ZnO Hybrid Research Articles

Toward a Highly Functional Hybrid ZnO Nanofiber–rGO Gas Sensor

Herein, a hybrid ZnO nanofiber/reduced graphene oxide (rGO) gas sensor is fabricated to detect acetone gas. Metal oxides, including ZnO, SnO2, and TiO2, have been widely used as gas sensors. This article investigates the implications of incorporating rGO into the network of ZnO nanofibers for the sensing characteristics of ZnO. Electrospinning, followed by a calcination treatment at 600 °C, is used to synthesize ZnO nanofibers. The synthesis is carried out with different ratios of zinc acetate (ZnAc) and GO. Scanning electron microscopy (SEM) is used to study the morphology of the nanofibers before and after calcination. Results show that the diameter of nanofibers before and after calcination is in the range of 400–650 and 190–480 nm, respectively. Results also confirm that rGO sheets are very well intermingled with ZnO nanofibers. It appear that the higher the weight fraction of ZnAc, the higher sensitivity to acetone can be attained. The addition of graphene to the ZnO‐based sensor is associated with an increase in the sensitivity of the fabricated sensor from 2.3 to 4 and a significant decrease in the operating temperature of the sensor from 400 to 200 °C.

An intelligent approach to predicting the effect of nanoparticle mixture ratio, concentration and temperature on thermal conductivity of hybrid nanofluids

Hybrid nanofluids are better heat transfer fluids than conventional nanofluids because of the combined properties of two or more nanoparticles. In this study, the thermal conductivity of Al2O3–ZnO nanoparticles suspended in a base fluid of distilled water is investigated. The experiments were conducted for three mixture ratios (1:2, 1:1 and 2:1) of Al2O3–ZnO nanofluid at five different volume concentrations of 0.33%, 0.67%, 1.0%, 1.33% and 1.67%. X-ray diffractometric analysis, X-ray fluorescence spectrometry and scanning electron microscopy were used to characterise the nanoparticles. The highest thermal conductivity enhancement achieved for Al2O3–ZnO hybrid nanofluids with 1:2, 1:1 and 2:1 (Al2O3:ZnO) mixture ratios was 36%, 35% and 40%, respectively, at volume concentration 1.67%. The study observed the highest thermal conductivity for Al2O3–ZnO nanofluid was achieved at a mixture ratio of 2:1. A “deeping” effect was observed at a mixture ratio of 1:1 representing the lowest value of thermal conductivity within the considered range. The study proposed and compared three models for obtaining the thermal conductivity of Al2O3–ZnO nanofluids based on temperature, volume concentration and nanoparticle mixture ratio. A polynomial correlation model, the adaptive neuro-fuzzy inference system model and an artificial neural network model optimised with three different learning algorithms. The adaptive neuro-fuzzy inference system model was most accurate in forecasting the thermal conductivity of the Al2O3–ZnO hybrid nanofluid with an R2 value of 0.9946.

Facile synthesis of Cr doped hierarchical ZnO nano-structures for enhanced photovoltaic performance

Transition metal doped ZnO has been widely used in various research areas such as optoelectronics, chemical sensors, solar cells and photo catalysts. Herein, we fabricated Cr-doped ZnO nanospheres by a facile solvothermal treatment for enhanced photovoltaic performance. A systematic study of the structural and optical properties of Cr doped ZnO were investigated by scanning electron microscopy (SEM), X-ray diffraction technique (XRD), Ultra violet-Visible spectroscopy (UV–Vis) respectively. XRD patterns confirm that the samples have hexagonal (wurtzite) structure with no additional peaks, which suggests that Cr ions replaces the regular Zn sites in the ZnO crystal structure. Furthermore, doped ZnO nanospheres were employed in the hybrid solar cells in combination with P3HT and gave better current densities than their corresponding undoped counterparts. The increase in solar cell efficiency of doped ZnO nanospheres is solely due to the improvement in the charge separation efficiency in the 4% Cr doped ZnO nanospheres. Optoelectronic analysis of the Cr doped ZnO hybrid solar cell showed comparable results of JSC −3.7 (mAcm−2), VOC 0.44 (V), Fill Factor 0.49 and Efficiency (ƞ) 0.79 (%). The enhanced photovoltaic activity of the Cr doped hierarchical ZnO nanostructures provides an interesting grounds for the design and enhancement of the low cost, feasible synthesis of photovoltaic nanostructure materials.

Efficient visible-light piezophototronic activity of ZnO-Ag8S hybrid for degradation of organic dye molecule

The usage of semiconductor photocatalyst has been received great attention in recent years due to their wide application in photocatalytic water-splitting and degradation of pollutants in waste water and environmental remediation application, etc. In this study, we demonstrated the efficient synergistically piezo-phototronic effect (which is combined activity of piezo- and photocatalytic) of ZnO-Ag8S hybrid for the degradation of an organic dye. Hydrothermal method was adopted for the growth of ZnO tetrapods on the surface of glass substrate. Ag8S modified ZnO obtained by successive ionic layer adsorption and reaction (SILAR) method, has shown an increased photo-decolorization rate compared with bare photocatalyst. This piezo-photocatalytic hybrid material plays an important role in electron trapping and also hindered the charge carrier recombination. The photo-degradation mechanism of Rhodamine-B dye with Ag8S modified piezoelectric ZnO hybrid material has shown 7.3 fold increment when compared with bare photocatalyst. Our study reveals that ZnO-Ag8S hybrid shows a better visible-light piezophototronic activity which further explores a new catalyst design approach for existing photocatalytic application in environmental remediation.

Seed-free growth of strongly UV emitting self-supported hybrid ZnO nanowire/graphite membranes

Self-supported membranes consisting of entangled 2 to 6 μm long ZnO nanowires (NWs) on graphite with excellent UV emission were fabricated by a vapor transport technique at high temperature in a tubular furnace. The NWs grew on catalyst-free graphite flakes that had been mechanically compacted within an alumina boat crucible (the “substrate crucible”). The self-supported ZnO NW/graphite membrane detached spontaneously from the graphite substrate during the cooling stage after NW growth. The inversion of the substrate crucible orientation to an upside down position (usually used by our group for rigid substrates) resulted in strong reductions of the UV/visible emission ratio; by a factor of ~20 for NWs grown on compacted graphite and of ~1000 for NWs grown on Au-catalyzed Si wafers. Simulations of the transport fluid dynamics within the synthesis tube demonstrate that the substrate holder shape and substrate position within the holder play crucial roles in the reduction of precursor velocities, which is likely a key factor for achieving the long entangled NWs with enhanced UV/visible emission ratios that conform the self-supported ZnO NW/graphite membranes.

Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation.

Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet–visible (UV–Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.

Enhancing the thermal performance of solar collectors using nanofluids

Solar energy remains the most ubiquitous and inexhaustible source of energy. This energy can be utilized by several approaches including the use of solar collectors. Several studies have illustrated that the efficiency of solar collectors can be significantly improved by the introduction of nanofluids which have shown improved thermal conductivity up to 160% with a subsequent reduction in greenhouse gases such as CO2. To produce nanofluids, nanoparticles such as Al2O3, hybrid ZnO + Al2O3, and metals (Al, Cu) particles are dispersed into the based fluids such as water, glycerol, and bio-fluids. The added nanoparticles enhance the viscosity, absorption rate, convective heat transfer coefficient and heat losses of the fluid. The performance of details the applications and effectiveness of different nanofluids in four types of solar collectors - parabolic trough, flat plate, direct absorption, and evacuated tube. In addition, the work sheds light on the future trend and challenges of nanofluids (including toxicity) in solar collectors. Regardless of its toxicity, researchers have shown more interest in nanofluids use in solar collectors because of its strong sustainability to a safe environment and the exploration of hybrid nanofluids to better enhance solar collectors. Solar collectors can also be modulated by using different nanofluids at varying concentrations.

Effect of different forms of nano‐ZnO on the properties of PVDF/ZnO hybrid membranes

AbstractIn this article, polyvinylidene fluoride (PVDF)/ZnO hybrid membranes with different forms of nano‐ZnO as additives were prepared by thermally induced phase separation. The effects of the morphology of ZnO particles on the microstructure and properties of hybrid membranes were systematically investigated. Three different forms of nano‐ZnO were characterized by X‐ray diffraction (XRD) and scanning electron microscope (SEM). Then a series of tests were made through XRD, Fourier transform infrared, differential scanning calorimeter, SEM, energy‐dispersive X‐ray spectroscopy, atomic force microscopy, mechanical strength testing, porosity measurement, water contact angle measurement, pure water flux measurement, rejection measurement, flux recovery rate (FRR) measurement, and photocatalytic degradation testing to characterize the hybrid membrane. The results show that the hybrid membranes which were doped with different forms of ZnO have different structures and properties. Porous ZnO has the best modification effect on PVDF membranes. The PVDF/porous ZnO hybrid membranes' water flux and OVA rejection can reach 1.6 and 1.3 times of pure PVDF membrane, respectively, and its FRR can reach about 95%. The hybrid membrane doped with porous ZnO has excellent self‐cleaning performance, and its degradation rate of MB can reach about 51%.

‘Sandwich’-like hybrid ZnO thin films produced by a combination of atomic layer deposition and wet-chemistry using a mercapto silane as single organic precursor

This study describes a straightforward preparation of hybrid organic–inorganic thin films containing a stable ‘sandwich’-like structure of two atomic layer deposited (ALD) ZnO layers separated by a thin organosilane phase, which is built from a single organic component (3-mercaptopropyl)trimethoxysilane (MPTMS). Grafting of MPTMS on the first ALD ZnO layer was performed in solution and driven by the strong affinity of the terminal thiol functionality (-SH) towards ZnO. We demonstrate that under different reaction conditions, either MPTMS monolayers are prepared or a 5 nm thick cross-linked polymeric network is formed due to the self-condensation of silane, which covers the ALD ZnO surface. This film served as a soft template for the nucleation of an ALD ZnO top layer by creation of S–Zn and Si–O–Zn bonds at the upper interface, as confirmed by XPS measurements. An increase in surface roughness, as compared to the initial ZnO film, is observed after removal of the organic layer from the hybrid structure by calcination, which is accompanied by an improvement in UVA photocatalytic activity towards the degradation of methyl orange dye. Thus, MPTMS can be used as a sacrificial agent in combination with low temperature ALD processes for building rougher and photocatalytically efficient ZnO coatings.

Effect of the PEDOT:PSS buffer layer on the performance of hybrid ZnO nanorods/polymer electroluminescent diode

Hybrid ZnO nanorods/polymer light-emitting diodes have excited much attraction because of the combination of high optoelectronic properties of ZnO nanorod with the variety and processability of polymers. In this research, the hybrid ZnO nanorods/polymer heterostructure UV-LED is investigated using ATLAS module of SILVACO TCAD software. In order to observe the influence of PEDOT:PSS hole injection layer/buffer layer in a AZO/ZnO NRs/MEH-PPV heterostructure device, first an ab initio approach have been done on PEDOT:PSS, MEH-PPV and AZO layers. The density of states, electronic band structure and the imaginary part of the dielectric function have been analyzed to deduce the electronic and optic features of the aforesaid layers. In continue, current–voltage characteristics and electroluminescence (EL) spectra of three structures of ITO/MEH-PPV/Al, ITO/ZnO/MEH-PPV/Al and ITO/ZnO/ZnO NR/MEH-PPV/Al have been simulated and compared with the literature experimental works to verify the simulation approach. Moreover, Langevin recombination rate, radiative recombination rate and luminescence power of the mentioned structures have been carefully investigated. Finally, the current–voltage characteristics, luminescence power and EL spectra of the novel proposed devices with the structures of ITO/PEDOT:PSS/AZO/ZnO NR/MEH-PPV/Al and ITO/PEDOT:PSS/ZnO/ZnO NR/MEH-PPV/Al have been investigated. The turn-on voltage of the proposed structure is decreased from 22 to 16 V because of the insertion of the PEDOT:PSS buffer layer and lowering of the hole injection barrier between ITO and ZnO layers. A little blue shift is observed around the wavelength of 380 nm which is attributed to the AZO layer.

Photo-induced degradation of bio-toxic Ciprofloxacin using the porous 3D hybrid architecture of an atomically thin sulfur-doped g-C3N4/ZnO nanosheet

Ciprofloxacin is a pharmaceutically active compound which belongs to a class of micropollutants that cannot be removed using conventional water treatment systems. In this study, photocatalytic degradation using materials with high surface area and active sites was proposed to remove such contaminants. We demonstrated an easily scalable and simple synthesis route to prepare a 3D porous sulfur-doped g-C3N4/ZnO hybrid material, and the preparation process parameters were optimized using response surface methodology targeting Ciprofloxacin degradation. The hybrid material removed up to 98% of the bio-toxic Ciprofloxacin from synthetic water. The porous, defect engineered, thermally stable, and chemically interconnected hybrid material presented an 18 and 38% improved degradation efficiency compared to ZnO and sulfur-doped g-C3N4 (or S–C3N4), respectively. Based on our experimental results, an empirical relation correlating synthesis process parameters and degradation efficiency was developed using face-centered central composite design (FCCD) and response surface methodology (RSM). The current model can be used to design catalytic materials for removing bio-toxic and other micropollutants from water.

Tailoring and optimization of hybrid ZnO:TiO2:CdO nanomaterials for advance oxidation process under visible light

The hybrid ZnO:TiO2:CdO (ZTC) nanomaterials were synthesized through a simple route sol-gel precipitation method for advance oxidation process (AOP). The morphology of ZnO:TiO2 to ZnO:TiO2:CdO has been changed from nanorods to nanoflakes and then to cauliflower by increasing the volume fraction of CdO in sample ZnO:TiO2.The particle sizes were found 34 nm and 51 nm for ZnO:TiO2 and [(0.4)ZnO:(0.6)TiO2]:CdO (1:1) samples, respectively and confirmed by HRTEM. The composite phase was observed in the XRD pattern and obtained different phases of hybrid ZnO:TiO2:CdO nanomaterials which is attributed to the synergistic effects in AOP. The optical bandgap were decreased from 3.24 eV to 2.16 eV by adding the CdO in [(0.4)ZnO:(0.6)TiO2]. The advance oxidation process was investigated via the degradation of methyle orange (MO) and methyle blue (MB) for all hybrid nanomaterials in visible light. The catalysts dose 7 gm/L of sample ZTC4 shows the highest degradation efficiency 98% and 96% in both organic dyes MO and MB with decreases rate of recombination and boosted photo induced charge carriers in the catalyst. The estimation of mineralization factors of dyes were examined through BOD and COD tests followed by AOP.

A fast and facile electrochemical method for the simultaneous detection of epinephrine, uric acid and folic acid based on ZrO2/ZnO nanocomposites as sensing material

A novel electrochemical sensor based on ZrO2 and ZnO hybrid nanocomposites was developed for simultaneous determination of epinephrine (EA), uric acid (UA) and folic acid (FA) with the highly selective and ultrasensitive. The nanocomposites have been synthesized by chemical precipitation and thermal calcine method with economical, eco-friendly and practical nature. Their structure and electrochemical properties were investigated by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical techniques. The results reveal that the ZrO2/ZnO nanocomposites can possesses highly exposed catalytic sites, favorable conductivity, and the sensor excellent signal response for EP, UA and FA under the optimal condition. The electrochemical sensing platform has a low detection limit of 0.039 μM, 0.29 μM and 0.037 μM and a wide detection range of 0.8–420 μM, 10–2400 μM and 2–480 μM, respectively. It was also tested with a human blood serum sample at physiological pH with recovery 97.3–103.8% and relation standard deviation less than 5%. It indicates that the electrochemical sensors has a hopeful capacity of extensive applications in bioanalysis and diseases diagnosis.

Effect of Photoelectrochemical Activity of ZnO-Graphene Thin Film on the Corrosion of Carbon Steel and 304 Stainless Steel

In this research, the ZnOG hybrid thin film was produced via solgel method. The surface morphology, band gap and photoactive properties of the films were studied by means of SEM, UV–Vis and photoluminescence analysis. In addition, the ability of the thin film in photocathodic protection of carbon steel (CS) and 304 stainless steel in 3.5 wt.% NaCl and Na2S solutions under dark and UV illumination was investigated by polarization test as well as OCP and current measurements during coupling of steels with ZnOG photoanode. The mix band gap is reduced to the orders of 1.17 eV through hybridization of ZnO with graphene oxide. In both NaCl and Na2S solutions, the ZnOG thin film could effectively protect the SS304 in dark condition. Moreover, UV illumination improved the level of protection via photoinduced electrons. The ZnOG film slightly accelerates the corrosion of CS in dark condition in NaCl solution. Nevertheless, UV illumination leads to photocathodic protection of CS in mentioned environment. In Na2S solution, while coupling to ZnOG photoanode had not much effect on the surface electrochemical activity of CS, UV illumination caused photocathodic protection.

Green and hydrothermal assembly of reduced graphene oxide (rGO)-coated ZnO and Fe hybrid nanocomposite for the removal of nitrate and phosphate

Abstract This study aimed to achieve an innovative, environmentally friendly, and effectual method for preparing a hybrid nanocomposite using reduced graphene oxide (rGO)-coated iron-doped zinc oxide (rGO/ZnO/Fe) to remove nitrate and phosphate from the reaction mixture. Prunus × yedoensis leaf extract was used as a reducer and was calcined at different temperatures (80 and 160 °C) for 24 and 48 h in a hydrothermal reactor. The physical characteristics of the rGO/ZnO/Fe composite nanostructure were studied by high-resolution transmission electron microscopy (HR-TEM). Elemental mapping and energy-dispersive X-ray spectroscopy (EDS) demonstrated the occurrence of elements, their distribution, and the magnitudes. The functional groups were confirmed by Fourier transform infrared spectroscopy (FTIR). The composite was further characterized using the Brunauer–Emmett–Teller (BET) technique, X-ray powder diffraction (XRD), and Raman spectroscopy. The composites treated at 80 °C for 24 h, 160 °C for 24 h, 80 °C for 48 h, and 160 °C for 48 h remove nitrate up to 82%, 86%, 92%, 96%, and phosphate up to 72%, 84%, 68%, 90%, respectively.

Investigation on influence of Hybrid Biodegradable Nanofluids (CuO-ZnO) on Surface Roughness in Turning AISI 1018 Steel

Machining occupies a prominent place in engineering industries. Dissipating of heat form the cutting zone has become an important factor for sustainability of machining industry. With increasing attention on environment and health impacts, the governmental regulation is forcing industries to reduce the use of conventional lubricants. With this focus is shifted towards biodegradable oils and Minimal Quantity Lubrication (MQL). Further improvement can be done by incorporating nanoparticles in lubricants. Experimental tests were conducted to find out appropriate biodegradable lubricating oil. In this study Palm oil and coconut oils were considered and compared to dry lubricating condition. Nanofluids were prepared in-situ with incorporations of hybrid nanoparticles (CuO-ZnO) with 50:50 combinations. The machining tests were carried out on AISI1018 steel. The inserts and tool holders used were from Kennametal beyond blast with ISO designation MCLNR2020K12BB and CNGG 120408. The objective of this work was to find out the effect of various biodegradable hybrid nanofluids and machining parameters on surface roughness, while machining AISI 1018 steel. The results reported that with coconut oil as basefluid incorporated with hybrid CuO and ZnO (50:50) combination nanoparticles gave a better result compared to other combinations

Hybrid ZnO Electron Transport Layer by Down Conversion Complexes for Dual Improvements of Photovoltaic and Stable Performances in Polymer Solar Cells

Polymer solar cells (PSCs) have shown excellent photovoltaic performance, however, extending the spectral response range to the ultraviolet (UV) region and enhancing the UV light stability remain two challenges to overcome in the development of PSCs. Lanthanide down-conversion materials can absorb the UV light and re-emit it at the visible region that matches well with the absorption of the active layer material PTB7-Th (poly[[2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbony]thieno[3,4-b]thiophenediyl]]) and PBDB-T-2F, thus helping to enhance the photovoltaic performance and UV light stability of PSCs. In this research, a down-conversion material Eu(TTA)3phen (ETP) is introduced into the cathode transport layer (ZnO) in PSCs to manipulate its nanostructure morphology for its application in hyperfine structure of PSCs. The device based on the ZnO/ETP electron transport layer can obtain power conversion efficiencies (PCEs) of 9.22% (PTB7-Th–PC71BM ([6,6]-phenylC71-butyric acid methyl ester) device) and 13.12% (PBDB-T-2F–IT-4F device), respectively. Besides, in the research on PTB7-Th-PC71BM device, the stability of the device based on ZnO/ETP layer is prolonged by 70% compared with the ZnO device. The results suggest that the ZnO/ETP layer plays the role of enhanced photovoltaic performance and prolonged device stability, as well as reducing photo-loss and UV degradation for PSCs.

Formation of ZnO@CuS nanorods for efficient photocatalytic hydrogen generation

It is imperative to design integrated functional composites that simultaneously facilitate efficient optical absorption, charge separation, and surface redox reactions for efficient photocatalytic hydrogen generation. Herein, we present a strategy for efficient hydrogen evolution by developing tunable ZnO nanorods and the hybrid ZnO nanorods decorated with CuS composite. The hierarchical nanostructured ZnO@CuS heterojunction is prepared via a simple hydrothermal reaction. While characterizations of its optical and photophysical properties, less is known about its charge carrier dynamics and photocatalytic activity in aqueous systems generating hydrogen. Time-correlated single photon counting (TCSPC) decay spectra of ZnO and ZCS2 clearly showed that the rate constant of electron transfer for ZCS2 is 8.35 × 109 s−1 and the average lifetime of ZnO decreases than ZCS2 which indicate fast electron transfer happens within the heterostructure through the CB of CuS to ZnO. Enhanced absorption of solar energy upon precise CuS concentration led to remarkably high photocatalytic H2 production (10113.59 µmol·g−1h−1) and an apparent quantum efficiency of 22.3% nm which is nearly ~35 times as high as that of pristine 287.96 µmol·g−1h−1. To our best knowledge, the obtained hydrogen evolution rate is among the maximum reported value in the literature under similar reaction systems. The excellent photocatalytic activity of the hybrid composite (ZnO@CuS) is attributed to the increase in light harvesting capability and efficient charge separation during the photocatalytic process as well as the synergistic role of CuS and ZnO in the nanostructured assembly. The work opens up new fundamental insights in designing hierarchical non-noble photocatalysts for solar applications.

Enhancement of UV Photodetection Properties of Hierarchical Core-Shell Heterostructures of a Natural Sericin Biopolymer with the Addition of ZnO Fabricated on Ultra-Nanocrystalline Diamond Layers.

A novel self-assembled hierarchical heterostructure is derived from cocoon-derived sericin biopolymer (CSP) biowaste with ZnO deposited on ultra-nanocrystalline diamond (UNCD) substrates using a scalable chemical deposition technique. Then, high-performance long-life UV photodetectors are fabricated using this hybrid sericin, diamond, and ZnO (SDZ) nanostructure. The microstructural analysis reveals a several nanometer-thick CSP shell coated with a highly uniform ZnO nanorod (ZNR) array grown on the UNCD substrate. The CSP shell also contains columnar nanograins on top of the ZNR as well as vertical sidewalls with unique alignments. The hierarchical core-shell SDZ heterostructures reveal superior UV diode performance, with an ultrahigh UV switching ratio of 1.1 × 105 at 5 V, an increase of up to 49 900% greater than that of as-grown ZNRs (220). High UV responsivity is observed around 3.6 A W-1 under 365 nm UV light illumination. The perfect distribution of the sericin in the ZNRs on the UNCD substrates resulted in the ultrafast electron-hole recombination. The sericin dopants and the UNCD interlayer enabled the device to reach new energy levels in the conduction band, with the reduced barrier height allowing for improved charge carrier transportation during UV light illumination. It is believed that the sericin dopants and the UNCD layer increased the UV adsorptivity and the amount of conducting carbon dopants within the ZNRs was sufficient for s0tability. These noteworthy features make the SDZ heterostructures promising candidates for the fabrication of cost-efficient biopolymers and UNCD hybrid-based UV photodetectors.

A facile surfactant assisted hydrothermal synthesis of ZnO and graphene loaded ZnO for efficient photocatalytic self-cleaning

Superhydrophilicity and photocatalysis are of great importance for self-cleaning applications. We report the synthesis of ZnO and ZnO loaded graphene nanostructures at different pH values with exposed polar facets by a simple hydrothermal method. Cetyltrimethylammonium bromide is used as surfactant and the synthesis is carried out without the aid of high temperature and demonstrated to have a superior photocatalytic activity. We observed a reduction in band gap for graphene loaded ZnO samples. Further, a one-step spin coating method is used for the preparation of optically transparent and photoinduced superhydrophilic ZnO hybrid films. We investigated the effect of cetyltrimethylammonium bromide capping agent on crystal growth and morphology of as synthesised samples. An effective improvement in photocatalytic activity of the nanohybrid (∼100%) compared to pure ZnO (85%) is observed within 150 min. This can be attributed to the synergetic interaction of the components of the hybrid. Also, the hybrid samples coated on the glass substrate exhibits good transparency and superhydrophilicity upon UV irradiation. An unexpected transmittance as high as 84%–97% throughout most of the visible light region of the spectrum of the hybrid samples along with good photocatalytic efficiency and photoinduced superhydrophilicity makes the samples more suitable for self-cleaning applications.