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In this study, magnetite (Fe3O4) was composited with graphene (Gr) and used as a non-enzymatic glucose sensor material based of surface plasmon resonance (SPR). The Fe3O4 nanoparticles were succesfully synthesized by ultrasonic co-precipitation method while variation composition of composite samples was successfully prepared at room temperature by varying the concentration ratio of graphene and Fe3O4. The resulting composites have good crystallinity and purity with Fe3O4 nanoparticles attach on the graphene surface. The commercial gold (Au) chip with a thickness of 50 nm was modified with a composite by depositing the various compositions of the composite on the Au chip surface using a spin coater. The most optimal SPR response was shown by the Fe3O4-Gr (3:1) sample with a shift in resonance intensity of 18.2 r.u in detecting 5 mM of glucose. Moreover, the detection limit of the synthesized sensor reaches 0.1995 mM and has good stability at 20 measurement cycles.

Due to its harmful nature, carbon monoxide (CO) should be detected at low temperature and in a wide range of CO concentration. A sensor based on WO3–graphene nanocomposite synthesized by the solvothermal method has been developed. Based on material characterizations, the synthesized monoclinical WO3 has a nanowire shape. The presence of graphene interestingly promoted the formation of the WO3 hexagonal structure as a minor phase in the composite. The gas sensor measurements were carried out at three different temperatures, 300 °C, 150 °C, and room temperature. It was found that at 300 °C, the composite with ratio WO3:graphene 2:1 or WG21 produces a 21.5 response value to 10 ppm of CO, which is higher than the other composites. The response and recovery times of WG21 are 16 and ∼4.4 min, respectively. The WG21 nanocomposite was also found to show a good sensitivity in the range concentration of 10–300 ppm.

This work reports on sonochemical synthesis of carbon paste electrodes modified with magnetic Fe3O4/graphene nanocomposites as a label-free electrochemical biosensor for prostate-specific antigen detection. To optimize their properties as a biosensor, the compositions of both Fe3O4 and graphene were varied. The as-synthesized nanocomposites possess good crystallinity and purity with Fe3O4 nanoparticles attached onto the graphene surface. From voltammetry measurements, the modified electrode shows an increase of reduction peaks as compared to the bare electrode which promisingly led to a more sensitive biosensing detection. The modified electrode was then used for biomarker detection through the immobilization of the anti-prostate-specific antigen (anti-PSA) antibodies onto it. The results showed that the electrochemical signal increased linearly against PSA concentration, from 1 to 150 ng/mL, with a detection limit of 0.38 ng/mL. Having all these characteristics, the Fe3O4/graphene nanocomposites offer a promising path towards the development of highly sensitive prostate biosensors, especially for cancer detection.

In this work, wearable resistive gas sensors based on hybrid graphene/zinc oxide (ZnO) nanocomposites were fabricated on a flexible cotton fabric and employed to monitor odorless and colorless carbon monoxide (CO). Dip-coating and chemical bath deposition (CBD) was used to deposit the graphene layer and grow the ZnO nanorods, respectively. The films were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-Ray diffraction (XRD) to investigate their morphological structures, elemental composition, and crystal phase, respectively. Those characterizations were also confirming the growth of ZnO nanorods on the already-deposited graphene layer on fabrics. From the gas sensor measurements at room temperature, it was revealed that these graphene/ZnO nanocomposites were highly sensitive and selective towards CO gas at low concentration down to 10 ppm. The shortest response and recovery times of the sensors were measured to be 280 s and 45 s, respectively. Moreover, in comparison to bare graphene sensors, the surface modification by ZnO nanorods could obviously enhance the sensing response by up to 40% (i.e., doubled sensitivity). These flexible hybrid sensors are therefore expected to be a promising alternative for the existing rigid CO sensors in the market by offering unique nanostructures, low-cost fabrication, high flexibility, and good sensing performances.

Highlights Various advanced strategies for improving gas sensing performances of molybdenum-based nanostructures are reviewed.The plausible mechanism of enhanced gas sensing properties from each strategy is discussed.The conclusive outlook, challenge, and suggestions for future development toward marked commercialization of molybdenum-based gas sensing devices are provided., Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications. Particularly, molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunable structural and physicochemical properties that meet sensor requirements. These materials have good durability, are naturally abundant, low cost, and have facile preparation, allowing scalable fabrication to fulfill the growing demand of susceptible sensor devices. Significant advances have been made in recent decades to design and fabricate various molybdenum oxides- and dichalcogenides-based sensing materials, though it is still challenging to achieve high performances. Therefore, many experimental and theoretical investigations have been devoted to exploring suitable approaches which can significantly enhance their gas sensing properties. This review comprehensively examines recent advanced strategies to improve the nanostructured molybdenum-based material performance for detecting harmful pollutants, dangerous gases, or even exhaled breath monitoring. The summary and future challenges to advance their gas sensing performances will also be presented.

Present-day science indicates that developing sensors with excellent sensitivity and selectivity for detecting early signs of diseases is highly desirable. Electrochemical sensors offer a method for detecting diseases that are simpler, faster, and more accurate than conventional laboratory analysis methods. Primarily, exploiting non-noble-metal nanomaterials with excellent conductivity and large surface area is still an area of active research due to its highly sensitive and selective catalysts for electrochemical detection in enzyme-free sensors. In this research, we successfully fabricate Metal-Organic Framework (MOF) FeBDC-derived Fe3O4 for non-enzymatic electrochemical detection of glucose. FeBDC synthesis was carried out using the solvothermal method. FeCl2.4H2O and Benzene-1,4-dicarboxylic acid (H2BDC) are used as precursors to form FeBDC. The materials were further characterized utilizing X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). The resulting MOF yields good crystallinity and micro-rod like morphology. Electrochemical properties were tested using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) with a 0.1 M of Phosphate Buffer Saline (PBS pH 7.4) solution as the supporting electrolyte. The measurement results show the reduction and oxidation peaks in the CV curve of FeBDC, as well as Fe3O4. Pyrolysis of FeBDC to Fe3O4 increases the peak of oxidation and reduction currents. The Fe3O4 sample obtained has a sensitivity of 4.67 &micro, A mM&minus, 1.cm&minus, 2, a linear range between 0.0 to 9.0 mM, and a glucose detection limit of 15.70 &micro, M.

Nowadays, the anthocyanin natural dye has been used as a good photosensitizer for TiO2 solar cells due to its availability as well as its performance. However, the dye still has a problem regarding its narrow absorbance at 550 nm. The aim of study will extend the dye’s absorbance up to NIR spectrum, so that it will increase the TiO2 solar cell performance. The cyanidin-3-glucoside-7- diphenilamine-2'-acrylic acid (CGDA) will be introduced as the new modification of D-π-A functional material in anthocyanin dye. The investigation of the material has been carried out by the density functional theory of TD-DFT/UB3LYP/6-31+G(d,p) level. The findings show that first; the dye absorbance has broadened up to 885 nm due to the reduction of gap energy and the increase of electronic transition probabilities from 84.7% to 96.0%. Second, the molecular orbital analysis shows that both diphenylamine and acrylic acid perform as promising donor and acceptor groups for anthocyanin. Third, CGDA has the light harvesting efficiency of 46.7% surrounding NIR spectrum area. Finally, the NIR anthocyanin dye possessing HOMO of -5.536 eV and LUMO of -2.886 eV fulfills the criteria of both the effective charge transfer from LUMO dye into conduction band TiO2 and the good dye regeneration by the electrolyte redox.

Magnetite (Fe 3 O 4 ) nanoparticles from iron sand as starting materials have been successfully synthesized by using coprecipitation- ultrasonicirradiation methods. This paper reports the preparation and optimization result of ultrasonic frequency and stirring rate during the synthesis process. The frequencies of ultrasonic conducted in this research are 300, 400 and 400 kHz. The stirring rates performed in the synthesis process are varied from 500 to 900 rpm. The qualitative analysis by using X-Ray Diffractometer (XRD) showed that the structure of Fe 3 O 4 nanoparticles have a same phase with ICCD No. 75-0449. Moreover, the quantitative analysis by using Debye-Scherer equation showed that the crystallite size of Fe 3 O 4 ranging from 21 to 25 nm depend on the ultrasonic frequency and stirring rate. Meanwhile, the transmission electron microscopy (TEM) result revealed that the Fe 3 O 4 tend to form spherical shape with little agglomeration on the morphology of the Fe 3 O 4 . The magnetic properties of Fe 3 O 4 were investigated by using vibrating sample magnetometer (VSM). The VSM measurement result showed that the Fe 3 O 4 have saturation magnetization (Ms), remanent magnetization (Mr) and coercivity field (Hc) at 25 emu/gram, 6,0562 emu/gram, and 0,0108 T, respectively. Based on the magnetic characterization, the Fe 3 O 4 nanoparticles have a potential to be appliedin biomedical field.

Biosensors based on nanomaterial have attracted so much interest due to their high-performance potential. Its structure allows the biosensor to have high sensitivity and selectivity. Nanopillar (NPLA) is one class of material with unique properties, especially optical properties. Its unique properties cause it to be the structure that has drawn so much attention recently. The advantages owned by NPLA, including high surface area and its unique optical properties, provide the possibility to build a sensitive layer for a biosensor that is very promising for health and medical applications. This structure also offers low-cost fabrication and can be produced on a mass scale due to its compactness and reliability. Furthermore, NPLA has a high capability to be used as optical biosensors. This article reviews diverse fabrication routes of NPLA structures. Their applications in biomolecular detection, mainly by optical approach, are highlighted. The comparison of the limit of detection of the different kinds of optical biosensors is also presented. The focus of this article lies on the possibilities of NPLA structure integrating into biosensors on-chip.

Cu2ZnSnS4 (CZTS) material has emerged as an attractive material for the absorber layer in solar cells application. CZTS has similar properties with its successful predecessor CIGS, but CZTS offers the advantage of low-cost constituents, material abundance, and nontoxicity. We fabricated CZTS thin-film using non-vacuum solution-based process and then the deposition process using the spin-coating technique in the present work. Afterward, we observed that the CZTS thin-film was successfully fabricated with kesterite structure crystal with an optical bandgap of 1.56 eV. We also confirmed that the CZTS thin-film exhibit a high light-harvesting efficiency at a low wavelength suitable for the solar cells application's absorber layer.

Natural dyes extracted from black rice are used as sensitizer for dye sensitized solar cell. The anthocyanin extracted with various pH in acidic and neutral coditions. Preparation of fotolectrode TiO2 film using doctor blade method and resulting average grain size 33,9 nm using X-Ray Diffractometer. Characterization of morphology and cross-section film TiO2 is confirmed by Scanning Electron microscopy (SEM). Optical absorption using UV-Visible Spectroscopy to obtain spectrum absorbance of anthocyanin in various pH. The current-voltage (J-V) characterization shows the performance DSSC have a match relation to the optical absorption. The best absorption of anthocyanin obtained at pH 6 as well as conversion efficiency reaches 2.26% at this pH condition.

In this work, (002) oriented ZnO thin film for carbon monoxide (CO) gas sensing application has been synthesized on the glass substrate using diethanolamine (DEA) as a chelating agent by two-step process. First, the seed layers were formed at a glass substrate using dip coating method, and second, ZnO nanostructure was grown using Chemical Bath Deposition (CBD) at low temperature. The structural and orientation of ZnO films were confirmed using x-ray Diffraction (XRD) while their morphologies and size were analyzed using Scanning Electron Microscopy (SEM). Diffraction pattern showed that the resulting film has wurtzite structure and an extremely sharp (002) peak was found, indicated that the ZnO nanostructure was growth along (002) orientation. The SEM image showed that the (002) oriented ZnO has hexagonal shape nanorods which vertically aligned. It was found that the diameter and length of ZnO nanorods were 71–96 nm and 666 nm, respectively. The gas sensing performance was investigated at various temperatures (160 °C, 200 °C, 250 °C, and 300 °C) and CO gas concentrations (10, 30, 50, 70 and 90 ppm). The results showed that the highest response, 53.25% was obtained at 200 °C toward 90 ppm CO gas. The response and CO gas concentration have a good linearity relationship which indicated that the (002) oriented ZnO has high potential for high sensitive CO gas sensor.

The development of non-noble-metal sensing material for sensitive and selective detection of uric acid with a simple material synthesis technique has not been frequently reported in recent years. Taking advantage of the unique properties of highly porous materials of Metal-Organic Frameworks, which incomparable in their structural diversity and tunability as well as their range of chemical and physical properties, open up a chance for developing novel nanomaterial for electrochemical sensor applications. In this article, we evaluated MOF-71 as a sensing material on a glassy carbon electrode (GCE) in a three-electrode system for electrochemical detection of uric acid. The MOF-71 was synthesized by a simple solvothermal method. Its structural characteristics that are examined by scanning electron microscopy and X-ray diffraction confirmed the successful formation of MOF-71. Cyclic voltammetry (CV) and differential pulse voltammetry DPV) analysis showed the successful uric acid detection in a phosphate buffer solution and showed good electrochemical catalytic activity toward uric acid. DPV was selected for the determination of uric acid with a sensitivity of 0.4811 mA.mM-1.cm-2, the detection range of 50.0- $1000~\mu \text{M}$ , and detection limit of $15.61~\mu \text{M}$ at an S/N = 3.

The extraction of chlorophyll pigment of Syngonium podophyllum Schott leaves which is used as natural dyes in this DSSC devices. The use of dye from nature with its simple production process is very effective to reduce DSSC production cost. Besides being used as a natural dye, chlorophyll can also be used as an alternative counter electrode. Chlorophyll that is used as a counter electrode has been through chemical activation and carbonization processes. The characterization were done using Uv-Vis, Cyclic Voltametry and DSSC device under solar simulator. Characterization of chlorophyll absorbance using UV-Vis has resulted in typical absorbance peak at visible light wavelength of 447 nm and 666 nm. The Tauc equation analysis of the Uv-Vis characterization showed 1.91 eV energy gap of chlorophyll. Chlorophyll carbonized dye is used as an alternative to Pt counter electrode. Carbonized chlorophyll dye resulted in lower conversion efficiency of 0.308% with HSE electrolyte.

The aim of this research is producing the electrochemical sensor, especially for working electrodes based on the nanocomposites of multi-walled carbon nanotube (MWCNT) and magnetite (Fe3O4) nanoparticles from iron sands. The sonochemical method by ultrasonic horn was successfully used for the synthesis of the nanocomposites. The characterizations of the sample were conducted via X-Ray Diffractometer (XRD), Fourier Transform Infra-Red (FTIR) Spectrometer, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) method for surface area, Vibrating Sample Magnetometer (VSM) and Cyclic Voltammetry (CV). The analysis of X-Ray Diffraction (XRD) pattern showed two phases of crystalline, namely MWCNT and Fe3O4, peak of MWCNT comes from (002) plan while peaks of Fe3O4 come from (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1), and (4 4 0) plans. From XRD data, MWCNT has a hexagonal structure and Fe3O4 has inverse spinel cubic structure, respectively. The FTIR spectra revealed that the functionalization process of MWCNT successfully generated carboxyl and carbonyl groups to bind Fe3O4 on MWCNT surfaces. Moreover, the functional groups of Fe-O bonding that showed the existence of Fe3O4 in the nanocomposites were also detected in those spectra. Meanwhile, the SEM and TEM images showed that the nanoparticles of Fe3O4 attached on the MWCNT surface and formed agglomeration between particles due to magnetic forces. Through Brunauer-Emmett-Teller (BET) method, it is identified that the nanocomposite has a large surface area 318 m2/g that makes this material very suitable for electrochemical sensor applications. Moreover, the characterization of magnetic properties via Vibrating Sample Magnetometer (VSM) showed that the nanocomposites have superparamagnetic behavior at room temperature and the presence of the MWCNT reduced the magnetic properties of Fe3O4. Lastly, the electrochemical characterization with Cyclic Voltammetry (CV) proved that Fe3O4/MWCNT nanocomposites with iron sands as the starting materials have high sensitivity and serve as excellent electron transfer materials. Based on the results of the research, the Fe3O4/MWCNT nanocomposites from iron sands are much recommended for electrochemical sensor.

Nano composite MWCNT-ZnO thin films have been synthesized to investigate their methanol sensing properties. MWCNTs have a large surface area, many adsorption site, are sensitive to their chemical environmental, and can be operated at room temperature. While zinc oxide was popular as gas sensor because its easy to fabricate, fast response, easy to control their morphology, and has unique properties depend on their size and shape. In this study, combination of MWCNT and ZnO were made to get their advantages. These nano composites were prepared with weight percent ratio 63:37. MWCNT-ZnO were synthesized by reflux method at 197°C in ethylene glycol. Heat treatment at 300°C were done to obtain powder of nano composite. X-ray diffraction (XRD) and scanning electron microscope were used to investigate the crystal phase and morphology of nano composite. Sensing behavior was investigated at 100°C to 300°C. The best response of 200 ppm methanol occurred at 300°C.

The effect of Al-doped ZnO (AZO) to the sensitivity improvement of ethanol vapor sensor was investigated. The pure ZnO and AZO thin films were synthesized by chemical bath deposition method. Analysis of the crystal structure, chemical composition, and morphology of the samples are carried out using X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). XRD results show that the phase formed is polycrystalline Zn, while the EDS measurements show that the composition of after synthesized AZO were 1.48 at%, 2.90 at%, and 3.55 at%. The SEM results showed flowerlike microstrcuture and nanosheet shaped are formed in the resulting thin films, which are captured by the formation of sheets of transparent structure in AZO. Moreover, the resulting ZnO and AZO sensors were exposed to the different concentration of ethanol vapor as much as 200, 400, and 600 ppm, respectively. The measurement of vapor sensor system performance was tested to analyze the sensitivity and the responsiveness of the AZO thin films. The sensors have highest sensitivity at certain amount of Al doping. It is obtained that the optimum sensitivity of the sensor is investigated at the sample of 2.9 at% Al-ZnO. The sensitivity for pure ZnO sample at concentration of 200, 400, and 600 ppm of ethanol were 70.88%, 78.21%, and 88.57%, respectively. The highest sensitivity for AZO samples is 95.29% at low ethanol concentrations (200 ppm) and 96.68% at the high concentration (parts per million), respectively.

The morphology of porous anodic alumina (PAA) formed by anodizing in inorganic electrolytes is reported. An impure aluminum was anodized in sulfuric acid, phosphoric acid and chromic acidat room temperature with a constant applied potential 2 – 30 V. The formation of porous anodic alumina was carried out by one and two steps anodization. It is clearly noted that anodizing impure aluminum at room temperature provide higher kinetic of oxide dissolution compared to oxide growth. Two steps anodizing aluminum in sulfate electrolyte always resulted in random porous alumina, while phosphate electrolyte provided strong anodization producing irregular porous alumina with average diameter of 61.6 nm. Two steps anodizing aluminum in chromate electrolyte produce better pore ordering with relatively large size pore distributions. The average pore diameter of alumina increases linearly with applied voltage, with proportionality factor lp 0.83 nmV-1. Annealing the sample increased the interpore distance, removed stresses providing lower activation energy for pore formation.

Metal oxide semiconductors materials such as zinc oxide (ZnO) are often used in the fabrication of chemoresistive gas sensors, but ZnO materials require high operating temperatures to operate. In another side, carbon nanotubes (CNT) have many distinct properties and recently have been exploited as the next generation of sensors, including chemoresisitive type gas sensors. This study was aimed to investigate the performance of MWNT-ZnO composites as SO2 gas sensitive layer. By fabricate composites of MWNT and ZnO, have been obtained a sensitive layer that can be utilized for application as gas sensitive layer with relatively lower operating temperature. A sensitive layer of MWNT-ZnO based composites have been successfully fabricated on a alumina substrate and several characterization techniques has been performed, i.e. XRD, SEM and EDS to study the formed crystalline phase, the morphology of the nanostructures, and the elemental composition of synthesized composites. MWNT-ZnO sensitive layer was tested by exposure to SO2 gas at various operating temperatures and gas concentration. From the performance testing results, it could be found that the composite materials have a prospective as a gas sensor at lower operating temperature with short response time and good sensitivity.

The composites of multi-walled carbon nanotube (MWCNT) and magnetite (Fe3O4) nanoparticles from iron sand were successfully prepared via the sonochemical route. In this experiment, the MWCNT-Fe3O4 nanocomposites were prepared with different compositions of MWCNT (0.01%, 0.02%, and 0.04%) with the constant composition of Fe3O4 particles. The characterizations were performed by means of X-Ray Diffractometry (XRD), Fourier Transform Infra-Red (FTIR) Spectrometer and Scanning Electron Microscopy (SEM) integrated with Energy Dispersive X-Ray (EDX). The XRD data analysis showed that the Fe3O4 crystallize in spinel structure in nanometric size. Furthermore, the crystallinity of the samples tended to reduce by increasing the MWCNT compositions. The SEM images showed that Fe3O4 tend to agglomerate in nanometric size. The FTIR spectra detected the functional groups of Fe-O bonding that showed the existence of Fe2+ and Fe3+. In the composites, the Fe3O4 nanoparticles were physically mixed with the MWCNTs constructing a unique structure. The as prepared MWCNT-Fe3O4 nanocomposites have the potential for bio-applications.

Sensitivity issue becomes a common problem on Electrical Impedance Tomography. One effort to overcome this issue is through inducing a magnetic field. It needs proper inducer coil configuration in order to produce a good reconstruction result. In this study, inducer coil configuration is obtained to 10 configurations of a rectangular object. Reconstruction results showed that the better results achieved through increasing of induction numbers and in 50 percent of shifting between each induction.

The adsorption characteristic of natural dye has been studied on harvesting light using purification process. The purification process used for separation pigment photosynthesis of syngonium leafs was called fractionation. The first fractionation of the dye contains pigment of β- carotene . The absorpton spectrum of β-carotene has been investigated by using Uv-Vis spectroscopy. The Fourier Transform Infrared revealed that the binding of the dye was on the surface of TiO2. Analysis absorbance and energy gap of the dye has been investigated by using Uv-Vis spectroscopy and Tauc relation. The cells were illuminated under 100 mW/cm2 AM 1.5 condition. The performance of the cells with sensitized the fractionation dye has a short circut current density (Jsc) of 0.27 mA/cm2, an open circuit photovoltage (Voc) of 0.4V, and Fill Factor (FF) of 68.89%. Furthermore, the overall efficiency of DSSC is 0.074%. The low efficiency for the fractionation cell based dye sensitized solar cells due to the weakness of interaction between dye molecule and the surface of TiO2.

A non wovenpolycarbosilane (PCS) fibers was successfully produced by electrospinning and processed by a thermal curing and electron beam curing. PCS solution composition was 1.2 g/ml PCS with 30% N,N-dimethylformamide (DMF)/70%toluene and the applied voltage at 10 kV in spinning process. The PCS fibers with average diameter ~8 µm cured by thermal at 200 o C with varied time (1, 1.5 and 2 hour(s)) were compared to thefiber that processed by electron beam curing with varied absorbed doses(approximately 23, 139, 231, 324, 509 and 787 kGy). The structural changes of PCS fibers after curing process was analyzed by FTIR. The fibers cured by thermal process all shows oxidation curing and fibers cured by electron beam all shows non-oxidation curing. The fibers cured by thermal process with holding time at 1 hour and cured by electron beam with absorbed doses at 231 kGy show the higher crosslinking degree. The fibersthat curing by electron beam are more brittle compared to the fibers that curing by thermal process. The empirical chemical formula for pyrolyzed fiber are SiO0.49C0.51for cured at 1 hour, SiO0.53C0.47for cured at 1.5 hours and SiO0.61C0.39for cured at 2 hours.

SnO2 thin films were deposited on glass substrate by chemical bath deposition (CBD) with stannous chloride (SnCl2..2H2O) as a precursor and urea (CO(NH2)2) as a buffer. X‐Ray Diffraction (XRD) are used to characterize the structure of the films; the surface morphology of the films were observed by Scanning Electron Microscope (SEM). Using this techniques, we specify the effect of stannous chloride concentration and weight ratio of urea/H2O on the crystallinity and morphology of these films. The rutile structure corresponding (110), (101) and (211) planes of SnO2 is obtained. The increasing of stannous chloride concentration and the decreasing weight ratio of urea/H2O is found to improve the crystallinity of the film. The average diameter of grain size is about 96 nm.

Al doped ZnO (AZO) is done to understand the effect of Al dopant on ZnO. The sensor response condition will be analyzed for ethanol detection. Chemical Bath Deposition (CBD) method is used to fabrication pure ZnO and AZO thin films. Al dopant concentrations used in this study is 2.9 at% Al. The crystallinity, composition and morphology were investigated by using XRD, EDS and SEM. The ZnO and AZO gas sensors were exposed to different concentrations of ethanol at room temperature, 2.5%, 5% and 7.5% volume ethanol, respectively. The sensor response at low concentrations (2.5% V) for pure ZnO sample is 70.88% and 88.57% for high concentrations of ethanol (7.5% V). The highest sensor response for AZO sample is 95.29% at low concentrations (2.5% V) and 96.68% V at the high concentration (7.5% V).

Nanosheets ZnO thin films were successfully fabricated on alumina substrate by chemical bath deposition method using Zinc Nitrate Tetra hydrate as precursor. Films were annealed at 300 °C for 30 minutes and observed by X‐Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X‐Ray Spectroscopy (EDS) to know crystal phase and structure, surface morphology, and elemental composition respectively. The gas sensing performance of ZnO thin films was studied on exposure to ethanol gas sensing in various concentration (300 and 600 ppm). The films showed higher response towards ethanol gas sensing at optimized temperature of 250 °C and exhibited excellent sensitivity of 62.45% upon exposure 300 ppm and 69% upon exposure of 600 ppm ethanol gas sensing. Further, the response and recovery times of ZnO thin films to ethanol become shorter at higher operating temperatures. A possible mechanism of ethanol sensing has been explained.