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Selective detection and quantification of biomarkers related to human diseases are essential for preventive healthcare. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical tool offering high sensitivity. However, the success of this promising analytical tool relies on the ability to effectively fabricate SERS substrate. Herein we have demonstrated a plasmonic paper-based flexible substrate (PPFS) for SERS sensing. In situ growth of silver nanostructures (AgNS) on the paper-based substrate was achieved by using a simple one-step silver mirror reaction (SMR). FESEM and TEM results depicts that the increasing silver ion content influences the morphology (growth of multifacets), as well as size of AgNS. Further, the PPFS substrate was tested with Rhodamine-6G (Rh-6G) dye and an attomole sensitivity with a LOD of 4.54 x 10-18 M was achieved. Further, two biomarkers, lactic acid (LA) and uric acid (UA) were detected on the PPFS substrate, with μM and pM sensitivity, having LOD values of 0.6 x 10-6 and 0.3 x 10-12 M respectively. Above detection levels for UA on PPFS is two orders better than reported values, whereas for LA it is comparable with reported substrates. Finally, UA, LA and their mixtures were tested on PPFS and results compared with commercial substrate. The performance of PPFS were found better in all cases, thus, multifaceted AgNS paper based PPFS offers the potential to be used as a biosensor for detection of various biomarkers from body fluids, responsible for the detection of the critical disease for preventive health care.

In this paper, we report the preparation of crystalline CZTS thin films by sol–gel method followed by sulphurization using 1,2- Ethanedithiol (EDT) at 400 °C in a three zone horizontal tubular reactor equipped with computer controlled vacuum system. These films were characterized by XRD, Raman, Hall measurements and UV–Vis-NIR spectroscopy. XRD and Raman studies confirmed highly crystalline and single phase CZTS. Hall study revealed p-type semiconducting CZTS film having charge carriers density of 1.70 × 1018 cm−3 and the resistivity (ρ) of the order of 5.00 × 10−1Ω-cm. It was found that the direct band gap of 1.44 eV for CZTS film was seen from optical study. Further, double metal oxide layers having slightly different band gap were used to form a p-n junction with CZTS film. Cadmium-free solar cells with structure ITO/ZnO/CZTS/Ag (cell-1) and ITO/ZnO/com-TiO2/CZTS/Ag (cell-2) were fabricated. Electrochemical Impedance Spectroscopy (EIS) measurements were performed in the low frequency range with applied bias of 0.1 Volt for the devices. The EIS studies showed that the solar cell with ultrathin compact TiO2 layer provide a favorable path for the efficient charge transport process at the interface. The external quantum efficiency measured at 520 nm was found to be 62.5%. Cell-2 exhibited improved photovoltaic parameters with short circuit current density (Jsc) of 4.721 mA/cm2, fill factor of 0.46 and open circuit voltage (Voc) of 400 mV. The short circuit current density and fill factor of double metal oxide layers (cell-2) were increased by 78% and 46%, respectively, as compared to single metal oxide layer (cell-1).

Utilization of Solar Photovoltaic (PV) cells underwater can mitigate the lack of enduring renewable energy sources in marine environments. In our recent studies, the performance of different commercially available silicon Solar cells have been analysed using Xenon Lamp Solar simulator at shallow depths up to 20 cm and the effect of the variation in the water environments was studied. The obtained results show an immense possibility to utilize various Solar PV cells in the submerged conditions. Therefore, it is essential to study a light source other than Xenon lamp with different spectra and its change in intensities in underwater conditions to analyse the performance of various Solar PV cells. In this work, a Halogen lamp was used, which can cover the IR spectrum efficiently, whereas the Xenon lamp spectrum performed well in the visible spectrum. Also, the halogen lamp spectrum was identical to the black-body irradiance of the real Sunlight and amenable to emit light from near-ultraviolet to deep-infrared. Further, the performance of different Solar PV cells underwater has been examined. Subsequently, the obtained results were compared with our previous studies reported with the standard Xenon lamp of Air mass 1.5. Further, it was observed that the variation of the light source could also play a significant role in the underwater transmission of Solar irradiance. Finally, it was shown that the performance of Solar PV cells, in submerged conditions using an artificial light, was similar to the actual Sunlight.

In the present paper, we report the effect of annealing temperature on optical properties of solution processed As2S3 Chalcogenide Glass (ChG) films. Solution processing of ChG films is a low cost, low temperature, scalable route for deposition of high quality films. Annealing of solution processed ChG films is a crucial step for the removal of residual solvent from the films. The optimization of the annealing temperature and corresponding optical properties of ChG films helps in better utilization of these films in functional devices. As2S3 glass was synthesized using melt quenching. The as-prepared As2S3 glass was dissolved in n-butylamine. The solution was then deposited onto glass substrates in the form of thin films. The as-prepared As2S3 glass films were annealed at different temperatures. As-annealed As2S3 glass films were studied using UV-Visible Spectroscopy, Infrared (IR) Spectroscopy, X-ray diffraction (XRD), Raman Spectroscopy and Energy Dispersive X-ray (EDAX) spectroscopy to undestand the effect of annealing on the structural and optical properties of the films

Thin film solar cells with ITO/ZnO/P3HT:PCM:CTSe NCs/Ag structure were fabricated employing a fast and cost-effective procedure using blended solution of P3HT:PCBM:CTSe NCs deposited by spin casting, followed by thermal annealing steps. The CTSe NCs are prepared via solvothermal method. An inverted architecture of device with structure ITO/ZnO/P3HT: PCBM:CTSe NCs/Ag have been fabricated with different concentration of CTSe NCs in poly(3-hexyle thiophene) (P3HT): [6,6]phenyl-C61-butyric-acid-methyl-ester (PCBM) matrix. The effect of CTSe NCs on the performance of hybrid solar cell with optimized blend ratio of P3HT:PCBM and CTSe NCs has been investigated for optimum power conversion. The charge carrier extraction and recombination at the interface of donor-acceptor material were studied using Electrochemical impedance spectroscopy (EIS) under dark condition. EIS study has demonstrated that the charge transfer rate was higher for the device having optimized wt% of CTSe NCs (10 wt%) in P3HT:PCBM active layer. A significant improvement in the device performances was observed on incorporation of CTSe NCs. The device exhibited open circuit voltage (Voc) of 0.475 V, short circuit current density (Jsc) of 6.95 mA/cm2, fill factor (FF) of 0.41 and power conversion efficiency (PCE) of 1.35%.

Selectivity and enhanced sensitivity for surface-enhanced Raman scattering (SERS) substrates are highly desirable attributes for their analytical applications. SERS substrate interaction with target molecules plays a key role in determining the enhancement magnitude and spectral profile of the SERS signal as well as their applications. Herein, we demonstrate a SERS active substrate based on reduced graphene oxide/silver nanoparticles (rGO/Ag NPs) composite material synthesized by a facile wet chemical route. The Ag NPs decorated rGO nanosheet has been achieved by reducing AgNO3 with ethylene glycol in the presence of poly vinyl pyrrolidone (PVP) and NaCl over layered graphene oxide. The addition of PVP stimulates the nano-phase growth as well as uniform distribution of the Ag NPs on rGO nanosheet. The well synthesized rGO/Ag composite was confirmed by using various characterization techniques such as FESEM, HRTEM, XRD, FTIR and Raman. Further, the rGO/Ag NPs composite material has been utilized as a platform for SERS based selective detection of Rhodamine-6G, 4-mercapto benzoic acid, and 2,4-dinitrotoluene analytes. The rGO/Ag NPs substrate demonstrates good homogeneity, stability and nanomolar sensitivity with Raman intensity enhancement of the order of 5 for Rh-6G and 4-MBA whereas 3 for 2,4-DNT. The observed enhancement of SERS signal for all the analytes has been attributes to the cumulative effect of rGO and Ag NPs.

Present work demonstrates an experimental approach to evaluate the optical performance of the Infrared (IR) microlens based on the Shack-Hartmann wavefront sensing at 10.6 µm wavelength. A Germanium microlens has been evaluated to validate the consistency and accuracy of the developed experimental methodology. The proposed IR optical setup has the capability to measure optical parameters like focal length, transmitted wavefront errors, Zernike coefficients, and PSF of a microlens with the diameter ranging from 500 to 2500 µm and the focal length ≥1 mm.

Flexible and free-standing polymeric fibers, coupled with metal nanoparticles, present an excellent opportunity for highly sensitive surface-enhanced Raman scattering (SERS) spectroscopy-based detection platforms. Such host matrices are prepared by only a few preferred methods, followed by induction of metal nanoparticle aggregation in a protected environment to afford functional SERS platforms. We provide an interesting advance in this area by choosing a thiol-modified purine (L)–polymer blend, obtained through the electrospinning process, for directed decoration with gold nanoparticles. The described SERS purine-nanomat substrate enables the detection of uric acid, an important indicator of gout, preeclampsia, cardiovascular and kidney diseases, in aqueous solution up to 100 nM, with good stability and high sensitivity, offering superiority over existing techniques in terms of sensitivity and cost-effectiveness.

The present paper deals with the synthesis and characterization of solution processed pure and multiwalled carbon nanotubes (MWCNTs) incorporated As2S3 glass films. As2S3 glass has been synthesized using melt quenching technique. The solutions of pure and MWCNTs containing As2S3 glass have been prepared in n-butylamine under inert atmosphere. These solutions have been used to obtain pure and MWCNTs incorporated As2S3 glass films on the glass substrates via spin coating. These films have been annealed, subsequently, to get rid of organic solvent. The morphologies of these films have been analyzed using scanning electron microscopy (SEM) which reveals the porous nature of these films. In the SEM micrographs, a very few MWCNTs are seen on the surface of the films and it is argued that most of the MWCNTs are buried in the film. Elemental and crystallographic analyses of these films have been carried out using energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) respectively. While EDS studies confirms the elemental composition of these films, XRD patterns depicts the amorphous nature of these films. Raman and Fourier transform spectroscopies have also been carried out and revealed some critical information regarding these films. Raman spectroscopy of these films indicates towards the functionalization of MWCNTs by intermediate active species which formed during annealing. dc-conductivity measurements and its analysis show that the dc-conductivity and carrier concentration of these films increases drastically with the increase in MWCNTs content in these films. The results obtained in this work may be useful for the chalcogenide glasses based electronic and optoelectronic applications such as energy harvesting and storage, photovoltaics and flexible electronics.

In this paper we report the composite of nanotubular polyaniline (PANI), titanium and iron for microwave absorption. Nanotubular structure of PANI is synthesized by the chemical polymerization of aniline. The diameter of the PANI (Nanotubular) is found to be ranging from 120–140 nm. Here in our experiment we observed resonance-antiresonance phenomenon in the permittivity and permeability of the material. The polymer nanocomposite of PANI/TiO2(np)-Fe+3 has the minimum reflection loss of −38 dB (99.99%) at the frequency of 10.80 GHz for the thickness 3.5 mm. The XRD results show the formation of different crystalline planes for the TiO2(np)-Fe+3 nanocomposite. The particle size of the TiO2(np)-Fe+3 is found to be ranging from 114.8 to 132.1 nm the FESEM result. The composite can also be used for the metamaterial applications.

This work demonstrates the fabrication of chalcogenide microstructures such as gratings, lenses and needles using a lithographically directed, evaporative self-organization of chalcogenide thin liquid films for the first time. Using a two-step annealing protocol, excess solvent of freshly coated ChG films is eliminated and then the liquid films are patterned using elastomeric masters with continuous or disconnected features during solvent evaporation. Although microcontact printing or capillary flow lithography has been proven to be useful to create continuous gratings and waveguide like structures in solid films, our method overcomes the limitation of structural continuity of the generated pattern and uses self-organization of solute ChG within the master's confinement to produce isolated microstructures. Fabrication of disjointed arrays of microlenses of various dimensions as well as conical shaped needles in ChG thin films has been demonstrated for relevant optical IR applications. This methodology establishes evaporative self-organization of ChG thin films as a viable alternative to creating microstructures in bulk ChG with hot-embossing, bypassing the need for ultra high temperature processing.

In this paper we report the synthesis and characterization of PVA/Ge10As40Se50 chalcogenide glass nanocomposites free standing films. Ge10As40Se50 nanoparticles are incorporated in PVA matrix via solution processing. From the structural characterization, it is revealed that hydrogen bonding is established between Ge10As40Se50 nanoparticles and PVA chains, which results in the increase of crystallinity of PVA/ Ge10As40Se50 nanocomposites films. Incorporation of Ge10As40Se50 nanoparticles has been observed to decrease the band gap of PVA/ Ge10As40Se50 nanocomposites free standing films which results in the shift of the absorption edge of PVA/ Ge10As40Se50 nanocomposites films with the increase in Ge10As40Se50 concentration. Incorporation of Ge10As40Se50 nanoparticles in PVA matrix may be considered as the simple way to shift the photosensitivity of the PVA/ Ge10As40Se50 nanocomposites films from UV to infrared region of the electromagnetic spectrum.

Chalcogenide Glasses (ChGs) are technologically promising materials widely used in different optical, electronic and optoelectronic applications. Solution processing of ChGs has provided a pathway for less complex thin film processing of these materials and their integration into flexible devices. This paper reviews the basic science behind the solution processing of ChGs, properties of solution processed ChG films and recent functional applications of solution processed ChGs. Solution processing of ChGs also provides the facile method of incorporation of nanostructures into ChG matrix which integrate the functional properties of nanostructures and ChGs in a single solution or thin film. This paper also reviews the research work undertaken on the incorporation of nanostructures in ChGs.

PPy/TiO2(np)/CNT nanocomposites are synthesized by ‘chemical oxidative polymerization’ of pyrrole. It is observed that polypyrrole along with TiO2(np) form core shell structure. The microwave measurements such as permittivity, permeability and reflection losses (metal back) are studied at X-band. Minimum reflection loss of microwave is due to dielectric loss in the nanocomposite and is − 51.11 dB (99.99%) at 8.64 GHz for sample (PPy/TiO2(np)/CNT) of thickness 3 mm. The nanocomposite is characterized by FESEM and XRD. The particle size of the TiO2(np) is found to be ranging from 60 to 150 nm. The average crystallite size is determined by Scherrer formula and is found to be 26 nm. We have observed negative value of µ″ (complex part of permeability) for the entire frequency range (8–12 GHz). In our study we also observed the resonance–antiresonance phenomenon in all the samples. We have also seen maximum attenuation of microwave for PPy/TiO2(np)/CNT polymer nanocomposite. The synthesized nanocomposites can be used for metamaterial applications.

In this paper, Arsenic sulfide (As 2 S 3 ) and Arsenic selenide (As 2 Se 3 ) chalcogenide thin films are prepared by solution phase spin coating and thermal evaporation technique. Optical properties (band gap and refractive index) and electrical properties (DC conductivity and Activation Energy) of the deposited films are studied. A comparative study of electrical and optical properties of thermally deposited films and spin coated films has been done. The value of electrical conductivity of As 2 S 3 and As 2 Se 3 solution based thin films increases with annealing temperature and found that beyond 70 °C, its conductivity is higher as compared to the value of thermally deposited thin films at room temperature. The band gap of solution phase spin coated films decrease with annealing temperature whereas refractive index increases and reaches approximately the same value of the thermally deposited thin film at room temperature.

Research in Enzymatic Biofuel cells (EBFCs) has evolved during the last decade. However, challenges, such as cost and endurance are the bottlenecks in harnessing their commercialization potential. To overcome these challenges, low cost, readily available pencil leads of various grades modified with polyaniline (PANI) and multi walled carbon nano tubes (MWCNT) have been examined as EBFC biocathode. Total four pencils of various grades (B, H, 3H, and 5H) were used to fabricate biocathode by covalently immobilizing Laccase(Lac) enzyme on to MWCNT coated (BC1) and electrodeposited polyaniline and MWCNT coated (BC2) on the surface of pencil graphite electrodes (PGEs). The fabricated biocathodes were characterized by scanning electron microscopy (SEM), BET surface area and conductivity measurements and electrochemical analysis was performed by the Open circuit potential (OCP) and Cyclic voltammetry (CV). Among the pencils tested in this work, the 5H pencil coated with PANI/MWCNT/Lacexhibited highest current density of 1209.23 μA/cm2 with OCP of 0.528 V. Moreover, the PANI/MWCNT/Lac modified PGEs showed significant enhancement (80%) in electrochemical behavior when compared with unmodified (bare) and MWCNT/Lac coated PGE. Both types of Bioelectrodes (PGE/MWCNT/Lac,PGE/PANI/MWCNT/Lac) showed good stability and maximum conservation of its activity during the experiments.

The SrS: Ce3+ thin film active phosphor layer of different thickness based alternating current thin-film electroluminescent (ACTFEL) devices are fabricated by electron beam evaporation deposition (EBED) method. The morphology and chemical composition of the deposited films are investigated by field emission scanning electron microscopy (FESEM). The optical transmittance in visible range for the optimum film and optical band gap of SrS: Ce3+ film is described on the basis of Ce3+ doping concentration.

The present paper reports the steady state photoconductivity and photosensitivity response of thermally evaporated amorphous thin films of Se90Sb10-xAgx(x = 2, 4, 6, 8, 10). Temperature dependence ...

In this paper we report the synthesis and characterization of as-deposited nanostructured As40Se60 chalcogenide glass films via thermal evaporation technique. The morphological investigation of the films reveals that the film is made up nanosized grains. A blueshift is also observed in the optical band-gap of the film which can be attributed to formation of nanosized grains in the film.In this paper we report the synthesis and characterization of as-deposited nanostructured As40Se60 chalcogenide glass films via thermal evaporation technique. The morphological investigation of the films reveals that the film is made up nanosized grains. A blueshift is also observed in the optical band-gap of the film which can be attributed to formation of nanosized grains in the film.

We demonstrate the detection of dipicolinic acid, (DPA), a biomarker of bacterial spores for Bacillus anthracis, 2,4-Dinitrotoluene (DNT) and picric acid (PA) nitroaromatic hazardous chemicals on ultra-sensitive, reusable femtosecond laser textured Au nanostructures decorated with hierarchical AuNPs as a SERS substrate. The AuNPs were achieved by ablating an Au sheet using two different laser scan speeds (1 and 0.1 mm/s) in linear and crossed patterns. The morphological studies revealed dense hierarchical nanostructures decorated with spherical AuNPs possessing 30–40 nm in size in 0.1 mm/s laser scan. The limits of detection (LOD) of the sensor were determined from the detailed SERS measurements and were estimated to be 0.83 pg/L, 3.6 pg/L and 2.3 pg/L for DPA, DNT, and PA, respectively. To the best of our knowledge, the achieved sensitivity is nearly 2 orders improved for DPA when compared with the currently reported LODs using other techniques and 1 order in the case of SERS. Moreover, for DNT and PA the LODs were found to be either superior or comparable with recent reports. We have also demonstrated the competence of our SERS substrates by testing a few real samples (water spiked with these analytes) and again obtained very good sensitivity.

The strontium sulfide (SrS) thin films doped with different concentrations (0.1, 0.5, 1 and 1.5 mol%) of cerium (Ce3+) ions are synthesized by electron-beam evaporation deposition (EBED) method. The SrS:Ce3+ thin films have been deposited on glass substrates. It is interestingly witnessed that both the structural and optical properties of as-deposited thin films are strongly influenced by the concentration of Ce3+ ions. The utmost photoluminescence (PL) emission intensity in visible region at 476 and 529 nm is observed for SrS:Ce3+ (0.5 mol%) thin film when excited suitably by an ultraviolet (UV–369 nm) light which is well supported by afterglow behavior of SrS:Ce3+ thin film for the same composition.

The present paper reports the comparative study of density of defect states (DOS) between bulk samples and thin films of glassy Se90Sb10. These glasses have been prepared by the quenching technique. Thin films of these glasses have been prepared by vacuum evaporation technique. Space-charge-limited conduction (SCLC) has been measured at different temperatures. The density of localized states near Fermi level is calculated by fitting the data to the theory of SCLC for the case of uniform distribution of localized states for bulk as well as for thin films. A comparison has been made between the density of states calculated in these two cases.

An attempt is made to observe light induced defects (LID) in amorphous chalcogenides Se90X10 (X = Sb, In, Ag) thin films prepared by vacuum evaporation technique. For the determination of light induced defects quantitatively, space charge limited current (SCLC) measurements have been made in a vacuum ∼10−3 Torr before and after exposing amorphous films to white light for different exposure times (0 to 6 h). Results indicate that light induced metastable defects are created due to prolonged exposure of light which is explained by a microscopic model for light induced metastable defects creation proposed by Shimakawa and co-workers. Fractional increase in density of defects due to light exposure is found to be least in case of Se90Ag10 indicating that this alloy may be used for optoelectronic applications as degradation upon light soaking is small in this case.

In this study, hollow silica nanoparticles (HSNPs) were prepared by acidic etching of core of core-shell nanoparticles (ZnSe@SiO2 shell). HSNPs were confirmed from X-ray diffraction (XRD), transmission electron microscope (TEM) and Raman spectroscopy, demonstrating amorphous silica peak, hollow structure, and prominent D1 and D2 Raman peaks of silica. Langmuir and Freundlich model analysis showed adsorption of methylene blue (MB) by HSNPs to be of chemisorption type, with adsorption capacity of 64.06 mg/g. Reaction kinetics was found to be of pseudo-second-order, interparticle diffusion model and Byod’s model predicts that adsorption mechanism follows both film and pore diffusion process, and external mass transport phenomenon. Moreover, adsorption study on bare and silica shell coated NPs of ZnSe and CdSe signifies that voids and hollow nature of HSNPs favors more adsorption of MB than its counterparts. Reusability experiments showed > 80% dye adsorption efficiency, after fifth cycle of reuse. Also, MB invitro release study form HSNPs was conducted, and different models like Higuchi, first order kinetic decay, Korsmeyer-Peppas model were applied suggesting a diffusion controlled mechanism of release. This study aims to provide knowledge about dye adsorption and its sustained release mechanism, finding applications in water treatment and invitro delivery process.

This paper presents a simple, novel and cost effective process to synthesize MWCNTs and α-Fe2O3 embedded in rGO sheet layers, which is found to be a highly selective and sensitive material for the detection of chloroform vapours in room temperature conditions. The nanocomposite rGO- MWCNT- α-Fe2O3 has showed enhanced chloroform vapour sensing performance characteristics compared to rGO- α-Fe2O3 and pure α-Fe2O3 which have been reported earlier. The MWCNTS alongwith rGO sheets provide improved sensitivity mainly due to a high surface area (49 m2/ g and 72 m2/ g) with doping of nanotubes in the composite matrix as compared to other established counterparts like α-Fe2O3 (12.6 m2/g) and rGO- α-Fe2O3 (19.05 m2/g). The nanocomposite films also show a faster response (2 s at 1 ppm) and recovery time (1 s at 1 ppm) due to a high diffusivity of vapours into the structure owing to the 3-Dimensional nature of the nano-composite structure which makes the directly exposed area multifolds. The material is suitably immobilized on SU-8 based nanocantilever platform which show enhanced deflection upto 250 ppb vapour detection. The nanocomposite functionalised cantilever are further tested with other types of volatile organic compounds and the sensor is found to show a high selectivity towards chloroform. The presence of trace volatile organic compounds (VOC) in human breath is a very common way of detection of malignancy and thus this sensor may eventually help in such recognition in the near future.

In the present work, two types of cost-effective bio-electrodes were fabricated by immobilizing Laccase on commercially available pencil graphite leads, and their electro catalytic activity have been examined. The first type of electrode (E 1 ) was fabricated by electro polymerization of polyaniline on pencil graphite leads on which multi walled carbon nanotubes (MWCNT) was immobilized by covalent bonding, while the second type of electrode (E 2 ) was fabricated by direct coating of MWCNT on pencil graphite leads. Two types of bio-cathodes were fabricated by immobilizing Laccase on the two types of electrodes by covalent bonding. The scanning electron microscopy (SEM) revealed three dimensional porous networks providing large surface area for enzyme immobilization. The maximum open circuit potential (OCP) for E 1 and E 2 bio-cathodes were measured 0.58 V and 0.60 V respectively vs Ag/AgCl reference electrode. The maximum current density observed for E 1 and E 2 electrodes were 295.7 μAcm −2 and 228.94 μAcm −2 respectively. Both electrodes exhibited excellent stability, conserving more than 75% of its optimum activity during the period of measurement.

Herein, Laccase catalysed oxygen reduction reaction on polyaniline coated copper nanotube bio-cathode was studied. The copper nanotubes were grown in anodic aluminium oxide template on which conductive polymer polyaniline was electrodeposited. Laccase was covalently immobilized using a linker molecule glutraldehyde. The effective wiring of enzyme with bio-cathode was confirmed by linear sweep voltammetry, chronoamperometry and open circuit potential measurement. All electro analysis was performed in conventional three electrode system using platinum wire counter electrode and Ag/AgCl reference electrode. The bio-cathode in air saturated phosphate buffer showed maximum OCP and current of 0.59 V and 140.12 μAcm −2 respectively. Moreover, electrochemical impedance analysis confirmed decrease in charge transfer resistance with the immobilization of enzyme on CuNTs/polyaniline electrode. The bio-cathode showed reproducibility and stability over the period of examination.

Display Omitted We demonstrate the fabrication method of enzyme-modified, 3D microelectrode arrays for microfluidic biofuel cells.The 3D microelectrode arrays were fabricated using CNT/Nafion nanocomposites and hydrogel microstencils.We could able to make micro-porous structure of the 3D microelectrode arrays using a plasma-etching process.This enzyme-modified, micro-porous, 3D microelectrode can improve performance of microfluidic biofuel cells. Enzyme-modified, three-dimensional (3D) microelectrode arrays for microfluidic biofuel cell applications were fabricated using carbon nanotube (CNT) reinforced Nafion? nanocomposites and hydrogel microstenciling. CNT/Nafion nanocomposites were prepared by dispersing oxidized, multi-walled CNTs in Nafion solution. A hydrogel microstencil was fabricated using photolithography, soft lithography, and capillary-force lithography. After structuring the nanocomposites with the microstencil, a plasma-etching process was applied to the surface of the nanocomposite in order to obtain a micro-porous structure. Enzymes could be successfully immobilized on the micro-porous structures of nanocomposite surfaces using direct covalent binding.

Fuel cell is an efficient energy conversion device converting chemical energy directly into electrical energy. It is a fact that, to boost the fuel cell performance, resistance (charge transfer resistance, mass transfer resistance and electrolyte resistance) should be decreased. For this, many techniques have been used for cell testing such as: cyclic voltammetry, current interruption measurement, chronoamperometry, chronopotentiometry, polarization curve and electrochemical impedance spectroscopy (EIS). Among these techniques, EIS is a well-established, non-intrusive, non-destructive, semi-quantitative, and an efficient technique for identification of each circuit element. In this review article, application of electrochemical impedance spectroscopy in identification of individual components of total resistance and their dependence on different factors in biofuel cell along with some recent advancement in this technique have been discussed.

The structural, optical and electrical properties of pure and tin (Sn) doped zinc oxide (ZnO) nanocrystalline materials prepared by co-precipitation method have been studied as a function of Sn doping concentration. The phase identification through powder X-ray diffraction methods confirmed that pure and Sn-doped zinc oxide powder have typical hexagonal wurtzite structure (a = 3.407 A and c = 4.592 A) with slight change in lattice parameters. The surface morphological examination with field emission scanning electron microscopy revealed the fact that the grains are closely and densely packed and pores/voids between the grains decrease with increasing the doping concentration of Sn from 0% to 15%. The energy bandgap of pure ZnO was found to be 3.35 eV from optical absorption spectra obtained by ultraviolet–visible (UV–Vis) absorption spectrophotometer. The variation of energy bandgap and electrical resistivity of Sn-doped ZnO were also determined with tin doping. Upon increasing the Sn dopant concentration...

The structural, optical and electrical properties of spray deposited antimony (Sb) doped tin oxide (SnO2) thin films, prepared from SnCl4 precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0 to 1.5 wt.% of Sb. The analysis of X-ray diffraction patterns revealed that the as deposited doped and undoped tin oxide thin films are pure crystalline tetragonal rutile phase of tin oxide which belongs to the space group P42/mnm (number 136). The surface morphological examination with field emission scanning electron microscopy (FESEM) revealed the fact that the grains are closely packed and pores/voids between the grains are very few. The resistivity (ρ) and mobility (μ) are in the range of 1.512 × 10−3–6.624 × 10−3 Ω cm and 9.75–22.96 cm2 V−1 s−1. The electron density lies between 4.11 × 1019 and 4.24 × 1020 cm−3. A thorough electrical investigation reveals that the film's resistivity depends on carrier concentration. It is found that ionized impurity scattering is the dominant mechanism, which limits the mobility of the carriers. The transmittance spectra for as-deposited films were recorded in the wavelength range of 200–1000 nm. The transmittance of the films was observed to increase from 57% to 68% (at 800 nm) on initial addition of Sb (up to [Sb]/[Sn] = 0.5 wt.%) and then it is decreased for higher level of antimony doping ([Sb]/[Sn] >0.5 wt.%).

The ability to use chalcogenide glass thin films as photoresists for one-step maskless grayscale lithographic patterning is demonstrated. It is shown that the chalcogenide photoresists can be used to fabricate grayscale patterns with smooth and continuous profiles such as arrays of cylindrical and spherical microlenses, which are useful as optical structures for IR applications. The etching and exposure parameters are optimized to obtain smooth reproducible lens arrays of 150 μm periodicity and up to ∼170 nm height on large areas (∼1 cm(2)). The roughness is found to increase as a function of the exposure dose and is attributed to the selective dissolution of the As-Se, As-As, and Se-Se bonds present in the nanodistributed phases and the presence of the oxide phase. Thus, a minimum exposure dose produces optimally patterned lens arrays. The focal length calculated for the smooth microlens array is ∼9.3 mm, indicating the suitability of the lens arrays for focusing applications in the IR region.

In the present work, multilayered sensing films were prepared by sol–gel spin coating process using precursor solutions of cobalt oxide and cobalt titanate. Cobalt oxide films were annealed at 150, 300 and 450 °C respectively; however, the films of cobalt titanate were annealed at 450 °C. XRD reveals the formation of crystalline Co3O4 and CoTiO3 nanocomposites at various annealing temperatures. UV–visible spectra exhibit the dependency of optical energy gap on annealing temperature and thickness of the film. Further the optical humidity sensing properties based on modulation in transmitted intensity due to variation in %RH were investigated. SEM micrographs confirm the dependency of sensitivity of the sensor on porosity and thickness of the film. Double layered sensing film of cobalt oxide annealed at 450 °C showed linear behavior having average sensitivity 0.76 μW/%RH, while single layered film of cobalt titanate is more sensitive to humidity over others having sensitivity 1.84 μW/%RH.

Nanocrystalline neodymium iron oxide (NdFeO 3 ) has been synthesized through sonication assisted precipitation technique. X-ray diffraction analysis reveals the formation of NdFeO 3 having orthorhombic structure (perovskite type). The minimum crystallite size was found 12 nm. Energy dispersive X-ray analysis confirms the elemental compositions of the synthesized material. The optical band gap of NdFeO 3 was found 3.8 eV using the Tauc plot. Surface morphological investigations show the uniform and bead structured surface morphology. LPG (liquefied petroleum gas) sensing properties of NdFeO 3 in the form of solid state pellet as well as thin film were investigated. These investigations have been focused on the response characteristics of the fabricated LPG sensor. The mechanism of LPG adsorption on the surface of sensing film has been discussed. Results illustrate that the fabricated film sensor was superior in comparison to the pellet sensor. The response and recovery times of the film sensor were ∼60 and 90 s, respectively. Electrical behavior of NdFeO 3 in air was also investigated. In addition, activation energies were estimated. The fabricated LPG sensor has high sensitivity, low response and recovery times, good reproducibility, operable at room temperature and simple construction, so it is promising.

Thin silicon oxynitride (SiO x N y ) films were deposited by low temperature (∼300 °C) plasma enhanced chemical vapour deposition (PECVD), using SiH 4 , N 2 O, NH 3 precursor of the flow rate 25, 100, 30 sccm and subjected to the post deposition annealing (PDA) treatment at 400 °C and 600 °C for nano optical/photonics on chip interconnects applications. AFM result reveals the variation of roughness from 60.9 A to 23.4 A after PDA treatment with respect to the as-deposited films, favourable surface topography for integrated waveguide applications. A model of decrease in island height with the effect of PDA treatment is proposed in support of AFM results. Raman spectroscopy and FTIR measurements are performed in order to define the change in crystallite and chemical bonding of as-deposited as well as PDA treated samples. These outcomes endorsed to the densification of SiO x N y thin films, due to decrease in Si N and Si O bonds strain, as well the O H, N H bonds with in oxynitride network. The increase in refractive index and PL intensity of as deposited SiO x N y thin films to the PDA treated films at 400 °C and 600 °C are observed. The significant shift of PL spectra peak positions indicate the change in cluster size as the result of PDA treatment, which influence the optical properties of thin films. It might be due to out diffusion of hydrogen containing species from silicon oxynitride films after PDA treatment. In this way, the structural and optical, feasibility of SiO x N y films are demonstrated in order to obtain high quality thin films for nano optical/photonics on chip interconnects applications.

We report design, fabrication and characterization of molded chalcogenide microlens array for Infrared sensing applications. A master of desired microlens array with high sag value is prepared using ultraviolet lithography and thermal reflow method on a positive photoresist (ma–P1275HV). The negative replica of the master is created using polydimethylsiloxane which serves as a mold for micro-molding. Further, chalcogenide solution is prepared in ethanolamine solvent and spin coated on a substrate to get a uniform film; these films are characterized and are found to have the same optical properties as the parent bulk chalcogenide glass. Finally, the microlens array is fabricated by the micro-molding of chalcogenide film. Fabricated chalcogenide microlenses are characterized for geometrical parameters, which are used to estimate the optical parameters.

Chalcogenide (ChG) are the choice materials for IR applications due to their high refractive index, mid IR transparency and high nonlinear optical properties. In this work, we study the characteristics of solution processed Chalcogenide films, As2S3 prepared by various amine solvents, for possible pattern fabrications. Since solution processed ChG films tend to contain solvent related defects, it is important to optimize the process parameters to create defect free films, structurally similar to bulk ChG. We have studied the physical integrity and morphology of solution processed ChG films as a function of annealing conditions and film thickness. Optical and morphological characterizations of these films are carried out in order to fabricate defect free, optically useful micro-structures.

An attempt is made to investigate light induced defects (LID) in amorphous chalcogenide Se90Ag10 thin films prepared by vacuum evaporation technique. For the determination of light induced defects quantitatively, space charge limited current (SCLC) measurements have been made in a vacuum ~ 10−3 Torr before and after exposing amorphous films to white light for different exposure times (0 to 6 hours). Results indicate that light induced defects are created due to prolonged exposure of light which is explained by a microscopic model for light induced defects creation proposed by Shimakawa and co-workers.

Synthesis of a copper ferrite system (CuFe2O4) via chemical co-precipitation method is characterized by X-ray diffraction, surface morphology (scanning electron microscope) and optical absorption spectroscopy. These characteristics show their dependence on the relative compositions of the two subsystems. They are further confirmed by the variation in the band gap. A study of gas sensing properties shows the spinel CuFe2O4 synthesized in 1:1 molar ratio exhibit best response to LPG adsorption/resistance measurement. Thus resistance based LPG sensor is found robust, cheap and may be applied for kitchens and industrial applications.

In this paper we report the synthesis of iron-antimonate (FeSbO4) via co-precipitation method for the LPG sensing application. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDAX) were used to confirm the crystal structure, crystallite size, surface morphology and elemental composition of the sensing material. Our XRD results confirm the single phase formation with tetragonal crystal structure of the synthesized material. Extremely broad reflections were observed indicating nanosized particle nature of the material obtained. The estimated value of average crystallite size was found 3 nm. Optical characterizations were done using UV-visible spectrophotometer and the value of energy band gap was found 3.8 eV by Tauc plot. Fine powder resulted from the chemical co-precipitation reaction was used to prepare the LPG sensing element in the form of pellet. The average sensor response of the FeSbO4 pellet was 2.2. LPG sensor based on iron-antimonate shows 97% reproducibility after one month, which illustrates the stability of the fabricated sensor. Electrical properties of iron-antimonate in air were also investigated. Copyright © 2012 VBRI Press.

In this paper, nanoparticles of zinc stannate in different compositions were synthesized via chemical precipitation method. The as-synthesized material was characterized using differential scanning calorimetry. For the formation of crystalline zinc stannate, the synthesized material was annealed at 600°C. Surface morphologies of the samples were analyzed using scanning electron microscopy. The XRD pattern indicates the formation of nanocrystalline zinc stannate and it has a perovskite phase with an orthorhombic structure having a minimum crystallite size 4 nm. Pellets of the sensing materials were made by hydraulic press machine under a pressure of 616 MPa. Furthermore, the humidity sensing investigations of these sensing pellets were completed. Our results illustrate that zinc stannate in 1:4 weight ratio was most sensitive to humidity in comparison to other compositions under same conditions. Maximum sensitivity of the sensor was 3 GΩ/%RH. The results were reproducible up to 72% after 2 mon of ...

We propose a novel and simplified method to fabricate complex 3-dimensional structures in SU-8 photoresist using maskless grayscale lithography. The proposed method uses a Digital Micro-mirror Device (DMD ® ) to modulate the light intensity across a single SU-8 photoresist layer. Top and back-side exposure are implemented in the fabrication of original structures such as cantilevers, covered channels with embedded features and arrays of microneedles. The fabrication of similar structures in SU-8 with other techniques often requires complex physical masks or the patterning of several stacked layers. The effects of critical process parameters such as software mask design, exposure and developing conditions on the quality of 3-D structures are discussed. A number of applications using bridges, cantilevers and micromixers fabricated using this methodology are explored.

Nanocrystalline (Mg–Zn–Ti) oxide films were deposited on an equilateral prism using sol–gel spin process and then annealed at 450 °C for 4 h. The humidity sensing properties of the films were investigated at different angles of incidence. It was observed that the intensity of reflected light increased with an increase in relative humidity (%RH) in the range 10–95% at a particular angle of incidence, which is quite significant for sensor fabrication purposes. The X-ray diffraction reveals the formation of TiO2, ZnTiO3 and MgTiO3 nanocomposites having minimum crystallite size 14 nm. UV–vis absorption spectroscopy was used for optical characterization of the film. It was found that the optical band gap of the composite material was 3.925 eV. Surface morphological study of the film and compositional analysis of elements were carried out using scanning electron microscopy and energy dispersive X-ray spectroscopy. The average sensitivity and reproducibility of the sensor for θi = 60° were found 2 and ∼88%, respectively. Response and recovery time of the sensor were 18 and 30 s respectively. These experimental results have well matches with the theory.

In this report, we describe the solution preparation conditions of various chalcogenide glasses. The dissolution mechanism of (As2S3)60Ge40, (As2S3)60Se40 in ethanolamine is studied. Dynamic light scattering (DLS)measurements confirms that the particles in suspension are

Erbium doped Ge–Ga–Se thin films were fabricated by the pulsed laser deposition (PLD) technique in vacuum using a KrF pulse laser with λ = 248 nm, and a pulse duration of 15 ns. The films were fabricated at room temperature onto glass substrates. The morphological, optical and thermal properties of the films showed good optical and thermal stability. The mechanical properties including film adhesion are relatively poor for thicker films and the microstructure reveals the presence of droplets. Annealing in vacuum improved the film adhesion and substantially enhanced the efficiency of photoluminescence.

We review various properties of chalcogenide glasses that make them promising materials for passive and active microphotonics. We then describe two processes for channel waveguide fabrication, using the chalcogenide glass As/sub 2/Se/sub 3/ as a core material and compatible polymers as claddings. In the first approach, waveguides are patterned directly in the chalcogenide film by photoexposure through a mask followed by selective wet etching. This technique has produced shallow rib waveguides with losses as low as 0.26 dB/cm and small modal area photonic wire waveguides with losses on the order of 10 dB/cm. In the second approach, waveguide patterning is achieved by using an organic photoresist as a mask for selective photodoping of silver into the chalcogenide glass. Selective wet etching produced strip waveguides with smooth and highly vertical sidewalls. We report preliminary light guiding results for these latter structures.

We demonstrate the fabrication and nonlinear optical (NLO) characterization of chalcogenide glass thin films obtained from the solution phase driven approach. The characterization of the films was ahieved using FESEM, AFM, micro-Raman, FTIR, UV-Visible spectroscopy, optical profilometry and XRD. The NLO studies were performed on the solution driven and thermally deposited As2S3 films with [Formula: see text]2[Formula: see text]ps, 800[Formula: see text]nm laser pulses using the Z-scan technique. The results obtained from AFM measurements demonstrated that the surface roughness of the film was considerably low ([Formula: see text]2[Formula: see text]nm) and Z-scan data indicated that the nonlinear refractive index was in the 1.0–[Formula: see text][Formula: see text]m2/W range.

The present paper reports the effect of illumination on the crystallization kinetics in amorphous Se80−xTe20Inx (0⩽x⩽10). The crystallization was monitored by measuring the electrical conductivity of isothermally annealed samples held at temperatures near the crystallization temperature. It is observed that the crystallization becomes faster in the presence of light as compared to a pure thermal case. There is no significant change in the activation energy under illuminated conditions as compared to the purely thermal case.