ZnO Nanoparticle Films Research Articles

Nanocomposite Films of Babassu Coconut Mesocarp and Green ZnO Nanoparticles for Application in Antimicrobial Food Packaging.

In this work, novel nanocomposite films based on babassu coconut mesocarp and zinc oxide nanoparticles (ZnO NPs), synthesized by a green route, were produced for application as food packaging films. The films were prepared using the casting method containing different contents of ZnO NPs (0 wt%, 0.1 wt%, 0.5 wt%, and 1.0 wt%). The films were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), instrumental color analysis, and optical properties. The water vapor permeability (WVP) and tensile strength of films were also determined. The antimicrobial activity of the films against cooked turkey ham samples contaminated with Staphylococcus aureus was investigated. The results showed that incorporating ZnO NPs into babassu mesocarp matrices influenced the structure of the biopolymer chains and the color of the films. The BM/ZnO-0.5 film (0.5 wt% ZnO NPs) showed better thermal, mechanical, and WVP properties. Furthermore, the synergistic effect of babassu mesocarp and ZnO NPs in the BM/ZnO-0.5 film improved the antimicrobial properties of the material, reducing the microbial count of S. aureus in cooked turkey ham samples stored under refrigeration for 7 days. Thus, the films produced in this study showed promising antimicrobial packaging materials for processed foods.

Low-temperature welding engineering of ZnO nanoparticles films via sol-gel method

ZnO nanoparticles is a highly promising semiconductor material as an electron transfer layer layer (ETL) in various optoelectronic devices. The cost-effective and low-temperature preparation method renders it ideal for the development of flexible and large-scale modules, aligning seamlessly with the commercialization process. However, Solution-derived ZnO exhibits a significant number of surface defects, which affect the device's photoelectric conversion performance and stability. Herein, a simple strategy focusing on controlling the nano size of ZnO was employed to mitigate these surface defects. Welded ZnO films were prepared via spin coating with a precise amount of ZnO sol into dispersion. These films were characterized via techniques such as TEM, FSEM XRD, DLS, UV/vis and so on. PL spectra revealed a notable decrease in defect density with the increase in nano size. AFM reveals that films doped with 15 % sol exhibit root mean square (RMS) values of less than 1 nm, indicative of improved smoothness. Moreover, the four-point probe detected enhanced electrical conductivity attributed to the compact structure and improved integrity of the films. The presence of nanoparticles facilitates the crystallization of ZnO sol, allowing for an annealing temperature during the welding process to as low as around 90°C, compatible with flexible plastic substrates such as PET. The welded ZnO films produced at a low temperature in this study demonstrate high potential as ETL for flexible optoelectronic devices, which is conducive to their commercialization and large-scale deployment.

Characterization of banana powder-based film reinforced with CNF and Bio-mediated ZnO nanoparticles for potential food applications

The formulation of a multifunctional nanocomposite packaging material with potential against agents of food deterioration, such as free radicals and microorganisms, has emerged as a solution for shelf-life extension and food security. This study developed banana powder (BP) film infused with cellulose nanofiber (CNF) and ZnO-PPW and ZnO-PSW nanoparticles (NPs) at different concentrations for food applications. The BP/CNF/ZnO films were characterized using UV–vis spectroscopy, XRD, FT-IR, and SEM techniques. The analyses confirmed the successful infusion of ZnO NPs into the BP/CNF matrix, leading to significant changes (p < 0.05) in color and appearance, enhanced UV–vis barrier properties, and increased thickness and flexibility of the films. Furthermore, the presence of ZnO in the base matrix influenced the moisture content (19%–29%), film solubility (68%–74%), and oil permeability significantly more than the control BP/CNF film. Adding ZnO significantly improved the UV barrier properties compared to the control. The nanocomposite BP/CNF/ZnO films demonstrated concentration-based antioxidant and good antimicrobial activity against five selected food pathogens (Escherichia coli, Enterococcus faecalis, Listeria monocytogenes and Staphylococcus aureus). Similarly, good antioxidant properties were reported in different assays, proving superior to the control BP/CNF. These key findings, especially those of the BP/CNF/ + 0.6% ZnO NPs films, showed that these films possess great potential for application as food packaging materials with antioxidant and antimicrobial properties.

Enhanced photoresponse of annealed ZnO nanoparticle film near its bandgap

Enhanced photoresponse of annealed ZnO nanoparticle film near its bandgap

SERS-substrates based on ZnO nanoflowers prepared by green synthesis

ZnO nanoparticles (NPs) with a flower-like morphology, synthesized by an affordable colloidal route using an aqueous fungi extract of Ganoderma lucidum as a reducing agent and stabilizer, are investigated as SERS-substrate. Each “flower” has large effective surface that is preserved at packing particles into a dense film and thus exhibits an advantageous property for SERS and similar sensing applications. The mycoextract used in our low-cost and green synthesis as surface stabilizer allows subsequent deposition of metal NPs or layers. One type of SERS substrates studied here was ZnO NPs decorated in situ in the solution by Ag NPs, another type was prepared by thermally evaporating Ag layer on the ZnO NP film on a substrate. A huge difference in the enhancement of the same analyte in the solution and in the dried form is found and discussed. Detection down to 10−7 M of standard dye analytes such as rhodamine 6G and methylene blue was achieved without additional optimization of the SERS substrates. The observed SERS-activity demonstrate the potential of both the free-standing flower-like ZnO NPs and thereof made dense films also for other applications where large surface area accessible for the external agent is crucial, such as catalysis or sensing.

Investigating the differences in structure, morphology, optical properties, laser photoluminescence and dielectric properties for chitosan-doped commercial and Polycladia myrica mediated ZnO nanoparticles films combined with TD-DFT simulations

A homogeneous solution of chitosan nanoparticles in acetic acid was prepared as nano-monoblend thin film [Chit]TF. The biosynthesis ZnO nanoparticles [ZnO(b)]NPs were prepared via Polycladia myrica algal extract. A mono-nanocomposite of the chitosan nano-monoblend with commercial ZnO nanoparticles and bio ZnO nanoparticles [Chit/ZnO(c)]MNC and [Chit/ZnO(b)]MNC was synthesized using the dip casting deposition technique, respectively. Geometry optimization was achieved using TD-DFTD/Mol3 and Cambridge Serial Total Energy Bundle (TD-FDT/CASTEP) modules of the Density functional theory (TD-DFT). Molecular structure was studied and confirmed by the close matching between the experimental and simulated XRD patterns. [Chit]TF, [Chit/ZnO(c)] MNC and [Chit/ZnO(b)]MNC found to have an average crystallite size of 95.03 nm, 63.33 nm and 50.44 nm according to the calculations of XRD data. Optical energy gab of the direct allowed transition for [Chit]TF, [Chit/ZnO(c)] MNC and [Chit/ZnO(b)]MNC found to be 2.95, 2.885 and 2.705 eV, respectively. While, the simulated calculations of the isolated molecules [Chit]Iso and [Chit/ZnO]MNC/Iso by TD-DFT/DMol3 measured the energy gab as 3.217 and 2.83 eV, respectively. The suggested optical properties using CASTEP in TD-DFT agree quite well with the experimental values. A small difference in the dielectric properties between [Chit/ZnO(c)] MNC and [Chit/ZnO(b)]MNC was observed since [Chit/ZnO(b)]MNC found to have lower dielectric constant and conductivity values and higher electric modulus and impedance values. The wide range optical energy gab and good optical and dielectric properties of [Chit/ZnO(c)] MNC and [Chit/ZnO(b)]MNC are advantageous for various optoelectronic applications.

A self-powered triboelectric UV photodetector based on coupling impedance matching and photoresistive effect by sensing-electrode model

Self-powered photodetectors can satisfy the development demands of Internet of things towards minimization, integration, intelligence and multifunctionality. In this work, we have reported a self-powered triboelectric UV photodetector (SPTUD) based on coupling impedance matching and the photoresistive effect. A sensing-electrode model is validated through replacing the traditional electrode by ZnO nanoparticle film in a single-electrode mode triboelectric nanogenerator (S-TENG). Working both as the photoresistive material and electrode, the resistance variation range of the ZnO film matches well with the resistance dependence of S-TENG. The output voltage is significantly affected by the variations in variable resistances of ZnO film altered by UV light intensity due to the impedance matching effect. As a self-powered UV photodetector, the voltage signal of SPTUD increases from 0.5 V to 1.1 V with increasing light intensity from 0 to 0.61 mW/cm2 under 375 nm UV light illumination. It can efficiently detect low-intensity UV light of 0.17 mW/cm2 with a voltage responsivity of 2.66 V (mW cm−2)−1. For demonstration, a wearable self-powered UV photodetection system based on the S-TENG and SPTUD is integrated in a bracelet. The reference-electrode and sensing-electrode are designed to connected with chip LEDs for visualized UV light photodetection to remind people to take effective measures for harmful UV light protection out of door. This work proposes the concept of sensing-electrode model, and we believe it will pave a new avenue for the next-generation of self-powered triboelectric sensors.

A simple approach for coffee-ring suppression yielding homogeneous drying patterns of ZnO and TiO2 nanoparticles

Evaporation-induced self-assembly in colloidal droplets is a method for organising nanoparticles on substrates, with various resulting patterns. The coffee-ring pattern is among the most common ones, but its non-uniformity limits its applicability, which led to efforts for developing coffee-ring suppression strategies. Considering the wide applicability of ZnO and TiO2 nanoparticles, there is a high demand for practical means to deposit them as uniform films. Here, we present a simple approach for obtaining highly uniform thin films of ZnO and TiO2 nanoparticles by drop-coating in ambient conditions, without using surfactants or other surface chemistry modifications. Disc-like films were obtained via a restricted evaporation achieved by covering the droplets with a lid during drying, seconded by the relatively high sedimentation rate of these nanoparticles. To better understand the assembly mechanism, the influence of suspension concentration, type and temperature of the substrate, droplet volume, colloid type, and evaporation rate were studied. The method allows preparing disc-like nanoparticle films with a good control over their diameter and thickness, onto different kinds of substrates (glass, Si, polyethylene terephthalate, polystyrene). By fabricating both two-dimensional lattices and custom disc patterns we highlight the versatility of this drop-coating method and its potential for, e.g., automatized serial production processes.

Low-Temperature UVO-Sintered ZnO/SnO2 as Robust Cathode Buffer Layer for Ternary Organic Solar Cells.

The cathode buffer layer (CBL) plays a crucial role in organic solar cells (OSCs), and it has been challenging to obtain high-quality CBL by using simple and reliable processes. In this paper, the bilayer structure consisting of ZnO nanoparticles (NPs) and sol–gel SnO2 was prepared by the low-temperature (<100 °C) UV-ozone (UVO) sintering process and used as the robust CBL for ternary OSCs based on PTB7-Th:PCDTBT:PC70BM. The results show that the insertion of SnO2 can effectively fill the cracks and pores on the surface of the ZnO NP film, thereby improving the overall compactness and flatness of the CBL and reducing the defect density inside the CBL. Furthermore, the insertion of SnO2 slightly improves the transmittance of the CBL to photons with wavelengths in the range of 400–600 nm, and also increases the electron mobility of the CBL thus facilitating the extraction and transport of the electrons. Compared to the devices using UVO-ZnO and UVO-SnO2 CBLs, the devices with UVO-ZnO/SnO2 CBL exhibit exceptional performance advantages, the best power conversion efficiency (PCE) reaches 10.56%. More importantly, the stability of the devices with ZnO/SnO2 CBL is significantly improved, the device (PCE) still maintains 60% of the initial value after 30 days in air. The positive results show that the UVO-ZnO/SnO2 is an ideal CBL for OSCs, and due to the low-temperature process, it has great application potential in flexible OSCs.

Motility Suppression and Trapping Bacteria by ZnO Nanostructures

Regulating the swimming motility of bacteria near surfaces is essential to suppress or avoid bacterial contamination and infection in catheters and medical devices with wall surfaces. However, the motility of bacteria near walls strongly depends on the combination of the local physicochemical properties of the surfaces. To unravel how nanostructures and their local chemical microenvironment dynamically affect the bacterial motility near surfaces, here, we directly visualize the bacterial swimming and systematically analyze the motility of Escherichia coli swimming on ZnO nanoparticle films and nanowire arrays with further ultraviolet irradiation. The results show that the ZnO nanowire arrays reduce the swimming motility, thus significantly enhancing the trapping ability for motile bacteria. Additionally, thanks to the wide bandgap nature of a ZnO semiconductor, the ultraviolet irradiation rapidly reduces the bacteria locomotion due to the hydroxyl and singlet oxygen produced by the photodynamic effects of ZnO nanowire arrays in an aqueous solution. The findings quantitatively reveal how the combination of geometrical nanostructured surfaces and local tuning of the steric microenvironment are able to regulate the motility of swimming bacteria and suggest the efficient inhibition of bacterial translocation and infection by nanostructured coatings.

Strong Potential Gradients and Electron Confinement in ZnO Nanoparticle Films: Implications for Charge-Carrier Transport and Photocatalysis

Zinc oxide (ZnO) nanomaterials are promising components for chemical and biological sensors and photocatalytic conversion and operate as electron collectors in photovoltaic technologies. Many of th...

Germanium nanoparticles film as a room-temperature electron transport layer for organic solar cells

The performances of the organic solar cells (OSCs) largely depends on the selection and preparation of the electron transport layer (ETL). In this paper, the uniform and compact Ge nanoparticles (NPs) film was fabricated by using the plasma enhanced chemical vapor deposition (PECVD) method at room temperature. The Ge NPs film is formed by close packing of amorphous Ge particles with an average diameter of 6.05 nm, and the film shows a fairly smooth surface with a root-mean-square (RMS) roughness of 0.6419 nm. The results shows that Ge NPs film exhibits n-type characteristics, and the longitudinal conductivity of the film is 1.90 × 10−5 S/cm, which is better than that of the ZnO NPs film. The excellent longitudinal charge transport characteristics is attributed to the existence of the columnar structures in the Ge NPs. In addition, the Ge NPs film shows a visible light transmittance comparable to that of the ZnO NPs film. More importantly, the energy levels of the Ge NPs film meets the requirements of the PTB7:PC70BM OSCs for the ETL, and the devices with the Ge NPs ETL shows the power conversion efficiency (PCE) of 7.38%. The characteristic of room temperature preparation make the Ge NPs ETL may become a reliable choice for the flexible devices in the near future.

Influence of ZnO nanoparticles on the performance of LED based on oligomer thin films

In this work, a set of thin films of ZnO nanoparticles doped with a conjugated oligomer {9,9,9′,9′,9″,9″-hexakis(hexyl)-2,7′;2′,7″-trifluorene} has been prepared. The optical and electrical measurements on pure oligomer, ZnO nanoparticles, and blended thin films have been investigated. The absorption spectra of the pure oligomer in thin films showed a single band at 350 nm. When the thickness was increased, there was no new band detected at the end of the spectrum. This is a strong indication that the oligomer cannot be present in the dimeric state. On the other hand, the photoluminescence (PL) spectra of the oligomer showed two distinguished peaks at 400 and 420 nm due to the monomer and excimer states, respectively. Furthermore, the results showed that the PL spectrum of the oligomer was affected by the thickness. For the blended thin films with different ratios of ZnO nanoparticles, the PL spectra showed an enhancement in intensity by increasing the concentration of ZnO nanoparticles. For the electrical properties, the addition of ZnO nanoparticles to oligomer had increased the current and luminescence. The luminescences of the pure and blend film at 10 V had reached 1000 and 4200 cd/m2, respectively; and the turn-on voltage was reduced from 10.5 to 5.8 V. The light emission in the device is due to the Auger-assisted energy up-conversion process. The lifetime of the blend’s diodes measured under standard atmospheric conditions was greatly improved.

Effect of electrodeposition temperature on the thin films of ZnO nanoparticles used for photocathodic protection of SS304

Abstract Films of ZnO nanoparticles were electrodeposited on indium-doped tin oxide (ITO) glass under different temperatures between 40 and 80 °C to study their photogenerated cathodic protection to stainless steel 304 (SS304). Morphology, crystallographic information and optical performance of the ZnO films were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis spectroscopy and photoluminescence (PL) spectroscopy, respectively. The photocathodic protection of ZnO films on SS304 were evaluated by electrochemical methods. It was found that the ZnO films obtained at 40 °C is cauliflower-like in microstructure, while those obtained between 60 and 80 °C are hexagonal nanorods. The films prepared at 40 °C cause the most negative shift of the open circuit potential (OCP) of SS304 and produce photocurrent more than 10 times greater than those of the films obtained at higher temperatures. The excellent photocathodic performance of the ZnO nanoparticles prepared at 40 °C is attributed to the abundance of defects in its microstructure, which greatly reduces the electron-hole recombination rate upon UV illumination. The findings in this paper reveal that the defective ZnO nanoparticles obtained at low electrodeposition temperature display more efficient photocathodic protection and controlling the defects in semiconductor material may be a feasible way to improve its photoactivity.

Optical and Photodetection Properties of ZnO Nanoparticles Recovered from Zn Dross

In this study, we report the synthesis of ZnO nanoparticles from Zn dross via hydrometallurgical method by using acetic acid as a leaching agent. D205 dye molecules were then adsorbed onto Zn dross originated ZnO nanoparticle film. The optical absorption confirms the photosensitization of the synthesized ZnO nanoparticles with dye. The photoluminescence spectra reveal the excitonic- and defect-related emission of ZnO nanoparticles. Compared to ZnO nanoparticles only, the longer emission lifetime of ZnO nanoparticles with adsorbed dye indicates the transfer of photoexcited electrons from dye to the ZnO nanoparticles. Furthermore, photodetection characterization of ZnO film show the enhanced current density with the presence of dye under simulated solar illumination, while that measured at dark is similar in both films with and without dye. This result confirms the potentiality of Zn dross to be recycled into valuable ZnO nanoparticles particularly for the applications in the visible light region, especially for sensing.

(Invited) Ultrafast X-Ray Studies of Electron Dynamics Underlying Molecular and Nanoplasmonic Light Harvesting Architectures

Chemically engineered light harvesting architectures based on molecular and nanoplasmonic chromophores in contact with semiconducting electron acceptors provide exciting opportunities for novel photocatalytic and photovoltaic applications. Optimizing their performance, however, often hinges on a deeper understanding of the underlying fundamental electronic and chemical dynamics. Processes evolving on spatial and temporal scales spanning many orders of magnitude have to be connected in order to enable molecular, interfacial, and macroscopic charge and energy transport. We will discuss the application of ultrafast X-ray spectroscopy techniques to gain deep insight into photoinduced electronic dynamics in complex, heterogeneous light-harvesting systems based on organic heterojunctions as well as molecule-semiconductor and metal nanoparticle-semiconductor interfaces.Femtosecond and picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS) is used to study photoinduced charge injection in N3 dye-sensitized films of ZnO nanoparticles. The elemental site-specificity and surface sensitivity of TRXPS provides a comprehensive real-time picture of the interfacial charge dynamics including the locations of intermittently trapped electrons, the emergence and decay of interfacial dipoles, as well as charge-injection induced band-bending dynamics in the semiconductor substrate. Potential consequences of the findings for the design of dye-sensitized nanoporous electrodes are discussed.TRXPS studies of photoinduced dynamics in copper-phthalocyanine(CuPc)-C60 heterojunctions provide a deeper understanding of the predominant energy transport and charge generation mechanisms. Ultrafast X-ray probing captures the actual moment of charge generation from interfacial charge-transfer (ICT) states and provides a quantitative measure of the exciton dissociation efficiency compared to photon energy loss by exciton recombination. The findings complement observations with ultrafast optical techniques, adding important aspects regarding the dynamic pathways and branching ratios that govern charge generation efficiencies in this canonical model system for organic light harvesting concepts.In a third showcase example, photoinduced charge transfer dynamics in a nanoporous film of TiO2 sensitized with gold nanoparticles (AuNPs) is monitored by TRXPS. Direct access to the absolute photon-to-charge conversion efficiency and subsequent electron-hole recombination dynamics is demonstrated with single-electron sensitivity. The results provide important boundary conditions for the design of AuNP-TiO2 based light harvesting systems. Opportunities for extending the measurements toward studies of photoinduced interfacial chemical transformations will be discussed.

Effect of Time-Dependent Characteristics of ZnO Nanoparticles Electron Transport Layer Improved by Intense-Pulsed Light Post-Treatment on Hole-Electron Injection Balance of Quantum-Dot Light-Emitting Diodes.

We investigated the effect of intense-pulsed light (IPL) post-treatment on the time-dependent characteristics of ZnO nanoparticles (NPs) used as an electron transport layer (ETL) of quantum-dot light-emitting diodes (QLEDs). The time-dependent characteristics of the charge injection balance in QLEDs was observed by fabrication and analysis of single carrier devices (SCDs), and it was confirmed that the time-dependent characteristics of the ZnO NPs affect the device characteristics of QLEDs. Stabilization of the ZnO NPs film properties for improvement of the charge injection balance in QLEDs was achieved by controlling the current density characteristics via filling of the oxygen vacancies by IPL post-treatment.

Modification of Cellulose Nanofibers by ZnO Nanoparticles for Gas Sensing

Nanocellulose crystals (NCC) were isolated from the palm fronds by sonication and hydrolyzed processes and modification of them by the prepared ZnO nanoparticles (ZNPs) utilizes pulsed laser ablation in water. NCC:ZNPs layers were fabricated using the spin coating technique. The morphological properties of NCCs and NCC: ZNPs layers were investigated by atomic force microscopy (AFM), scanning electron microscopy and field-effect scanning electron microscope (FESEM) respectively. NCC fibers have been shown a long fibrous shape with layer fibrous sheets about 60 nm of thickness consist of nano tapes between 30 nm to 70 nm of width and thickness sequentially. ZNPs clusters appeared clearly in FE-SEM image as individual growths between 20 nm to 240 nm of size and around NCC fibers. The structural properties of prepared layers have been characterized by X-ray diffraction (XRD) technique, the domain peak of cellulose is found at 22.54° mostly. There is increasing in the crystallinity indices with the number of layers were increased in both NCC and NCC: ZNPs films. The sensing of N2, H2 and NH3 gases were measured, generally the sensitivity of gases increased with adding of ZNPs expect N2.

SYNTHESIS AND CHARACTERIZATION OF ZnO NANOPARTICLE FILMS ITS APPLICATION IN DYE-SENSITIZED SOLAR CELLS

ZnO nanoparticle films were prepared using facile precipitation with low-toxic solvents. The nanoparticle films were observed in compact formation with uniform nanoparticle sizes, good distribution, and high specific surface areas. The chemical composition of Zn and O was detected and the optical band gap was estimated. The hexagonal wurtzite structure of ZnO nanoparticle films was confirmed by XRD and Raman. For dye-sensitized solar cell application, power conversion efficiency of 2.51% was measured due to the concurrent improvements of dye adsorption and charge collection efficiency. Therefore, ZnO nanoparticle films be considered as a well-functional material to turn suitable structures for DSSC application.

Improvement of hydration properties of pectin/ alginate films with ZnO nanoparticles

This study aims to develop hydration properties of P/AG films by using ZnO nanoparticles. Pectin/ alginate/ ZnO nanoparticles (P/AG/ZnO-NPs) films are fabricated at various ZnO-NPs contents (0, 0.01, 0.05, 0.1 and 0.5 g/100g solution). The addition of ZnO-NPs at content 0.1 g/100g solution in the film decreases swelling degree (SD) from 327.98% to 110.12% and water vapor permeability (WVP) from 0.873 g.mm/m2.day.kPa to 0.358 g.mm/m2.day.kPa. Moisture sorption isotherm shows that P/AG/ZnO-NPs films should be used at lower than 86% RH. The Peleg model is the best model for predicting the equilibrium moisture content (EMC) of P/AG/ZnO-NPs films. Scanning electron microscope (SEM) micrographs of surface and cross section morphology of P/AG and P/AG with 0.1% ZnO-NPs films have indicated that there are interactions between ZnO-NPs and pectin-alginate matrix. Results have suggested that it would be favorable to prepare P/AG/ZnO-NPs film by using ZnO-NPs at the amount of 0.1 g/100g solution for food preservation.