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India has the highest population belonging to the teenage group who are by default techno savvy. Being the generation zee; they are well versed with the social media and the content streaming on web portals. Parents have dual task now; to moderate the content on screen time of the children but also provide the infrastructure to learn on digital platform. Cell phone is now the essential evil. The constant screen time impacts on the cognitive and psychological growth of the child. All the virtual games make the kids lazy and believe that all outdoor games could be played through the computers; sitting in air conditioned houses without a drop of sweat. This is equally dangerous preposition to the healthy lifestyle of the teenagers. As of toddlers, they won't have their meal till the parents turn on the cartoons on the YouTube. YouTube is highly addictive!

Uniform and ultrafine CuO nanoparticles were prepared via an easy chemical route. This CuO material was utilized to fabricate a p-type semiconductor sensor device for high performance acetaldehyde sensing properties. The crystal structure and molecular structural fingerprint of CuO were revealed via X-ray diffraction data and Raman spectrum analysis respectively. Morphological studies of CuO were carried out using field emission scanning electron microscopy as well as transmission electron microscopy images. Elemental atomic states in sensor material were analyzed by X-ray photoelectron spectroscopy technique. The CuO sensor exhibits a high response of 2923% towards 100 ppm acetaldehyde at 200 °C operating temperature. The lowest acetaldehyde concentration was measured at 10 ppm with the response of 46% for the CuO sensor. The acetaldehyde sensing was tested at different operating temperatures as well as concentrations. Transient response and stability of CuO sensor were also studied. An acetaldehyde sensing mechanism for CuO sensor was discussed.

Heterojunction based gas sensor was fabricated by forming two semiconductor nanostructures interface i.e. n-type ZnO nanorods and p-type NiO nanoplates. These nanostructures were synthesized via chemical routes. Palladium (Pd) nanoparticles (NPs) were synthesized and sensitized on the surface of heterojunction sensor material to enhance the gas response. Sensor materials were characterized using XRD, TEM, FESEM, EDS, Elemental mapping, and XPS techniques for their physicochemical properties. The n-ZnO/p-NiO heterojunction sensors with and without Pd NPs sensitization were investigated for low hydrogen gas concentration 2–100 ppm. Pd NPs sensitized n-ZnO/p-NiO heterojunction sensor showed higher response of 72% towards 100 ppm hydrogen (H2) gas concentration at the operating temperature 225 °C, whereas 53% response was noted by p-NiO/n-ZnO heterojunction sensor for 100 ppm concentration at 237 °C operating temperature. Both the sensors were investigated for selectivity studies using methane (CH4), carbon monoxide (CO), nitrogen dioxide (NO2), carbon dioxide (CO2) and H2 gases. Higher selectivity was observed towards H2 gas for both the sensors. The gas responses of both sensors were investigated at various operating temperatures and concentrations. Transient response, repeatability, and stability were also confirmed for both sensors. The gas sensing mechanism for heterojunction sensors was elucidated.

High quality, closely packed nanorods (NRs) textured ZnO hollow particles were prepared via thermal treatment of polystyrene@ZnO core-shell structures at 300 °C. Polystyrene@ZnO core-shell structures were synthesized using a chemical route. These hollow ZnO particles were investigated for hydrogen gas sensing properties. Morphological properties were studied using field emission scanning electron microscope (FE-SEM). Structural parameters and molecular fingerprint confirmation were carried out by x-ray diffraction (XRD) and Raman analysis respectively. The elemental compositions and atomic species of sensor materials were studied using energy dispersive spectrometer (EDS) analysis and x-ray photoelectron spectroscopy (XPS) spectra respectively. The study of atomic planar arrangements and crystalline nature were examined by using a high-resolution transmission electron microscope (HR-TEM) micrograph and selected area electron diffraction (SAED) pattern respectively. Hollow ZnO particles sensor was revealed remarkable selectivity towards hydrogen (H2) gas. The lowest H2 detection limit of ZnO sensor was at 2 ppm with the response of 7%, whereas 89% gas response was recorded for 100 ppm at optimized temperature 225 °C with response time 139 s. Gas response as a function of operating temperatures as well as gas concentrations was tested along with good sensor stability. The transient gas response and selectivity studies were carried out and analyzed. ZnO growth and gas sensing mechanisms were elucidated.

A quest for the room temperature operated gas sensing lead to development of graphene oxide-based nanocomposite as the potential sensor materials. Room temperature operation is one of the major challenges which is being addressed over the years as it allows less power consumption as well as simplifies device configuration. Trivial chemical synthesis route and mass production are the key features that make GO an ideal sensing material. The presence of oxygen functional group and surface defects on GO act as receptor functions for adsorption and chemical reaction of target gas sensing molecules. The present chapter comprises the various GO nanocomposites materials developed for room temperature gas sensor application. The structural, chemical, and electrical properties of GO are also discussed. Various synthesis routes for GO have been summarized starting with the advantages of GO nanocomposites materials and the principle of operation for gas sensing. The synergetic effect due to the addition of multi-sensing element plays a vital role in enhancing sensing performance. Incorporation of noble metal nanoparticles to GO has a significant effect on gas response enhancement. Finally, the challenges and probable development of GO-based nanocomposites are described.

Hydrogen gas sensing were investigated using nano-bitter gourd like structured CuO material synthesized via a chemical route. Morphology of CuO was revealed using FE-SEM and TEM image analysis. CuO phase confirmation and molecular structural fingerprint were verified by XRD and Raman analysis respectively. Elemental composition and atomic states of elements were investigated by EDS and XPS techniques respectively. A remarkable high gas response of 175% was recorded by CuO sensor towards 100 ppm hydrogen (H2) at the operating temperature 200 °C with response time 150 s. The lowest detection of H2 was observed at 2 ppm concentration with the gas response of 5%. The gas response was studied as functions of different operating temperatures and concentrations. Transient gas response and stability were also confirmed for CuO sensor. Hydrogen sensing mechanism of CuO sensor was elucidated.

High quality nanocrystalline NiO nanoplates were synthesized using surfactant and template free hydrothermal route. The gas sensing properties of NiO nanoplates were investigated. The nanoplates morphology of NiO with average thickness ~ 20 nm and diameter ~ 100 nm has been confirmed by FE-SEM and TEM. Crystalline quality of NiO has been studied using HRTEM and SAED techniques. Structural properties and elemental compositions have been analyzed by XRD and energy dispersive spectrometer (EDS) respectively. The detailed investigation of structural parameters has been carried out. The optical properties of NiO were analyzed from UV–Visible and photoluminescence spectra. NiO nanoplates have good selectivity towards hydrogen (H2) gas. The lowest H2 response of 3% was observed at 2 ppm, whereas 90% response was noted for 100 ppm at optimized temperature of 200 °C with response time 180 s. The H2 responses as functions of different operating temperature as well as gas concentrations have been studied along with sensor stability. The hydrogen sensing mechanism was also elucidated.

The surfactant and template free Co3O4 and NiO nanoplates have synthesized using microwave assisted method. Synthesized Co 3 O 4 and NiO nanoplates were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS) for their Structural, morphological and elemental analysis respectively. The Fourier transform infrared (FTIR) spectra of both samples were recorded for the oxide compound confirmation. Optical and magnetic characterizations were studied by using UV–Visible absorption spectroscopy, photoluminescence (PL) and vibrating sample magnetometer (VSM) respectively. Average crystallite sizes for Co 3 O 4 and NiO nanoplates were found to be 21 nm and 17 nm respectively by using Debye–Scherrer’s formula. The energy band gaps for Co 3 O 4 and NiO nanoplates were calculated using Tauc plot and values are 3.3 eV and 3.1 eV respectively. BET surface areas of Co 3 O 4 and NiO nanoplates were measured to be 29 m2/g and 92 m2/g respectively. The magnetization of Co 3 O 4 and NiO nanoplates as a function of magnetic field were recorded at room temperature showing a small hysteresis loop with coercivity of ∼ 534 and ∼ 152 Oe respectively. Microwave assisted method can be useful for the synthesis of Co 3 O 4 and NiO nano morphological materials for supercapacitor application.

The thin film of nickel oxide (NiOx) nanoparticles was successfully applied as the hole transporting layer (HTL) in inverted (p-i-n) perovskite solar cells (PSCs), but inevitable surface defects and hydroxyl groups present on the NiOx surface are limiting of performance and stability improvements. For overcome these problems, we introduce 3-(Triethoxysilyl)propylamine (TSPA), self-assembly molecule, as an interfacial modifier between NiOx and perovskite film to attenuate the surface defect and prevent deterioration caused by direct contact of the hydroxyl groups and the perovskite. Self-assembled monolayer is formed by hydrogen-bond between amino group of TSPA and hydroxyl group on the surface of the NiOx, which passivate surface and reduce defect density. In addition, a positive dipole was formed by the TSPA monolayer, which resulted in deeper work function at the NiOx interface and improved energy level alignment in PSCs, improving charge extraction-transportation capabilities and reducing recombination of charge carriers at the interface. In consequence, PSCs based on NiOx with TSPA monolayer have boosted PCE by up to 20.21% and showed long-term stability over 60 days under ambient air and varying humidity condition. This approach is expected to be further advanced as one of the methods for the development of high-performance PSCs.

The effect of preparation methods on the formation of gold doped ceria–lanthana solid solution (Au-CLSS) nanoparticles (NPs) was studied. The nanoparticles were prepared by surfactant assisted precipitation methods viz., co-precipitation (CP) and deposition precipitation (DP) in the presence of cetyltrimethylammonium bromide (CTAB). The as prepared nanoparticles were characterized using BET, FESEM, EDS, Raman, TEM, XRD and UV–Vis. spectroscopic techniques to investigate the preferred method for the preparation of nanoparticles for catalytic applications. The cubic fluorite phase formation of nanoparticles was confirmed by XRD analysis and the average crystallite size was calculated to be around 7–10 nm. Surface area studies revealed that the NPs formed by CTAB assisted method have higher surface area. The morphology of NPs formed by both methods was flaky. Raman studies confirmed that the samples prepared by DP method generated increased oxygen vacancies than those prepared by CP method. In the present work, catalytic oxidation efficiency of the catalysts studied with toluene vapours showed maximum efficiency for Au-CLSS at low temperatures (450 K) as compared to undoped CLSS.

The two-dimensional (2-D) nanocrystalline NiO nanoparticles were prepared using a chemical route. The prepared NiO material was well characterized and used for sensor device fabrication. The NiO sensor device exhibited a remarkable response for acetaldehyde in the concentration range of 2–100 ppm. The response of the NiO sensor was investigated for acetaldehyde sensing at different operating temperatures. The high response of the sensor device was noted to be 108% for 100 ppm acetaldehyde concentration at 250 ˚C. The low detection of acetaldehyde was achieved as 3% response for 2 ppm at 250 ˚C. The selectivity of the sensor was tested among gases such as ethanol, methane, carbon monoxide, carbon dioxide, and acetaldehyde. The real-time sensor’s response was studied for different concentrations of acetaldehyde. The effect of acetaldehyde concentrations on the sensor’s response was analysed. The NiO sensor’s stability was confirmed and the sensing mechanism for acetaldehyde gas was briefed.

Two dimensional (2-D), unstacked Bi2MoO6 nanosheets are directly grown on nickel foam and prepared as powder via easy, template-free hydrothermal route. The prepared material was systematically characterized using techniques viz XRD, Cs-TEM, HRTEM, FESEM, XPS, elemental mapping, EDS. Bi2MoO6 nanosheets grown on Nickel foam employed for supercapacitor application, whereas powder form was utilized to fabricate ethanol sensor. The electrochemical characteristics viz cyclic voltammetry (CV), galvanic charging-discharging (GCD), and electrochemical impedance spectroscopy (EIS) were investigated for Bi2MoO6 nanosheets grown nickel foam in 1 M KOH aqueous solution within −0.2 to 0.8 V potential window. The areal capacitance of 655.5 mF/cm2 was achieved at 1 mA/cm2 current density with the energy density of 22.76 × 10−3 Wh/cm2 and 347.18 × 10−3 W/cm2 power density. The 5000 charge–discharge cycles were performed with excellent capacitance retention. The Bi2MoO6 sensor was tested for 10–100 ppm ethanol. A high response of 82% was noted for 100 ppm ethanol concentration at 275 °C. The dynamic resistance response, selectivity, and sensor’s stability were tested and analysed.

The p-CuO/n-TiO2 heterojunction sensor was fabricated by using CuO and TiO2 nanoparticles. The physicochemical properties of the sensor materials were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), elemental mapping, and energy dispersive spectroscopy (EDS). As-fabricated heterojunction sensors were investigated for sensing carbon monoxide (CO) in the range of 50–800 ppm and showed a highest response of 854 % for 800 ppm CO at 250 °C, whereas 177 % response for 50 ppm CO. The sensor selectivity was tested for gases such as CO, carbon dioxide (CO2), nitrogen dioxide (NO2), ethanol (C2H5OH), hydrogen (H2) and methane (CH4), which showed remarkable selectivity for CO. The CO sensors were examined for different operating temperatures and gas concentrations to elucidate their transient response, repeatability and stability. Furthermore, the plausible sensing mechanism of the p-CuO/n-TiO2 heterojunction device was proposed.

We report the rapid (superhydrophobic to superhydrophilic) transition property and improvement in the liquefied petroleum gas (LPG) sensing response of zinc oxide (ZnO) nanorods (NRs) on UV-irradiation and platinum (Pt) surface sensitization, respectively. The morphological evolution of ZnO NRs is evidenced from the field emission scanning electron microscope and atomic force microscope digital images and for the structural elucidation X-ray diffraction pattern is used. Elemental survey mapping is obtained from energy dispersive X-ray analysis spectrum. The optical properties have been studied by UV–Visible and photoluminescence spectroscopy measurements. The rapid (120 sec) conversion of superhydrophobic (154°) ZnO NRs film to superhydrophilic (7°) is obtained under UV light illumination and the superhydrophobicity is regained by storing sample in dark. The mechanism for switching wettability behavior of ZnO NRs has thoroughly been discussed. In second phase, Pt-sensitized ZnO NRs film has demonstrated considerable gas sensitivity at 260 ppm concentration of LPG. At 623 K operating temperature, the maximum LPG response of 58% and the response time of 49 sec for 1040 ppm LPG concentration of Pt- sensitized ZnO NRs film are obtained. This higher LPG response of Pt-sensitized ZnO NRs film over pristine is primarily due to electronic effect and catalytic effect (spill-over effect) caused by an additional of Pt on ZnO NRs film surface.

Ceria-Lanthana solid solution (CLSS) demonstrates excellent catalytic activity due to its redox behaviour and bulk oxygen mobility. The present work deals with the size controlled preparation of CLSS by modified co-precipitation method. The formation of oxides was confirmed by TGA and FTIR studies. The oxides of CLSS were sintered at 500, 600, 700, 800 and 900 °C and characterised using SEM, EDAX, XRD, BET surface area analyser and UV-Visible spectrophotometer to ascertain the optimal sintering temperature of the size controlled nanoparticles.

In recent years, organo-metal halide perovskite and p-i-n planar perovskite solar cells (PSCs) based on it have received tremendous attention due to their high efficiency close to silicon, low temperature process, and ease of cost-effective large-scale manufacturing. However, p-i-n planar PSCs have low fill factor and low current density due to poor interface properties, resulting in low performance. In this work, to solve these problems, we introduce boron nitride (BN) as an interface modifier and demonstrate that the BN incorporated NiOx (NiO:BN) is effectively working as hole transport layer of p-i-n planar PSCs. The NiO:BN hole transport layer (HTL) has a deep energy level of highest occupied molecular orbital (HOMO) and smooth surface compared to pristine NiOx, which provide the better energy level alignment and better interface contact between NiO:BN HTL and perovskite, improving charge extraction and transportation and inhibiting recombination of charge. As a result, NiO:BN based p-i-n planar PSCs represent an improved power conversion efficiency of 20.74% and long-term stability in ambient air for 60 days (maintained over 84% of their initial PCE). Therefore, it can be suggested that the NiO:BN HTL is a promising alternative HTL for high performance p-i-n planar PSCs.

Fullerene derivatives, such as PCBM i.e. [6] , [6] -phenyl C61 butyric acid methyl ester, are actively used as electron-transport layers (ETL) in inverted perovskite solar cells (PSC). However, limitations, such as low electron transportation, large electron trap region, poor film formation, and profuse non-radiative recombination, at the perovskite/PCBM interface result in relatively low performance in inverted PSC. Herein, a significant strategy to overcome these challenges was envisaged via using tin disulphide (SnS2) combined with PCBM, forming a uniform mixture of PCBM-SnS2 with high electron transportation and favorable energy levels. In addition, the greater relative permittivity of SnS2 permits shrinkage in critical electron captured radius from 0.62 nm to 0.22 nm, thus reducing leakage current and non-radiative recombination at the perovskite/PCBM-SnS2 interface. The efficiency of PCBM-SnS2 ETL based inverted PSC reached up to approximately 20% having a high 82% fill factor along with improved internal and external quantum efficiencies. The PCBM-SnS2 ETL reduced the charge transportation resistance and increased recombination resistance. The device stability was improved due to increased hydrophobicity and electrical compactness of the PCBM-SnS2. Hence, the synergetic effect of PCBM-SnS2 as an efficient ETL has great potential in improving the performance of planar inverted PSC.

Unstacked two dimensional (2-D) NiO nanosheets are synthesized via easy surfactant-free hydrothermal chemical route. NiO sensor is investigated for high performance and selective hydrogen (H2) gas sensing properties. Structural analysis is carried out using XRD pattern. The morphology of NiO is confirmed by using FESEM and TEM micrographs. Atomic state and elemental composition are analyzed by recording XPS and EDS spectra respectively. NiO sensor exhibited a high gas response of 191% for 150 ppm H2 concentration at 250 °C operating temperature with response time 150 s. The lowest H2 detection is observed at the concentration of 10 ppm having the gas response of 22%. The H2 response of NiO sensor was tested at different operating temperatures as well as gas concentrations. The dynamic gas response and sensor stability were recorded and analyzed. The sensing mechanism of NiO sensor was discussed.

Coating procedure for ceramic monoliths was optimized by wash coating with ϒ-alumina for the deposition of Au sensitized La–CeO2 catalyst. Effect of four different catalyst coating methods on ceramics monolith surface for toluene catalytic activity was investigated. Au sensitized La–CeO2 catalyst was prepared via wetness impregnation and co-precipitation chemical methods. The catalyst was characterized using XRD, FESEM, EDS, TEM, XPS, Raman, BET and Elemental mapping techniques. Nanoparticles composed flakes morphology of catalyst was confirmed by electron microscopy. Average nanocrystalline size of 6.7 nm and surface area 33 m2/g of catalyst was estimated using Scherrer's formula and BET analysis respectively. Adherence tests were carried out by applying ultrasonic vibrations and hot air blower to optimize ϒ-alumina coating on ceramics monolith. Toluene catalytic activity studied at different operating temperatures and concentrations. Stability and reuse of catalyst coated ceramics monoliths for toluene activity were confirmed. A mechanism of toluene degradation was briefed.

High quality nanocrystalline CdO thin films have prepared by versatile spray pyrolysis deposition (SPD) method. The CdO film sensor has shown highest gas response at room temperature with good selectivity for liquefied petroleum gas (LPG). The spherical nanoparticle (7–8 nm) like morphology of CdO has been revealed using field emission scanning electron microscope (FE-SEM) as well as atomic force microscopy (AFM). Structural properties and elemental compositions have analysed by performing x-ray diffraction (XRD) and energy dispersive spectrometer (EDS) respectively. The detail investigation of structural parameters has been carried out. The optical energy bandgap for CdO has estimated to be ∼2.3 eV by using UV-vis spectroscopy and Tauc's plot. The lowest LPG response of 4.6% has observed at 1 vol%, whereas 20% response noted for 10 vol% at room temperature. The rapid response and recovery times of CdO sensor for LPG sensing have recorded to be 18 s and 32 s respectively. The LPG responses as function of operating temperature and gas concentration have studied along with sensor stability.

We report LPG sensing of gold (Au)-sensitized SnO2 nanostructured film fabricated by an easy spray pyrolysis deposition method whose surface morphology is confirmed by field-emission scanning electron microscopy and atomic force microscopy images and structure by X-ray diffraction pattern. Energy dispersive X-ray spectrometer analysis has carried out for finding elemental composition. The SnO2 film is uniform and consists of spherical particles of ∼10 nm. The highest gas response observed at 780 ppm LPG concentration for pristine SnO2 is 28%, at operating temperature 623 K, which is greatly improved on Au sensitization up to 57% with 60 s rapid response time at 598 K operating temperarture. The high gas response is due to electronic effect and catalytic spill-over effect of Au sensitization. The improved sensing mechanism has throughly been explored .