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In this study, natural crystalline material collected from the head of the Pomadasys maculatus fishes are characterized for their potential applications in various fields including laser optics. Interestingly, the natural otolith crystals exhibit two-photon absorption-induced optical limiting characteristics under Nd:YAG laser excitation. The optical limiting threshold for otolith crystals was found to be $6.22\times 10^{12}$W/m². The presence of Calcium (Ca), Copper (Cu), Potassium (K), and Sodium (Na) is confirmed by ICP-OES analysis. The presence of Ca is primarily from the functional group of otolith that was found on the surface of otolith. From the GCMS analysis, 25 compounds were found in the methanol extract of otolith. The magnetic property of Pomadasys maculatus fish sample was analyzed by vibrating sample magnetometer (VSM). The decomposition/mass loss over a temperature was analyzed by thermogravimetric analysis (TGA) and also the endo and exothermic event temperatures and phase transitions were observed from Differential Thermal Analysis (DTA).

A third-order nonlinear optical crystal of lithium hydrogen maleate dihydrate (LHMD) is grown by the process of slow evaporation at room-temperature. The LHMD crystal system is orthorhombic and is a member of P space group. Using FTIR spectral investigation, the presence of main functional groups in LHMD crystal is identified. The optical behavior of the crystal is determined by UV-Visible spectroscopy. The bandgap energy of the LHMD crystal is calculated to be 3.4 eV. By Vickers microhardness measurements, the mechanical behavior has been assessed. The melting point of LHMD is determined by TG-DTA analysis. The defects present in the LHMD crystal are studied by dielectric loss and dielectric constant. SHG studies are performed for the LHMD crystal by Kurtz and Perry method. The third-order nonlinear characteristics of the LHMD crystal are analyzed by Z-scan technique. The laser damage threshold (LDT) study is carried out to verify the suitability of the crystal for laser applications.

Single crystals of pure and various amount of L-lysine doped KDP crystals were grown from aqueous solution. The doping of L-lysine was confirmed by CHN analysis and FT-IR spectroscopy. Powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was carried out by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. It was found that as the amount of doping of amino acid, L-lysine, increased the thermal stability of the grown crystals decreased. However, the second-harmonic generation (SHG) efficiency of Nd:YAG laser and UV-vis spectroscopy studies indicated that as the L-lysine doping increased in KDP crystals the SHG efficiency and optical transmission percentage increased. The dielectric constant and the dielectric loss of L-lysine doped KDP crystals are lower than the pure KDP crystals. Hence L-lysine doped KDP crystals are found to be more beneficial from an application point of view as compared to pure KDP crystals. The results are discussed.

Bis-thiourea strontium chloride was synthesized and single crystals were grown by the slow solvent evaporation technique using aqueous solvent. The solubility curve was obtained and the determination of the induction period as well as the evaluation of kinetic parameters of nucleation was carried out. The powder XRD analysis suggested orthorhombic crystal structure. The FT-IR spectrum confirmed the presence of various functional groups. The thermo-gravimetry analysis was carried out and the crystals were found to be stable up to 170°C. Applying Coats and Redferm relation to the thermo-gram, the kinetic and thermodynamic parameters of dehydration were calculated. The dielectric study was carried out in the frequency range of applied field from 500 Hz to 1 MHz. The variations of dielectric constant, dielectric loss, AC resistivity and AC conductivity were studied with frequency. It was found that the dielectric constant and the dielectric loss decreased as the frequency of applied field increased, whereas the AC resistivity increased as the frequency increased.

Calcium phosphate based biomaterials play important roles in clinical applications. Calcium pyrophosphate (CPP), a kind of calcium phosphate, can be used as a bone substitution material as well as a bone graft. Because of its similarity to inorganic component of bone and teeth it can be used for surface coating of metallic dental and orthopedic implants. In the present study, calcium pyrophosphate dihydrate (CPPD) nanoparticles were synthesized using surfactant mediated approach. Crystalline nature and average crystallite size was studied using Powder XRD. The CPPD nanocrystallites were found to be triclinic from powder XRD. The TEM study indicated that CPPD nanoparticles were in the range of 13 nm to 20 nm. The presence of various bonds was confirmed by FTIR spectroscopy. The amount of water of hydration and the thermal stability was studied by thermogravimetry. The variations of various dielectric parameters with the frequency of applied field in 3.2 kHz to 32 MHz range and within a temperature range from 60°C to 120°C were studied. The formation of other phases such as β-CPP and α-CPP on heating of CPPD at 900°C and 1250°C, respectively, were studied by the Powder XRD. The results are discussed.

Ammonium penataborate (APB) crystals are well known for their nonlinear optical (NLO) properties. Attempt is made to study the changes produced by addition of chalcogenide compound sodium sulphide in APB crystals. Di-sodium sulphide (Na₂S) is soluble in water and its solubility is further increased for Na₂S nanoparticles. The Na₂S nanoparticles are synthesized by using co-precipitation method followed by microwave irradiation. The slow solvent evaporation method is used to grow pure and Na₂S added APB crystals. Pure and Na₂S added APB crystals possess orthorhombic crystal structure with the mixed phase nature for the Na₂S added APB. The presence of sodium in APB is confirmed by AAS study. In FTIR spectra the absorption peak of S–H asymmetric stretching is observed for Na₂S added APB indicating the presence of sulphur. The thermal stability of APB crystal is enhanced on doping the Na₂S in it. The dielectric study is also carried out within this frequency range. The Jonscher’s power law is applied to AC conductivity data. The impedance spectroscopy study is carried out at room temperature within 100 Hz to 1 MHz frequency range. The complex impedance and modulus plots are drawn. The complex impedance plots indicate only the grain contribution. The Kurtz and Perry powder study indicates that all the crystals are exhibiting NLO properties with varying SHG efficiency.

Modification of surface of natural fibers by high energy electron beam irradiation (6 MeV) is a process for enhancing the adhesion between fiber and matrix. Composites reinforced with natural fiber have gained a prominent place in the field of research and innovation due to the advantages such as low cost, light weight and environment friendly factors. We have studied the thermal properties such as thermal degradation and crystallinity behavior of biodegradable composites using biodegradable polymer poly (lactic) acid (PLA) and fiber of luffa cylindrica (LC) fabricated by using injection molding technique. First, reinforcement LC fibers are irradiated with electron beam of 0.5, 1.0, 2.0, 4.0 and 10.0 Gy using 6 MeV linear accelerator at room temperature in presence of air. The thermal properties like glass transition temperature $(T_g)$, cold crystallization temperature $(T_{cc})$, melting peak temperature $(T_m)$ and thermal stability of the composites are studied using differential scanning calorimetry (DSC) in the temperature range from 30${}^{\circ }$C to 250${}^{\circ }$C and thermogravimetric analysis (TGA) in temperature range from 20${}^{\circ }$C to 700${}^{\circ }$C. The variation of these properties in response to the irradiation dose is analyzed in detail. It is observed that with increase in irradiation dose, glass transition temperature and crystallization temperature increase. However, the thermal stability of the composites is found to increase with increase in irradiation dose.

A spectrophotometric study of 1:1 donor–acceptor complex, cobalt (III) acetylacetonate (donor) and iodine (σ-acceptor) has been preformed. The equilibrium constants, (K) and the absorpitivity (ε) for the formation of the iodine complex have been calculated. The predicted structure of the solid triiodide charge-transfer complex reported in this study is further supported by thermal, far and mid infrared spectroscopic measurements. Electron transfer from Co (acac = 2, 4-pentanedionate)₃ to iodine leads to the formation of an organic semiconductor with the formula of . The kinetic parameters (nonisothermal method) for their decomposition have been evaluated by graphical methods using the equations of Freeman–Carroll (FC), Horowitz–Metzger (HM) and Coats–Redfern (CR). The ac conductivity and dielectric properties of have been measured over the frequency 50–10⁶ Hz at temperature 298 K.

The decomposition of goethite and goethite/siderite concentrates into hematite with thermal modification was studied through the measurements of X-ray diffraction (XRD), scanning electronic microscope (SEM) and thermal gravimetric analysis (TGA). The experimental results showed that goethite decomposed into hematite directly at around 300°C without any intermediate phase and the decomposition of siderite completed at 500°C. Nanoscale granular structures were observed in the thermally treated products. It deserves highlighting that the decomposition processes proceeded from surfaces into bulks.

The aim of this study is to provide information about microstructural and thermal properties of tungsten-based composites. Phase composition and microstructural characterization of tungsten composites were performed using X-ray diffractometer (XRD), Scanning Electron Microscopy (SEM), and Raman Spectroscopy. SEM images revealed the distribution of tungsten (W), vanadium carbide (VC) and graphite (C) powders in the tungsten matrix. The Raman spectra showed two major peaks, which are recorded at 1331 (vs) cm⁻¹, and 1583 (vs) cm⁻¹. These bands can be attributed to disorder graphite (D) and graphite (G). Thermogravimetric analysis (TGA) measurements were performed to determine the weight loss and thermal stability of the tungsten-based composites under argon gas atmosphere and at high temperatures. TGA measurements were performed to determine weight loss and thermal stability of tungsten-based composites under argon gas atmosphere and at high temperatures. The TG curve showed a slight weight loss in this temperature range. Mass loss is thought to be due to oxidation and gas desorption of materials.

The staircase/stair-stepping effect causes wrapping, shrinkage, and surface roughness in additively manufactured (AM) parts. Consequently, abrasive flow finishing (AFF) or abrasive flow machining (AFM) may be employed to improve the AM part surface finish. This study developed an environmentally friendly AFM media using rice husk ash as base material, waste vegetable oil as a liquid synthesizer, and natural additives, i.e. glycerin. The new newly developed rice husk ash-based AFM media (HSAFM) characterization was done using Fourier Transform Infrared (FTIR) spectroscopic method and thermogravimetric analysis (TGA). AFM medium viscosity was optimized using a Taguchi design ($L_9$). These FDM-printed extrusions die inserts were finished using optimized AFM media in a one-way AFM system. A new AFM fixture with a mandrel guide was developed to direct media flow inside the die cavity to ensure uniform finishing. Experimental research has been done on finishing the FDM-printed extrusion die insert pattern using the Box–Behnken Design (BBD)-based experimental design of the response surface methodology (RSM) technique. The surface roughness Ra$\mathrm{\Delta }$28.16 $\mu$m was improved by 96% with the following process parameters: media viscosity of 60 Pa/s, the layer thickness of 0.3, and 90 min of finishing time.

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The oxidation of p-toluidine in acetonitrile by hydrogen peroxide is a very slow reaction which produces 4,4'-dimethylazoxybenzene as the product. The presence of functionalized multiwalled carbon nanotubes (CNT) in the above reaction produces 4,4'-dimethylazobenzene. The reactions have been followed by GC/MS, which show the following mass nos.: 226,92 (without CNT) and 210,120,92,28 (with CNT). UV-VIS absorption spectroscopy shows maximum corresponding to 4,4'-dimethylazobenzene at 444 nm. The rate of formation of 4,4'-dimethylazobenzene has been determined as 0.0093 s^-1.

Aniline is oxidized to nitrosobenzene as the initial product, which undergoes further oxidation to nitrobenzene. The nitrosobenzene formation is catalyzed by functionalized multiwalled carbon nanotubes (CNT) followed by a coupling reaction between nitrosobenzene and aniline to produce azobenzene. This coupling requires close proximity of the reactants. It proceeds rapidly resulting in the UV-VIS absorption spectrum showing maxima at 327 nm and 425 nm. The nitrosobenzene yield in the presence of CNTs is controlled by the amount present in the medium. As the reaction is not catalyzed by unfunctionalized CNTs or graphitic particles, the uniqueness of the functionalized multiwalled CNTs in this catalysis suggests a nanodimensional reaction pathway.

Nanosized metal hydroxides are synthesized in the presence of Poly(vinyl alcohol). Polymer controls the size and growth of the nanometal hydroxides. PVA-assisted synthesis of metal hydroxides is characterized by FTIR, XRD, TGA, and HRTEM methods. This method of synthesis is an eco-friendly and economically viable method.

Various pyrimidine derivatives are well known for their different pharmaceutical applications. The n-butyl 4-(3, 4-dimethoxyphenyl)-6-methyl-2-thioxo-1,2,3,4 tetrahydropyrimidine-5-carboxylate (n-butyl THPM) was synthesized by using n-butylacetoacetate. The n-butyl acetoacetate was obtained by transesterification of ethyl acetoacetate with n-butyl alcohol using Biginelli condensation. The synthesized powder was used to obtain the nanoparticles of n-butyl THPM by using water/oil microemulsion technique. The average particle size was calculated from the powder XRD pattern by applying Scherrer's formula. The nanoparticles of n-butyl THPM were observed by Transmission Electron Microscope (TEM). The diameter of the nanoparticles varied from 15 nm to 65 nm. The nanoparticles were also characterized by FT–IR spectroscopy, TG–DTA–DSC and mass spectroscopy. The n-butyl THPM nanoparticles were stable up to 280°C. Thermodynamic and kinetic parameters of decomposition were obtained by applying Coats and Redfern relation to the thermogram. The dielectric study was carried out in the frequency range of 50 Hz to 5 MHz. The dielectric constant, dielectric loss and ac conductivity decreased as the frequency of applied field increased.

Calcium tartrate finds various applications. In the present study, calcium tartrate nanoparticles were synthesized by wet chemical method using surfactant mediated approach. The powder XRD pattern revealed the typical broadening of peaks indicating the nanostructured nature. The average crystallite size was calculated by applying the Scherrer's formula to powder XRD pattern and was found in the range of 22.8–23.9 nm. The particle size and morphology of the synthesized nanoparticles was confirmed by using transmission electron microscopy (TEM). FTIR spectroscopy was used to confirm the presence of various functional groups. From TGA, it was found that calcium tartrate nanoparticles remained stable up to 120°C and were having two water molecules associated with them. The results are compared with the bulk crystalline materials available in the literature.

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay. The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (IV) values. The relative intensity of C=O/CH is increased while increasing the amount of clay. DSC showed the appearance of multiple endotherms of poly(glycolic acid). TGA showed the percentage weight residue remain above 750°C for polymer-nano composite system was 21% and hence proved the flame retardancy (char forming) nature. TEM confirmed the nano size of the clay used to catalyze the condensation reaction. The intrinsic viscosity value was increased with the increase of percentage weight of Hectorite type clay.

Two new zinc phthalocyanine derivatives bearing four 3,5-di-tert-butyl-4-hydroxyphenyl (ZnPc1) and 3,5-dimethylphenoxy (ZnPc2) have been synthesized and proved by elemental analyses and UV-vis, ¹H NMR, FTIR and MALDI-TOF mass spectra as spectroscopic determination. Thermal stabilities of these neutral Zn-phthalocyanines were performed by thermal gravimetric analysis and, significantly, were found stable up to 373 °C for ZnPc1 and 550 °C for ZnPc2. In addition, the photostability of the sensitizers was quite successful within 240 min. Furthermore, photodynamic therapy has been investigated using these neutral phthalocyanines. Singlet oxygen generation capacities of ZnPc1 and ZnPc2 were studied using 1,3-diphenyl-iso-benzofuran (50.0 μM) as a selective singlet oxygen trap in DMSO and both of them demonstrated very high singlet oxygen generation capacity. Photodynamic therapy is of considerable interest for its potential as an antimicrobial therapy on the grounds that the photodynamic activity of these compounds was tested against a Gram-negative bacteria, Escherichia coli and a Gram-positive bacteria, Staphylococcus aureus. Suspensions of the microorganisms were irradiated for 240 min in the presence of ZnPc1 (with hydrophilic group) and ZnPc2 phthalocyanines. In order to simulate solar radiation, we used a 750 W xenon lamp. Minimum photosensitizer concentration was used as 0.1 mg.10 mL^-1 in 1% dimethylsulfoxide/phosphate buffer saline solution (DMSO/PBS). Moreover, the photostability of these compounds has been investigated and the effect of the amount of DMSO tested against selected bacteria. In the dark, with and without Pcs, bacterial inactivation did not occur. Bacterial inactivation by light with ZnPc1 was observed in response to Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus, whereas the photoinactivation studies with ZnPc2 have revealed that the lack of its activity is due to its poor affinity for either of the organisms. These results suggest that a neutral amphiphilic photosensitizer may be easily used in an application concerning photoinactivation of bacterial cells as well as ionic photosensitizers.

A series of 11 low melting ionic liquids based on meso-substituted A₃B-porphyrins and A₂B₂-porphyrins containing one or two pyridyl substituents have been synthesized in high yields. Three of them are liquids at room temperature. All these porphyrinic salts were characterized by ¹H NMR, ¹⁹F NMR, MALDI-TOF mass spectrometry, elemental analysis and UV-visible spectroscopy. The thermal properties and conductivity values of these salt derivatives have been also measured. A specific conductivity value of up to 4 mS.cm^-1 could be obtained for a compound having the counter-anion B(C₆F₅)₄^-.