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1.
A novel CdMoO 4–ZnO composite film is prepared by spin‐coating CdMoO 4 microplates on ZnO film and is constructed as a heterojunction photodetector (PD). With an optimized loading amount of CdMoO 4 microplates, this composite film PD achieves a ≈18‐fold higher responsivity than pure ZnO film PD at 5 V bias under 350 nm (0.15 mW cm −2) UV light illumination, and its decay time shortens to half of the original value. Furthermore, Au nanoparticles are then deposited to modify the CdMoO 4–ZnO composite film, and the as‐constructed photodetector with an optimized deposition time of Au nanoparticles yields an approximately two‐fold higher photocurrent under the same condition, and the decay time reduces by half. The introduced CdMoO 4 microplates form type‐II heterojunctions with ZnO film and improve the photoelectric performance. The hot electrons from Au nanoparticles are injected into the CdMoO 4–ZnO composite film, leading to the increased photocurrent. When the light is off, the Schottky barriers formed between Au nanoparticles and CdMoO 4–ZnO composite film block the carrier transportation and accelerate the decay process of current. The study on Au‐nanoparticle‐modified CdMoO 4–ZnO composite film provides a facile method to construct ZnO film based PD with novel structure and high photoelectric performance. 相似文献
2.
We report a new method to synthesize Ag/ZnO heterostructures assisted by UV irradiation. The formation of Ag/ZnO heterostructures depends on photogenerated electrons produced by ZnO under UV light to reduce high valence silver. Functional property of the Ag/ZnO heterostructures is evaluated by photodegradation of methylene blue (MB) under UV illumination. Results of photodegradation tests reveal that the optimal photocatalytic activity of as-syntheszied samples is about 1.5 times higher than the pure ZnO synthesized in the same condition or commercial TiO 2 (P-25), showing the advantage of the unique structure in the Ag/ZnO heterostructure. Besides, due to the reduced activation of surface oxygen atom, photocatalytic activity of the photocatalysts has no evident decrease even after three recycles. 相似文献
3.
A feasible strategy for hybrid photodetector by integrating an array of self‐ordered TiO 2 nanotubes (NTs) and selenium is demonstrated to break the compromise between the responsivity and response speed. Novel heterojunction between the TiO 2 NTs and Se in combination with the surface trap states at TiO 2 help regulate the electron transport and facilitate the separation of photogenerated electron–hole pairs under photovoltaic mode (at zero bias), leading to a high responsivity of ≈100 mA W ?1 at 620 nm light illumination and the ultrashort rise/decay time (1.4/7.8 ms). The implanting of intrinsic p‐type Se into TiO 2 NTs broadens the detection range to UV–visible (280–700 nm) with a large detectivity of over 10 12 Jones and a high linear dynamic range of over 80 dB. In addition, a maximum photocurrent of ≈10 7 A is achieved at 450 nm light illumination and an ultrahigh photosensitivity (on/off ratio up to 10 4) under zero bias upon UV and visible light illumination is readily achieved. The concept of employing novel heterojunction geometry holds great potential to pave a new way to realize high performance and energy‐efficient optoelectronic devices for practical applications. 相似文献
4.
SnO 2 semiconductor is a new-typed promising photocatalyst, but wide application of SnO 2-based photocatalytic technology has been restricted by low visible light utilization efficiency and rapid recombination of photogenerated electrons–holes. To overcome these drawbacks, we prepared B/Fe codoped SnO 2–ZnO thin films on glass substrates through a simple sol–gel method. The photocatalytic activities of the films were evaluated by degradation of organic pollutants including acid naphthol red (ANR) and formaldehyde. UV–Vis absorption spectroscopy and photoluminescence (PL) spectra results revealed that the B/Fe codoped SnO 2–ZnO film not only enhanced optical absorption properties but also improved lifetime of the charge carriers. X-ray diffraction (XRD) results indicated that the nanocrystalline SnO 2 was a single crystal type of rutile. Field emission scanning electron microscopy (FE-SEM) results showed that the B/Fe codoped SnO2–ZnO film without cracks was composed of smaller nanoparticles or aggregates compared to pure SnO2 film. Brunauer–Emmett–Teller (BET) surface area results showed that the specific surface area of the B/Fe codoped SnO 2–ZnO was 85.2 m 2 g ?1, while that of the pure SnO 2 was 20.7 m 2 g ?1. Experimental results exhibited that the B/Fe codoped SnO 2–ZnO film had the best photocatalytic activity compared to a pure SnO 2 or singly-modified SnO 2 film. 相似文献
5.
BiOBr and BiOCl were decorated on TiO 2 QDs through n-p-p heterojunctions by a simple strategy and they were applied for degradation of three organic dyes upon visible illumination. The obtained photocatalysts were analyzed via XRD, FESEM, EDX, UV–vis DRS, PL, BET, TEM, HRTEM, FT-IR, EIS, XPS, and transient photocurrent measurements. The TiO 2 QDs/BiOBr/BiOCl nanocomposite with 20% wt. of BiOBr and 30% wt. of BiOCl displayed superior photoability in the degradation of methylene blue, rhodamine B, and fuchsine, which was almost 34.5, 176, and 78.7-times larger than TiO 2 and 27.8, 13.5, and 51.5-folds greater than TiO 2 QDs, respectively. The results show that the construction of intimate n-p-p heterojunctions between BiOBr, TiO 2 QDs, and BiOCl counterparts leads to enhanced visible-light harvesting and improved charge separation, resulted efficiently increased photocatalytic activity. The trapping results proved that h +, •O 2−, and OH • species have considerable effects on the degradation reaction. We think that the improved efficiency of the ternary TiO 2 QDS/BiOBr/BiOCl photocatalyst is a splendid alternative for the removal of toxic contaminants from wastewater. 相似文献
6.
TiO 2/SnO 2 branched heterojunction nanostructure with TiO 2 branches on electrospun SnO 2 nanofiber (B‐SnO 2 NF) networks serves as a model architecture for efficient self‐powered UV photodetector based on a photoelectrochemical cell (PECC). The nanostructure simultaneously offers a low degree of charge recombination and a direct pathway for electron transport. Without correcting 64.5% loss of incident photons through light absorption and scattering by the F‐doped tin oxide (FTO) glass, the incident power conversion efficiency reaches 14.7% at 330 nm, more than twice as large as the nanocrystalline TiO 2 (TiO 2 NC, 6.4%)‐film based PECC. By connecting a PECC to an ammeter, the intensity of UV light is quantified using the output short‐circuit photocurrent density ( Jsc) without a power source. Under UV irradiation, the self‐powered UV photodetector exhibits a high responsivity of 0.6 A/W, a high on/off ratio of 4550, a rise time of 0.03 s and a decay time of 0.01 s for Jsc signal. The excellent performance of the B‐SnO 2 NF‐based PECC type self‐powered photodetector will enable significant advancements for next‐generation photodetection and photosensing applications. 相似文献
7.
Strong near‐surface electromagnetic field formed by collective oscillation of electrons on Cu nanostructure a shows a strong dependence on geometry, offering a promising approach to boost the light absorption of ZnO photoactive layers with enhanced plasmon scattering. Here, a facile way to fabricate UV photodetectors with tunable configuration of the self‐assembled Cu nanostructures on ZnO thin films is reported. The incident lights are effectively confined in ZnO photoactive layers with the existence of the uplayer Cu nanostructures, and the interdiffusion of Cu atoms during fabrication of the Cu nanostructures can improve the carrier transfer in ZnO thin films. The optical properties of the hybrid architectures are successfully tailored over a control of the geometric evolution of the Cu nanostructures, resulting in significantly enhanced photocurrent and responsivity of 2.26 mA and 234 A W ?1 under a UV light illumination of 0.62 mW cm ?2 at 10 V, respectively. The photodetectors also exhibit excellent reproducibility, stability, and UV–visible rejection ratio ( R370 nm/ R500 nm) of ≈370, offering an approach of high‐performance UV photodetectors for practical applications. 相似文献
8.
Ultraviolet (UV) photodetectors based on pure zinc oxide (ZnO) and Ag-doped ZnO (Ag:ZnO) thin films with different Ag doping contents (0.05, 0.15, 0.65, 1.30 and 2.20 %) have been prepared by sol–gel technique. Photoresponse characteristics of the prepared detectors have been studied for UV radiation of λ = 365 nm and intensity = 24 μW/cm 2. The Ag:ZnO thin film-based photodetector having an optimum amount of 0.15 at. wt% Ag dopant exhibits a high photoconductive gain ( K = 1.32 × 10 3) with relatively fast recovery ( T 37 % = 600 ms) and minimal persistence in comparison to other prepared photodetectors. The incorporation of Ag dopant (≤0.15 %) at Zn lattice sites (Ag zn) in ZnO creates acceptor levels in the forbidden gap, thereby reducing the value of dark current. Upon illumination with UV radiation, the photogenerated holes recombine with the captured electrons at the Ag zn sites. The photogenerated electrons increase the concentration of conduction electrons, thereby giving an enhanced photoresponse for Ag:ZnO photodetector (0.15 % Ag). At higher dopant concentration (≥0.65 %), Ag incorporated at the interstitial sites of ZnO leads to the formation of deep energy levels below the conduction band along with increase in oxygen-related defects, thereby giving higher values of dark current. The incorporation of Ag at interstitial sites results in degradation of photoresponse along with the appearance of persistence in recovery of the photodetector in the absence of UV radiation. 相似文献
9.
Pure TiO2 and Cu–doped TiO2 containing different amounts of copper ions with anatase/rutile/brookite triphasic structure were successfully synthesized through a simple hydrothermal method. The obtained samples were characterized by X–ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), X–ray photoelectron spectroscopy (XPS), UV?vis diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL) and Brunauer–Emmett–Teller surface area analyze (BET). Both pure and Cu–doped TiO2 show relatively high photocatalytic activity owing to their considerable surface areas. Moreover, the three–phase coexisting structure and the conversion between Cu2+ and Cu+ ions facilitate the separation of photogenerated electrons and holes, which is favorable for photocatalytic performance. 1%Cu–TiO2 exhibits the highest photocatalytic activity and the degradation degree of rhodamine B (RhB) reaches 93.5% after 30 min, which is higher than that of monophasic/biphasic 1%Cu–TiO2. ·O2? radical is the main active species, and h+ and ·OH species are subsidiary in the degradation process. 相似文献
10.
Two tungsten-based Keggin-type heteropolyacids (PW 12: ([PW 12O 40] 3−) and SiW 12: ([SiW 12O 40] 4−)) were hybridized with brookite-type TiO 2. Then photocatalytic decomposition activity, photoinduced hydrophilicity, and sustainability of the hydrophilicity in the dark were evaluated using gaseous 2-propanol (IPA) decomposition and sessile drop method. The obtained films were transparent in the visible wavelength range. Both hybrid films exhibited higher photocatalytic decomposition activity and had higher photoinduced hydrophilicizing rates than pure brookite films under UV illumination. The PW 12/TiO 2 film exhibited better photocatalytic performance than the SiW 12/TiO 2 film did. Atmosphere dependence, XPS analysis, and electrochemical experiments indicated the cause of these two films' different levels of sustainability of hydrophilicity to be differences in their electron storage capability. Results show that the electron scavenger capability and reoxidation efficiency of the heteropolyacid are key factors affecting the overall performance of wettability conversion of this hybrid film system before and after UV illumination. 相似文献
11.
Antibacterial packaging is introduced as a new method to prevent microbial food spoilage. Antibacterial effects of TiO 2, ZnO and mixed TiO 2–ZnO nanoparticle‐coated low‐density polyethylene (LDPE) films on Escherichia coli PTCC1330 were investigated. Bactericidal efficiency of 0.5%, 1% and 2% TiO 2 and ZnO nanoparticles and also 1% mixed TiO 2–ZnO nanoparticles with ratios of 25/75, 50/50 and 75/25 were tested under ultraviolet (UV) and fluorescent lights at two states: films alone and fresh calf minced meat packed. Maximum colony‐forming unit (CFU) reduction of 99.8% and 99.7% were obtained using 1% and 2% ZnO nanoparticle‐coated LDPE film under fluorescent light for films alone as well as 99.8% and 99.6% for fresh calf minced meat packed. 90.3% and 51.8% CFU reduction were recorded for 1% TiO 2 nanoparticle‐coated LDPE films in the presence of UV light at direct contact with bacteria and fresh calf minced meat packed, respectively. Maximum CFU reductions of 96% and 64.1% were obtained using 50/50 ratio of TiO 2/ZnO nanoparticles at the presence of UV light for film alone and fresh calf minced meat packed, respectively. ZnO nanoparticle‐coated LDPE films were identified as the best case to improve shelf life and prevent E. coli growth in fresh calf minced meat. 相似文献
12.
ZnO/TiO 2 thin films were fabricated on quartz glass substrates by E-beam evaporation. The structural and optical properties were investigated by X-ray diffraction (XRD), Raman spectra, optical transmittance and photoluminescence. XRD analysis indicates that the TiO 2 buffer layer can increase the preferential orientation along the (002) plane of the ZnO film. PL measurements suggest that co-emission of strong UV peak at 378 nm, violet peak at 423 nm and weak green luminescence at 544 nm is observed in the ZnO/TiO 2 thin film. The violet luminescence emission at 423 nm is attributed to the interface trap in the ZnO film grain boundaries. 相似文献
13.
Ultraviolet (UV) photodetectors based on ZnO nanostructure/graphene (Gr) hybrid‐channel field‐effect transistors (FETs) are investigated under illumination at various incident photon intensities and wavelengths. The time‐dependent behaviors of hybrid‐channel FETs reveal a high sensitivity and selectivity toward the near‐UV region at the wavelength of 365 nm. The devices can operate at low voltage and show excellent selectivity, high responsivity (RI ), and high photoconductive gain ( G). The change in the transfer characteristics of hybrid‐channel FETs under UV light illumination allows to detect both photovoltage and photocurrent. The shift of the Dirac point ( V Dirac) observed during UV exposure leads to a clearer explanation of the response mechanism and carrier transport properties of Gr, and this phenomenon permits the calculation of electron concentration per UV power density transferred from ZnO nanorods and ZnO nanoparticles to Gr, which is 9 × 10 10 and 4 × 10 10 per mW, respectively. The maximum values of RI and G infer from the fitted curves of RI and G versus UV intensity are 3 × 10 5 A W ?1 and 10 6, respectively. Therefore, the hybrid‐channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices. 相似文献
14.
The effect of a nickel oxide (NiO x) seed layer on the crystallization and photocatalytic activity of the sequentially plasma-enhanced chemical vapor deposited amorphous titanium oxide (TiO x) thin film processed by a post-annealing process was investigated. The evolution of the crystalline structures, chemical bond configurations, and surface/cross-sectional morphologies of the annealed TiO x films, with and without a NiO x seed layer, was examined using X-ray diffractometer, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscope measurements. Thermo- and photo-induced hydrophilicity was determined by measuring the contact angle of water droplet. Photocatalytic activity after UV light irradiation was evaluated from the decolorization of a methylene blue solution. The crystallization temperature of the TiO x film, deposited on a NiO x seed layer, was found to be lower than that of a pure TiO x film, further improving the thermo- and photo-induced surface super-hydrophilicity. The TiO x film deposited onto the NiO x seed layer, resulting in significant cluster boundaries, showed a rough surface morphology and proved to alleviate the anatase crystal growth by increasing the post-annealing temperature, which yielded a more active surface area and prohibited the recombination of photogenerated electrons and holes. The photocatalytic activity of the NiO x/TiO x system with such a textured surface therefore was enhanced and optimized through an adequate post-annealing process. 相似文献
15.
A novel graphene/Ag nanoparticles (NPs) hybrid (prepared by a physical method (PM)) was incorporated into electrospun TiO 2 fibers to improve visible-lightdriven photocatalytic properties. The experimental study revealed that the graphene/Ag NPs (PM) hybrid not only decreased the bandgap energy of TiO 2, but also enhanced its light response in the visible region due to the surface plasmon resonance (SPR) effect. In addition, compared with those of TiO 2 fibers incorporating the graphene/Ag NPs hybrid (prepared by a chemical method (CM)), TiO 2-graphene/Ag NPs (PM) fibers exhibited a higher surface photocurrent density and superior photocatalytic performance, i.e., the visible-light-driven photocatalytic activity was enhanced by 2 times. The main reasons include a lower surface defect density of the graphene/Ag NPs (PM) hybrid, a smaller particle size (10 nm) and a higher dispersity of Ag NPs, which promote the rapid transfer of photoexcited charge carriers and inhibit the recombination of photogenerated electrons and holes. It is expected that this kind of ternary electrospun fibers will be a promising candidate for applications in water splitting, solar cells, CO 2 conversion and optoelectronic devices, etc. 相似文献
16.
Flower-like Ag/ZnO heterostructure composites were prepared through a solvothermal method without surfactants or templates. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL) spectroscopy. Results demonstrate that flower-like Ag/ZnO heterostructure composites were composed of wurtzite ZnO flowers coated by face-center-cubic Ag nanoparticles. The growth process of flower-like ZnO crystals was investigated, and a possible growth mechanism was proposed. The photocatalytic activity of the as-prepared flower-like Ag/ZnO samples, pure ZnO samples, and commercial TiO 2 (Degussa, P-25) was tested with the photocatalytic degradation of methylene blue. Results show that the Ag/ZnO heterostructures were superior in photocatalytic activity to the pure ZnO samples and the commercial TiO 2 (Degussa, P-25), but the mixture of Ag (0.1 wt%) particles and ZnO flowers did not, which implies that the heterostructure promoted the separation of photogenerated electron–hole pairs, enhancing the photocatalytic activity. That was primarily verified by the PL results. 相似文献
17.
Self‐powered UV photodetectors based on TiO 2 nanotree arrays have captured much attention in recent years because of their many advantages. In this work, rutile/anatase TiO 2 (R/A‐TiO 2) heterostructured nanotree arrays are fabricated by assembling anatase nanowires as branches on rutile nanorods. External quantum efficiencies as high as 90% are reached at 325 nm. These high quantum efficiencies are related to the higher amount of light harvesting due to the larger surface area, the better separation ability of the photogenerated carriers by the rutile/anatase heterostructure, and the faster electron transport, related to the 1D nanostructure and lattice connection at the interface of the two kinds of TiO 2. Furthermore, a self‐powered wireless UV photodetector is shown with excellent wireless detection performance. Such devices will enable significant advances for next‐generation photodetection and photosensing applications. 相似文献
18.
In this study, a novel oxygen vacancy-rich BiOCl/ZnMoO4 composites were successfully prepared by a simple two-step method. Experimental results indicated that the content of BiOCl with oxygen vacancies played an important role in photocatalytic performance of OBZM heterostructures. OBZM-5 exhibited a highly enhanced photocatalytic activity under visible light irradiation compared to pure BiOCl, Ov-BiOCl, ZnMoO4 and other OBZM composites, which can be attributed to the efficient separation and transfer of photogenerated charge carrier. The photocatalytic degradation efficiency of rhodamine B (RhB) can reach 99% within 40 min and almost all of norfloxacin (NOR) can be degradated after 100 min by OBZM-5. In addition, OBZM-5 displayed a good stability during the photocatalytic process, which favored a long-term use. Moreover, a possible photocatalytic mechanism was proposed based on the active species trapping experiments and electron spin resonance (ESR) tests, verifying that the photogenerated holes (h+) and ·O2? radicals were the dominating active species. 相似文献
19.
It is of great significance to develop an efficient photocatalyst through simple methods for solar energy conversion and environmental pollution treatment. In this research, chlorophyll (Chl) and Mg co-modified hierarchical BiOCl microsphere photocatalyst with high performance was synthesized using a simple low temperature wet-chemical method. The synthesized photocatalyst with the optimal content of Chl and Mg showed superior photocatalytic performance for CO 2 reduction, where the maximum yield of methanol was 100.2 µmol/(h·g cat), which was about three times superior than that of pure BiOCl. Besides, the Chl-Mg/BiOCl also showed high performance (93.7%) for degradation of ciprofloxacin (CIP, a kind of antibiotic). Various characterization techniques were applied to determine the structure and evaluate the origin of the improved performance of Chl-Mg/BiOCl. Meanwhile, a possible mechanism for the excellent photocatalytic performance of Chl-Mg/BiOCl was proposed. Notably, Chl on the surface of BiOCl can lead to the formation of singlet state of Chl-Mg* after absorbing light and act as an electron donor which can enhance the stability and activity of the photocatalyst. What’s more, Mg not only acts as an electron capture site to inhibit the photogenerated carrier recombination, but also forms a complex with Chl to improve the stability of catalyst. This study would represent a promising candidate organic–inorganic hybrid photocatalyst for solar energy conversion and antibiotic pollution treatment. 相似文献
20.
ZnO nanopillars coated on various surfaces are able to kill adhered bacteria and fungi due to their physical structure through a rupturing mechanism. Remarkably, zinc foil and galvanized steel surfaces with ZnO nanopillar coatings demonstrate an excellent remote bacteria‐killing property. Their bacterial killing efficacy is several orders higher than ZnO nanopillars coated on other surfaces as well as ZnO nanoparticles themselves. Mechanistic study shows that the nanostructure surface kills adhered microbial cells by rupturing the cell wall, while superoxide ( ?O 2?) released from the ZnO coating with electrons donated from zinc via the Zn/ZnO interface rather than photoirritation is responsible for the superior remote killing. The results of this study represent a novel mechanism of surface disinfection and its application in water disinfection is also demonstrated. 相似文献
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