ZnO Nanoparticle Layer Research Articles

Circular economy reinforcement through molecular fabrication of textile wastes with microbial synthesized ZnO nanoparticles to have multifunctional properties

The fibrous wastes generated from the mills of textile production can be recycled and converted into high add-values products to be implemented in several applications. The current study aimed to employ commercial free cellulase enzyme to partially hydrolyze (activate) the polyester cotton blended (PET/C) fibrous wastes by creation functional groups such as OH and COOH on their surfaces. The activated fibrous wastes were then modified by coating with ZnO nanoparticles (ZnO-NPs) biosynthesized by actinobacterial cultures free supernatant. The isolate was identified as Streptomyces pseudogriseolus with accession number of OR574241. The conditions that influence the actino-synthesis of ZnO-NPs were optimized and the product was characterized using spectroscopic vision, FTIR, XRD, TEM and SEM. The characteristic ZnO peaks were obviously observed by EDX analysis with 0.38 and 0.75% (wt%), respectively. TEM analyses proved the nanoscale of ZnO-NPs (5–15 nm) which was followed by cytotoxic evaluation for the produced NPs. Fortunately, the tested actino-ZnO-NPs didn’t have any cytotoxicity against human normal fibroblast cell line (BJ1), which means that the product can be safely used in a direct-contact with human skin. The treated PET/C blended waste fabrics coated with ZnO-NPs showed high antimicrobial activity and ultraviolet protection values after functionalization by cellulase. EDX analysis demonstrates the presence of Zn peaks on the coated fabrics compared with their absence in blank and control samples, while SEM images showed the formation of a thin layer of ZnO-NPs on the fabric surface. The obtained smart textile can be applied several needed sectors.

Zinc Oxide-Based Rotational–Linear Triboelectric Nanogenerator

In this study, we evaluate a prototype harvesting device that converts rotational motion to linear motion for harvesting rotational energy. Triboelectric materials are attached to the parts of the device that execute linear motion, resulting in a contact-separation mode of operation of triboelectric generators. As a triboelectric material, thin layers of ZnO nanoparticles deposited on Kapton films are evaluated. The design of the rotational–linear triboelectric nanogenerator (RL-TENG) exhibits several advantages since it does not suffer from the issues related to rotational tribogenerators such as wear and increased temperature during operation. Moreover, our approach can result in the modular design of energy-harvesting devices for a variety of applications. As a demonstrator, cups were attached to the rotating axis of the RL-TENG to harvest wind energy that is suitable for maritime applications.

Study of dual Z-scheme photocatalytic response of TiO2/Ag/ZnO coating on plasma-modified cotton fabric for self-cleaning application

An innovative approach was adopted to improve the photocatalytic response of nanoparticle-coated cotton fabric for self-cleaning application. Fabrics with layers of TiO2, Ag, and ZnO nanoparticles were assessed for photodegradation of Rhodamine B, methyl orange, and methyl red. A dual-scheme charge transfer method was designed for the photocatalytic activity of TiO2/Ag/ZnO nanoparticles on cotton fabric. To produce the multilayer structure of nanoparticles, the fabric was first functionalized with atmospheric pressure nonthermal plasma and then sonochemically coated with TiO2/Ag/ZnO in a layered form. The plasma functionalization enhanced the stability of TiO2/Ag/ZnO nanoparticles on the fabric. It was revealed that a combination of Ag, TiO2, and ZnO nanoparticles produced a Schottky barrier among the silver metal and metal oxides (TiO2 and ZnO), resulting in enhanced photocatalytic properties. Methyl red underwent the highest photocatalytic degradation of 93% over the designed photocatalyst-coated fabric after 120 min of light exposure. This study provides a promising strategy for improving the photocatalytic self-cleaning efficacy of nanocoated fabrics.

Scalable Bilayer MoS2‐Based Vertically Inverted p–i–n Light‐Emitting Diodes

AbstractHerein, a vertically inverted p–i–n architecture of light‐emitting diodes (LEDs) is designed for manufacturing feasibility and demonstrated scalable bilayer MoS2‐based LEDs. A 4 inch scale bilayer MoS2 is prepared by a two‐step growth method allocating the pre‐deposition of a few‐nm thick metal film and post‐sulfurization. To apply bilayer MoS2 for an active layer in LEDs, the film is transferred over ZnO nanoparticle layers, an electron transfer layer, and then the rest of the LED components are constructed by thermal deposition. This vertically inverted LED architecture allows individual organic or inorganic components to incorporate without degradation during the wet‐transfer process and transfer electron or hole carriers across separate layers, resulting in efficient radiative recombination in the MoS2 emitting layer. MoS2‐based LEDs exhibit electroluminescence of ≈5.41 cd m−2 throughout four active areas of 6.25 mm2 at a driving voltage of 7 V. Therefore, this achievement can overcome the drawbacks of existing transition metal dichalcogenides (TMDs)‐based optoelectrical applications and extend its potential in various fields, such as flexible, ultrathin, or transparent displays.

Investigating of transition state on the Pd–Au decorated ZnO nanoparticle layers for gas sensor application

In this work, the mechanism of the transition state of electron transfer reaction on the surface of the ZnO nanoparticles-based gas sensor has been investigated. The deposited ZnO nanoparticles thick films on glass slides had been synthesized by the current heating method and modified its surface by coating novel metals of gold and palladium with a sputtering technique with different sputtering times of 45–180 s. Field emission electron microscopy (FE-SEM), x-ray diffraction spectroscopy (XRD), and energy dispersive spectroscopy (EDS) were used for the characterization of ZnO nanoparticle thick films. After that, the reflectance spectra of films were investigated using Near-IR spectroscopy in the range of 900–2500 nm to study the surface absorption efficiency. The decrease in reflectance spectra was observed for conditions over 90 s of sputtering time. The particle size distribution and zeta potential of ZnO nanoparticles were analyzed using the dynamic light scattering technique for the calculation of particle size and the electrical charge potential. The results showed that the size particle distribution ranged from 155 to 245 nm and the more extensive range of 360–1100 nm. The optimized zeta potential of −14.44 mV was exhibited at the sputtering time of 45 s. Finally, the gas sensing mechanism in terms of surface charge density was proposed and used to explain the sensitivity enhancement of both resistive and capacitive gas sensors.

To improve device performance of self-driven heterojunction photodetectors by inserting a thin layer of silver nanoparticles into the electron-transporting layer

Lead selenide colloidal quantum dots (CQDs) are widely used in infrared photodetectors due to their size-dependent bandgap tunability, facile solution-processing techniques and low cost. Heterojunctions (HJs) are usually used to construct device to facilitate the separation of excitons and the transportation of photogenerated carriers. Based on the solution-processed HJ photodetector ITO/ZnO/PbSe/Ag, in which PbSe CQDs layer acts as the active layer and ZnO nanoparticles (NPs) layer as the electron-transporting layer, a greatly enhanced-performance was obtained after inserting 10 nm Ag NPs layer within the ZnO NPs layer close to the HJ ZnO/PbSe interface. By optimizing the concentration of Ag NPs solutions and the location of Ag NPs thin layer in ZnO film, the maximum responsivity of the self-driven HJ photodetector ITO/ZnO(50 nm):Ag-NPs(10 nm):ZnO(50 nm)/PbSe(300 nm)/Ag reaches to 6.25 mA/W with a specific detectivity D* of 5.17 ×1011 Jones under 8.5 μW/cm² 1550 nm illumination at zero bias. Further, the underlain physical mechanisms for the enhanced-performance were discussed in details. In this way, it provides a very efficient method for enhanced-performance self-driven HJ photodetectors by inserting a thin layer of metal NPs into the electron-transporting layer close to the heterojunction interface.

Solution-processed ZnO nanoparticles (NPs)/CH3NH3PbI3/PTB7/MoO3/Ag inverted structure based UV–visible-Near Infrared (NIR) broadband photodetector

This paper reports a ZnO Nanoparticles (NPs)/CH3NH3PbI3/PTB7/MoO3/Ag inverted structure based UV–visible-Near Infrared (NIR) broadband photodetector fabricated on the fluorine-doped tin oxide (FTO) coated glass substrate. ZnO NPs layer acts as the electron transport layer (ETL), CH3NH3PbI3 acts as the active layer, PTB7 acts as the hole transport layer (HTL) and MoO3 is used to optimize the recombination current in the proposed photodetector structure. Spin coating method has been used for depositing the layers of ZnO NPs, CH3NH3PbI3 and PTB7 in the proposed structure while the MoO3 layer has been grown by the thermal evaporation method. The optical measurements over 350–850 nm wavelength range give the maximum photoresponsivity, detectivity and external quantum efficiency (EQE) of ∼0.36 A/W, ∼7.8x1012 Jones and ∼83.67% under −2 V, respectively. The proposed photodetector gives a rise time and fall time of 81 ms and 75 ms, respectively.

Silver Nanowire Electrodes Integrated in Organic Solar Cells with Thick Active Layer Based on a Low‐Cost Donor Polymer

Transparent electrodes are a key component in the manufacturing of optoelectronic devices such as light‐emitting diodes, touch screens, and solar cells. The transparent electrode commonly used in this field is based on indium tin oxide (ITO). It contains indium, which is an expensive, rare, difficult to extract, and depleting element, hence the need to find an alternative. Silver nanowire (AgNW) electrodes are one of the best alternatives due to their excellent electrical, optical, and mechanical properties. Herein, it is shown that embedding AgNWs between two layers of ZnO nanoparticles (ZnONPs) leads to superior optical and electrical performance. The validation of the ZnONPs/AgNWs/ZnONPs electrode using the reference PF2:PC70BM organic active layer, known to present a long carrier lifetime, in inverted solar cell architectures shows an increased absorption of the active layer. This enhancement is due to the electrical field resulting from plasmonic resonance because the absorption is proportional to the square of the electric field amplitude. Through photoluminescence spectroscopy, a shorter exciton lifetime in PF2 in the presence of AgNWs is also observed. All these processes lead to improved photovoltaic performance compared to ITO‐based reference, with approximately 20% increase in photocurrent and overall power conversion efficiency.

Electrochemical investigation of carbon paper/ZnO nanocomposite electrodes for capacitive anion capturing

In this work, we demonstrate an effective anion capturing in an aqueous medium using a highly porous carbon paper decorated with ZnO nanorods. A sol–gel technique was first employed to form a thin and compact seed layer of ZnO nanoparticles on the dense network of carbon fibers in the carbon paper. Subsequently, ZnO nanorods were successfully grown on the pre-seeded carbon papers using inexpensive chemical bath deposition. The prepared porous electrodes were electrochemically investigated for improved charge storage and stability under long-term operational conditions. The results show effective capacitive deionization with a maximum areal capacitance of 2 mF/cm2, an energy consumption of 50 kJ per mole of chlorine ions, and an excellent long-term stability of the fabricated C-ZnO electrodes. The experimental results are supported by COMSOL simulations. Besides the demonstrated capacitive desalination application, our results can directly be used to realize suitable electrodes for energy storage in supercapacitors.

Boosting Efficiency of InP Quantum Dots-Based Light-Emitting Diodes by an In-Doped ZnO Electron Transport Layer

InP quantum dots (QDs)-based light-emitting diodes (QLEDs) are considered as one of the most promising candidates for environmentally cadmium (Cd)-free electroluminescence devices. However, the performance of InP QLEDs still lags far behind that of Cd-containing QLEDs, which limits their practical applications in next-generation displays and lighting. Here, we report an all-solution processed green InP QLED, which is enabled by an electron transport layer (ETL) of In-doped ZnO (IZO) nanoparticles (NPs). The ETL of IZO NPs can not only suppress the exciton quenching of InP QDs emitting layer due to the reduced defect states, but also improve the charge balance by partially blocking the injection of electrons, and thus the device performance. The optimized InP QLED exhibits a maximum external quantum efficiency (EQE) of 5.42% corresponding to a current efficiency (CE) of 21.22 cd A <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , which is three times higher than that of the control device based on ZnO ETL, respectively. Our work suggests that IZO NPs can function as a good ETL material in QLEDs and other optoelectronic devices.

Recyclable Composites of Mo/Fe Co-Doped ZnO1−x/Cu2O for Enhanced Photocatalytic Nitrogen Fixation

A layer of Cu2O crystal film and ZnO nanoparticles doped with bimetallic Mo and Fe were successively grown on the surface of a copper mesh, which was applied in a liquid membrane photoreaction apparatus for photocatalytic nitrogen reduction reaction (PNRR). The characterization results indicate that the excellent ammonia yield benefits mainly from the synergistic effect of bimetallic doping, moderate oxygen vacancies (OVs), and p-n heterojunction. Surface defects caused by in situ doping of Mo and Fe ions act as active centers to capture and migrate electrons from the catalyst to adsorbed N2 molecule. With the introduction of bimetallic ions, the formation of more mesoporous enlarges the specific surface area, causing abundant reaction sites on the surface of the catalyst, which enhances the adsorption and activation of dinitrogen molecules. The existence of oxygen vacancy reduces the band gap and enhances the absorption of visible light. Furthermore, the p-n heterostructure promotes the effective transfer and separation of photogenerated carriers. Compared with the original Cu2O or ZnO, the photocatalytic ammonia yield of Mo–Fe co-doped ZnO/Cu2O is increased by 6.6 and 7.3 times, respectively, reaching 119.42 μmol cm−2 h−1.

Improved blue quantum dot light-emitting diodes via chlorine passivated ZnO nanoparticle layer* *Project supported by the National Key R&D Program of China (Grant Nos. 2016YFB0401702 and 2017YFE0120400), the National Natural Science Foundation of China (Grant Nos. 62005114, 62005115, and 61875082), Key-Area Research and Development Program of Guangdong Province, China (Grant Nos. 2019B010925001 and 2019B010924001), Guangdong University Key Laboratory for Advanced

In blue quantum dot light emitting diodes (QLEDs), electron injection is insufficient, which would degrade device efficiency and stability. Herein, we employ chlorine passivated ZnO nanoparticles as electron transport layer to facilitate electron injection into QDs effectively. Moreover, it suppresses exciton quenching at the QD/ZnO interface by blocking charge transfer channel. As a result, the maximum external quantum efficiency of blue QLED was increased from 2.55% to 4.60%, and the operation lifetime of blue QLED was nearly 4 times longer than that of the control device. Our work indicates that election injection plays an important role in blue QLED efficiency and stability.

Accelerated CO2 transport by synergy effect of ionic liquid and Zn particles

In this experiment, an ionic liquid (BMIMBF4) was used to prepare a composite membrane containing ZnO nanoparticles. Our previous study indicated that a composite membrane composed of ZnO and the ionic liquid (BMIMBF4) showed high CO2/N2 separation performance with a GPU of 101 and a selectivity of 42.1. The oxide layer of ZnO nanoparticles with the imidazolium ring of ionic liquid (BMIMBF4) increased the solubility of CO2 and acted as a barrier for N2, leading to an overall improvement in the performance. However, the liquid film was absorbed into support over time and became thickened, leading to instability. In order to solve this problem, a solid polymer composite film was manufactured and investigated as a solution. The polymer PEBAX2533 was used as a polymer matrix to produce a composite membrane capable of showing both high separation performance and long-term stability.

Flexible ultraviolet detector with robust ZnO nanoparticle nanoassemblies on catechol‐functionalized polysiloxane nanofilms

AbstractAs a result of the vast Young's moduli difference between an inorganic semiconducting channel and flexible substrates, flexible optoelectronic devices readily lose their functionality through material delamination and local fracturing, which lead to short‐circuiting of devices. For this study, we synthesized a catechol‐containing polysiloxane (CFPS) adhesive and applied it to ZnO nanoparticle (NP) assembly on plastic substrates for flexible UV detector applications. The 30 nm thick CFPS adhesive can anchor 70 nm thick ZnO NPs strongly through a coordination bond, thereby forming an ultra‐stable ZnO NP channel layer. A peeling test of ZnO NP layer was conducted using transparent tape (Scotch®; 3 M Inc.). The ZnO NPs were firmly immobilized, reflecting the outstanding mechanical stability of CFPS adhesives. A UV detector also exhibited stable photo‐response performance even after a thousand iterations of bending with 3 mm curvature radii. The result indicates the polycyclosiloxane‐based flexible device as promising for wearable detector applications.

Short-Wave Infrared PbS Colloidal Quantum Dot ZnO Nanowire Solar Cells Aimed at Tandem Solar Cells

Solution-processed tandem solar cells, that stack two or more single junction subcells with different band gaps to harvest photons in the full solar spectrum more efficiently, have attracted increasing attention recently. Organic photovoltaics and perovskite solar cells are promising candidates for the top and/or middle subcells of tandem solar cells because the solar cells are able to capture visible and near-infrared photon energy. However, there are few materials to choose from for the infrared bottom subcell. While PbS and PbSe colloidal quantum dots (CQDs) have been gaining much attention for short-wave infrared solar cells owing to their wide-range bandgap tunability and solution process compatibility. Among various CQD-based solar cells, PbS / ZnO depleted heterojunction solar cells showed a power conversion efficiency (PCE) over 13% in 2020 (Nat. Commun. 2020, 11 , 103). But there is a limited number of literatures reporting PbS-QD-based solar cells working in the low photon energy region (< 1.0 eV) where optical absorption of PbS QDs is weak. Thus, we have focused on PbS QD/ZnO nanowire (NW) structures with the aim of achieving efficient carrier transport and light absorption simultaneously (J. Phys. Chem. Lett. 2013, 4, 2455). We then investigated the performance of PbS QD/ZnO NW solar cells using PbS CQDs with the first exciton absorption peak locating in the short-wave infrared region. (ACS Energy Lett. 2017, 2, 2110). Here, we develop high efficiency infrared PbS CQDs solar cells aimed at the bottom subcell of tandem solar cells, and discuss the potential for the bottom subcell.We constructed two different solar cells using infrared PbS QDs with the first exciton absorption peak at 1550 nm, which is nanowire-type solar cell (NW-cell) and planar-type solar cell(P-cell). The ZnO nanoparticles layer (P-cell) or ZnO nanowire (NW-cell) as an electron acceptor formed on highly infrared transparent 1% Ta-doped SnO2 (TTO) conductive glass substrates. PbS CQD were deposited on the ZnO layers from a PbS QD octane solution via a layer-by-layer dip coating method. The PbS-QD layer were treated with a tetrabutylammonium iodide (TBAI) methanol solution to replace the insulating oleic acid ligands with iodide anions (PbS-I). The external quantum efficiency (EQE) spectra and the structures of the P-cell and NW-cell are shown in the figure. In the almost entire wavelength region ranging from 380 to 1700 nm, the EQE gave higher in the NW-cell than in the P-cell. The best performing planar-type solar cell exhibited a PCE of 2.68% (Jsc= 18.9 mA/cm2; Voc=0.316 V; FF=0.451) under 100 mW/cm2 simulated AM 1.5G illumination. On the other hand, ZnO nanowire-type solar cells gave a PCE of 5.38% (Jsc=38.7 mA/cm2; Voc=0.335 V; FF=0.415), and showed almost twice as high Jsc value (38.7 mA/cm2) as that of the planar-type solar cells. The integrated Jsc of the nanowire-type solar cells obtained from the EQE spectrum 38.5 mA/cm2 is approximately the measured Jsc value. To investigate the potential for the bottom subcell of the tandem solar cell, infrared-performance of nanowire-type solar cells were studied using different short-cut filters. The solar cells exhibited 2.50 % PCE (Jsc=19.2 mA/cm2; Voc=0.307 V; FF=0.424) and 1.11% PCE (Jsc=8.6 mA/cm2; Voc=0.282 V; FF=0.460) under a long-pass filtered one-sun illumination (l >810 nm (perovskite solar cells equivalent), and l>1100 nm (Si solar cells equivalent)), respectively. All these results indicate that the ZnO nanowire PbS QD solar cells are promising candidates to construct tandem devices with perovskite and c-Si solar cells. Figure 1

Fabrication and Evaluation of Electroluminescence Devices Using Quantum Dots As Light Emitting Materials

Colloidal quantum dots (QDs) have been attracting intense attention as promising candidates for new generation photoluminescent materials due to their fascinating optical properties, such as wide-band absorption, narrow-band emission, and high photoluminescence efficiency. These unique properties originate from semiconducting nature of the QD cores. The core is usually protected by an inorganic shell made of wider-gap semiconductors, resulting in photoluminescence quantum yield (PLQY) as high as 80%. CdSe-CdS and CdSe-ZnS core-shell QDs are such typical examples. Electroluminescence (EL) devices containing QDs in their emitting materials, which are known as QLEDs, have been demonstrated as a new type of display device providing better monochromaticity than conventional organic LED (OLEDs). However, the electroluminescence efficiencies of QLEDs have been inferior to that of OLEDs due probably to mismatch of the structure that has been developed based on OLEDs. Typically, the deep energy level of a valence band-edge (VB-edge) of the QDs hinders hole injection into QDs from HOMO of organic hole transport materials. Although developing new type of hole transport material is essential, one of the “indirect” strategies to solve this problem would be use of ZnO nanoparticles as an electron transport layer (ETL), which make use of deeper energy level of a VB-edge of ZnO nanoparticles. The resulting structure allows to accumulate holes in QD layer and facilitates hole injection into the QDs. However, the device structure of QLEDs still needs to be improved for more enhancing electroluminescence efficiencies. This study was carried out to design QLEDs structure which allows efficient charge injection into QDs by changing materials and thickness of the hole injection layer (HIL), and electron transport layer (ETL). The device performance was evaluated by voltage– current and voltage–luminance plots, and external quantum efficiency (EQE). CdSe-CdS-ZnS core-shell-shell nanoparticles used here were synthesized by the previously reported methods. Figure 1(a) shows the structure of the devices which consisted of layers of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT:PSS, 6 nm)/poly(N-vinylcarbazole) (PVK, 37 nm)/CdSe-CdS-ZnS core-shell-shell QDs (14 nm)/ZnO nanoparticles (x nm)/LiF (1 nm)/Al (100 nm), where the thickness of the ZnO layer was varied between 10 nm and 70 nm. Except for LiF and Al layers, which was deposited using the vacuum thermal evaporation, each layer was sequentially formed on ITO-patterned glasses by spin-coating. Figure 1(b) shows the normalized EL spectrum of the QLEDs having an emission peak at 628 nm with a narrow full-width at half-maximum of 35 nm. The inset shows the picture of device (3×3 mm) demonstrating the formation of uniform emission. Figure 1(c) shows the voltage–luminance plots for CdSe-based QLEDs. The device of x = 12 nm only attained a maximum luminance of 298 cd/m2 and a maximum EQE of 0.063% although enough current was flowing (~100 mA). This result indicates the occurrence of charge imbalance, probably because the holes were leaked out to reach the cathode (Al) due to the insufficient ZnO nanoparticle layer thickness. Then, the thickness of ZnO nanoparticle layer was gradually increased to x=31, 48, 68 nm, raising steady the values of maximum luminance and EQE. These results suggested that the thickness of each layer might have effects on hole-electron balance. The hole-only and electron-only devices were fabricated using the same CdSe-CdS-ZnS core-shell-shell QDs and voltage–current curves were measured. The electron-only device passed larger current than the hole-only device, indicating the lower resistance for electron injection and transport than hole injection and transport. These facts corresponded with the previous results that increment of ZnO layer improved the device performance. Finally, the device was modified based on that with x = 68 nm. The use of PEDOT:PSS (HIL) having lower resistance were fabricated to further improve the charge balance. As a result, the device achieved a maximum luminance of 6500 cd/m2 and a maximum EQE of 1.3%. Figure 1

Reduction of response time in transmissive optically addressed spatial light modulator using solution-based ZnO NP/PEDOT:PSS heterojunction

An optically addressed spatial light modulator (OASLM) works by using the intensity of a ‘write’ light to modulate the phase of a ‘read’ light. OASLM using ZnO nanoparticles (NPs) as a photoconductor is important to holographic displays because of its record-high spatial resolution. However, its response time to the write light is long and the switch-off time (τoff) can take tens of seconds due to the trap states in the ZnO NP layer. This results in residual images and poses limitations to its application in dynamic holographic displays. In this work, a ZnO NP photoconductor was replaced by a solution-processed ZnO NP/PEDOT:PSS heterojunction photodiode and the τoff of OASLM was significantly reduced to about 0.6 s. Electrical and optical properties of the heterojunction were characterized and a barrier height of 0.604 eV was determined by CV measurement. The heterojunction-based OASLM was then fabricated and its light modulating performance was investigated by using a diffractive phase grating. Finally, impedance spectroscopy was used to analysis the device equivalent circuit and optimize the operation of the OASLM.

An in-depth study of photocathodic protection of SS304 steel by electrodeposited layers of ZnO nanoparticles

Thin layers of ZnO nanoparticles were deposited potentiostaticly on the surface of stainless steel 304 (SS304) at various potentials (−0.7 V, −1.0 V, −1.3 V, −1.6 V) to study the effect of photo-generated cathodic protection on the substrate. Electrochemical methods of open circuit potential (OCP), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were employed to investigate the electrochemical behaviors of ZnO-covered SS304 system (ZnO/SS304) in 3.5 wt% NaCl solution under the conditions with and without UV illumination. It is found that the ZnO nanoparticles deposited at −1.0 V was in the shape of hexagonal nanorods, which caused a negative shift to lowest OCP upon UV illumination. Polarization curves were also performed on ZnO/ITO glass system to reveal the photoelectrochemical behavior of ZnO nanoparticles only. Possible anodic and cathodic reactions on the ZnO/SS304 and ZnO/ITO systems at the absence and presence of light illumination have been analysed and discussed in detail. It is found that traditional Tafel extrapolation of the polarization curves cannot be used to get the free corrosion current density of ZnO/SS304 system under light illumination due to the superposition of photo-generated current density. The charge transfer resistance obtained from EIS also includes the influence from the photo-generated reactions on the ZnO/SS304 system. Long-term immersion of the ZnO/SS304 in NaCl solution indicates that the ZnO nanorods underwent morphological transitions to nanotubes at 5 days and finally to needles and thin plates at 10 days. Correspondingly, the photocathodic protection of the ZnO layer decreases with the extension of immersion time. The transformation in morphology is postulated to be caused by the attack of Cl− ions on the surface of ZnO nanoparticles.

Large-size updatable optically addressed spatial light modulator (OASLM) based on ZnO nanoparticles for large-area holographic 3D displays

Optically addressed spatial light modulators (OASLMs) provide an appropriate solution for large-area and wide-viewing angle holographic displays because of the possibility of uploading holograms on it through tiling and with sub-micron diffraction feature sizes. A prototype with a large-size OASLM of 100 mm × 100 mm was fabricated using a solution-based deposition process for ZnO nanoparticles (NPs). ZnO NP-based OASLM is suitable for hologram tiling because of the extended charge carrier lifetime as a result of trap states in the ZnO NP layer annealed at a low temperature of 180°C, of which the activation energy was determined firstly by low-temperature measurements. Operating the ZnO NP OASLM in a DC driving mode was subsequently proposed, to utilize the extended charge carrier lifetime in the photosensor layer for temporary information storage. Finally, techniques to tile computer generated holograms (CGHs) spatially on a single OASLM were explored and evaluated, including the demonstration of simultaneous image replay from sequentially tiled two separate phase-only CGHs.

In-Situ Surface Modification of Terpinen-4-ol Plasma Polymers for Increased Antibacterial Activity.

Surface modification of thin films is often performed to enhance their properties. In this work, in situ modification of Terpinen-4-ol (T4) plasma polymer is carried out via simultaneous surface functionalization and nanoparticle immobilization. Terpinen-4-ol plasma polymers surface were decorated with a layer of ZnO nanoparticles in an oxygen plasma environment immediately after polymer deposition. A combination of hydrophilic modification and ZnO nanoparticle functionalization of the T4 polymer surface led to an enhancement in antibacterial properties by factor of 3 (from 0.75 to 0.25 CFU.mm−2). In addition, ZnO nanoparticle-modified coatings demonstrated improved UV absorbing characteristics in the region of 300–400 nm by 60% relative to unmodified coatings. The ZnO modified coatings were transparent in the visible region of 400–700 nm. The finding points towards the potential use of ZnO nanoparticle-modified T4 plasma polymers as optically transparent UV absorbing coatings.