In the present work, pure silver nanowires (AgNWs) have been synthesized using the CuCl2⋅2H2O salt-modified polyol method. Polyvinylpyrrolidone (PVP) and silver nitrate have been used as capping agent and silver source respectively, while ethylene glycol has been used as the reducing agent as well as a solvent for the reaction. The PVP/AgNO3 molar ratio values of 1.0, 2.0, 3.0 and 4.0 were chosen to synthesize the AgNWs so that the effect of PVP capping agent on the fabrication of silver nanowires may be studied. The FCC crystal structure of AgNWs was confirmed through the XRD analysis. The morphology and aspect ratio of synthesized AgNWs has been studied by scanning electron microscopy (SEM) images. AgNWs of average length of 21 μm and an average diameter of 111 nm were obtained for the sample having a PVP/AgNO3 molar ratio of 2.0. However, silver nanoparticles and other nanostructures together with the nanowires were formed when the PVP/AgNO3 molar ratio values of 1.0, 3.0 and 4.0 were taken in synthesizing the nanowires samples. The out-of-plane quadrupole resonance and transverse localized surface plasmon resonance phenomenon were occurred in UV-Vis spectroscopy analysis of prepared AgNWs samples. A red shift in the peak of the carbonyl bond (–C=O–) in FTIR spectra indicates the interaction of the capping agent with the silver. The highest transmittance value of 88

Fabrication of hybrid heterostructures, consisting of two different nanostructured materials are an efficient approach for further improving photodetecting performance over their individual counterparts. In this paper, we demonstrate the fabrication of an inorganic-organic hybrid heterostructure comprising of Si-nanopillars (SiNPLs) and cobalt phthalocyanine (CoPc). Photodetecting performance of SiNPLs/CoPc heterostructure is investigated in photoconductive mode. It exhibits a low dark current of 2.05×10−8 A and enhanced sensitivity (∼4.5 times) in contrast to pristine SiNPLs. Suppression of dark current with enhanced sensitivity is ascribed to the transfer of electrons from SiNPLs to CoPc layer and their trapping in disorder states present in CoPc layer. The process of electron transfer is confirmed by work function measurements. These results indicate that by employing heterostructure method, the trap states originating from the non-uniform molecular packing of organic semiconductors may be used to further improve the photodetecting performance of one-dimensional nanostructured materials. Additionally, the long-term stability of the SiNPLs/CoPc heterostructure was evaluated by exposing it to ambient conditions for 20 days.

Low temperature, microcube-shaped zinc stannate (ZnSnO3) nanostructures using a low-power microheater sensor platform to detect NO2 gas with high sensitivity and selectivity.

For many years, gas sensors using semiconducting metal oxides and 2-D materials have provided a platform for environmental monitoring for more than two decades. However, these sensors require high operating temperature and external power supply or batteries, which is a great hindrance to their application in modern wearable/smart devices and the Internet of Things (IoT). Self-powered systems based on piezoelectric and triboelectric nanogenerators have the potential to overcome aforesaid limitations to some extent. These nanogenerators can scavenge environment mechanical energy into electrical output, which could be a promising alternative to external power source required for sensing devices, and can also be used as a source of energy for our rapidly increasing daily requirements. In this regard the new research has been proposed using the triboelectric or piezoelectric concept by coupling with gas sensing ability of semiconducting materials to avoid the inevitability of external power sources. A brief overview of the history and fundamentals about nanogenerators and potential applications of the self-supporting gas sensing system based on nanogenerators are provided in this chapter. This chapter could serve as a road map for leading researchers in the field of self-powered sensors of the next generation and highlight current developments in the area.

There is an increasing need of gas sensing device for environmental monitoring and human’s health safety. Particularly, chemiresistive gas sensors having the capability to detect the chemical species (gases or vapors) at room or close to room temperature with good selectivity and high stability are very appealing. In this chapter, we present the fundamental properties of polyaniline (PANI)) responsible for chemiresistive sensing at room temperature. The sensing performance (sensitivity, response, recovery, stability, operating temperature and selectivity) of pure PANI are reviewed. Nanocomposites formed by incorporation of TiO2 nanoparticles (NPs) into PANI matrix show unique properties and offer various functionalities due to the synergic/complementary effects. These nanocomposites display high sensitivity with improved selectivity and stability, which is also discussed in this chapter.

The reaction of [PdCl2(dppf)] with the sodium salt of pyridyl/pyrimidyl tellurolate resulted a mononuclear cis configured complex [Pd(TeAr)(2)(dppf)] (Ar = C5H4N, C4H3N2). These complexes were characterized by NMR (H-1, P-31) spectroscopy and elemental analysis. In addition, the thin film of this complex was fabricated on the glass using solution process and it was found to be sensitive towards detection of H2S gas. The chemi-resistive response of the film was ascribed to the fact that an auxiliary tellurolate ligand attached to palladium metal centre substituted reversibly by thiolate (HS-) species of hydrogen sulphide gas.

In the present study, we demonstrate a solution-phase synthesis of silver nanowires (AgNWs) using poly vinyl pyrrolidone (PVP). NaCl was added as a precursor to the reaction for controlling the free Ag+ions concentration during the formation of initial Ag seeds. By controlling the experimental conditions, the Ag nanostructures can be transformed from nanoparticles to nanowires. Field emission scanning electron microscopy results show that AgNWs of diameter ∼50−80 nm and length ∼5−30 μm can be achieved. UV−Visible absorption spectroscopy and energy dispersive spectroscopy results indicate the formation of Ag nanowires in highly pure phase. In addition, thin film of AgNWs has been fabricated on polyethylene terephthalate (PET) substrate to form a flexible transparent electrode. The optical and electrical studies on AgNWs coated PET substrate show the formation of transparent and electrically continuous network of AgNWs with a resistance of ∼60 Ω/sq. and maximum total transmittance (T) of ∼86%.

In this paper, we report the synthesis of silver nanowires (AgNWs) via polyol method towards the fabrication of low cost high sensitive hybrid photodetector. During AgNWs synthesis, NaCl was added to the reaction for controlling the free Ag+ ions concentration during the formation of initial Ag seeds. Field emission scanning electron microscopy results show that AgNWs of diameter ~ 50–80nm and length ~ 5–30µm can be achieved. UV–Visible absorption spectroscopy and energy dispersive spectroscopy results indicate the formation of AgNWs in highly pure phase. Hybrid detector was fabricated by depositing the AgNWs film on silicon nanopillar (SiNPLs) substrate. Fabricated hybrid AgNWs/SiNPLs photodetector exhibits ~ 10 times more sensitivity as compared to SiNPLs based detector. In addition, AgNWs/SiNPLs detector shows outstanding stability against 20 days exposure to ambient conditions. These results indicate that AgNWs can be utilized to fabricate the high performance one dimensional hybrid photodetectors. The effectiveness of AgNWs to make the transparent flexible devices has also been demonstrated. AgNWs film deposited on a flexible polyethylene terephthalate (PET) substrate revealed a maximum total transmittance and sheet resistance of ~ 94% and ~ 200/sq., respectively.

We demonstrate a very simple and effective approach to improve the sensitivity and the low detection limit of cobalt phthalocyanine films towards the detection of chlorine by creating a porous nanostructured surface on a glass substrate via a vapor phase etching process.

Si nanopillars (SiNPLs) were fabricated using a novel vapor phase metal-assisted chemical etching (V-Mace) and nanosphere lithography. The temperature dependent current–voltage (I–V) characteristics have been studied over a broad temperature range 170–360 K. The SiNPLs show a Schottky diode-like behavior at a temperature below 300 K and the rectification (about two orders of magnitude) is more prominent at temperature < 210 K. The electrical properties are discussed in detail using Cheung's and Norde methods, and the Schottky diode parameters, such as barrier height, ideality factor, series resistance, are carefully figured out and compared with different methods. Moreover, the light sensitivity of the SiNPLs has been studied using I–V characteristics in dark and under the illumination of white light and UV light. The SiNPLs show fast response to the white light and UV light (response time of 0.18 and 0.26 s) under reverse bias condition and the mechanism explained using band diagram. The ratio of photo-to-dark current shows a peak value of 9.8 and 6.9 for white light and UV light, respectively. The Si nanopillars exhibit reflectance < 4% over the wavelength region 250–800 nm with a minimum reflectance of 2.13% for the optimized sample. The superior light absorption of the SiNPLs induced fast response in the I–V characteristics under UV light and white light. The work function of the SiNPLs in dark and under illumination has been also studied using Kelvin probe to confirm the light sensitivity.

In this paper, we have demonstrated a simple and cost effective HF-vapor phase etching method to fabricate the broadband quasi-omnidirectional antireflective surface on glass substrate. Both-sides etched sodalime glass substrates under optimized conditions showed a broadband enhancement in the transmittance spectra with maximum transmittance as high as similar to 97% at 598 nm. FESEM results confirmed the formation of a graded nanoporous surface, which lowers it refractive index. The etched surface exhibited excellent AR property over a wide range of incidence angles (8 degrees-48 degrees), which is attributed due to the formation of graded porosity. Silicon solar cell covered with plain glass showed Isc of 0.123A and efficiency of 8.76%, while it showed I-sc of 0.130A and efficiency of 9.2% when it was covered by etched glass. Furthermore, it exhibited an excellent anti-soiling property as compared to plain glass. All these results show its strong potential in the photovoltaic application.

Poly (ethylene terephthalate) (PET) substrate is a widely used polymer in the optoelectronics industry, its optical properties, such as light transmittance, haze, etc., are of significant importance in organic light emitting diodes and photovoltaics. In this paper, we present a broadband anti-reflective nanostructure on PET substrate prepared by means of plasma etching in a mixture of argon and oxygen gas. Etching time was varied for optimizing the optical transmittance. Field emission scanning electron microscopy images revealed formation of nanostructures of sub-wavelength dimensions resembling pores at the surface. Atomic force microscopy confirmed that the graded porosity was generated from the randomly distributed pores of different sizes and depths. Due to the formation of a gradient refractive index, nanostructured surface exhibited broadband and quasi-omnidirectional anti-reflection properties. A maximum total transmittance of ~99% at 835nm was achieved for both sides treated PET without significant increase in light scattering or haze. Moreover, both sides treated PET showed polarization insensitivity upto 48°, which was not exhibited by untreated PET. X-ray photoelectron spectroscopy revealed generation of degradation products, which consisted of carbon and oxygen containing functional groups. Durability of the anti-reflection layer was tested and proved to be satisfactory.

In this paper, we report the fabrication of broadband antireflection porous nano-network on the glass substrate using the combination of candle soot and HF-based vapor phase etching method. Candle soot layer plays a key role to control the pore size during the etching process. Field emission electron microscopy results showed that the pores have the tapering profile, and the pores size was restricted to the sub-wavelength dimension. Therefore, an excellent broadband antireflection with an enhancement of ∼7% in the maximum total transmittance as compared to plain glass has been achieved. Moreover, reflectance from the etched surface remains quite low (<4%) over a broad range of incident angles up to 58°. The broadband antireflection property was further examined by finite difference time domain simulation. Further, we demonstrate a relative improvement of ∼6% in the Jsc (ΔJsc/Jsc) of solar cell covered with the etched glass.

In this paper, we present a simple method to fabricate the antireflective porous surface on sodalime glass using a single step HF-vapor phase etching method. Under optimal conditions, both-sides etched glass substrate exhibited a broadband enhancement in the transmittance with maximum transmittance as high as 99.2% at similar to 500 nm with extremely low diffusive scattering. The measured transmittance exceeds by similar to 7.6% as compared to plain glass (91.6%). X-ray photoelectron spectroscopy results confirmed the formation of a fluoride layer comprising of NaF and CaF2 on sodalime glass substrate after etching. Field emission scanning electron microscopy results showed the formation of porous structure with randomly distributed pores of size <150 nm. The refractive index of the porous fluoride layer was found to be 1.28 and lowest reflectance of 0.6% has been achieved. Moreover, reflection (measured at 500 nm) remains below 1.5% over a range of incident angles (8-48 degrees), which is ascribed to the fact that refractive index follows a gradual change in the nanoporous surface. The theoretical transmittance of the optimized etched glass determined by finite difference time domain simulation shows a good agreement with the experimental results. The silicon solar cell covered with both-sides optimized etched glass showed a relative increase of similar to 4% in power conversion efficiency as compared to a solar cell covered with a plain glass. (C) 2016 Elsevier Ltd. All rights reserved.

A cost effective, facile and scalable method to fabricate the stable broadband antireflective (AR) surface on glass substrates for solar energy applications is still a challenge. In this paper, we have demonstrated a simple and non-lithographic method to fabricate the broadband quasi-omnidirectional AR nanoporous surface on glass substrates by hydrofluoric (HF) acid based vapor phase etching method. Both-sides etched sodalime glass substrate under optimized conditions showed broadband enhanced transmittance with maximum total transmittance of ~97% at 598nm. The measured transmittance exceeds by ~5.4% as compared to plain glass (91.6%). Field emission scanning electron microscopy results showed that an AR nanoporous surface with graded porosity was formed on sodalime glass substrate after etching. Due to the graded porosity, the fabricated nanoporous surface on sodalime glass substrate showed excellent broadband enhanced transmittance, and exhibited low reflectance <2.8% over a wide range of incidence angles (8–48°). The mechanism of nanostructured surface formation and the effect of etching parameters on transmittance have been discussed in detail. To get more insight, the theoretical transmittance of the optimized sample has been determined by finite difference time domain simulation, which confirms a good agreement of AR property with the experimental results. Furthermore, these AR nanoporous surface showed good adhesion property, excellent thermal and chemical stability, and exhibited outstanding stability against outdoor exposure. These properties signify its strong potential in various solar energy devices.

Hexadecafluorophthalocyanine (F16CuPc) and Cobalt phthalocyanone (CoPc) thin films of different thickness (20-200nm) have been grown by Molecular Beam Epitaxy (MBE) using different deposition rate (0.2 – 1.0 Å/s). For nanowire type growth lower deposition rate and for films of smooth surface higher deposition rate are found suitable. Charge transport (J~V) of CoPc and F16CuPc films is governed by bulk-limited processes with a bias dependent crossover from Ohmic to trap-free space-charge-limited conduction. The mobility (μ) values at 300 K were found 4.5 and 5.5 cm2 V−1 s−1 for CoPc and F16CuPc films respectively. Mechanism of reverse rectification behavior of an organic heterojunction comprising of CoPc and F16CuPc is explained by Kelvin Probe measurement.

We report chemiresistive gas sensing characteristics of cobalt phthalocyanine films deposited on flexible bi-axially oriented polyethylene terephthalate substrates. Charge carrier mobility in these films systematically decreases upon bending, which implies that bending reduces pi-pi interactions among molecules. At room temperature, these films exhibited a reversible change in resistance on exposure to ammonia (5-50 ppm) along with high sensitivity and selectivity as well as fast response and recovery. The chemiresistive sensing properties were found to improve significantly under bend conditions owing to creation of more numbers of interaction sites. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4800446]

We have synthesized n-n isotype organic heterojunction comprising of n-type cobalt hexadecafluorophthalocyanine (F16CoPc)/n-type tris(8-hydroxyquinoline)zinc (Znq(3)) thermal evaporation method. Using Kelvin probe we found that electrons are accumulated at F16CoPc and depleted in Znq(3) sides of interface. The total thickness of electrons accumulation and depletion were found to be 16 nm. Electron accumulation was further confirmed by charge transport measurement.