ZnO Nanostructures Research Articles

Effect of Nanostructure Morphology and Concentration on the Piezoelectric Performance of Flexible Pressure Sensor based on PVDFTrFE/ Nano-ZnO Composite Thin Film

Background: The development of high-performance piezoelectric pressure sensors with outstanding sensitivity, good linearity, flexibility, durability, and biocompatibility is of great significance for smart robotics, human healthcare devices, smart sensors, and electronic skin. Thus, considerable progress has been achieved in enhancing the piezoelectric property of PVDF-TrFEbased composite pressure sensors by adding various ZnO nanostructures in PVDF-TrFE polymer acting as a nucleating agent and dielectric material. Aims: In this work, flexible pressure sensors with a sandwich structure based on PVDFTrFE/ nano-ZnO composite sensing film were fabricated using a simple spin-coating method and post-annealing process, while electrospinning and high-voltage polarization processes were not adopted. Methods: Poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)/nano-ZnO composite films were prepared via spin coating to fabricate flexible piezoelectric pressure sensors. ZnO nanoparticles (ZnO NPs), tetrapod ZnO (T-ZnO) and ZnO nanorods (ZnO NRs) were used as nano-fillers for piezoelectric PVDF-TrFE, to enhance the beta-crystal ratio as well as the crystallinity of PVDF-TrFE. The structural and surface morphologies of the composite films were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results: Among three different types of ZnO nanostructures with a concentration range (0-7.5 wt%), the sensor with 0.75 wt% ZnO NRs nanofiller exhibits a maximum output voltage of 1.73 V under an external pressure of 3 N and a maximum sensitivity of 586.3 mV/N at the range of 0-3 N. Further, the sensor can generate a clear piezoelectric voltage under bending and twisting deformation as well as compression and tensile deformation. Conclusion: To summarize, the addition of different concentrations of nano-ZnO can remarkably improve the piezoelectric performance of the composite sensor, and ZnO NRs can achieve better piezoelectric properties of the sensor as compared to ZnO NPs and T-ZnO. In addition, the sensor with 0.75 wt% ZnO NRs as nanofiller has the highest piezoelectric response, which is about 2.4 times that of the pure PVDF-TrFE sensor. It is demonstrated that the sensor has great potential applications in wearable health monitoring systems and mechanical stress measurement electronics.

Investigations of adsorption and photoluminescence properties of encapsulated Al–ZnO nanostructures: Synthesis, morphology and dye degradation studies

This study focuses on the solution combustion approach to examine the nanostructures of undoped and doped ZnO with different concentrations of Al (0.1 % and 0.2 %). Various physical techniques were utilized to characterize the synthesized nanoparticles. X-ray diffraction (XRD) revealed the crystalline materials, while scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) findings confirmed the products with particle size and the insertion of Al into the ZnO lattice. Fourier-transform infrared spectra (FTIR) confirmed the presence of different functional groups in the obtained material. The results indicate that Al-doped ZnO (Al–ZnO) nanoparticles show promising properties for optoelectronics and photoluminescence. Photoluminescence analysis indicated that an increase in Al3+ (0.2 %) concentration resulted in a decrease in peak intensity and an increase in the full width at half maximum. The band gap was calculated using the Taucs plot. The study also highlights the effectiveness of Zn1-xAlxO nanostructures in degrading organic pollutants, particularly in adsorbing Malachite Green (MG) dye. Among the samples, the 0.2 % Al-doped ZnO exhibited superior dye degradation efficiency due to its enhanced adsorption capacity and smaller particle size, as evidenced by multilayer adsorption capacity and chemisorption during the degradation process. This study provides valuable insights into the potential applications of Al-doped ZnO nanoparticles in various environmental and technological fields, emphasizing their significance in the degradation of organic pollutants.

Enhanced H2S gas sensing utilizing UV-assisted In2O3@ZnO nanosheets

In the realm of environmental protection, there is a growing demand for efficient and environmentally friendly gas sensors. In this study, we employed a simple hydrothermal method to synthesize nanosheets composed of zinc oxide (ZnO)-doped indium oxide (In2O3), utilizing zeolitic imidazolate framework-8 (ZIF-8) as a precursor. These nanosheets demonstrated exceptional sensitivity and selectivity in detecting hydrogen sulfide (H2S) gas. A comprehensive analysis of crystal structure, chemical states, elemental composition, surface area, and morphology was conducted. Brunauer–Emmett–Teller (BET) surface area measurements to assess the materials' textural properties revealed that the nanosheets labeled In2O3/0.1ZnO possessed a high specific surface area of 49.02 m2/g, greater than the 45.65 m2/g of pure In2O3 nanosheets, a crucial factor contributing to the observed exceptional sensitivity and selectivity in detecting H2S gas. Particularly noteworthy is the substantial improvement in gas detection response from 109.9 to 146.2 (approximately 24.7 %) observed in the In2O3/0.1ZnO material under UV irradiation at the optimal temperature of 250 °C. This enhancement emphasizes the material's potential for superior gas detection. The incorporation of ZIF-8-derived ZnO nanostructures played a crucial role in creating additional active sites, further enhancing the gas-sensing capabilities. Importantly, this innovative synthesis technique ensures the production of clean, non-toxic materials, aligning with environmental conservation objectives, and holds promise for achieving heightened sensitivity and selectivity in the detection of environmentally harmful gases.

EFFECT OF NIOBIUM DOPANT CONCENTRATION ON ZNO NANOSTRUCTURES ON SI POROUS SUBSTRATE

Zinc oxide (ZnO) nanostructures have gained popularity in sensor technology due to their unique properties and facile device integration. However, the intrinsic optical and electrical properties of ZnO are suboptimal for direct industrial applications, necessitating enhancements through doping. This study investigates the impact of niobium (Nb) doping concentrations on the physical, optical, and electrical characteristics of ZnO nanostructures. FESEM analyses indicate successful deposition of ZnO on silicon nanoparticles substrates, with nanostructure sizes peaking at 88 nm and 115 nm for 6% and 8% Nb dopant concentrations, respectively. XRD results suggest that the structural integrity of the nanostructures is maintained up to a 10% doping level, with an optimal concentration at 6%. UV-Vis spectroscopy shows a shift in the absorption peak into the visible range and a decrease in maximum reflectivity from 47.5990% at 2% doping to 40.9205% at 6% doping, indicating enhanced light absorption suitable for optoelectronic applications. Electrical measurements reveal that a 6% Nb dopant concentration yields the lowest resistivity and highest conductivity among the tested samples. These findings underscore the potential of Nb-doped ZnO nanostructures in improving the performance of optoelectronic devices through tailored doping strategies.

Investigation of the Structural, Electrical, and Optical Properties of Co-Precipitation-Synthesized Aluminum-Doped ZnO Nanostructures

Abstract: This study examines the Structural, Electrical, and Optical characteristics of Zinc Oxide substituted with aluminum (AlxZn1-xO; x = 0, 0.02, 0.04, 0.06, 0.08). The coprecipitation technique is used to synthesize the powders, and X-ray diffraction (XRD) is used to analyze the powders' structural properties. Field Emission Scanning Electron Microscopy (FESEM) is used to study the morphological characteristics of the produced powders. The UV-visible absorbance spectrum (UV-Vis.) was used to assess the particles' optical characteristics. Using photoluminescence (PL) spectra, the effects of morphology on the optical and electrical characteristics of produced powders were examined. The XRD patterns verified that a single-phase hexagonal wurtzite structure formed for each sample. The powders' FESEM pictures reveal how, as the Al concentration increases, the particles' morphology alters from hexagonal to spherical. The synthesized samples have crystallite sizes between 19 and 26 nm. The predictable variations noticed with Al3+ concentration are consistent with Al3+ incorporation into the ZnO lattice, as confirmed by the UV-Vis spectroscopy measurements.

Nanostructured ZnO thin film to enhance gutta-percha’s adhesion to endodontic sealers

BackgroundGutta-percha (GP) combined with an endodontic sealer is still the core material most widely used for tridimensional obturation. The sealer acts as a bonding agent between the GP and the root dentinal walls. However, one of the main drawbacks of GP core material is the lack of adhesiveness to the sealer. ZnO thin films have many remarkable features due to their considerable bond strength, good optical quality, and excellent piezoelectric, antibacterial, and antifungal properties, offering many potential applications in various fields. This study aimed to explore the influence of GP surface’s functionalization with a nanostructured ZnO thin film on its adhesiveness to endodontic sealers.MethodsConventional GP samples were divided randomly into three groups: (a) Untreated GP (control); (b) GP treated with argon plasma (PT); (c) Functionalized GP (PT followed by ZnO thin film deposition). GP’s surface functionalization encompassed a multi-step process. First, a low-pressure argon PT was applied to modify the GP surface, followed by a ZnO thin film deposition via magnetron sputtering. The surface morphology was assessed using SEM and water contact angle analysis. Further comprehensive testing included tensile bond strength assessment evaluating Endoresin and AH Plus Bioceramic sealers’ adhesion to GP. ANOVA procedures were used for data statistical analysis.ResultsThe ZnO thin film reproduced the underlying surface topography produced by PT. ZnO thin film deposition decreased the water contact angle compared to the control (p < 0.001). Endoresin showed a statistically higher mean bond strength value than AH Plus Bioceramic (p < 0.001). There was a statistically significant difference between the control and the ZnO-functionalized GP (p = 0.006), with the latter presenting the highest mean bond strength value.ConclusionsThe deposition of a nanostructured ZnO thin film on GP surface induced a shift towards hydrophilicity and an increased GP’s adhesion to Endoresin and AH Bioceramic sealers.

Green Synthesis of ZnO Nanostructures and Their Antibacterial Activity Against Catfish Pathogen

Due to its antibacterial activity against clinical bacterial pathogens at the time of tissue development, zinc oxide (ZnO) is considered one of the most important metal oxide nanostructured materials. In this study, ZnO nanostructures were prepared using Aloe vera gel juice, which is easy, inexpensive, and ecofriendly. The nanostructures of ZnO were characterized using a variety of analytical techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and dynamic light scattering (DLS). As a result of the XRD study, the hexagonal phase of ZnO with the structure of wurtzite has been identified. ZnO material with high heterogeneity morphology has been observed by SEM analysis. As-prepared ZnO nanostructures were tested for their antibacterial activity against the newly discovered pathogen of catfish. A ZnO sample prepared with a high concentration of Aloe vera gel possessed an inhibition zone of 13.21±0.04 mm, whereas a ZnO sample prepared with a low concentration of Aloe vera juice had an inhibition zone of 6.23±0.02 mm and a pure ZnO sample had an inhibition zone of 3.31±0.03 mm. Furthermore, we examined the effectiveness of the ZnO nanostructures on bacterial strains based on the type of nanoparticles applied to the commercial strains. In addition to their modified surface properties, small particle size, and highly toxic effects for the killingof bacterial cell growth, the Aloe vera juice assisted ZnO nanostructures demonstrated excellent antibacterial activity against the catfish pathogens.

Incorporation of zinc oxide and cobalt doped zinc oxide nano-rods in commercial sunscreen sample to optimize its UV-ray absorption

In the last two decades, the ozone layer in the atmosphere has been depleted, and the sun rays are now more harmful to human skin because they no longer filters it completely. Long-term exposure to harmful ultraviolet rays (UV-rays), which have wavelengths between 220 nm and 380 nm, causes catastrophic damage to skin cells. Sunscreens are therefore absolutely necessary to protect the skin. The co-precipitation method was used to synthesize both pure and cobalt-doped zinc oxide nano structures. In sunscreens, these nanostructures serve as a UV filter. The obtained nano structures have been characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). The ability of a sunscreen sample containing nano structures to yield results for a period of various hours at different temperatures (20 °C, 30 °C, and 50 °C) has been tested. According to XRD results, prepared samples exhibits hexagonal wurtzite crystalline structures and are of 22 nm in size for pure zinc oxide and 20 nm in size for cobalt- doped zinc oxide. SEM was used to find morphologies, i.e., nano rods (NRs) at 200 nm and 2 μm. DRS provided evidence of sunscreen’s endurance, with a 97% absorption of UV-rays at 50 °C for up to 6 h when incorporated with NRs. In order to boost UV-ray absorption in sunscreen, nanotechnology has been successfully applied.

Fe-doped ZnO nanoparticles prepared by high energy ball milling with enhanced sonophotocatalytic performance

Zinc oxidenanostructures were synthesized using a thermal decomposition method and subsequently doped with Fe (III)in this study. Techniques such as X-ray diffraction, Field emission scanning electron microscopy, and Fourier transform infrared spectroscopy were used to investigate the structural and chemical composition of nanomaterials. Fe-doped ZnO was synthesized using a simple, low-cost planetary high-energy ball milling process. The sonophotocatalytic activity of Fe-doped ZnO under visible light and ultrasonic waves was then studied. Another aspect of this study is the utilization of visible light, which is far more accessible and cost-effective than UV light. Malachite green (MG) and phenol were applied as water-soluble contaminants. MG degraded about 87.65% after 1 h in the presence of a Fe-doped ZnO catalyst under visible light and ultrasonic waves simultaneously. Phenolwas degraded by approximately 64.50% under the same conditions.

0, 1, 2, and 3-Dimensional zinc oxides enabling high-efficiency OLEDs

In the pursuit of high-efficiency organic light-emitting diodes (OLEDs), this paper unveils the potential of zinc oxide (ZnO) nanostructures of various dimensions (0,1,2, and 3D), doped in hole injection layer (PEDOT:PSS). Unique enhancements were demonstrated in forms from nanoparticles (0D) to nanowires (1D), nanosheets (2D), and nanoflowers (3D), revolutionizing OLED performance. Specifically, the incorporation of 0D-ZnO doped in PEDOT:PSS resulted in remarkable efficiency improvements of 19 % in maximum power efficacy (PEmax), 19 % in maximum current efficacy (CEmax) and 24 % in maximum external quantum efficiency (EQEmax), compared with the undoped counterpart. Elevating the dimensions to 1D-ZnO (20 nm), when doped in PEDOT:PSS, enabled an increment of 46, 54 and 64 % in PEmax, CEmax and EQEmax, respectively. Furthermore, 2D-ZnO (annealed at 400 °C) doped in PEDOT:PSS achieved notable performance improvements, with enhancements of 24 % in PEmax, 23 % in CEmax, and 28 % in EQEmax. Despite size limitations, 3D-ZnO doped in PEDOT:PSS exhibited enhancements of 11 % in PEmax, 15 % in CEmax, and 20 % in EQEmax. We achieved the best results by integrating 1D-ZnO into PEDOT:PSS, which may be attributed to the small diameter of the 1D-ZnO structure when compared to 0D, 2D, and 3D ZnO, resulting in superior OLED performance. These findings demonstrate the significant potential of ZnO nanostructures doped in PEDOT:PSS in enhancing the performance of green OLEDs, and paving the way for more sustainable, cost-effective, and efficient OLEDs for display and lighting applications. Continued research on ZnO and other inorganic materials holds promise for further advancements in OLED technology and a brighter, more energy-efficient future.

Electrochemical detection of nalbuphine drug using oval-like ZnO nanostructure-based sensor

Monitoring pharmaceutical drugs in various mediums is crucial to mitigate adverse effects. This study presents a chemical sensor using an oval-like zinc oxide (ZnO) nanostructure for electrochemical detection of nalbuphine. The ZnO nanostructure, produced via an efficient sol-gel technique, was extensively characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible spectrophotometry, and fourier transform infrared spectroscopy (FTIR). A slurry of the ZnO nanostructure in a binder was applied to a glassy carbon electrode (GCE). The sensor's responsiveness to nalbuphine was assessed using linear sweep voltammetry (LSV), achieving optimal performance by fine-tuning the pH. The sensor demonstrated a proportional response to nalbuphine concentrations up to 150.0 nM with a good regression coefficient (R2) and a detection limit of 6.20 nM (S/N ratio of 3). Selectivity was validated against various interfering substances, and efficacy was confirmed through real sample analysis, highlighting the sensor's successful application for nalbuphine detection.

Ferromagnetic ZnO nanostructures from an organo zinc complex formulated via Piper Longum L-assisted green synthesis: Multifaceted prospects in photocatalysis, antimicrobial activity, and cell viability studies

Transition metal oxides like ZnO nanostructures are pivotal in various scientific and technological fields due to their chemical stability, high electrochemical coupling efficiency, and broad radiation absorption spectrum. This study offers an in-depth examination of ZnO nanostructures synthesized via the green route using Piper Longum L, emphasizing their photocatalytic efficacy in degrading organic pollutants such as Sulphanilamide and Chromium. The ZnO nanostructures with a rod-like morphology exhibited an average crystallite size of 26 nm and an optical bandgap of 2.8 eV. Solid state structure of ZnO was investigated by Fourier Transform Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD). Zinc in the synthesized organo zinc complex and zinc oxide was estimated to 324.325 and 133.02 ppm, respectively. The saturation magnetization obtained from Superconducting Quantum Interference Device-Vibrating Sample Magnetometer (SQUID-VSM) for organo zinc complex and ZnO is 2.1 × 10−3 and 1.7 × 10−3 emu/g, respectively. These nanostructures achieved 99 and 93 % degradation of chromium (VI) ions present in solutions of two different concentrations in about 30 and 80 min, respectively, under UV and visible radiation, a remarkable achievement. Almost the same efficiency was maintained during three consecutive runs and then deactivation of the catalyst was observed. Additionally, a rapid 84 % degradation of Sulphanilamide was observed in 42 min, underscoring the potential of ZnO nanostructures as efficient photocatalysts for environmental remediation.

ZnO nanostructures with controlled morphological and optical properties for applications as efficient photocatalyst for malachite green degradation

This study aims to comparatively investigate the morphological and optical characteristics of zinc oxide nanoparticles as a function of the preparation conditions. A series of ZnO nanoparticles were synthesized by facile precipitation method at constant temperature, by varying the zinc sources (zinc acetate, zinc nitrate and zinc chloride) or the precipitant nature (hexamethylenetetramine, urea). The structural, morphological and optical attributes of the prepared ZnO samples were assessed by SEM, XRD, FTIR, UV–Vis and photoluminescence analyses. The morphology of the achieved samples varies from spiky sticks to hexagons or foils with irregular shapes, observing that urea favour the development of two- or three-dimensional ZnO nanostructures, while hexamethylenetetramine predominantly triggered the formation of highly organized one-dimensional structures. The XRD patterns of all ZnO samples matches zincite crystalline hexagonal phase and the evaluation of crystallite size revealed higher values for the samples prepared in the presence of hexamethylenetetramine (HMTA). The optical band gap of ZnO NPs, as estimated from the UV–Vis absorption spectra, varied slightly from 3.13 to 3.21 eV, while fluorescence investigation proves that samples prepared with urea precipitant have a lower rate of charge recombination. Tests on the photocatalytic degradation of malachite green dye under UV light irradiation demonstrated that the dynamics of photogenerated charge carriers play a significant role in the photocatalytic performance of ZnO samples.

Nanostructured ZnO‐CQD Hybrid Heterostructure Nanocomposites: Synergistic Engineering for Sustainable Design, Functional Properties, and High‐Performance Applications

AbstractHybrid nanocomposites integrating nanostructured zinc oxide (ZnO) and carbon quantum dots (CQDs) with designed heterostructures possess exceptional optical and electronic properties. These properties hold immense potential for advancements across diverse scientific and technological fields. This review article investigates the synthesis, properties, and applications of ZnO‐CQD heterostructure nanocomposites. Recent breakthroughs in fabrication methods are examined, including hydrothermal, microwave‐assisted, and eco‐friendly techniques. Key preparation methods such as sol‐gel, co‐precipitation, and electrochemical deposition are discussed, emphasizing their role in controlling heterostructure formation. This review analyses the impact of heterostructures on optical and electronic properties, such as fluorescence, photoluminescence, and photocatalytic activity. Synergistic interactions between ZnO and CQDs within heterostructures are highlighted, demonstrating how they lead to substantial performance improvements. Applications of ZnO‐CQD heterostructures span solar cells, LEDs, photodetectors, water purification, antimicrobial treatments, gas sensing, catalysis, biomedical imaging, drug delivery, environmental sensing, and energy storage. Insights are provided into refining synthesis methods, enhancing characterisation techniques, and broadening the application landscape. Challenges like stability are addressed, along with strategies for optimised performance and practical implementation. This comprehensive review offers a thorough understanding of ZnO‐CQD heterostructure nanocomposites, emphasising their significance within materials science and engineering. By addressing core concepts and future directions, it lays a foundation for continued innovation in this dynamic field.

Biosynthesis of ZnO nanoparticles using the young fruit of Borassus flabellifer: Characterization and photocatalytic removal of biohazardous safranin-O dye using solar irradiation

Here, ZnO nanostructures were synthesized for the first time from the young fruit of the Borassus flabellifer. X-ray diffraction study revealed that the unit cell of ZnO was hexagonal with particle size 39.83 nm. The field-emission scanning electron microscope (FESEM) images showed that spherical nanoparticles were formed. A sharp absorption peak was seen at 375 nm in the UV-vis absorption study, and the calculated excitonic band gap was 3.37 eV. The biosynthesized ZnO was used as a photocatalyst to remove the biohazardous safranin-O (SO) dye using solar irradiation. Freundlich isotherm model was used to study the adsorption behavior of SO onto ZnO. At optimum conditions, nearly 96.89% of the dye was degraded in just 80 minutes. Furthermore, the impact of catalyst dose, initial dye concentration, solution pH, and temperature on photodegradation was also investigated.

High-Sensitivity of Self-Powered Gas Sensors Based on Piezoelectric Nanogenerators With Y-Doped 1-D ZnO Nanostructures

High-Sensitivity of Self-Powered Gas Sensors Based on Piezoelectric Nanogenerators With Y-Doped 1-D ZnO Nanostructures

Hole scavenger effect on hexagonal ZnO nanostructures decorated with SnO2 nanoparticles for generating high current densities via photoelectrochemical activity

This study investigated the effects of the heterostructure and interface kinetics on the photocurrents generated by ZnO-coupled SnO2 nanostructures. Electrochemical impedance spectroscopy was utilized to understand the nanostructure heterostructure and interface charge kinetics in a 0.1 M NaOH under a ON/OFF state; the lowest charge kinetic resistance of 370.84 Ω was attained for ZnO sample decorated with SnO2 particles in the light state, which is ten times lower than that of ZnO structures, with a current density of 0.94 mA cm−2. In addition, the effect of the applied potential on the charge production of all the electrodes was examined at an applied voltage of 0.55 V vs. reference electrode, which showed the maximum generation of induced-current density for ZnO nanostructures decorated with SnO2 particles compared with other pristine electrodes. Furthermore, the hole scavenger effect on the interface kinetics and photocurrent generation for all the photoelectrodes was investigated under similar conditions, such as without a scavenger and in the same electrolyte. All electrodes in the presence of the scavenger exhibited better resistance, charge transfer kinetics, and photocurrent densities than the electrodes without a scavenger. The maximum current density of 8.96 mA cm−2 was attained for ZnO nanostructures decorated with SnO2 nanoparticles. This was higher compared with other pristine electrodes with scavengers, owing to better charge migration and reduced recombination due to the hole scavenger.

Bicone nanoflower evolution and multi-peak emission of polymer caped Cu doped ZnO.

A low-temperature polymer-assisted wet chemical method was used to synthesise Cu-doped ZnO bicone nanoflowers at three different PEG concentrations.The effects of PEG concentration on the structural, morphological and optical properties of Cu doped ZnO nanostructures were studied. X-ray diffraction studies revealed that the as-synthesized ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase. The scanning electron microscopy (SEM) analysis showed that the prepared nanostructures have bicone-nanoflower morphology and PEG concentration has strongly influenced the size as well the shape of nanoflowers. The surface passivation effect of PEG on the band gap energies was studied by analysing UV -visible spectra of all the samples. The room-temperature fluorescent spectra of all the nanoflowers showed multiple peak emissions, both in the ultra-violet and visible regions, with varying intensities.These recasted multiple peaks are attributed to the morphological modification caused by the PEG addition.&#xD.

Integrated photodetectors embedded within fiber laser based on hybrid rGO:ZnO nanostructures

Online power monitoring is helpful in fiber-optic communication applications. This report introduced an innovative all-fiber photodetector based on the polished side of an arc-shaped fiber for the optical signals’ in situ measurements. For this purpose, a metal-semiconductor–metal photodetector was designed with multiple interdigitated metal fingers of gold electrodes. A waveguide structure containing polymethyl methacrylate (PMMA), graphene layers, and zinc oxide nanostructures was developed and covered over the arc-shaped fiber. Due to the PMMA’s refractive index (n = 1.4905), the evanescent field of propagating mode was drawn out of the core, thus increasing the light interaction with semiconductor nanostructures. To study the influence of graphene flakes on the optoelectrical behavior of zinc oxide nanostructures, a suspension of graphene oxide (GO) and ZnO nanorods was synthesized and transferred onto the PMMA thin film, which was deposited on the polished side of the arc-shaped fiber. The morphological analysis indicates the formation of ZnO nanorods with different orientations, and these nanorods have the potential to enhance incident photon trapping greatly. Upon photon exposure, the guiding photons in the fiber evanescently coupled with the deposited nanostructures, and the photoexcited electron–hole pairs were generated in the semiconductor material. Using applied voltage across the interdigitated electrodes, the generated excitons were separated and increased the photocurrent, which was monitored precisely by source-measure equipment. The optoelectrical properties of fabricated devices showed that incorporating graphene layers can improve the photon detection performance of the fabricated all-fiber photodetectors based on ZnO nanostructures.

Synthesis of nanostructured zinc oxide and its composite with carbon dots for DSSCs applications using flexible electrode

ZnO nanowires (ZnO NWs), ZnO nanoparticles (ZnO NPs) and carbon dots (C-dots) were synthesized by hydrothermal, sol-gel and hydrothermal methods respectively. They were also characterized and applied for dye sensitized solar cells (DSSCs). The effects of C-dots on ZnO NWs and ZnO NPs have been evaluated. The C-dots were used at a mole ratio of citric acid (CA) to ethylene diamine (EDA) of 1 : 1.5. These C-dots were found to enhance the performance of the flexible electrode DSSCs. After the addition of C-dots, the power conversion efficiency (PCE) of ZnO NPs was boosted to be two times higher than that of ZnO NPs DSSCs without C-dots. Similarly, the ultraviolet (UV)-band revealed a blue shift, resulting in a lower band gap and a reduced charge transfer resistance, which can enhance the PCE of DSSCs. The loaded quantity on the flexible electrode substrate made of polyethylene terephthalate (PET) was optimized (50 mg). For DSSCs, the PET flexible electrode conductive polymer has produced positive outcomes. For ZnO NWs and ZnO NWs@C-dots, the PCE values were 1.45% and 4.25%; while for ZnO NPs and ZnO NPs@C-dots, they were 2.34% and 5.81%, respectively. This work achieved remarkable and competitive performance when compared to solid (indium tin oxides/glass)-based substrate.