International Journal of Nanoscience

We investigated temperature and magnetic field dependences of conductivity of multi-walled carbon nanotubes (MWNTs) with different average outer diameter. We separated out the quantum corrections to magnetoconductivity for interaction electrons and determined the dependence of constant of electron–electron interaction λ versus curvature of graphene layers in MWNTs.

The adsorption of cytosine on graphene surface is studied using density functional theory with local density approximation. The cytosine is physisorbed onto graphene through π–π interaction, with a binding energy around -0.39 eV. Due to the weak interaction, the electronic properties of graphene show little change upon adsorption. The cytosine/graphene interaction can be strongly enhanced by introducing metal atoms. The binding energies increase to -0.60 and -2.31 eV in the presence of Li and Co atoms, respectively. The transport behavior of an electric sensor based on Co-doped graphene shows a sensitivity one order of magnitude higher than that of a similar device using pristine graphene. This work reveals that the sensitivity of graphene-based bio-sensors could be drastically improved by introducing appropriate metal atoms.

This paper considers the effects of bending moment on the structure of double-walled carbon nanotube (DWCNT). Two types of DWCNTs with almost the same aspect ratio (length/radius) are selected; also continuum modeling is utilized to study the bending stability of inner and outer tubes. As a result of the van der Waals interaction between adjacent tubes the critical bending moment of inner tube is higher than this moment of outer tube which is indicated from the obtained results of this research; thus, achieving higher reliability in nanostructures, the critical bending moment of outer tube should be taken into account.

Hydrogenated amorphous carbon (a-C:H) films were deposited using direct-current plasma enhanced chemical vapor deposition (DC PECVD) process. The resulting film properties were studied with respect to the introduction of hydrogen (H₂) and helium (He) in methane (CH₄) plasma. The analysis techniques used to assess the film properties included optical transmission spectroscopy, Fourier transmission infrared (FTIR) spectroscopy and photoluminescence (PL) spectroscopy. Hydrogen dilution has significant effect on the deposition rate and optical band gap (E_g) of the film but helium dilution produces insignificant effects on these parameters. However, the hydrogen content in the film decreases steeply to a saturation value with increase in helium dilution. Increase in dilution of CH₄ by both H and He gases result in decrease in PL efficiency.

We measured the conductivity of multi-walled carbon nanotubes (MWNTs) and onion-like carbon (OLC) in different gaseous media: helium, air, oxygen, hydrogen and methane. The MWNTs had different mean outer diameters varied from 5 to 15 nm. The OLC was synthesized at 1400–1850 K. The adsorption of nitrogen, oxygen, hydrogen and methane leads to decrease of conductivity because these gases are the donors of electron for semi-metallic band structure of investigated objects.

Composites of polyethylene oxide and carbon nanotubes were produced by first deagglomerating highly agglomerated multi-walled carbon nanotubes in water, using a high-intensity ultrasonic probe, and then mixing with a solution of the polymer using a high-speed mixer. The deagglomeration of the nanotubes was carried out at different amplitudes of the vibrating ultrasonic probe. Differential scanning calorimetry results show an increase in melting temperature with increase in amplitude of sonication. Also, tensile test results show improved mechanical properties, with increased degree of deagglomeration of the nanotubes. SEM images show that the extent of nanotubes dispersion in the polymer matrix correlates with the extent of deagglomeration.

In this study, thin sheets like carbon nanostructures and carbon nanoparticles have been effectively synthesized with CH₄ and Ar as precursors at low temperature (< 400°C) by inductively coupled radio frequency plasma enhanced chemical vapor deposition on silicon and glass substrates. The surface morphology and chemical composition were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. AFM studies show that the nanoparticles roughly about 70 to 80 nm in diameter surrounded by nanosheets. Nanosheets are about 100 nm in thickness, which attain approximately 1.75 μm lengths. EDS results revealed that the atomic percentage of carbon in the particle like structure is more than that in the nanosheet like structures.

Specific heat of carbon nanotube (CNT) is affected by its diameter. Increasing of the CNTs diameter increases its specific heat. This phenomenon is due to transversal acoustic phonon modes. The contribution to specific heat from TA modes varies linearly with temperature and becomes saturated after specific temperature. In this paper, the effect of CNTs diameter on the specific heat is theoretically simulated. The result indicates that transversal phonon modes play an important role in the increasing of specific heat with respect to the diameter.

Hydrogen storage in a metallic nanoparticle was simulated by classical molecular dynamics. Distribution of hydrogen atoms inside nanoparticle was investigated by changing length and energy parameters of metal–H bonds. Hydrogen atoms diffused into the particle and distributed homogeneously in case of weak metal–H bonds. In case of strong metal–H bonds, a hydrogen-rich surface layer was observed which suppresses the inward diffusion of hydrogen atoms. Structural modification of nanoparticle accompanied by grain boundary formation due to hydrogen loading was also observed. These variations in dynamical and structural features are considered to affect the hydrogen storage properties in nanoparticles.

In this study, we report the hydrogen storage in aluminum hydride coated single-walled carbon nanotube. All the H₂ adsorption is molecular with H–H bond length of 0.756 Å. The hydrogen storage capacities with half and full coverages are 6.01 (8.3) wt% and 7.2 (10.3) wt%, respectively, without (with) H₃ of AlH₃. At high coverage of AlH₃ (C10AlH₃) interesting clustering/ dimerization of AlH₃ is observed. These systems are quite stable and the H₂ can be extracted from the system without disturbing the C–Al bonding or detaching the AlH₃ from the carbon nanotube. This present study on a full molecular adsorption of hydrogen via light metal-hydride AlH₃ is new and it leads to a practically viable hydrogen storage process.

First principles calculation is performed in order to analyze hydrogen hopping between sites in LaNi₅. Potential energy map for hydrogen is calculated on the plane which contains hydrogen sites 6m, 12o, and 4h. Applying nudged elastic band method to 12o–12n′ hopping, its hopping path and activation energy are determined. The effect of Ni atom position relaxation is discussed.

We investigated the stability of aminoborane with electron withdrawing groups such as –CF₃ and –CN using density functional theory calculations. For the electron withdrawing groups of –CF₃ and –CN, we observed similar tendency of B–N bond strength: electron withdrawal from the N atom reduces the strength of B–N bonds. And we find that the electron density localized on B and N is also reduced through the charge analysis. These electron withdrawing substituents make cyclic dimers and trimers stabilized less than electron donating ones.

Storage of hydrogen as hydrogen hydrate is a promising alternative technology to liquefied hydrogen at cryogenic temperatures or compressed hydrogen at high pressures. In this paper, computer simulation is performed based on the solid solution theory of clathrates of van der Waals and Platteeuw with some modifications that include in particular the account of multiple cage occupancies and host relaxation. The quasiharmonic lattice dynamics method employed here gives the free energy of clathrate hydrate to first order in the anharmonicity of intermolecular potential and permits to take into account quantum zero-point vibration of host lattice and hydrogen in the cages. It is employed to study the thermodynamic functions of binary (mixed) H₂–CH₄ hydrates of cubic structure II (sII) and hexagonal structure H (sH). It is shown that at divariant equilibrium "gas phase–gas hydrate" with increasing pressure the filling of large cavities by hydrogen proceeds gradually from single filling to the maximal number of hydrogen molecules in clusters included in large cages (four in sII and five in sH) preserving stability of the hydrogen–methane hydrates sII and sH. The results show that mass fraction of hydrogen in the mixed sH hydrate is significantly lower than in the mixed sII hydrate. Pressure of monovariant equilibrium "IceIh–gas phase–mixed sII hydrate" with increasing methane concentration in the gas phase lowers in comparison with the pressure of pure hydrogen hydrate formation. For the mixed hydrogen + methane sH hydrates, it was demonstrated that thermodynamic stability depends on the filling degree of small cavities by methane molecules and stability area shifts to lower pressure with increasing filling.

High-quality hydrophobic or hydrophilic ferrofluid based on magnetite (Fe₃O₄) nanoparticles can be synthesized by one-pot direct synthesis which involves thermolysis of Iron(III) acetylacetonate, Fe(acac)₃ in hydrophobic or hydrophilic stabilizing agent, respectively. The structure of the nanoparticles dispersed in the ferrofluid was studied using XRD, FTIR, XPS, and TGA analysis, while morphology and size of the nanoparticles were determined by TEM. The magnetic properties of the samples were measured using VSM and SQUID measurement. The results show that oleylamine (OM) and tri(ethylene glycol) (TREG) coated Fe₃O₄ nanoparticles which are well stabilized in hydrophobic and hydrophilic ferrofluid, respectively, are relatively monodisperse, single crystalline and superparamagnetic in nature with the blocking temperature at around 100 K.

We present a GaAs/AlGaAs-based quantum well device capable of achieving an appreciable spin polarization coupled with high electron transmission. Our numerical results indicate that the device is able to achieve a high spin polarization without the need for less commonly used materials with high g-factors required by previously proposed semiconductor-based systems. The electron transmission and spin polarization amplitude of our structure is found to be robust to the length of the parabolic well, which could ease the fabrication of such structures in practical applications.

Single- and poly-crystalline metal and alloy nanowires have been successfully fabricated into anodic aluminum oxide (AAO) template by electroplating. The single crystal-crystalline Ni and Co nanowires have been found at relatively high current density. Moreover, Ni and Co nanowires have a preferred orientation along the [2 2 0] and [1 0 0] direction, respectively. Single-crystal Ni nanowires showed coercivity 1 kOe with remanent 0.997, while Co nanowires showed coercivity 1.3 kOe and remanent 0.797. The different structures of NiCo nanowires have been obtained by varying the deposition conditions and current densities. The unique bamboo-like nanostructure was found in the product. Bamboo-like structure is achieved when the composition of 15 at% Co. The investigation of the mechanisms shows the special structures are related to the different diffusion rates of Ni and Co on the surface of AAO template. The work shows the possibility to control the sub-nanostructures in nanowires.

Multiferroic Bi_0.95La_0.05Fe_0.7Sc_0.3O₃ (BLFS) thin films with different thicknesses have been prepared on (1 0 0) LaAlO₃ (LAO) substrates using a sol–gel process and annealed in N₂ ambient at 650°C for 5 min. From the X-ray diffraction (XRD) analysis, it was observed that BLFS thin films had (h 0 0)-preferred orientation for the film thickness 63, 125, 186, and 240 nm and became isotropic thereafter. The films developed in-plane epitaxial growth with respect to the substrate. The surface morphology became denser and the surface roughness increased as thickness increased up to 241 nm. The highest dielectric constant observed for the 241 nm thick BLFS film too. No prominent of the leakage current density observed for the film thickness up to 241 nm. However, two fold increase in the leakage current density observed for the film thickness 382 nm. For the BLFS films with thickness 241 nm, we observed the highest dielectric constant (ε) value of 1675 and remnant polarization (P_r) polarization value of 52 μC/cm² using a sol–gel spin coating process.

The present study elucidates the synthesis of magnesium ferrite magnetic nanocrystallites via hydroxylation–condensation reaction followed by an auto-combustion process. Nanocrystallites with diameter of 3–7 nm were successfully formed via this method. The ignition temperature of the redox reaction was apparently improved to 200°C by the modification of the pH of the metal aqueous solution. The crystallite size was altered by varying the hydrolysis parameters. The XRD analysis of the as-synthesized powder confirms the formation of a single-phase MgFe₂O₄ spinel structure. Importantly, the crystalline particles were obtained at low temperature without further calcination. The thermodynamic behavior of the precursor was characterized by DTA-TG. TEM observations showed the morphology and crystal structure of the nanocrystallites.

In this study, we adopted extended Huckel theory (EHT) combined with nonequilibrium Green's function (NEGF) to deal with the transport problem of single 4,4′-bipyridine molecule sandwiched between two gold electrodes. The dependence of the transport characteristics on gold–nitrogen bond length and torsion angle is investigated. Furthermore, the influence of the charging effect on the transport characteristics is emphasized. We note that the orientation of the molecule plays a crucial role in electronic conduction and the current is also strongly dependent on distance between the molecule and electrodes. The results we obtained are in general agreement with previous works and are discussed.

In order to supply high quality silver source to photothermographic material based on silver carboxylate, silver plamitate was prepared by chemical deposition method using palmitic acid, sodium hydroxide, silver nitrate as raw materials and PVP as surfactant in water system. The morphology, crystal structure and thermal properties of silver palmitate were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and Thermogravimetry (TG). The results indicate that silver palmitate has good purity and well-defined layer structure with triclinic phase. The diameter of fiber-like silver palmitate is about 200 nm, which shows excellent dispersion properties. DSC curves demonstrate that silver palmitate has seven endothermic peaks below 240°C. Five endothermic peaks below 190°C assign to different phase transitions. Silver palmitate decomposed step-by-step at 204.1, 223.6, and 253.9°C.

This study focuses on the correlation between simulation and experiment using UV curable gap fill materials for global planarization in advanced lithographic and nanoimprinting techniques. A novel gap fill material has been optimized and developed for global planarization properties. Gap fill materials planarize irregular substrates such as patterned steps, vias, and trenches to increase depth of focus and patterning resolution. After planarizing the substrate surface, the gap fill materials provide dry etching selectivity to the under-layer to avoid damaging the dielectric materials. In the characterization of UV curable gap fill materials, two key factors were identified. The factors were the specific dependence of planarization on the spin speed and film thickness. By optimizing these factors, an appreciable reduction in via topography was realized. An array of 1.1 μm deep, 300 nm diameter holes was planarized to 10 nm thickness bias with a 380 nm thick planarizing film. In addition of global planarization, a final design consideration was to reduce the amount of outgassing during the process. UV curable gap fill material was optimized for sublimate reduction resulting in a defect-free coating. The sublimate produced from the developed gap fill material during baking was significantly decreased when compared with that produced from a thermal curable material. And, the third evaluation of UV curable gap fill materials was reported, to avoid resist poisoning issues in an advanced via-first dual damascene process. The resist poisoning properties in UV curable gap fill material were observed better performance than that of thermal curable material. The resulting UV curable gap fill materials based on this study will be extremely useful for lithographic and nanoimprinting techniques.

A novel approach for intermixing of InAs/GaAs quantum dot (QD) structure by direct imprinting of SiO₂ strips using silicafilm is presented. The silicafilm SiO₂ strips were imprinted on a InAs/GaAs QD structure by an Obducat nanoimprinter using a polyethylene terepthalate soft mold. Inductively coupled plasma etching of GaAs waveguide structures using the imprinted SiO₂ strips as hard mask has been demonstrated. By using the silicafilm SiO₂ as a capping layer, the effects of impurity-free vacancy disordering intermixing on optical characteristics of the InAs/GaAs QD structure have been examined. The measured photoluminescence spectra of the InAs/GaAs QD structure suggest that differential wavelength blueshift of up to 105 nm for region with and without the SiO₂ film can be achieved. A cost effective one step SiO₂ hard mask with graded thickness profile for quantum well or QD intermixing by imprinting technique is proposed for application in broadband lasers and superluminescent diodes.

We study the electrostatic and quantum transport properties of nanoscale double-gated Si-based field effect transistors within the framework of density functional theory combined with nonequilibrium Green's function approach. In our model device system, a Si slab is sandwiched between two insulator slabs and connected to two semi-infinite Si electrodes at its left and right ends. The effect of the double gates is taken into account by applying proper electrostatic boundary conditions and solving the Poisson equation self-consistently in the system. In the representation of localized SIESTA linear combination of atomic orbitals, the study is carried out with the help of Atomistix ToolKit (ATK) package together with an efficient multigrid Poisson solver. We find that the surface potential versus gate voltage curve shows similar characteristics as in conventional MOSFETs even for devices of 1 nm size, though the shape of the curve varies with the shrink of the system. In different working regimes of the devices, the electrostatic potential and the transmission spectrum are analyzed for an atomistic understanding of the device behavior.

Highly ordered arrays consisting uniform fluorescent cadmium selenide (CdSe) quantum dots (QDs) ring or dot structures were obtained by self-assembly of QDs on chemically patterned substrates. In this method, Au substrates with alternating hydrophobic and hydrophilic square patterns are firstly fabricated by microcontact printing, which allows water droplets to condense on the hydrophilic regions to provide two-dimensional template arrays. The CdSe QDs are then assembled at the liquid/liquid interfaces to give uniform micro or nanostructures. The shape and size of the rings and dots can be tailored by controlling the relative evaporation speed of the water and the organic solvents. The obtained nanostructures have ideal topography to avoid substrate-induced fluorescence quenching.

This contribution firstly elucidates a structure–property relationship in third-order nonlinear optical molecular systems with singlet diradical characters. It turns out that the second hyperpolarizabilities (γ) of the singlet open-shell molecules with intermediate diradical characters are significantly enhanced as compared with those of closed-shell and pure diradical molecules. The hybrid density functional theory method, i.e. UBHandHLYP, is applied to the calculations of γ of dimer models composed of singlet diradical diphenalenyl molecules, which show a remarkable enhancement of γ per monomer as decreasing the intermolecular distance. The second contribution is concerned with a development of ab initio molecular orbital configuration-interaction-based quantum master equation (QME) approach. This is found to provide both coherent processes, e.g. dynamic polarization and exciton (electron–hole pair) recurrence motion, and incoherent processes, e.g. exciton migration, in molecular systems. Using this approach, the electron/hole dynamics for dynamic polarizabilities α(ω) are examined for several π-conjugated linear chain systems, and the structural dependences of α(ω) are elucidated.

Plasmonic crystal or gratings with periodicity and amplitudes suitable for plasmon coupling can be fabricated using interference lithography technique. The grating structure is holographically formed in a photoresist film. This technique offers an easy way to control the vertical and horizontal ratio of the corrugated profile. Since surface polaritons are extremely sensitive to the changes at the metallic and dielectric interface, one can expect that by controlling this refractive index, an effective control of the SPP can be realized. Different diffracted orders can be explored by controlling the dielectric medium, in this case hybrid materials. A comprehensive simulation that models the effect of dielectric medium to the changes of SPP coupling condition has been undertaken for the reflectivity and azimuthal angle dependence. An active porous thin film, which is hybrid organic–inorganic materials synthesized by sol–gel techniques, starting from bridged polysilsesquioxanes with phenol red, is coupled on plasmonic crystals in order to exploit enhanced effective refractive index sensitivity for sensing purposes; in this case, we use hydrochloric acid as analyte. The porosity of film increases reacting surface area and chemical reactivity of the plasmonic crystal. This film will change color from yellow to orange red when exposed to the acid. The change of optical characteristic after matrix wetting in HCl 0.01 molar solution has also been characterized. The activity of the film is determined by the dielectric properties depending on an applied external electric and magnetic field. They constitute molecular-engineered materials that exhibit a fine control in porosity in order to control the permittivity of the dielectric medium. The optical, thermal, and structural characterizations of these films are investigated by ellipsometry, DTA, and FTIR measurements. We present this configuration as a sensitive architecture for plasmonic-based sensor application.

Indoped ZnO nanorods (ZnO:In NRs) were grown on Si(111) substrates by using AuGe as a catalyst. In-concentration was controlled as high as 0.33 at.%. The length L to diameter D relationship of NRs revealed that the growth mechanism should be explained in terms of not a simple vapor–liquid–solid (VLS) mechanism but a diffusion-induced growth model. In-induced changes have been investigated from the viewpoint of photoluminescence (PL) property. At room temperature, an increase of extrinsic carrier concentration and interaction with excitons were estimated from the blueshift of peak position and decrease of luminescence intensity. Also, narrow linewidth of low-temperature PL spectra characterized the high structural quality of ZnO:In NRs. We have assigned several PL lines and confirmed the assignment by using excitation power and temperature dependence PL. Considerable evidence of crystal quality degradation was not observed from both measurements; however, we could observe that a defect and donor-bound-exciton complex dominate the PL spectrum. ZnO:In NRs shows good optical quality within our experimental range, and this result strongly supports the feasibility of In-doping to enhance the electrical property of ZnO-based nanostructure.

A simple device of VO₂ film with two terminal electrodes revealed current jump phenomena at certain applied voltage. In this study, we investigated the effect of light irradiation on the electric field-induced resistance switching phenomenon. Based on changes of current–voltage characteristics under light irradiation, we discussed the effect of light irradiation on this device.

Nanoimprint lithography (NIL) technology has aroused great interests in both academia and industry due to its high resolution, low-cost, and high-volume nanopatterning capability. And as an expoxy resin-based negative amplified photoresist, SU-8 is an ideal candidate for NIL because of its low-glass-transition temperature, low-volume shrinkage coefficient, and good optical properties. In this reviewing paper, we highlight the major technical achievements in NIL on epoxy resin and its applications for bio- and nanophotonic structures. NIL was also applied for the duplication of imprint templates, originally fabricated by e-beam lithography (EBL) followed by reactive ion etch (RIE), using a SU-8/SiO2/PMMA tri-layer technique. And nanoimprint properties were systematically investigated for optimization. The developed nanoimprint process for different applications indicates promising industrial potentials in the next generation lithography resolution.

Tin oxide doped with fluorine (SnO₂:F) thin films were deposited on polyethylene terephthalate (PET) foils by RF reaction cosputtering at low temperature in different oxygen partial pressures. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) were used to study the effects of the processing parameters on the crystallization and surface topography of the as-prepared SnO₂ films. The results showed that high quality SnO₂:F thin films could be obtained by optimizing deposition conditions without intentional annealing, i.e. oxygen partial pressure to total pressure of higher than 50%, RF power higher than 50 W. The optical transmittance measurements revealed that the SnO₂:F films were highly transparent in the visible region (90%) and showed an absorption edge redshift with increasing oxygen partial pressure from 1/4 to 3/4. The optical bandgap energy was calculated to be about 3.6 eV. Hall effect measurements confirmed that the as-prepared SnO₂ thin films possessed good electrical properties with a low resistivity of 10^-3 Ω · cm, a high carrier concentration of 9.6 × 10¹⁸ cm^-3, and a Hall mobility of about 200 cm²/V · s.

The development of new fluorophores has experienced a tremendous advance over the last two decades. Here, we discuss the photophysical properties of traditional fluorescent labels and the comparatively advantageous properties of quantum dots. The unique spectral properties of quantum dots, such as their large Stokes shifts and exceptional brightness, make them attractive probes in biological applications and prime candidates for further research and development in the field of solid-phase immunoassay and cell analysis.

Monoolein (2,3-dihydroxypropyl (Z)-octadec-9-enoate) is one of the monoacylglycerol and has been studied for various applications in food, pharmaceutical, and cosmetic industry. Those applications make use of the phase behavior of monoolein. In order to understand the lipid bilayer phase of monoolein in mesoscale, a coarse-grained model has been built and tested in this work. The monoolein molecule was represented by two hydrophilic heads and six hydrophobic tails. The three water molecules were also represented as one bead. For comparison, the atomistic model has also been used for molecular dynamics simulation on the lipid bilayer phase in isothermal-isobaric (NPT) ensemble. The interaction and bond bending potential parameters for dissipative particle dynamics (DPD) were obtained with molecular dynamics simulations on lipid bilayer in water. And we also obtained the interaction parameters of the coarse-grained model, which agree well with the atomistic model. We compared the simulated phases using the coarse-grained model with using the atomistic model. With these parameters, we successfully reproduced the lamella phase of monoolein in DPD simulations.

Quercetin is a naturally occurring cytotoxic compound where clinical use has been limited by its low water solubility. Therefore, liposomes were explored for solubilizing quercetin. Liposomes composed of DPPC (1,2 dipalmitoyl-sn-glycerol-3-phosphocholine)/DSPE-PEG₂₀₀₀ (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)₂₀₀₀])/quercetin (90:5:5 mole ratio) incorporated quercetin efficiently at 100.9 ± 4.6% and increased quercetin concentration in water 11.2-fold. Stability studies at storage temperature of 4°C showed that the liposomes were stable for up to 16 weeks, without any significant changes in diameters. Liposomal quercetin showed a delayed release profile and reduced quercetin degradation. In vitro cytotoxicity tests also showed that the ED₅₀ of liposomal quercetin was 17.6 times lower than free quercetin in MDA-MB-231 breast cancer cells. In conclusion, the DPPC/DSPE-PEG-based liposomes were stable and were capable of solubilizing quercetin, preventing quercetin degradation, and increasing quercetin in vitro cytotoxicity. Hence, liposomes are a suitable nanocarrier for quercetin.

Naked and molecular encapsulated Au nanoparticles with a diameter of 3 nm were prepared on top of Si in order to elucidate the effect of the molecules on the electronic structures of Au nanoparticles. We have found that the naked particles showed the finite densities of states at the Fermi level while the molecular encapsulated particles exhibited the edge being away from the Fermi level, indicating that the naked and molecular encapsulated Au particles should show metallic and nonmetallic features, respectively. Furthermore, because the naked Au nanoparticles became nonmetallic upon the particles adsorbing the molecules, the highly occupied states of the molecules might be hybridized with the valence states of Au particles, resulting in nonmetallic properties of the molecular encapsulated nanoparticles in the present system.

Hybrid light emitting nanoparticles with diameter range from 2 to 4 nm were prepared via grafting organic-conjugated chains directly onto an inorganic rigid cage polyhedral oligomeric silsesquioxanes (POSS). The unique properties of these particles show evidence of quantum confinement effect on the conjugated short chains by two barriers of POSS cage and alkyl chains. The confinement effects are revealed in five aspects. First, the UV and PL spectra redshift as increasing the length of conjugated chains. This phenomenon can be considered as size effect. Second, PL spectra of these nanoparticles in solid film blueshift from that in most of organic solvents, which can be considered as limited intra- or inter-molecular interactions existed within the nanoparticles. Third, the Raman bands of the conjugated chains in these nanoparticles are redshifted and broadening with respect to their bulk counterparts. The systematic peak shifting and broadening of the Raman bands provided additional confirmation that the conjugated chains in hybrid nanoparticles at bulk state are isolated without any π–π stacking. Fourth, TEM and SEM images showed the particle size in a range of 2–4 nm and the nanoparticles in bulk state are noncrystalline materials. Lastly, the PL spectrum of the nanoparticle at low temperature was studied and found no change in PL position and intensity as temperature increasing from 4 K to 150 K.

The gill mucosa is a convenient route for the administration of DNA vaccine to fish and other aquatic organisms. Nanocarriers have been considered for delivery; however, a suitable formulation is required. To devise an appropriate carrier, we have synthesized chitosan nanoparticles entrapping pDNA at N/P ratios of 1:1 and 2.5:1, using ionic gelation and microemulsion (μE) methods. For nanoparticle characterization, the size, morphology, zetapotential, and IR spectra were determined. The efficiency of pDNA entrapment was established by gel retardation assay. On the basis of the investigations, the loaded nanoparticles synthesized by μE method appear to have the required characteristics for effective delivery by this route.

In_xGa_1-xN quantum dots (QDs) were grown on GaN epitaxy using nitridation of nano-alloyed droplet (NNAD) method by metal-organic chemical vapor deposition (MOCVD) system. Before the In_xGa_1-xN QDs formation, In + Ga droplets were initially formed by the flow of TMI and TMG, which acts as a nucleation seed for the QDs growth. Density of the alloy droplets was increased with the increasing flow rate; however, droplet size was scarcely changed about 100–200 nm by flow rate. And In_xGa_1-xN QDs size can be easily changed by controlling the nitridation time or various factors. Also, the influence of GaN capping layer on the properties of In_xGa_1-xN QDs was discussed.

Nanocrystalline Pd electrocatalyst promoted with transition metal oxide (Co₃O₄, NiO, and CoNiO_x) is successfully synthesized on high surface carbon support by using intermittent microwave heating (IMH) method. The physical properties of the catalysts are characterized by XRD, TEM, and EDX. The results show that there is no significant microstructure change between Pd and Pd-oxide electrocatalysts and the particle sizes are in the range 5.8–3.9 nm. The linear sweep voltammogram and chronoamperometry results for the electro-oxidation of ethanol show that Pd-oxide/C electrocatalysts exhibit much better electrochemical activity and stability as compared with pure Pd/C electrocatalyst. The results show that Pd–CoNiO_x/C exhibits the best stability and highest electro-oxidation activity, indicating the promising potential as an alternative electrocatalysts for the direct ethanol fuel cells.

Colloidal gold nanoparticles were produced by irradiating a gold disc with a femtosecond laser beam in pure deionized water. Variation of laser fluence between 38 and 330 J/cm² was used to control the nanoparticle size distribution. The nanoparticles produced were spherically shaped with average diameter between 9 and 10 nm. The effect of ablation time on the nanoparticle production efficiency and size distribution was also studied.

A method is presented that enables the determination of transient absorption in Langmuir films made from a monolayer of spiropyran on water. This is achievable even though the optical pathlength of such a monolayer is < 10^-9 m. The approach is to monitor reflectivity changes close to the Brewster angle, where the background of reflected light is minimized. This is the key to the sensitivity of the method. Relatively speaking the small changes in reflectivity due to changes in both real and imaginary parts of the refractive index are easier to observe with the intrinsically low backgrounds at the Brewster angle. Notably using Fresnel equations we can show that the real and imaginary parts of the refractive index can be independently assessed for ultrathin films and monolayers using the approach presented.

We propose a novel stress sensing methods using water soluble, sugar-displaying quantum dot and digitonin-permeabilized semi-intact HeLa cells. The amount of GlcNAc-QDs (N-acetylglucosamine-displaying quantum dots) binding to heavy metal ion exposed cells was investigated by fluorescence intensity, and it increased in a dose-dependent manner. This result suggests that GlcNAc-QD could be applied for a new stress sensing probe.

Effect of ligand exchange on the optical and photoluminescence properties of Au₂₅SG₁₈ (SG-glutathione thiolate) clusters was investigated. A fluorescein-based dye, 5-((2-(and-3)-S-(acetylmercapto)succinoyl)amino)-fluorescein (SAMSA) was anchored on water soluble Au₂₅SG₁₈ clusters by the place exchange reaction and the solid-state emission of the exchange product was studied. Inherent fluorescence image of these clusters was mapped. Organic soluble Au₂₅(SC₂H₄Ph₁₈ clusters were synthesized as a model system which also showed temperature-dependent solid-state emission, in good agreement with the results from water soluble Au₂₅ clusters.

When conjugated polymer is used as dye sensitizer in dye-sensitized solar cell (DSSC), the device performance is usually limited by the poor penetration of conjugated polymer into the network formed by TiO₂ nanoparticles. In this regard, we develop a novel photoanode composed of electrospun TiO₂ nanofibers. Scanning electron microscopy (SEM) reveals the uniformity of the calcined TiO₂ nanofibers. X-ray diffraction (XRD) analysis indicates that the calcined TiO₂ nanofibers are polycrystalline and composed of pure anatase phase TiO₂ grains. To demonstrate the application of the synthesized nanofibers in electronic devices, DSSCs are fabricated and investigated under illumination with AM 1.5 (100 mW cm^-2) simulated sunlight. The initial results demonstrate the great potential of using conjugated polymer as the dye sensitizer for devices with TiO₂ nanofiber electrode.