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Novel CuBi2O4nanocrystals incorporated in the polyaniline matrix utilized for the fabrication of a flexible and bio-compatible device for the detection of low-intensity photons by using a photomultiplication type photodetector.

Abstract This research deals with study of enhanced liquefied petroleum gas (LPG) and humidity sensing properties of Sn-doped NiO pellets synthesized by chemical precipitation route. XRD, FTIR, SEM, and UV–Vis studies were employed to understand the effect of Sn doping on the structural, morphological, and optical properties of the NiO nanoparticles. XRD results revealed that doping of tin in NiO had a significant impact on the crystallite size, peak intensity, strain, lattice parameter, etc. The calculated crystallite size of pure and 3 mol% doped NiO was 33.2 nm and 13.3 nm, respectively. SEM micrographs revealed that the structure of the samples was irregular spheres and non-homogeneous. The dependence of LPG sensing properties on the structural and surface morphological properties has also been studied. The maximum response of 30.46% to 2.0 vol% of LPG was observed at room temperature (300 K). The same sample also shows high humidity sensing response of 87.11% towards 90% RH. Graphic abstract

The present work mainly focuses on the fabrication of a porous glass 40SiO2–35H3BO3–19V2O5–6P2O5via a melt-quenching technique.

Covalent triazine frameworks (CTFs), belonging to the super-family of covalent organic frameworks, have attracted significant attention as a new type of photosensitizer due to the superb light-harvesting ability and efficient charge transfer originating from the large surface area. However, the wide optical band gap in CTFs, which is larger than 3.0 eV, hinders the efficient light harvesting in the visible range. To overcome this limitation, we developed the new type CTFs photocatalyst based on the donor-acceptor conjugation scheme by using melamine (M) and 2,6-diaminoanthraquinone (AQ) as monomeric units. The melamine-2,6-diaminoanthraquinone-based covalent triazine frameworks (M-AQ-CTFs) photocatalyst shows the excellent light-harvesting capacity with high molar extinction coefficient, and the suitable optical band gap involving the internal charge transfer character. Combination of M-AQ-CTFs and artificial photosynthetic system including the organometallic rhodium complex, acting as an electron mediator, exhibited the excellent photocatalytic efficiency for the regeneration of the nicotinamide cofactors such as NAD(P)H. In addition, this photocatalyst showed the high photocatalytic efficiency for the metal-free aerobic oxidation of sulfide. This study demonstrates the high potential of CTFs photocatalyst with the donor-acceptor conjugated scheme can be actively used for artificial photosynthesis.

Commercially available compound CuInGa (S, Se) can be replaced with emerging quaternary compound Cu2ZnSnS4 (Copper Zinc Tin Sulphur or CZSS) for photovoltaic applications due to the high absorption coefficient and optimum bandgap. Unstable sulphur and the co-existence of binary and ternary phases in CZSS are the main obstacles for a single-phase kesterite quaternary compound. To overcome these issues, the researchers are synthesising the CZSS in presence of sulphur and selenium environment. The sulphurization and selenization are the constraints for the synthesis of CZSS and these processes make it costlier. In the present work, the wet-chemical method (i.e., co-precipitation method) was used to synthesise CZSS without vacuum annealing where the sulphur constituent was controlled by changing the stoichiometric ratio. X-ray diffraction (XRD) and Raman analysis confirm that the synthesised CZSS was in polycrystalline and single-phase kesterite nature. The average crystallite sizes for thiourea 16, 18, 20 mmol were found 15 nm, 17 nm and 17 nm, respectively. Surface morphology of the as-prepared film was identified by scanning electron microscope (SEM) and optical bandgap of the film was obtained ~1.33 eV by UV-visible (UV-vis) analysis. The 18 mmol of thiourea with stoichiometric ratio 4:2:2:9 is found the best optimisation for synthesising the CZSS without vacuum annealing by the co-precipitation method. Thus, the thin film of such synthesised CZSS may be employed for the low-cost photovoltaic application.

Green synthesis procedure assisted with lemon juice was adopted to prepare MgFe2O4 ferrite nanoparticles. Structural analysis revealed the purity of the ferrite phase of the samples without any secondary phases. Lemon juice as a chelating agent seems to be playing crucial role in the formation ferrite phase. The crystallinity of ferrite samples was found to be ripened with the heat treatment and higher average size of 32.9 nm was reported for crystallite size. The average particle size (estimated from the SEM histograms) is well matched with the average crystallite size (estimated from the XRD peaks). The dielectric behaviour is similar to the usual spinel ferrite systems, as the dielectric constant is maximum at lower frequencies and decreases at higher frequencies due to hopping of electrons showing the dielectric dispersion. This dielectric behaviour is influencing the humidity sensing behaviour in the way of interfacial polarization of water molecules for conduction mechanism to increase the impedance of the material with the decrease of dielectric constant. Moreover, in the present ferrite systems hopping mechanism appears to be dependent on the location of Mg2+ ion in the spinel structure. The as-prepared and sintered samples are showing a humidity response over the humid range of 10–95% RH. The sample sintered at 900 °C is showing highest average sensor response 6.02 MΩ/%RH among the as-prepared sample (5.56 MΩ/%RH) and sintered sample at 600 °C (5.70 MΩ/%RH).

The present work mainly focuses on the fabrication of a porous glass 40SiO

Diabetes is a major health challenge, and it is linked to a number of serious health issues, including cardiovascular disease (heart attack and stroke), diabetic nephropathy (kidney damage or failure), and birth defects. The detection of glucose has a direct and significant clinical importance in the management of diabetes. Herein, we demonstrate the application of

This paper presents the surface modification and characterization of h-BN-doped PVP thin film and its use as a humidity sensing probe. The thin film of h-BN-doped PVP has been prepared by spin coating method and characterized by XRD, SEM, TEM, UV–Vis, and FTIR spectroscopy. SEM and TEM images indicate that the PVP is densely packed with h-BN. The bandgap calculated by UV–visible spectroscopy varies from 4.9 to 5.2 eV on increasing the doping level. .The crystalline nature of the blend has been observed through X-ray diffraction spectrum with minimum crystallite size of 2 nm. The h-BN-doped PVP thin film was employed as a sensor with a sensitivity of 98.75 kΩ/%RH and 4.67 pF/%RH for impedance and capacitance, respectively. The minimum response/recovery time of the sensor (14/18 s) indicates that the blend can be used as a cost-efficient humidity sensor. Density functional theory (DFT) has been applied to simulate the adsorption of water molecules on the h-BN-doped PVP nanocomposite. The dipole moment, adsorption energy, and HOMO–LUMO gaps have been evaluated with increasing the number of water molecules. PDOS plots show alteration in the makeup of HOMO and LUMO on the adsorption of water molecules. MESP map illustrates the transfer of charge density from h-BN to the water molecules.

Triboelectric nanogenerators (TENGs) are an advanced mechanical energy harvesting system that has a wide range of advantages and has great prospects for use in various fields of science and technology. Among the factors that have a significant impact on the performance of TENGs, a special role belongs to the nature of triboelectric polymer materials. Over the past few years, there has been an exponential growth in research on polymers with shape memory assisted self-healing (SMASH) properties for TENGs. This mini review presents the state of the art in SMASH polymers for TENGs and attempts to assess the impact of modern polymer chemistry on the development of advanced materials for TENGs. Particular attention is paid to the relationship between these polymeric materials and the performance of TENGs. Finally, the problems and promising research directions for polymers with SMASH properties for TENGs are outlined.

A global challenge faced by light harvesting photocatalyst is how to promote the selective organic transformation, such as C-S bond formation via radical-radical coupling under solar light. Here, we report a two-dimensional covalent organic frameworks (2D-COFs), poly (perylene-imide-benzoquinone) nanorod through in situ condensation on flexible activated carbon cloth (PPIBNR-FACC) to function as a light harvester material for highly selective radical-radical coupling to vinyl sulfides (i.e. C-S bond activation). Such a structure supports charge transfer from PPIBNR to FACC, which is essential for the selective radical-radical coupling. Hence, organic transformation is attaining high yields and selectivity (˜99%) under solar light using in situ prepared PPIBNR-FACC photocatalyst. The structural virtues of PPIBNR-FACC will trigger the utmost investigations into designable and versatile 2D-COFs for fine chemical synthesis.

Even if there is a market for specifically designed ammonia sensors, room temperature and long-term stable detection of low trace airborne ammonia represent a serious challenge that calls for immediate alternatives. This communication reports single-step hydrothermally engineered ZnCo2O4 nanoflakes for developing energy-efficient and economic ammonia-detecting chemiresistor. The formation of ZnCo2O4 nanoflakes was revealed through scanning electron microscopy. The X-ray diffraction outcomes reveal the crystal structure of ZnCo2O4 to be of cubic phase and Fd-3m space group. Optical absorbance analysis exhibits the optical band gap of the ZnCo2O4 nanoflakes to be 2.71 eV. Further, a chemiresistor was fabricated and used as the ambient room temperature ammonia sensor. The sensor exhibits a superior sensing response of around 34.13 for 30 ppm of ammonia, whereas at 5 ppm the sensor response of 3.49 with prompt response and recovery times of 1.52 s and 2.12 s respectively. The fabricated chemiresistor demonstrated excellent sensing performance in terms of 3 essential S’s (Selectivity, stability and sensitivity) and 5 R’s (Recovery, response, range, room temperature operation and repeatability). The enhanced sensing performance in an energy-efficient module is attributed to nanoflakes morphology of engineered ZnCo2O4 with a high surface area and its stable crystal structure.

The present work focuses on the synthesis of Fe3O4 magnetite core@shell type nanoparticles modified with three types of ligands: Magnetite with activated carbon (MAC), Magnetite with silica (tetraethoxysilane, TEOS, and 3-aminopropyltriethoxysilane, APTES) (MTA) and Magnetite with silica, APTES and humic acids (MTAH). The MTAH sample shows greater porosity in comparison to MTA, and MAC samples. The band gap of MTAH is 4.08 eV, which is higher than MTA (2.92 eV), and MAC (2.80 eV). Rietveld quantitative phase analysis of all derivatives was performed and compared with all three samples. The LPG sensing at room temperature shows the highest sensor response of 9.42, in comparison to 3.87 sensor response for MAC, and 4.60 for MTA. This approximately double sensor response increment is justified with the help of band gap, porosity, and size of all 3 the samples. The MTAH sample shows the lowest response-recovery time of 9.33 and 10.78 s respectively in comparison to MAC and MTA samples. In conclusion, this manuscript describes the synthesis procedure of different derivatives of Fe3O4 core@shell materials along with the relation of LPG sensing with different parameters of the materials.

Multiwall carbon nanotube (MWCNT) based metacomposites with negative permittivity have received significant interest over the past decade due to their unique electromagnetic properties. Here, markedly percolating Bi2SiO5 (BSO)/MWCNT metacomposites with adjustable negative permittivity were prepared by the facile hydrothermal method. Three-dimensional conductive networks formed by interconnected MWCNT are present in BSO/MWCNT metacomposites with 10 and 20 wt% of MWCNT. The detailed microstructure and resistivity studies of the metacomposites led to realize that the adjustable negative permittivity of the BSO/MWCNT metacomposites attributes to the low-frequency plasmon resonance of free Drude carriers. In this work, the effect of the direct-current biasing voltage in the radio frequency region is investigated on the negative permittivity characteristics. For below percolation threshold ( f c ) metacomposites, the Maxwell-Wagner polarization effects increase in low-frequency region immediately after dc bias is applied. In case of above percolation threshold ( f c ) metacomposites, the Drude free carrier concentration increases due to the formation of conductive network among MWCNT led to the rise of negative permittivity values in the low frequency region. This work provides a novel strategy for the adjustment of the negative permittivity value, which can expand the potential application in the field of sensors based on the changes in permittivity properties.

We synthesized gold (Au) nanoparticles via a rapid chemical route by reducing chloroauric acid by trisodium citrate. TEM micrographs revealed that particles were spherical with well-defined lattice structures and most of them were within the size range of 8–12 nm. A single surface plasmon resonance peak observed at 525 nm indicated the uniformness of the spherical morphology of the particles. XRD analysis showed that the particles were well crystalline. An impedance-based humidity sensor device was fabricated for depositing these gold nanoparticles in their non-functionalized state and the sensor revealed fast response time of 54 s, high stability and repeatability, and an impressive average sensitivity of 7.57 MΩ/% RH within the humidity range of 10–95%. SEM micrographs revealed the presence of cracks on the film surface and our analysis of the sensing mechanism correlated the sensitivity and the surface cracks along with smaller particle sizes. Our results show that gold nanoparticles without further functionalization are able to perform as a well-performing humidity sensor.

The present paper demonstrates the effect of humidity on the (Ge11.5Te12.5Se67.5)80Sb20 and (Ge11.5 Te12.5Se67.5)70Sb30 thin film deposited on a glass substrate. The films prepared using a thermal evaporation technique reveal an amorphous nature as observed from the x-ray diffraction (XRD) graph. The light absorption taking place in the UV-visible region was confirmed using a UV–Vis spectrophotometer, and optical bandgap values of 1.46 eV and 1.42 eV were found for (Ge11.5Te12.5Se67.5)80Sb20 and (Ge11.5 Te12.5Se67.5)70Sb30 alloys using Tauc’s plot. The films were investigated for an impedance-based electrical humidity sensor. The maximum sensitivity of the chalcogenide sensing element was 13.86 MΩ/%RH and 15.31 MΩ/%RH for (Ge11.5Te12.5Se67.5)80Sb20 and (Ge11.5 Te12.5Se67.5)70Sb30, respectively, in the range 10–25%RH at room temperature, and the average sensitivity for the entire range of %RH was 7.33 MΩ/%RH and 9.42 MΩ/%RH, respectively, for the two glasses. The aging effect for samples was found to be negligible; hence they are stable against time, which makes them suitable for use as humidity sensors. The repeatability of the sensors was 89% and 94.45%, respectively.

The present paper details on the synthesis and characterization of the modified Graphene and its moisture sensing application. The characterization tools as Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM), Electron Dispersive X -rays (EDX), Particle size distribution, Fourier-Transform Infrared (FTIR), UV–Vis spectrophotometry and Raman are employed for characterizing the synthesized material. The BET demonstrations of the synthesized material have a specific surface area as 10.55 m2/g together with pore size distribution range from 10.34 to 97.44 nm, confirming the mesoporous material. The SEM, EDX, FTIR, UV–Vis spectroscopy and Raman analysis of the synthesized material confirmed that it is the modified Graphene (m-Graphene). Presence of the ID/IG = 1.55 confirms more defects along with many dangling bonds which are more beneficial for the humidity detection. The humidity sensing characteristics of m-Graphene based sensor have been observed from 100 Hz to 10 kHz frequencies and the best sensitivity was found at 100 Hz. The sensor shows high sensitivity of 2.51 MΩ/%RH along with the calculated repeatability, response and recovery time of 96.05%, 24 and 13 s, respectively, at room temperature.

This work reports a room temperature operative ZnSnO3 nanoflakes-based CO2 gas sensor. The perovskite ZnSnO3 nanoflakes are synthesized by a one-pot hydrothermal technique. The prepared material was characterized via XRD, SEM, UV-visible spectroscopy, and DLS measurement for confirming the crystal structure, surface morphology, optical properties, and size distribution. The X-ray diffraction pattern revealed that ZnSnO3 was in the orthorhombic phase and average crystallite size examined by the Scherrer formula was 8.05 nm. Optical studies were done by the UV–vis spectroscopy and a direct optical band gap was found to be 3.27 eV. The surface morphology of ZnSnO3 was found to nanoflakes are almost uniform dimensions. The fabricated sensor device of ZnSnO3 detected the CO2 gas at room temperature (RT) for different concentrations. The best sensor response was found to be 4.93 for 1000 ppm of CO2 whereas at 200 ppm the response and recovery times were found to be 5.92 s and 7.23 s respectively. HOMO-LUMO gap energy of ZnSnO3 without and with interaction from CO2 molecule was found 1.165 eV and 1.577 eV, respectively. DFT studies are used for a better understanding of sensing mechanisms.

The present paper describes the effect of co-catalyst on the growth of multiwall carbon nanotube (MWCNT) by chemical vapor deposition (CVD) technique. The fascinating properties of CNT make them a suitable material for optoelectronic devices such as sensors, LED, solar cell, and field emission displays. MWCNTs were fabricated using CVD, by decomposing ethanol over finely dispersed Co metal as a catalyst at 750 °C. The effects of growth condition on the quality and morphology of MWCNTs were investigated by SEM, FTIR and XRD. SEM photographs show that the nanotubes are densely packed having a diameter of 10–15 nm. The bandgap was calculated by UV–visible spectroscopy and it was found varying from 3.08 to 3.5 eV by changing the substrates. The average size of tubes (length) was found to be 250 nm. FTIR exhibited that the synthesized MWCNTs were semiconducting in nature with the oxygen vacancies causing the variations in refractive index with the exposure of moisture.

In this work, a bilayered ultra responsive self-healable photodetector that can restore both its structure as well as sensing property after deformation has been reported. This photodetector is based on ferrite with ultrafast sensing ability along with restoration property. In this dual-layered structure, the upper layer is Ni0.2Zn0.8Fe2O4 (NZF) prepared by citrate gel method and acts as sensing layer, whereas, the lower layer is Urea-Formaldehyde (U-F) microcapsules with flaxseed oil and NZF core. Here bottom layer acts as a healing layer, which can successfully restore film sensing property after deformation. Flaxseed oil acts as a medium to transport NZF from lower layer to the upper sensing area, which was deformed manually. The evaluated photoresponse and recovery time of NZF before deformation are 1.74 sec and 3.28 sec at 100 mW/cm2 respectively, whereas, response and recovery after healing were 1.75 sec and 2.84 sec respectively. The solar light photodetector based on microcapsule that can restore its sensing property ∼98.5%. The purpose of this work is to develop a method by which anyone can fabricate the different types of self-healable solar light photodetector.

This paper reports the characterizations and humidity sensing properties of Fe–GO. Thin films of GO and Fe–GO have been made by using the spin coating technique with 1500 rpm. After fabrication of thin film, variations in capacitance of the film with relative humidity (%RH) have been recorded. The thin film has been characterized by various techniques and a unique flower-like structure was found after the functionalization of GO with iron. The XRD analysis confirmed that the GO consists of a minimum of five layers of the graphene. BET surface analysis reveals that the synthesized Fe–GO is the mesoporous material partaking the surface area 45.23 m2/g together with a mean pore diameter of 32 nm. The sensitivity of the Fe–GO based sensor found as 14.12 pF/%RH for higher humidity (70–95%RH) region along with average sensitivity, response and recovery time as 5.18 pF/%RH, 31 s and 11 s respectively at room temperature.

Copper zinc tin sulphide (CZTS) microsphere comprising thin nano sheets with high porosity and the wide surface area was developed via the surfactant-assisted hydrothermal method and was further characterized using XRD, FESEM, and TEM revealing its crystalline nature, efficient morphology, and internal structural, respectively. The band gap of CZTS is found to be 1.8 eV owing minimum crystallite size and the average crystallite size of 13 and 34 nm, respectively. The absorption analysis of CZTS was done using UV-Vis, FTIR, and Raman spectroscopy. Finally, the humidity sensing capability of the material was enquired using both the electrical and optical modes. Electrical mode gave an excellent sensitivity of 10.77 $\text{M}\Omega $ /%RH with the fast response and recovery times of 7.4 and 57 s, respectively, whereas optical mode gave a sensitivity of $\sim 1.051~\mu \text{W}$ /%RH with the response and recovery times of 46 and 80 s, respectively.

The present paper reports the polymer matrix of Ni(NO3)2(AAm)4·2H2O thin film as an electrical and opto-electronic humidity sensor. For this purpose, films were prepared by spin-coating method to investigate the adsorption/desorption of humidity at room ambient. The sensing element was investigated through X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and UV–Vis absorption techniques. XRD exhibited the crystalline nature of the nanomaterial thin film and evaluated average crystallite size was 30 nm. SEM showed highly porous nanostructures of different size distributed throughout the film. Energy band-gap of the film was estimated as 4.034 eV. TEM image showed the nanostructures with the average grain size of 4-21 nm and SAED confirmed the crystalline nature of the material. The film was further employed for two different modes of humidity sensing i.e., impedance-based electrical humidity measurement and transmission based opto-electronic humidity measurement which gave a maximum average sensitivity of 37.79 MΩ/%RH and 1.31 µW/%RH respectively at room temperature.

Diabetes is a major health challenge, and it is linked to a number of serious health issues, including cardiovascular disease (heart attack and stroke), diabetic nephropathy (kidney damage or failure), and birth defects. The detection of glucose has a direct and significant clinical importance in the management of diabetes. Herein, we demonstrate the application of in-situ synthesized Ti2C-TiO2 MXene nanocomposite for high throughput non-enzymatic electrochemical sensing of glucose. The nanocomposite was synthesized by controlled oxidation of Ti2C-MXene nanosheets using H2O2 at room temperature. The oxidation results in the opening up of Ti2C-MXene nanosheets and the formation of TiO2 nanocrystals on their surfaces as revealed in microscopic and spectroscopic analysis. Nanocomposite exhibited considerably high electrochemical response than parent Ti2C MXene, and hence utilized as a novel electrode material for enzyme-free sensitive and specific detection of glucose. Developed nanocomposite-based non-enzymatic glucose sensor (NEGS) displays a wide linearity range (0.1 µM-200 µM, R2 = 0.992), high sensitivity of 75.32 μA mM−1 cm−2, a low limit of detection (0.12 μM) and a rapid response time (~3s). NEGS has further shown a high level of repeatability and selectivity for glucose in serum spiked samples. The unveiled excellent sensing performance of NEGS is credited to synergistically improved electrochemical response of Ti2C MXene and TiO2 nanoparticles. All of these attributes highlight the potential of MXene nanocomposite as a next-generation NEGS for on the spot mass screening of diabetic patients.

The purpose of this research was to investigate the adsorption of arsenic (As) from aqueous solutions using MPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum (pea) pyrolyzed at 500

Sulfur-doped graphitic carbon nitride (S-g-CN) has gained significant attention in recent years. Sulfur-doped graphitic carbon nitride (S-g-CN) is a promising metal-free photocatalyst because of its band orientation, natural abundance and groundwork. Improved photocatalytic activity of S-g-CN material for solar chemical production persists a hot yet challenging problem. Herein, we provide an adaptable method for the synthesis of S-g-CN nanocomposite decorated with the moiety of giant polyoxometalate (S-g-CN/Mo-368) that subsequently showed highly efficient photocatalytic activity. The as-synthesized S-g-CN/Mo-368 as a recyclable artificial photocatalyst revealed excellent activity for solar chemical production, that is nicotinamide adenine dinucleotide (NADH) regeneration under visible light. The immobilized Mo-368 on the S-g-CN surface increased the visible light adsorption capacity of the S-g-CN/Mo-368 photocatalyst. The visible light absorption activity, morphology, element compositions, particle size and zeta potential of S-g-CN powder and S-g-CN/Mo-368 were thoroughly investigated. From the application point of view, S-g-CN/Mo-368 was applied to determine the solar chemical production (i.e. NADH regeneration) under visible light with a higher yield% of about ~ 94.85%.

In the present work, nanostructured nickel oxide (NiO) powder has been synthesized using the sol–gel method and is annealed at different temperatures to study the impact of annealing temperature on its structural, optical, morphological, and LPG sensing properties. The obtained powder was analyzed by several characterization techniques such as field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV–Visible spectroscopy (UV–Vis), particle analyzer, and Fourier-transform infrared spectroscopy. XRD patterns show that NiO nanoparticles have a cubic unit cell structure. The average crystallite size for each of the samples was calculated to be 27–77 nm using the Debye–Scherrer formula and Williamson-Hall uniform deformation model plot. FESEM images revealed the mesoporous morphology of prepared NiO nanoparticles and found that the particle size increases with an increase in annealing temperature. The UV–Vis absorption spectrum shows that the energy band gap decreases with an increase in annealing temperature for NiO nanoparticles. Liquefied petroleum gas (LPG) sensing properties of the prepared pellets were also examined at room temperature (300 K) in the range of 0.5–2.0 vol% concentration of LPG. The gas sensing response of the NiO:500 sample is 244.4% which is the highest among all the samples due to the combined effect of nanocrystal defects and specific surface area. The sensing response of the synthesized material increased significantly as the concentration of the test gas rose.

This work demonstrates an easy and cost-effective synthesis of PANI-PPY conducting nanoflakes (NFs) with a self-healing capability. Scanning electron microscopic (SEM) analysis shows the minimum width of NFs as 30 nm, while HRTEM analysis confirms the shape, size, and semi-crystalline nature of the polymer. These PANI-PPY NFs were used to fabricate a contact separation mode triboelectric nanogenerator (TENG) based self-powered photosensor which gave the maximum output voltage (149 V), maximum output current (16 µA), current density 0.56 µAcm−2, and power density 83.56 µWcm−2. Detailed literature survey shows the comparative study of PANI-PPY NF’s with other photo-sensing materials. This literature review highlights the tremendous ability of PANI-PPY to self-restore and ultra-fast self-powering nature. This work also demonstrates a very easy and cost-effective method to develop polymeric nanomaterials via temperature-assisted polymerization, which need only a stirrer with a hot plate. Theoretical analysis (DFT calculations using Gaussian 09 and Gauss view 05) shows a consistent increase in stability when the number of molecules in the polymer chains analyzed was increased. The developed self-healing triboelectric nanogenerators exhibited stable performance before and after healing.

The main objective of present work was to synthesize sodium doped polycrystalline hydroxyapatite NaHAp (NaOH-HAp) powder by employing wet chemical precipitation method and its composites with alumina (Al2O3; 0, 10, 40, 70 wt%) using a scalable solid-state reaction method. Detailed investigations of NaHAp and its composites using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV–visible spectroscopy, scanning electron microscopy followed by energy-dispersive X-ray spectroscopy and sensing behaviour is carefully described. XRD results exhibited major and minor phase of HAp, Ca2P2O7 and NaOH for NaHAp sample while for all fabricated composites of HAp–NaOH–Al2O3 and revealed the major phase of hibonite CaO(Al2O3)6 along with secondary phases of Ca2P2O7, Na4[Al(PO4)2(OH)], Na3Al(OH)(HPO4)(PO4), NaAl3(PO4)2(OH)4 and NaOH. The crystallite size of NaHAp-based composites was also determined and lies in the range of 200–2800 nm, which is larger than that of Al2O3. FTIR and Raman spectroscopic studies reveal the bonding formation of P–O, O–P–O and Al–O due to intramolecular interaction of Na4(Al(PO4)2(OH)), Na3Al(OH)(HPO4)(PO4) and NaAl3(PO4)2(OH)4 in the HAp–NaOH–Al2O3 composite, while bonding formation of Al–O–H recognized to intermolecular interaction in between Al with H atoms of Na4(Al(PO4)2(OH)), Na3Al(OH)(HPO4)(PO4) and NaAl3(PO4)2(OH)4. The SEM and energy dispersive spectroscopy analysis revealed the presence of all constituent elements of used chemicals which also validate the purity of used materials. It is concluded that the fabricated sensor (60 NaHAp–40 Al2O3) shows lowest response and recovery time, 4 and 3 s for the 0.5 vol.% concentration of the LPG. Therefore, among all composites, this fabricated composite can be used for LPG gas sensing applications.

Triboelectric nanogenerators (TENGs) as a revolutionary system for harvesting mechanical energy have demonstrated high vitality and great advantage, which open up great prospects for their application in various areas of the society of the future. The past few years have seen exponential growth in many new classes of self-healing polymers (SHPs) for TENGs. This review presents and evaluates the SHP range for TENGs, and also attempts to assess the impact of modern polymer chemistry on the development of advanced materials for TENGs. Among the most widely used SHPs for TENGs, the analysis of non-covalent (hydrogen bond, metal–ligand bond), covalent (imine bond, disulfide bond, borate bond) and multiple bond-based SHPs in TENGs has been performed. Particular attention is paid to the use of SHPs with shape memory as components of TENGs. Finally, the problems and prospects for the development of SHPs for TENGs are outlined.

Metallopolymers (MPs) or metal-containing polymers have shown great potential as self-healing and shape memory materials due to their unique characteristics, including universal architectures, composition, properties and surface chemistry. Over the past few decades, the exponential growth of many new classes of MPs that deal with these issues has been demonstrated. This review presents and assesses the latest achievements and problems associated with the use of MPs as self-healing and shape memory materials. Among the most widely used MPs with self-healing properties, metal complexes based on polymers containing phenol, carboxylic acid, pyridine, azole, histidine and urethane donor fragments are identified. Particular attention is paid to the principles of action of the shape memory MPs. Of considerable interest is the use of MPs as functional materials for sensors, soft electronic devices, transistors, conductors, nanogenerators, bone tissue engineering, etc. Finally, the problems and future prospects of MPs with self-healing and shape memory properties are outlined. This review also analyzes articles published over the past five years.

Solvent-free synthesis of nanocomposite for flexible humidity sensor is gaining immense interest to fulfill the criteria for its practical application. Herein, present paper reports the development of cadmium sulfide/polyacrylamide nanocomposite as a flexible humidity sensor, which was fabricated by the facile spin-coating technique on PET (polyethylene terephthalate) substrate. Morphological, optical and crystalline nature of CdS/polyacrylamide nanocomposite were investigated using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetric (DSC), Fourier transmission infrared spectroscopy (FTIR), UV–Visible, and Particle size analysis. Characteristic surface area and pore volume were estimated using BET analysis whereas the hydrophilicity of the sample was investigated using contact angle measurement. As fabricated sensor showed an outstanding humidity sensing response with good linearity in the humidity ranging from 11% to 95%RH. The sensitivity of nanocomposite at high humidity range (50–95%RH) was calculated as 306.47 nF/%RH and is utilized for moisture detection of commonly used baby diapers with alarm. The simulated & optimized computer model of the synthesized composite (Cd-S & Polyacrylamide) using density functional theory and performed several analyses. HOMO-LUMO and correspondingly obtained other electronic parameters were evaluated, which revealed that band gap of the synthesized composite material tends to decrease upon increasing the level of water molecules owing to be better humidity sensing mechanism, and therefore, can be used as humidity sensor.

The present paper reports deviation in the intensity of light transmitted through the film of ZnO spherical nanostructure (SNSs) with the exposure of humidity at room temperature. For this purpose, the precursor of ZnO SNSs was prepared and used for coating thin film on borosilicate substrates. The efficient dye-sensitized solar cells (DSSCs) are promisingly low-cost molecular solar cell devices. ZnO SNSs are promising materials used to use to create photoanodes for DSSCs. The film was then investigated using SEM, HR-TEM, XRD and UV–visible transmittance techniques. Further, it was employed as transmission based optical humidity sensor, the maximum sensitivity of which was found a ∼ 1.81 μW/%RH with response and recovery time of 36 s and 124 s respectively. The sensor showed ∼97% reproducible results. The fabricated ZnO SPSs based DSSC shows a short circuit current density ( J s c ) of 3 mA/cm2, open circuit voltage ( V o c ) of 0.62 V and efficiency (ɳ) of 1.3% at one sun condition.

This paper reports the investigation of transmitted power through the nanostructured scandium polyacrylate (Sc(III) PAcr) deposited on flat borosilicate substrates to examine the adsorption/desorption of humidity at room temperature. For this purpose, the precursor of Sc(CH2 = CH-COO)3 was prepared and used for film deposition. The film was then investigated using scanning electron microscope (SEM) and UV–Visible (Vis) absorption techniques. SEM showed the spherical-shaped clusters of the material. Energy band gap of the film was estimated as 3.887 eV by UV–Vis spectrophotometer. Transmission electron microscope revealed the minimum grain diameter of ~21 nm and selected-area electron diffraction showed its polycrystalline nature. From Zeta nanosizer, minimum particle size was found as 18 nm. Fourier transforms infra-red spectroscopy confirmed the bond formation in the material. The surface area analysis shows that the pore volume of Sc(III) PAcr is 0.15 cm3/g, which is quite small, whereas the surface area and mean pore radius of the spherical structure are 60.1 m2/g and 41.2 A, respectively. The film was employed as transmission-based opto-electronic humidity sensor. Maximum sensitivity was found as 2.1 $\mu \text{W}$ /%RH with 89% reproducibility. Response and recovery times of the sensor were found as 25 and 155 s, respectively.

The present paper reports the investigation of transmitted power through the nanostructured zinc (II) nitrate polyacrylamide deposited substrate to investigate the adsorption/desorption of humidity at room temperature. For this purpose, the precursor of Zn(NO3)2·(AAm)4·2H2O was prepared and used for the deposition of films on borosilicate flat substrates. The film was then investigated using SEM, XRD and UV–Vis absorption techniques. Scanning Electron Microscope showed the macroporous nature of the film with multiple pores in situ. XRD revealed the nature of monomer and polymer. Energy band-gap of the film was estimated as 3.865 eV by UV–Vis spectrophotometer. SAED confirmed the crystalline nature of the material. From Zeta nanosizer, the minimum range of particles was found as 5–20 nm. The film was employed as transmission based opto-electronic humidity sensor. Maximum sensitivity was found as 1.831 µW/%RH. Response and recovery times of the sensor were found as 250 and 37 s respectively. Experiments were repeated time to time and found that the sensor was ~ 96% stable after a long run. Thus the investigated opto-electronic sensor being polymeric is flexible in nature.