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Over the past few decades, nanomaterials of metal oxide such as zinc oxide (ZnO) have been significantly researched for sensing various toxic gases like ethanol, acetone and ammonia. The sensing performance of semiconducting materials depends primarily on their surface structure and the interaction behavior with target gas molecules. The surface quality of ZnO is highly influenced by deposition methods. Although several ZnO surfaces have been rigorously studied for detecting gas leakages, it still possesses drawbacks such as high operating temperature, slow response and recovery times. Henceforth, this investigation was carried out to resolve these issues in the fabrication of future ZnO-based gas sensors. In this work, we report the major findings of the ZnO-based nanoparticle film gas sensor prepared by a doctor blade method to gain insight towards detecting various concentrations of acetone gas at different temperatures. The XRD and FTIR results confirmed the phase purity of ZnO. The results showed the highest response ratio of 25.697 0.012 at 285 oC with an exposure of 800 ppm of acetone along with the quick response and recovery times of 39 sec and 79 sec, respectively. This operating temperature was found to be lower than the reported value for a similar system than that prepared via different methods.

This article reports the effects of natural plant proteins on the morphology of zinc oxide nanoparticles (ZnONPs) prepared via a precipitation method. Green synthesised ZnONPs have a wide range of uses such as biomedical applications, water purification, optical devices and gas sensors. The non-toxic and economical technique described in this article is favourable for large-scale production too. ZnONPs were produced from a zinc acetate precursor with dye extract of Ixora Coccinea (IC) leaves as a capping agent. The as-prepared ZnONPs were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV-visible (UV-vis), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. The XRD analysis showed an average crystallite size of 23 nm. The SEM analysis revealed a reduction in aggregation of ZnO crystallites due to addition of dye extracts of IC. EDX and UV-vis results confirmed the formation of pure ZnONPs. Finally, the gas sensing properties of ZnO films, prepared by doctor blade method, were used to detect ethanol vapour. The results showed gas response ratios of 28.7 and 5.4 at 800 ppm and 40 ppm exposure, respectively. Furthermore, the response time and recovery time were found to be 24 sec and 47 sec, respectively at 200 ppm exposure of ethanol vapour.

In recent times, the research on ZnO is growing tremendously, because of its potential use in many applications such as optical devices, dye sensitized solar cell (DSSC), gas sensors and biomedical. ZnO thin films of various thicknesses were prepared by the spin coating method using the zinc acetate precursor with diethanolamine and ethanol. The structural and optical characterizations of as-prepared ZnO films carried out using XRD and UV-Vis spectrophotometer, respectively. The XRD results showed polycrystalline wurtzite structure of ZnO. The average crystallite size of ZnO as calculated using Debye Scherrer’s formula was 26 nm. The optical band gap of ZnO was found to decrease with film thickness. The dye extracted from the leaves of Tectona Grandis (Sagun) which possesses a high and wide absorbance was used in this experiment. The study on the effect of acid treatment on ZnO films in dye loading showed enhanced absorbance in acid treated ZnO as compared to untreated ZnO.

X-ray diffraction, Raman investigations, band gap energy of zinc oxide nanoparticles (ZnO NPs) along with current-voltage characteristic curves of an assembled dye-sensitized solar cell (DSSC) are presented in this article. ZnO NPs were first synthesized with and without potassium nitrate (KNO3) salt by precipitation method from precursor solutions of zinc acetate and sodium hydroxide. Then, their thin films were deposited on FTO substrates from the paste made with acetic-acid glacial, and Triton X-100 in ethanol by doctor blade method. The X-ray diffraction (XRD) pattern of ZnO NPs prepared without KNO3 annealed at 500°C showed a hexagonal wurtzite structure with preferred orientation along (101) planes and crystallite size of 25 nm. Very similar XRD pattern was found for ZnO NPs prepared with KNO3. The crystallite size was found decreased to 17 nm for ZnO NPs made with KNO3 salt. Raman spectrum of ZnO NPs showed the presence of E2 high or E2 (2) peak at 437 cm-1. The optical band gaps of the ZnO thin films prepared from ZnO NPs with and without KNO3 were measured to be of 3.16 eV and 3.26 eV, respectively. After sensitizing the above-prepared ZnO films by dye extract of Artocarpus lakoocha, the dye-sensitized solar cells were prepared, and their performance was tested by measuring I-V curves under light illumination of the power density of 1000 W/m2. The measurement showed highest Isc and Voc of 44 μA and 326 mV, respectively.

The dispersed solution of activated carbon (AC) is utilized in the fabrication of electrodes of many optoelectronic devices with good electrical and mechanical performance. But, AC in aqueous solution self-associates and aggregates downwards. These aggregates need to be dispersed in a solution, which is a challenging problem. Presented work is focused on the dispersion of AC with sodium dodecyl sulfate (SDS) in aqueous solution using a modified dispersion system. The conventional dispersion system is modified by introducing a direct current (DC) field in such a way that sonication can be performed in situ DC field in the solution. Here, the influence of the DC field on the dispersion of AC for different sonication times and different weight ratios of SDS to AC is reported. The results show that the sonication in situ DC field improved dispersion of AC. Also, the amount of SDS for dispersion of AC can be reduced by performing sonication under suitable DC field. The dispersed solution prepared under the DC field can be applied for thin film deposition by using the electrophoresis deposition method (EPD).

Thin films of Zinc Oxide (ZnO) of average thickness 364 nm were deposited on glass substrates via hydrothermal process using a mixture of 25 mM aqueous solutions of zinc nitrate and hexamethylenetetramine at a constant temperature of 75 ± 5°C. The structure of ZnO film was analyzed by using X-ray diffraction (XRD). Our result showed that ZnO film is of polycrystalline nature with preferential orientation along (002) perpendicular to the substrate. Average crystallite size of prepared ZnO film was found to be 18 nm. The Scanning Electron Microscope (SEM) image clearly showed the growth of nano-plate structure with an average thickness and breadth of 90 nm and 390 nm respectively. The band gap of ZnO was determined from transmittance spectrum captured in the visible wavelength. The calculated value of direct band gap was 3.24 eV.Journal of Institute of Science and TechnologyVol. 21, No. 1, 2016, page: 61-64

Fluorine doped Tin Oxide (FTO) thin films were deposited on glass substrates by home built spray pyrolysis setup at (400 ± 5)ºC. The method was found to be very economic and functional. The deposited FTO films were highly transparent and had low resistivity. The structural investigation of as-prepared films was performed using X-ray diffraction. Our results showed that a deposited FTO film was of polycrystalline nature with preferential orientation along (211) planes. The direct band gap value was found to be 3.25eV for 10% FTO film. The sheet resistance of this film was measured to be 68 Ω/ square. The effect of fluorine doping concentration on its band gap was also studied in this report.The Himalayan Physics Vol. 6 & 7, April 2017 (58-60)

In recent times, the importance of nanostructure of metal oxide semiconductor (MOS) as a gas sensing material is rising tremendously. Among various metal oxide semiconductors ZnO has potential to be used as a sensor for several toxic gases. In this work, we investigated the influence of Fe doping into ZnO to detect various concentrations of ethanol vapour. Pristine and Fe doped ZnO (Fe-ZnO) films were deposited on glass substrates using a spin coating technique wherein the concentration of Fe can be easily controlled. The crystallite size and surface morphology of ZnO samples were characterized by XRD, SEM and EDX techniques. The sensor performance in terms of gas response (R) of ZnO and Fe-ZnO gas sensors towards ethanol vapour were measured in the 100 to 300°C temperature range using DC electrical resistance. Fe doped ZnO samples showed enhancement in gas response due to increase in specific surface area originated from reducing grain size after doping. The 2% Fe-ZnO sample showed the good response of 40.9 for 400 ppm of ethanol vapour exposure at 260°C. This was found to be better than reported values for ZnO prepared by different methods.

The relationship between strain-dependent macroscopic elastic behavior and the changes in microscopic structure of the smectic-C liquid crystal elastomer (LCE), C11MeHQSi8 were investigated using synchrotron X-ray studies. At very low strains e ≤ 0.2, the smectic layers are randomly oriented. As the strain increases beyond 0.2, the smectic layers reorient and become parallel to the direction of the applied strain. The polydomain to monodomain (P–M) transition accompanied by the formation of chevron structure ensues for e > 0.2 and is nearly complete for e = 0.7. The chevron structure relaxes after the applied strain changes, with a time constant τα ∼ 45 min while the orientation order parameters of the mesogenic and elastomeric components gradually increase and saturate at 0.83 and 0.4, respectively at e = 1.7 which is near the end of the plateau region. Relaxation rates τα for the tilt angle and τd corresponding to the smectic layer spacing both become about 10 times faster when the strain exceeds 0.7. The LCE remains “locked” into the monodomain state and retains 90% and 80% values of α and S, respectively for 24 hours after the applied strain is removed. The viscoelastic properties of the liquid crystal appear to dominate the equilibration process at low strains while the elastomeric properties control the system's response at high strains.

Thin films of Cu2ZnSnS4 (CZTS) with different molar concentrations of thiourea were prepared on glass substrates using spray pyrolysis technique. The structural, optical and electrical properties of the CZTS thin films were investigated using X-ray diffraction (XRD), UV-vis spectroscopy and sheet resistance measurement respectively. The XRD analysis demonstrated the polycrystalline nature of the CZTS. We observed better crystallanity in CZTS film prepared with thiourea concentration of 0.20 M and optical band gap value at this concentration was observed to be 1.60 eV. The optical study showed that band gap increased with an increase in thiourea concentration. The sheet resistance of the sample prepared with 0.20 M concentration of thiourea was 10.73 Kohm/sq.

The surface morphology plays a very important role in the performance of supercapacitive properties. The concept of fractal analysis, using the Higuchi algorithm, has been applied to study the surface morphology of Cu doped Sr(OH)2 thin films. The hierarchical tuberose with flakes structures of 1, 2 and 3 at.% Cu doped Sr(OH)2 morphologies have been synthesized by an easy and economical chemical route, namely, successive ion layer adsorption and reaction (SILAR) technique. The structural analysis and qualitative morphological studies have been done by XRD and SEM technique respectively and the relationship between crystallite size and the supercapacitive property has been explored. Higuchi algorithm has been used to study the fractal characterization of SEM micrographs of prepared samples. It has been observed that 3 at.% Cu doped sample has the highest value of fractal dimension as 1.6922 and specific capacity of 817 C g−1 for 0.4 mA current rate. The Hurst exponent for 3 at. % Cu: Sr(OH)2 is 0.3078, which is less than 0.5 that shows the anti-persistent behaviour, i.e., signifies the height variations at neighbouring pixels are negatively correlated. Further, the Bode plot and the capacitive behaviour of the electrode have been studied by the complex capacitance method. The results obtained using the fractal analysis for the deposited materials agree with the electrochemical characterization.

Ceramide-1-phosphate, the phosphorylated form of ceramide, gained attention recently due to its diverse intracellular roles, in particular in inflammation mediated by cPLA(2)alpha. However, surprisingly little is known about the physical chemical properties of this lipid and its potential impact on physiological function. For example, the presence of Ca(2+) is indispensable for the interaction of Cer-1-P with the C2 domain of cPLA(2)alpha. We report on the structure and morphology of Cer-1-P in monomolecular layers at the air/water solution interface in the absence and presence of Ca(2+) using diverse biophysical techniques, including synchrotron x-ray reflectivity and grazing angle diffraction, to gain insight into the role and function of Cer-1-P in biomembranes. We show that relatively small changes in pH and the presence of monovalent cations dramatically affect the behavior of Cer-1-P. On pure water Cer-1-P forms a solid monolayer despite the negative charge of the phosphomonoester headgroup. In contrast, pH 7.2 buffer yields a considerably less solid-like monolayer, indicating that charge-charge repulsion becomes important at higher pH. Calcium was found to bind strongly to the headgroup of Cer-1-P even in the presence of a 100-fold larger Na(+) concentration. Analysis of the x-ray reflectivity data allowed us to estimate how much Ca(2+) is bound to the headgroup, approximately 0.5 Ca(2+) and approximately 1.0 Ca(2+) ions per Cer-1-P molecule for the water and buffer subphase respectively. These results can be qualitatively understood based on the molecular structure of Cer-1-P and the electrostatic/hydrogen-bond interactions of its phosphomonoester headgroup. Biological implications of our results are also discussed.

Two azo substituted achiral bent-core mesogens have been synthesized. Optical polarizing microscopy and synchrotron X-ray scattering studies of both compounds reveal the existence of the thermotropic uniaxial and biaxial nematic and three smectic phases at different temperatures in these single component small molecule systems. The transition from the uniaxial to biaxial nematic phase is confirmed to be second order. The transitions from the biaxial nematic to the underlying smectic phase and between the smectic phases have barely discernible heat capacity signatures and thus are also second order.

As of late, research on the fabrication of natural dye-sensitized solar cells has been growing tremendously, largely due to its low cost and environmentally friendly nature. We have fabricated Zinc Oxide (ZnO) based Dye-sensitized Solar Cell (DSSC) using Delonix Regia, locally known as the Gulmohar flower natural dye extract. Zinc Oxide nanostructure films were allowed to grow on Fluorine-doped Tin Oxide (FTO) substrates via hydrothermal process. The seed layer for this was prepared by the spin coating method. The ZnO film’s structure, topology, and optical properties were then studied using X-ray Diffraction (XRD), an Atomic Force Microscope (AFM) and an Ultraviolet Visible (UV-Vis) Spectrophotometer respectively. The X-ray results showed the hexagonal system structure of ZnO oriented along (101) planes. The effect of ethylene glycol on the structural property of ZnO film was also studied. The current voltage curve of DSSC showed the open circuit voltage and short circuit current of 360 mV and 80 μA respectively.Journal of Nepal Physical SocietyVolume 4, Issue 1, February 2017, Page: 1-6

The dye sunset yellow (SY) forms columnar aggregates via pi-pi stacking in aqueous solutions. These aggregates develop orientational and translational order at elevated concentrations to exhibit the nematic (N) and columnar (C) mesophases. Positional-order correlation lengths of the aggregates in the directions parallel and perpendicular to the stacking direction were measured as functions of temperature, concentration, and ionic content of solutions with synchrotron x-ray scattering in magnetically aligned samples. Average length of aggregates (i.e., the number of SY molecules in an aggregate) grows monotonically with concentration while their effective transverse separation decreases. The scission energy, E , determined from the Arrhenius thermal evolution of the longitudinal correlation length, is found to be 4.3+/-0.3 kBT and 3.5+/-0.2 kBT , in the N and C phases, respectively. Temperature and concentration dependence of E suggests that chromonic aggregation is not an isodesmic process. The aggregate length decreases with decreasing pH when HCl is added to the solution.

Transport of fat in the bloodstream is mediated by lipoprotein particles. These hydrophobic particles are covered by a (phospho-)lipid monolayer and further stabilized by exchangeable apolipoproteins. Their amphipatic helix bundle is thought to unfold upon interaction with the (phospho)lipid monolayer. The dynamics of this interaction at lipid interfaces has not been directly shown experimentally. Here we report on the structure of monolayers formed by a representative exchangeable apolipoprotein, apoLpIII from Locusta Migratoria, using surface-sensitive X-ray techniques. This model exchangeable apolipoprotein contains a 5-helix bundle and shows high structural homology to the 4-helix bundle in the N-terminus of apoE, a major mammalian exchangeable apolipoprotein. We found that the structure of two diacylglycerols, the proposed binding partner of apoLpIII, dioleoylglycerol (DOG) and 1-palmitoyl, 2-oleoylglycerol (POG), showed great resemblance to other (phospho)lipid monolayers except for details due to differences in the headgroup region. Despite their near identical chemical structures small differences in organization as monolayers were observed between DOG and POG. For the pure apoLpIII monolayer we observed that the unfolded protein was best represented by two distinct regions. This surprising result may originate from the high degree of glycosylation of apoLpIII. The interaction of apoLpIII underneath a densely packed diacylglycerol monolayer causes the surface pressure to increase rapidly. The analysis of the X-ray reflectivity of the lipid/protein system, right after the injection of apoLpIII, shows a diffuse layer underneath the lipid monolayer due to the binding and unfolding of apoLpIII. This may be the first direct visualization of the dynamic unfolding of an exchangeable apolipoprotein at a lipid interface. Our data suggest that the initial interaction occurs when the protein is tilted with respect to the lipid monolayer, a process that would favor the opening of the helix bundle.