigate the irradiation effect. Atomic force microscopy studies showed the presence of nanosized hills separated with valleys at the surface of irradiated gallium phosphide. The average diameters of hills were found to be 19.76, 19.81, 20.70, and 22.64 nm for ion fluences 5 × 10¹², 1 × 10¹³, 5 × 10¹³, and 1 × 10¹⁴cm^-2, respectively. Root mean square surface roughness analysis has been used to characterize the nature of the surface under swift heavy ion irradiation. The features observed in the Raman spectra at 402.18 cm^-1 and 365.05 cm^-1 were assigned to the characteristic first-order longitudinal optical (LO) phonon mode and transverse optical (TO) phonon mode of gallium phosphide, respectively. We have also observed the second-order overtones and combinations of optical modes giving rise to three characteristic peaks in the region between 700 and 800 cm^-1. X-ray diffraction technique has been used to determine the crystallite size. The crystallite size was found to decrease with increase in ion fluence.

Influence of Ni¹¹⁺ swift heavy ion (SHI) irradiation induced modifications on structural and morphological aspects of CuFe₂O₄ nanoparticles have been studied. The bulk sample is synthesized using co-precipitation technique. The cubic spinel structure is identified using X-ray diffraction technique and these nanoparticles have an average grain size of about 10 nm. These materials are irradiated at various fluences of 1 × 10¹¹, 1 × 10¹², 1 × 10¹³, 1 × 10¹⁴, and 5 × 10¹⁴ions/cm² using Ni¹¹⁺ ion beam of 150 MeV energy. The XRD pattern of the irradiated material shows the change in crystalline nature. The spinel ferrite (311) peak, which is having maximum intensity in the pristine, decreases at the fluence of 1 × 10¹¹ and 1 × 10¹²ions/cm² and then completely vanishes on further irradiation. However, a new X-ray peak arises in the (222) direction. All the other peaks in the pristine sample vanish on irradiation elucidating the creation of amorphization nature. Scanning electron microscope (SEM) analysis shows fine blocks of material for pristine and partial agglomeration on irradiation. Notably, a large number of holes are present at the fluence of 5 × 10¹⁴ions/cm² due to heavy ion irradiation. The phase change from crystalline to amorphous nature on XRD and the creation of holes from SEM is discussed on the basis of electrophonon coupling and it invokes the thermal spike theory.

In the advent of GaN photonic devices, there is renewed interest in looking at the growth of nanostructures of III-Nitrides that can yield novel properties. To grow a high density of self-assembled GaN nanostructures on a large scale, there is a need to use templates with well-defined nanometer scale features. The Si(5 5 12)-2 × 1 surface is a naturally faceted stable surface that has several nanotrenches of (225) and (337) with a large unit cell of 5.35 × 0.77 nm². In this work we present here, the first report on the X-ray photoelectron spectroscopy study of the adsorption kinetics of Ga on Si(5 5 12)-2 × 1 reconstructed surface. The uptake curve which is the plot of the ratio of Ga(2p) to Si(2p) intensity with deposition time, shows that Ga grows in a Stranski–Krastnov growth mode on Si(5 5 12) surface. The core level spectra of Si(2p) and Ga(2p) have been deconvoluted to see the evolution of the interface during the adsorption process of Ga. The valence-band spectra show the modification of the electronic structure and the secondary electron emission spectra yield the change in work function during Ga adsorption. Correlating the electronic and structural aspects of the interface formation results the study demonstrates the possibility of integrating Si and group III-nitride technologies while exploiting the novel properties due to reduced dimensions.

Growth of Ag nanostructures on Si(111)-7 × 7 surfaces has been investigated at the atomic scale regime by studying the evolution of nanoscale surface morphology with Ag coverage. Ag growth on Si(111)-7 × 7 surfaces at room temperature showed a strongly preferential height with even atomic layer thick flat top percolated islands. Here we report that the roughness scaling exponent α and growth scaling exponents β associated with such electronic growth mode are determined by statistical analysis of rough surfaces obtained from scanning tunneling micrograph images of Ag nanostructures grown on Si(111)-7 × 7 surfaces. Observed roughness and growth exponent for this system are 0.82±0.02 and 0.45±0.04, respectively.

The growth of the self-assembled Si atomic wires on Pb-covered Si(111) 7 × 7 substrate has been studied using homemade scanning tunneling microscope (STM) at room temperature (RT). These surfactant-mediated epitaxially grown Si atomic wires (SiAWs) are quite stable at RT. It is interesting that they always appear in pairs having a distance of ~9 Å in between them. They have only three special growth directions, parallel to the three possible crystal directions of the Si(111) substrate underneath. The SiAW can be imaged down to few mV bias voltages, and the voltage current characteristic investigated with scanning tunneling spectroscopy reveals metallic electronic structure of this special kind of SiAW.

Nanosized particles of α-Fe₂O₃ in the range of 17–64 nm were synthesized via hydroxide precipitation. The synthesized powder was investigated by XRD employing CuK_α radiation and 2θ geometry. SEM images show the nanosheet like morphology. The pellet of this sensing material was made by hydraulic press under a uniaxial pressure of 616 MPa. The LPG sensing properties of α-Fe₂O₃ were investigated at room temperature for different exposure times of LPG. A maximum value of sensitivity and sensor response were found 3 and 213%, respectively for an exposure time of 300 s. Electrical properties of α-Fe₂O₃ in air were also investigated by measuring temperature–resistance (R–T) characteristics and plotting them as Arrhenius plot. Activation energy was calculated by thermal resistance method and found to have a value 1.07 eV.

Indium-rich In_xGa_1-xN thin films were prepared on glass substrates by a mixed source modified activated reactive evaporation technique. All the films exhibit hexagonal wurtzite structure preferentially oriented along the c-axis. The band gap values obtained through Urbach fitting of the absorption edge were found to be in good agreement with the values obtained from photoluminescence spectra. The decrease in band gap below 1.9 eV (i.e., for pure InN) for indium-rich films is mainly due to the compensation of Burstein–Moss shift due to gallium incorporation into the lattice which is further confirmed from the carrier concentration measurements.

Here, we report the surface energy transfer from Rhodamine 6G dye to assembled gold nanoparticles. There is a pronounced effect on the PL and a shortening of the lifetime of the dye, and the calculated distances (d) between the donor and acceptor are 85.5 Å, 91.3 Å, and 109.5 Å for 50, 75, and 125 μM MNA capped Au NPs, respectively. Analysis suggests that the energy transfer from dye to the assembled Au nanoparticles is dominant by surface energy transfer and it follows 1/d⁴ distance dependence.

Time-resolved fluorescence spectroscopy has been employed to study the ultrafast heat dissipation dynamics of silver nanoparticles dispersed in methanol, tetrahydrofuran, and hexane. The average relaxation time obtained is in the order of several hundreds of picoseconds indicating lack of band-edge emission where lack of scaling of these times with the thermal conductivity of the surrounding medium indicate disparate heat dissipation pathways.

Gold nanoparticles (AuNP)-embedded indium oxide and indium tin oxide thin films were prepared by DC and DC magnetron reactive co-sputtering techniques. The concentration and size distribution of AuNP were changed by deposition conditions. The nanoparticles-embedded films were characterized by X-ray diffraction, transmission electron microscopy, and optical spectrophotometry. The X-ray diffraction data showed the polycrystalline nature of indium oxide and indium tin oxide along with the Au (111) peak confirming the presence of elemental AuNP in the matrices. The transmission electron microscope studies revealed that AuNP are distributed in the matrices in different shapes and sizes with the average sizes as 40 nm and 10 nm, respectively for DC-sputtered and DC magnetron-sputtered films. The optical absorbance measurements showed the SPR peak due to AuNP to be around 600 nm. The position and intensity of the SPR peak could be tuned from 650 to 570 nm by changing the concentration of AuNP and annealing the films in oxygen and Ar for different durations.

Swift heavy ion (SHI) (energy > 1 MeV/u) irradiation of polymer nanostructures is a novel technique to tailor their structure and properties. Polyaniline nanofibers synthesized by interfacial polymerization using HCl and camphor sulfonic acid (CSA) as dopants have been irradiated with 90 MeV O⁷⁺ ion at different fluences of 3 × 10¹⁰, 3 × 10¹¹, and 1 × 10¹² ions/cm². TEM micrographs of the irradiated nanofibers reveal a gradual decrease in the size of the nanofibers with an increase in fluence, which could be attributed to the strain-induced fragmentation upon SHI irradiation. The generation of strain in the PAni nanofibers upon SHI irradiation can be explained on the basis of the Coulomb explosion model. X-ray diffraction analysis for both the HCl and CSA-doped nanofibers shows broadening of the peak at 2θ = 20.05⁰, which can be attributed to the reduced domain length and enhanced strain in the material. The two contributions have been separated out. The samples have been characterized with microRaman spectroscopy, which shows a decrease in the intensity of the Raman active modes that can be attributed to the reduction in size of the nanofibers leading to the amorphization of the material.

Multilayer ensembles of alumina capped, widely dispersed silicon nanoparticles (Si-nps) with mean diameter in the range of about 1–4 nm were grown using pulsed laser deposition. With photo-excitation at ~3.82 eV, photoluminescence (PL) was found to emanate from these Si-nps mainly in the UV spectral region centered at about 3.37 eV due to the Γ₂₅–Γ₁₅ transitions. It was found that while the bandgap measured from photoabsorption spectra showed blueshift with decreasing mean size of the Si-nps, spectral position of the PL peaks remained almost insensitive to variation in the mean size. The PL peak at about 3.37 eV was observed to vanish at temperatures higher than 70 K and another one at about 3.31 eV attributed to the TO phonon replica disappeared above 100 K. In general FWHM of both these PL peaks was found to increase monotonically from about 6 to 19 meV and the peak positions were found to undergo redshift with increase in the sample temperature from 10 to 100 K. These observations could be explained by applying Bose statistics for a 6 meV confined phonon mode broadening of the Si-nps and using the Varshni equation, respectively. Si-nps grown in oxygen ambient at 600°C showed significant enhancement in the PL intensity with increasing pressure. These findings elicit that light emission from Si-nps is either due to the nanoparticles of about 1 nm and smaller size primarily driven by the quantum confinement or due to an interface state pumped by these Si-nps.

Three-dimensional photonic crystals prepared by self-assembly method from polymethyl methacrylate colloids are infiltrated with zinc oxide (ZnO) prepared using sol–gel technique. The polymer template is removed by chemical method and heat treatment to obtain inverse photonic crystals of ZnO. The inverse crystal fabricated by the chemical method is further heated at high temperature and the X-ray diffraction establishes the presence of single-crystalline ZnO. The photoluminescence is recorded from the inverse photonic crystals by exciting them with He–Cd laser at 325 nm. The as-prepared inverse crystals show only UV emission while the inverse crystal obtained by the chemical route and treated at high temperature shows the visible emission due to oxygen vacancy defects.

Three- and four-photon nonlinear absorptions are reported by z-scan techniques in ZnS and 1% Mn²⁺ doped ZnS quantum dots (QDs) with 532 and 1064 nm radiations, respectively, obtained from a Q-switched Nd:YAG laser fundamental and its second harmonic radiation. The obtained maximum value of the 3PA coefficient in the doped ZnS QDs is ~10⁵ times that of bulk ZnS. Also, intensity-dependent saturation of 3PA has been observed and the measured experimental data are explained theoretically using a 3PA saturation model and the characteristic saturation intensity is estimated to be 0.92±0.04 GW/cm².

A dual optical tweezer has been built around an inverted microscope with high numerical aperture objective (N.A 1.4). The setup is versatile and can be used both as a single and a dual tweezer, and in the dual mode, enables us to optically trap two micron-sized latex beads within a few microns from each other in solution. Using this setup, we report measurements of the microrheological parameters of Pseudomonas fluorescens and Bacillus subtilis bacterial suspensions. We study the variation of viscoelastic moduli of these bacterial suspensions as a function of their cell count in solution. A comparison with inactive bacteria of corresponding cell count enables us to characterize the activity of the bacterial samples in terms of an average force that the bacteria exerts on the trapped bead. This work paves way for studies of interesting nonlinear rheological phenomena at small length scales.

Sleeping sickness (causal agent, Trypanosoma sp. parasite) causes huge morbidity and mortality in Africa (both human and livestock) in particular and zoo animals worldwide. Three of the four currently approved drugs (Pentamidine, Melarsoprol, Eflornithine, and Nifurtimox) were developed over 50 years ago. Current therapies are unsatisfactory due to unacceptable level of side effects. Pentamidine, an aromatic diamidine, safest so far, inhibits mitochondrial enzymes. Furthermore, it is effective only in early stages of infections and not on the later stage. Melarsoprol, practically insoluble in water, is very toxic and it is given intravenously (i.v.) for later stage infections only. Other drugs like eflornithine and nitfurtimox are also unsatisfactory for various reasons. Human serum derived high-density lipoprotein (HDL; not mouse or any other mammalian HDL) shows trypanolytic effect in vitro and in vivo on T. brucei. But the mechanism of action of human HDL is far from clear. In the absence of novel drug leads, nanodrugs might be valid options as nanoparticles show better accessibility to cells, supramolecular interactions due to enormous increase in surface area to volume ratio, altered partition coefficient, etc. Surface-modified hydrophobic microsilica (FS), mixture of micro- and nanosilica (Dsethvasan) and nanosilica (AL) were characterized by UV–Vis, DLS, SEM, EDAX, AFM, and XRD. Trypanosoma evansi collected from infected horses were injected in mice. Control infected mouse (n = 30) showed 100% mortality within 72±24 h of injection. Dsethvasan-treated mice (n = 30) survived for 192±24 h. FS-treated mice (n = 30) survived for 120±24 h but the AL-treated mice (n = 30) died within 72±24 h of inoculation like infected control. Hydrophobic Dsethvasan which consists of pure amorphous forms of micro- and nanosilica works better than FS (AL is not at all effective). Therefore, micro- and nanomixture of amorphous silica is best suited for treating Trypanosoma infection in mice. The possible role of ratio of higher to lower size class has been discussed.

Branched polyethylenimine, (b PEI, 25 kDa), was converted into nanoparticles by using three different crosslinkers, 1,6-hexanebisphosphate (HP), adipic acid (AA), and 1,4-butane dialdehyde (BA), having same carbon chain length (C-6), and the effect of ionic and covalent crosslinking on the transfection efficiency was studied. The synthesized nanoparticles were characterized by ¹H-NMR, IR, DLS, AFM, and TEM. The entire series of nanoparticles was tested for their toxicity and ability to deliver genes in COS-1 and CHO cell lines. It was observed that, AAP-3 nanoparticle/DNA complex exhibited highest transfection efficiency (~2.1–10.7 folds) than the native PEI and commercially available transfection reagents, such as GenePORTER 2^TM, Lipofectamine^TM, and Superfect^TM, with cell viability >80%. Among the series, the highest cell viability was observed with BAP nanoparticles (>96%). These nanoparticles were able to deliver GFP-siRNA very efficiently inside the cells with ~76%–90% suppression of EGFP expression. Cellular trafficking studies showed that these nanoparticles carry pDNA inside the nucleus of the cells within 2 h of the addition to the cells.

A sensitive and rapid method for the detection of pathogenic bacteria (Salmonella typhi) in water sample was developed using core-shell CdSe/ZnS quantum dots (QDs) as fluorescence label. Surface-functionalized core-shell quantum dots were synthesized by successive ion layer adsorption and reaction (SILAR) technique and were made hydrophilic by ligand exchange method. Developed hydrophobic and hydrophilic QDs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and spectrofluorimetry. Carboxy- terminated QDs were conjugated with bacteria-specific antibodies (S. typhi-specific IgG) for the preparation of photostable fluorescent label and were characterized by various techniques like spectrofluorimetry and enzyme-linked immunosorbent assay (ELISA) for their photoluminescence and successful bioconjugation. Antibody (Ab)-conjugated QDs were incubated with bacteria-contaminated water for S. typhi detection. Microscopic images and spectral profile of bacteria–Ab conjugated QDs complex were recorded by confocal laser scanning microscopy (CLSM). A sensitivity of 10³ organisms/mL of targeted bacteria (S. typhi) could be attained in a period of about 2 h.

This paper deals with the amide functionalization of multiwalled carbon nanotubes (MWNTs) and its evaluation for mercury removal from water. The functionalized MWNTs were characterized using FTIR for structural modification. The properties of MWNTs such as hydrophilic character, nature of surface, selective chemical interaction with mercury, etc., were significantly improved after functionalization making them promising adsorbents for mercury removal. The equilibrium is achieved in short time of 5 h resulting in up to 80% removal of Hg(II). Kinetics of adsorption was established and found to follow first-order reversible kinetics with forward and backward reaction rate constants 0.6648 and 0.1662, respectively.

The use of materials created through nanotechnology is expected to dramatically increase over the next few years. Nanotechnology can provide high durability for fabrics because nanoparticles have a large surface area to volume ratio and high surface energy, thus presenting better affinity for fabrics, leading to an increase in durability of the function. In this study herbal plants such as Curcuma longa and Datura metel were selected, and bioactive compounds were extracted and standardized. Nanoparticles of the medicinal plant extracts were prepared by coacervation method using bovine serum albumin, cross-linked with gluteraldehyde and finished on 100% pure cotton by pad-dry-cure method. The antimicrobial activities of the nanoparticles-treated cotton fabrics were found to be higher than that of the control fabrics in both AATCC 147 and Hohestein Challenge test.

The current study deals with the aspects of surface modification of Polyurethane (PU) foam using chitosan nanoparticles to purify the water from bacteria. The present work also addresses the synthesis and characterizations of chitosan nanoparticles. The particles were characterized by evaluating their topography, size via SEM. These nanoparticles were then coated onto PU foams in order to evaluate these filter samples for purification efficiency through standardized test procedures. The percentage bacterial reduction with the chitosan nanoparticle coated PU foam was 100%, whereas it was only 58.33% with uncoated PU foam. The results were confirmed by flow test which showed coliform count of 30 CFU/mL in the input water, whereas in the Output water the coliform count was 0. Hence, from the overall results it can be confirmed that the PU foams coated with chitosan nanoparticles have good purification efficiency and can be used as an antibacterial water filter.

Drinking colloidal gold as elixir of life is an age-old practice worldwide. A large body of data containing patients' experiences after intake of colloidal gold for long duration would be available in the medical records of hospitals. ZnO has been approved by FDA for topical use and not for oral intake. Drosophila melanogaster (wild type) strains were fed with physiologically relevant concentrations of nano-gold and nano-ZnO along with appropriate controls. Citrate-capped nano-gold (average particle size is 15–20 nm) synthesized by reducing hydrogen tetrachloroaurate with 1% trisodium citrate and custom-made nano-ZnO, purchased from M K Implex, Canada (average particle size 50 nm) were used as treatments. Microarray studies revealed that fly trehalose receptor genes, Tre and Tre1, are both unaffected after nano-gold and nano-ZnO treatment. Gr64 subfamily members (encoding sugar receptors like glucose, sucrose, and maltose), for example, Gr64a-b become downregulated, but Gr64c, Gr64d, Gr64f remain unaltered in case of both the treatments. Among bitter receptor genes, Gr66a is the most well studied and shows significant downregulation by nano-gold and not by nano-ZnO. Ppk11 and Ppk19 are gustatory ion channel genes which modulate salt perception. Ppk11 was found to be downregulated by both nano-gold and nano-ZnO, while ppk19 expression is suppressed by nano-gold treatment but not by nano-ZnO. The effects of these two nanoparticles on pheromone receptors (Gr32a, Gr39a, and Gr68a) and _CO2 receptors (Gr21a and Gr63a) are presented. To the best of our knowledge, this is the first report on the effect of pure nanoparticles on gustation. Data has been analyzed in the light of the age-old tradition of oral administration of the nano-gold viz-a-viz topical use of nano-ZnO. These results would have far reaching implications in the design of nano-gold mediated oral drug delivery of cancer and other drugs as well as nano-ZnO coated drugs/cosmetics and nano-ZnO carrier based drug delivery in skins and in other topical applications.

A simple inexpensive wet chemical technique at room temperature to prepare hybrid structure of multiwalled carbon nanotubes (MWCNT) and cadmium sulfide (CdS) nanoparticles has been reported in this paper. Cadmium sulfide nanocrystals of average size 5 nm have been synthesized and attached with the surfaces of MWCNTs. The hybrid material is characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy. Interesting optical properties of the composite are revealed through UV–visible and photoluminescence (PL) spectroscopy. Significant blue-green PL emission covering a region from 450–600 nm wavelength has been observed when excited by UV radiation of 220–240 nm wavelength. Sharp emission peak has been obtained and this may find wide applications in optical sensors and optoelectronic devices.

TiO₂ nanoparticles and TiO₂:ZnO (80:20) nanocomposites were prepared by chemical method, and X-ray diffraction, high resolution transmission electron microscopy, and Raman analysis of the samples showed a strong anatase phase and they are further used to find and compare the particle size.

The present work emphasizes on the synthesis of CNT-reinforced nanocrystalline AA4032 alloy powders and their consolidation by equal channel angular pressing (ECAP). Nanocrystalline AA4032 alloy reinforced with 2 wt% CNTs was produced by high-energy ball milling. The XRD analysis and TEM observation revealed the formation of nanocrystalline AA4032 alloy and uniform distribution of CNTs in the nanocrystalline matrix. The nanocomposite powders were canned in commercially pure aluminum sheath and subjected to ECAP for consolidation. More than 98% of density was achieved after four passes in route B_A at the center of the can. The hardness obtained is around 218 HV_5.0 after four passes in the core of alloy with 2 wt% of CNTs. Increase in hardness was significant even with minimum addition of CNTs.

The synthesis of composite magnetic nanomaterials has received increasing attention due to their electronic, magnetic, catalytic, and chemical or biological sensing properties. We have prepared cobalt ferrite–zinc sulfide nanocomposites by a chemical route. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and photoluminescence spectrometer (PL). The fluorescent magnetic nanoparticles (FMNPs) had a typical diameter of 30±5 nm and saturation magnetization of 5.8 emu g^-1 at room temperature. So, these FMNPs may be potentially applied in different fields such as optoelectronic devices, biolabeling, imaging, drug targeting, bioseparation, magnetic fluid hyperthermia, etc.

The phenomenon of enhancement of ionic transport and electrochemical behavior of a new poly (propylene glycol) (PPG 4000)–silver triflate (AgCF₃SO₃) as a result of incorporation of varying concentrations of ZrO₂ nanoparticles have been investigated. The significant conformal changes and the strength of interactions along with chain enlargement of polymer matrix have been analyzed by means of FT-IR and DSC studies as well. From the ac impedance measurements, it is clear that the addition of filler particles favors an increase in the conductivity by more than two orders of magnitude and that the typical sample PPG₄–AgCF₃SO₃:10 wt% ZrO₂ exhibits a maximum conductivity of 2.9 × 10^-3 Scm^-1 along with the cationic transference number of 0.49 at room temperature.

Carbon nanotubes have been used as a reinforcing element to improve the properties of polymer matrix. An attempt has been made to investigate the mechanical behavior of carbon nanotubes–high-density polyethylene (CNT–HDPE) nanocomposites using a small punch technique. The designed punch assembly was fabricated and mounted on the Universal Testing Machine. The experimental setup was calibrated using aluminum and mild steel where the relative error was found to be within 7%. The mechanical properties of the nanocomposites, were studied by varying the weight fraction of CNT in HDPE. It was found that Young's modulus and ultimate strength of nanocomposites were increased by 37% and 36%, respectively for 1 wt% of CNTs in HDPE and they were found to increase linearly with an increase in CNT concentration. It is concluded that the small punch technique was successfully developed and tested to characterize the mechanical properties of HDPE and CNT–HDPE nanocomposites.

Photocatalytic degradation of methylene blue was investigated using nanocrystalline ZnO prepared by chemical precipitation and thermal decomposition routes. In both preparation routes zinc acetate dihydrate was used as the precursor. In the case of precipitation route, sodium hydroxide was used as the precipitating agent at room temperature, but in thermal decomposition method the precursor was just calcined at 450°C for 30 min. The structural and morphological properties were studied by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The sample prepared by precipitation route exhibits higher photocatalytic activity than that by thermal decomposition method and the reasons for the enhanced photocatalytic activity have been discussed in detail.

In this paper we report poly N-isopropylacrylamide (NIPAAm) nanogel used as sensing medium in Rayleigh wave type surface acoustic wave (SAW) devices to measure relative humidity. NIPAAm is synthesized by single-step surfactant-free emulsion polymerization reaction method. The prepared nanogel particles have dimensions less than 180 nm. Dynamic light scattering (DLS) analysis of these particles shows increase in size of the particles up to 100% when dispersed in water at room temperature. In this work we have developed two types of relative humidity (RH) sensors. In the first type commercial SAW resonators with resonance frequency at 315 MHz from EPCOS^TM were used in our experiment. The casings of two resonators were removed carefully and one of them was left as such to serve as the reference device. The other was coated with the NIPAAm nanogel and used as the sensor. In the second type of SAW-based humidity sensor aluminum interdigital transducers (IDT) are fabricated over YZ lithium niobate piezoelectric substrate using metallization and lithography techniques. The fabricated IDTs have the pitch length of 34 μm and a resonance frequency of 51.6 MHz. Response of sensor to RH is measured by measuring the scattering parameters of both the types of sensors and reference devices recorded using the network analyzer.

Quantum dot cellular automata (QCA) define the nanostructure of basic computer. It is used as an alternative for designing high-speed computer over CMOS technology. The basic logic in QCA is the logic state that does not measure with voltage level; rather it measures the polarity of electrons in cell. The Majority Voter (MV) is first introduced to design the logic circuits, but only using MV, designing complex logic circuit became inefficient. Many proposals had been made for designing QCA logic gate. In this paper we focus on different useful nanostructures, reduced size and efficient design of Nand–Nor Inverter (NNI), 3 × 3 tile structures for implementing NNI, And–Or Logic, and AOI also present logic synthesis using proposed gates. We analyze QCA defect on proposed gates and describe its permissible defect tolerance. In QCA we describe application for implementing standard functions using proposed structures in this paper and describe effective area of proposed structures.

A sensor for detection of acetone vapors using nanostructured ITO thin film is reported. The ITO film was sputter-deposited on glass substrate using RF magnetron sputtering at 200 W RF power in argon atmosphere at 20 mTorr pressure. The film was then annealed at 450°C for 1h in air. The sensing area was kept to be 3 mm × 3 mm. Two aluminum pads of 7 mm × 4 mm size were formed using lift-off technique for electrical contacts. The crystallinity, microstructure, and acetone vapor-sensing properties were systematically investigated. The stability of the sensing films with aging and temperature variations was also investigated.

A quantum-mechanical model, by combining the quantum mechanical carrier distribution and short channel effects (SCEs) with the classical carrier transport is used to predict the I–V characteristics at sub-90 nm technology nodes. I–V characteristics of 90, 65, and 45 nm for developed model are benchmarked. The analysis of SCEs, namely, velocity saturation, mobility degradation, and threshold voltage shift, has been carried out in this paper for these technology nodes. The detailed physical view of the variation of these effects with channel length (L) and drain voltage (V_ds) has been presented. Also, the impact of including these effects in I–V equations of nanoscale MOSFETs is included in the paper. The observations presented in this paper will help in developing a clear understanding of physical behavior of nanoscale MOSFETs.

Titanium oxide films were deposited on Si and quartz substrates by RF magnetron sputtering of titanium target under various oxygen partial pressures. The films were annealed in air at different temperatures and the influence of annealing temperature on the structural and optical properties was studied. The XPS studies revealed that the films formed at oxygen partial pressure of 2 × 10^-2 Pa were nearly stoichiometric. The as-deposited films were amorphous, the films annealed at 573 K were anatase, while those annealed at 973 K were mixed anatase and rutile phases of TiO₂. The as-deposited films showed an optical bandgap of 3.32 eV while those annealed at 973 K was 3.19 eV.

Half-doped Sm_0.5Ca_0.5MnO₃ nanoparticles with varying particle size down to ~14 nm are synthesized by chemical "pyrophoric reaction" route and their electronic transport and magnetotransport behaviors are investigated in detail in order to understand the nanodimensional size effect on the charge ordering in manganites. The experimental result shows that reduction of particle size (having same chemical composition) down to nanometer scale destabilizes the charge ordering. Weak ferromagnetism and metal–insulator transition are observed in the sample having lowest particle size (14 nm) as a consequence of such suppression of charge ordering. The observed phenomena have been attributed to enhanced surface pressure in the nanoparticles.

Vanadium-substituted La_0.67Ca_0.33MnO₃ is synthesized fully in phase pure and nanocrystalline form for the first time, using nebulized spray pyrolysis. Highly uniform nanoparticles of average size in the range of 31–40 nm as revealed by XRD and TEM studies have been prepared. Rietveld refinement of XRD patterns shows small changes in lattice parameter compared to the parent compound La_0.67Ca_0.33MnO₃. The transition from ferromagnetic to paramagnetic state takes place over a broad temperature range, which can be attributed to the substitution of V at Mn sites as well as the nanometer size of the particles. Peak magnetic entropy change of these nanopowders was estimated to be about 4.5 J/kgK for a magnetic field of 5 T at 255 K. Compared to the bulk La_0.67Ca_0.33Mn_0.9V_0.1O₃, the entropy change of the nanoparticles is found to be smaller.

The mixed ferrite nanometric Co–Zn ferrites [Co_1-xZn_xFe₂O₄] with x = 0, x = 0.35, x = 0.5, x = 0.65, and x = 1 having particle size down to ~20 nm, synthesized through chemical sol–gel route have been found to have higher Curie temperature and higher resistivity as compared to the ones derived from conventional processes. Studies were made to estimate the effect of Co concentration (x) on these mixed ferrite nanometric Co–Zn ferrites having a AB₂O₄-type cubic inverse spinel structure. Investigation of magnetic properties of all Co–Zn nanoferrites with varying Co content has been made using a VSM at room temperature. The saturation magnetization and coercive field have been observed to be highest for x = 0.35 and x = 0, respectively. The magneto-impedance characteristics and the complex impedance spectroscopy [Z(ω,T) = Z′+iZ″] have also been investigated in detail for all the samples at different frequencies.

We report the evolution of microstructure, domain structure, and soft magnetic properties of amorphous and nanocrystalline Fe_89-xZr₁₁B_x(x = 0 - 10) alloys. High-resolution electron microscopy observations reveal that the annealed alloys exhibit a two-phase microstructure. Addition of B enhances the ferromagnetic properties of Fe–Zr amorphous phase in the two-phase structured microstructure, resulting in good soft magnetic properties. Large-sized domains with smooth domain walls are observed in the alloys annealed below 873 K, which exhibit excellent magnetic softness. On the other hand, in the alloys annealed above 873 K, small-sized domains with irregular domain walls and domain wall pinning by Fe–Zr compound are seen. The soft magnetic properties in Fe–Zr–B alloys not only depend on mean grain size, but also on the strength of the intergranular magnetic coupling and structural inhomogeneities.

We report on the occurrence of room temperature ferromagnetism in Co-doped ZnO nanoparticles (NPs). Doping is performed by ball milling of 3 wt% of Co mixed with ZnO nanopowders (commercial) for durations of 2–8 h. X-ray diffraction data and high-resolution transmission electron microscopy (HRTEM) confirm the absence of metallic Co clusters or any other phase different from würtzite-type ZnO. The magnetization (M–H curve) measured at room temperature exhibits the clear ferromagnetic characteristic with saturation magnetization (M_s) and coercive field (H_c) of the order of 3–4 emu/g and 225 Oe, respectively. Post-growth annealing at 250°C results in an increase of M_s by a small magnitude, while annealing at 500°C results in reduction of M_s. UV–visible absorption spectra show small redshift in the absorption peaks in the Co-doped ZnO NPs due to the incorporation of Co atoms in ZnO lattice. Room temperature photoluminescence studies show enhanced near-band-edge emission at 378 nm in the doped NPs as compared to the undoped NPs indicating low density of defects in the doped ZnO crystals. Contribution of intrinsic defects and magnetic impurities in the observed ferromagnetism is discussed.

Nanocrystalline samples of pure and 2 at% Co-doped SnO₂ was prepared by a co-precipitate technique with a crystallite size of the order 10 nm. The homogeneity and single-phase nature of the sample was confirmed by using various characterization techniques, such as X-ray diffraction, transmission electron microscope, and Fourier infrared spectroscopy. Magnetization measurement shows a signature of room temperature ferromagnetism. The reduction in magnetization with decrease in crystalline size has been explained as a result of restriction in the range of bound magnetic polaron interaction. The samples prepared under nitrogen gas environment exhibit improvement in ferromagnetic behavior and enhanced electrical conductivity.

The design of artificial gene regulatory networks has paved way for the construction of therapeutic gene circuits that would find application in next generation gene therapy approaches. The main challenge in such designs is in selecting the appropriate genetic components to make up the circuit in order to produce the anticipated or desired behavior. To eliminate this complexity, computational simulation tools are used to guide circuit design. This involves selection and genetic modification of components, until the required system behavior is achieved.

In this work, we have designed a model for a synthetic nanogene network. The gene expression involved in diseases caused by mutation, like cancer, Alzheimer's disease (AD), etc., can be effectively controlled by "Nanogene silencing genetic switch". Here, we have considered the case of Alzheimer's disease.

Genes that are responsible for genetic AD are APP, PSEN1, and PSEN2. Antimutagenic study of phytochemicals has been carried out with the common AD causing APP gene mutation. By our computational analysis, phytochemicals like curcumin, eugenol, and limonene have been identified as "molecular switch" devices to prevent mutation of AD gene. All these chemicals are found to be strongly interacted with the AD gene without making changes to the remaining part of the sequence. Among the analyzed chemicals, curcumin is found to be most interacting with AD gene protecting it from mutation. Hence, inclusion of curcumin-containing food items in our menu would prevent Alzheimer's disease to a large extent.

This technique is a type of gene therapy leading to silencing of the mutated part of the gene and preventing mutation.

Magnetic nanoparticles (MNPs) can be used in a wide variety of biomedical applications like contrast agents for magnetic resonance imaging, magnetic labeling, controlled drug release, hyperthermia, and in cell isolation. Most of these applications need distinct and controllable interactions between the MNPs and living cells and can be made possible by a proper functionalization technique. This paper describes a computational approach for the identification of magnetic nanoparticles for the development, design, and demonstration of a novel, incorporated system for selective and rapid removal of biological, chemical, and radioactive biohazards from human body.

The attraction between an external magnetic field and the MNPs facilitate separation of a wide variety of biological materials. This principle can be used for the isolation and aggregation of wandering cancer cells from the blood or the bone marrow to make a proper and early diagnosis of leukemia. Similarly, toxins, kidney stones, and other unwanted particles in the human body can be easily diagnosed and removed by the same technique.

Nanoparticle-sized iron oxides have been studied in this work by computational modeling and molecular dynamic (MD) simulation techniques. Structural, thermodynamic, and magnetic properties have been formulated. In this work, nanoparticles of size varying from 0.5 to 2.5 nm have been analyzed. Cell isolation ability of the nanoparticles has been compared based on the computational results.

MNPs are biologically activated and permitted to bind with the targeted cells through various pathways, thereby allowing certain cellular compartments to be specifically addressed. Once the cells are identified, the preferred cellular compartments can be magnetically isolated and removed with the help of an external magnetic field. Out of the iron oxides analyzed in this work, 1.1 nm Fe₃O₄ is found to be most interacting with leukemia protein. Hence, leukemia cells can be effectively targeted, separated, and removed using Fe₃O₄ of the suggested dimension.

Bridge-like structures have been reported in recent studies for a binary mixture with square well fluids in 2D and 3D using different techniques. In this paper, we present our NVT simulation results in 3D with symmetric additive water and oil-like molecules. We use Dirac's delta function defined using theta step function for evaluating pressure components and surface tension values. Our investigation reveals that though 3D NVT MC results are in qualitative agreement with the published results showing all the structures as bridge-like, complete wetting of the walls by the preferred component and micelle structures but the critical parameters as surface attraction strength significantly alter to lower values for PW and CW cases in comparison to the 2D MD cases. We have studied cases with pore width as H = 6.0, 8.0, and 10.0 at T = 0.70, 0.80, and 0.90 for ε_AB = 0.0, 0.25, 0.50, and 1.0. For all of the bridge cases ε_Wall-A = -0.50 and λ_wall-A = 1.0. For fluid–fluid interaction λ_ff = 1.2 and 1.5 are taken with ε_AA = ε_BB = -1.0. Our pressure and surface tension values show clear signature of confinement effect and dependence on other parameters for the bridge cases but it is concluded that different structural transitions depend only on the predefined energetically favorable and unfavorable interfaces which in turn comes from the separation of the two walls and average initial density. Our density profiles confirm the evolved structures.

We have observed prominent change in the velocity of dislocation in thin films due to the proximity of free surfaces using molecular dynamics simulations. A simple model has been introduced and the numerical implementation of our model is in accord with the simulation results. Such surface effects have been attributed to the change in lattice resistance to dislocation motion.

The stability, structural, electronic, and optical properties have been studied for most stable zinc sulfide nanoclusters Zn_xS_y (x + y = n = 2 to 4). A B3LYP-DFT/6-311G(3df) method is employed to optimize the geometries, and a TDDFT method is used for the study of the optical properties. The binding energies (BE), HOMO–LUMO gaps and the bond lengths have been obtained for all the clusters. We have considered also the zero point energy (ZPE) corrections ignored by the earlier workers. For a fixed value of n, we designate the most stable structure the one, which has maximum final binding energy per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), charge on atoms, dipole moment, and optical properties have been investigated for the most stable structures. The nanoclusters containing large number of S atoms for each "n" are found to be most stable. Except for ZnS nanocluster, the HOMO–LUMO gap increases with the number of S atoms. Similarly, except for ZnS, IP and EA fluctuate with the cluster size but reveal downward trend. The optical absorption is quite weak in visible region but is strong in the ultraviolet region in most of the nanoclusters except a few. The growth of most stable nanoclusters may be possible in the experiments.

Hofstadter's fractal energy spectrum, which is also called Hofstadter butterfly, remained as one of the most interesting topics of condensed matter physics for decades. We study, in this paper, how different patterns of energy spectrum emerge when a graphene sheet is subjected to in-plane uniaxial and shear strain in the presence of transverse magnetic field. We discuss these patterns in the context of opening of the electronic energy band structure of graphene. We thus provide a unified framework for graphene under the coupled effect of strain and magnetic field. Due to such coupling, the energy bandgap opens when certain threshold of strain in the zigzag direction of graphene is crossed. The threshold strain value depends on the rationality of the parameter ϕ/ϕ_o, i.e., the ratio of magnetic flux through the deformed hexagonal plaquette and the quantum flux (h/e). Numerical results shows that the energy bandgap depends nonlinearly on the magnitude of strain, and that the threshold strain and energy gap decrease with decreasing magnetic field.

On growth beyond critical thickness, interfacial misfit dislocations partially relax the misfit strains in epitaxially grown nanofilms. In this study the stress state and growth of nanofilms are simulated using Finite Element Method (FEM) by imposing stress-free strains, corresponding to the lattice mismatch between Nb nanofilm and Sapphire substrate. On growth of the Nb nanofilm, a triangular network of edge misfit dislocations nucleates at the (0001)Al₂O₃∥(111)Nb interface. Using a combined simulation of a coherently strained nanofilm and an edge dislocation, the critical thickness for the nucleation of an edge dislocation is determined using an equilibrium energy criterion. Theoretical analyses in literature use only the component of the Burgers vector parallel to the interface, which is an erroneous description of the stress state and energetics of the system. In this investigation the full interfacial edge dislocation is simulated using standard commercially available software and comparisons are made with results available in literature to bring out the utility of the methodology.

Effect of vacancy and Stone–Wales defects on the oscillatory behavior of (5,5)/(10,10) carbon nanotube-based oscillator are studied using NVE molecular dynamics simulations. Results show that defects reduce stability of the oscillators. Effect of single vacancy defect on stability is very small, whereas Stone–Wales defect considerably reduces the stability thereby damping the oscillations quickly. Further increase in density of vacancy defects causes a monotonic decrease of stability of oscillator. In all cases the initial temperature (1 and 300 K) had almost no effect on the oscillation stability.

The optical properties of (8,0) single wall carbon nanotubes (SWCNTs) alloyed with nitrogen (N) are computed using ab initio density functional theory (DFT). Both the real as well as imaginary dielectric constant in the long wavelength limit depends essentially on the nature of electromagnetic field. It is observed that for CN₃ systems, the reflectivity vanishes at 3.45, 6.95, and 8.20 eV, respectively for parallel, perpendicular polarization, and unpolarized light with incidence (1,0,0), while for C₃N the vanishing reflectivity occurs only for parallel polarization at 8.05 eV. Although the magnitude of the significant peaks of loss function of CN₃ systems are comparable to C₃N in perpendicular and unpolarized situation, however, they are significantly one order of magnitude higher in CN₃ for parallel polarization.

Polarizability of small Si_n (n = 3 to 9) clusters has been calculated using density functional theory (DFT) with Vosko–Wilk–Nusair (VWN) correlation functional. The computed values of polarizability per atom tend to decrease with increasing cluster size. Frequency-dependent polarizability of Si₃, Si₄, Si₆, and Si₉ clusters demonstrates that the polarizability increases slowly with the increase in the energy for energy values less than 1.2 eV but exhibit the same size-dependent features as the static polarizability. The first resonance energy for Si₃, Si₄, Si₆, and Si₉ clusters occur at 1.25, 1.63, 2.5, and 1.98 eV, respectively. Moreover, the anisotropic polarizability is found to be the highest for Si₉ cluster.