Layer Of Zinc Oxide Nanoparticles Research Articles

Non-monotonic evolution of the responses of ZnO-nanoparticle UV-sensitive devices under ambient aging

Ultraviolet (UV) sensitive devices based on spin-coated zinc-oxide nanoparticles (ZnO) were fabricated and characterised. They were subsequently stored in the ambient and dark conditions with low humidity for 56 days, during which time they were intermittently recharacterised to determine the aging effect on their sensing properties, including responsivity, sensitivity, and response and recovery times. Over the 56-day period, both the dark and illumination currents increased, causing the non-monotonic evolution of the performances of the devices – the responsivity improved by 9–18 folds, the sensitivity remained stable, and the response and recovery times deteriorated as they were 46 and 33 times longer, respectively. These changes were associated with an increase in the number of adsorbed oxygen molecules on the ZnO surface with time. This resulted in more photodesorbed oxygen molecules and thus more remaining charge carriers under illumination, which increased the photo-generated current and consequently responsivity. However, it also caused the current to rise and decay more slowly when the illumination appeared and disappeared, respectively, leading to the prolonged response and recovery times. The longer recovery times led in an increase in dark current, which, when combined with an increase in illumination current, resulted in a stable sensitivity. The trends of these sensing parameters were similar, but to varying degrees, regardless of the change in the radiation levels and ZnO layer thicknesses.

Effect of Plasticisers and Zinc Oxide Nanoparticle Concentration on the Properties of Polyethylene Thin Films

The present work describes the preparation of a polyethylene film covered with a protective layer of zinc oxide nanoparticles (ZnO NPs). The presence of ZnO NPs on a slide supplemented with polyethylene was confirmed by the appearance of white cloud-like spots. Various ZnO NP concentrations were examined for their impact on optical and physical properties and in terms of inhibiting the growth of bacteria that can cause excessive irritation or intolerable skin sensitivity in the long term. This newly developed film holds potential for use in baby diapers to reduce bacterial contamination.

Metal oxide nanoparticles as solid contact in ion-selective electrodes sensitive to potassium ions

In recent years, various types of nanomaterials and nanoparticles have been very popular, also in analytical chemistry for sensors preparation. Ion-selective electrodes with solid contact were constructed, in which a layer of nanoparticles of selected metal oxides (zinc, copper and iron oxides) obtained by pulsed laser liquid ablation (PLAL) was placed between the glassy carbon solid electrode material and the ion-selective membrane. The basic analytical parameters of the obtained sensors were determined using potentiometric methods. Additionally, the electrochemical impedance spectroscopy method (EIS) was also used to investigate the electrical properties of the sensors. The obtained results were compared for all types of electrodes, both modified and unmodified, in order to investigate the effect of the type of nanoparticles and the thickness of their layer used as solid contact. It was found that the addition of metal oxide nanoparticles improved the analytical parameters of the sensors, mainly the potential stability and electrical parameters. The best results were obtained for an electrode with an intermediate layer of zinc oxide nanoparticles. In this case, a slope of −56.07 mV/dec, a linearity range of 1 × 10−5 – 1 × 10−1 mol L−1 and a limit of detection of 3.66 × 10−6 mol L−1 were obtained. Particularly noteworthy is the significant improvement in the stability of the potential of this electrode and the long life of more than 5 months.

Effects of Ambience on Thermal-Diffusion Type Ga-doping Process for ZnO Nanoparticles

Various annealing atmospheres were employed during our unique thermal-diffusion type Ga-doping process to investigate the surface, structural, optical, and electrical properties of Ga-doped zinc oxide (ZnO) nanoparticle (NP) layers. ZnO NPs were synthesized using an arc-discharge-mediated gas evaporation method, followed by Ga-doping under open-air, N2, O2, wet, and dry air atmospheric conditions at 800 °C to obtain the low resistive spray-coated NP layers. The I–V results revealed that the Ga-doped ZnO NP layer successfully reduced the sheet resistance in the open air (8.0 × 102 Ω/sq) and wet air atmosphere (8.8 × 102 Ω/sq) compared with un-doped ZnO (4.6 × 106 Ω/sq). Humidity plays a key role in the successful improvement of sheet resistance during Ga-doping. X-ray diffraction patterns demonstrated hexagonal wurtzite structures with increased crystallite sizes of 103 nm and 88 nm after doping in open air and wet air atmospheres, respectively. The red-shift of UV intensity indicates successful Ga-doping, and the atmospheric effects were confirmed through the analysis of the defect spectrum. Improved electrical conductivity was also confirmed using the thin-film-transistor-based structure. The current controllability by applying the gate electric-field was also confirmed, indicating the possibility of transistor channel application using the obtained ZnO NP layers.

Integration of nanocomposite finishing on polyester fabric for enhanced UV protection, performance, and comfort properties

This research focuses on the integration between functional finishing and the performance properties of polyester fabric for comfortable clothes. The effects of nanofinishing (zinc oxide nanoparticles and nano-polyurethane nanocomposite) on the ultraviolet protection properties of polyester fabric, the whiteness index, and the Kawabata Evaluation System were studied. Under the optimum finishing conditions, excellent protection (150) was achieved at lower concentrations of the nanocomposite, and zinc oxide nanoparticles individually enhanced the whiteness index (73). The results of the Kawabata Evaluation System showed that the finishing processes improved mechanical and performance properties (tensile, shearing, bending, compression, surface roughness, thermal, and hand properties), indicating that all the finished fabrics offered enhanced functionality, thermal and comfort properties. Enhanced total hand value properties (3.7 for summer and 5.1 for winter) were realized by finishing, assuming the finished fabrics were applied to men’s shirts and women’s dresses for summer and winter apparel. Scanning electron microscopy and energy disperse X-ray spectroscopy analyses showed a uniform layer of zinc oxide nanoparticles and nano polyurethane on the fiber surface. Fourier transform infrared spectroscopy confirmed the structural changes in the finished fabric.

Power conversion efficiency of hybrid solar cells based on Camellia sinensis doped polyvinyl alcohol and ZnO nanoparticles

Hybrid solar cells were fabricated by Camellia sinensis blended polyvinyl alcohol (PVA) as an active medium and using zinc oxide (ZnO) incorporated as light scattering nanoparticles (NPs). The power conversion efficiency of such hybrid solar cells was enhanced. This was due to the broad absorption spectra of PVA upon doping with Camellia sinensis and ZnO NPs employed as an interfacial layer. J-V characterization indicated that hybrid solar cells were more efficient than organic solar cells having no ZnO NPs layer. The maximum power conversion efficiency of 6.7% was obtained for the hybrid solar cell with the configuration of Camellia sinensis doped PVA, ZnO NPs thin film, and silver used as an active layer, light scattering particles, and counter electrode, respectively. Minimum efficiency of 3.1% was found in the case of organic solar cells. This work signifies the use of recyclable green resources for solar energy harvesting purposes.

Antibacterial fabric with contradictory functions of water repellency and absorbency realized by electrophoretic deposition of hydrophobic SiO2 and hydrophilic ZnO nanoparticles

Clothing and fabrics used in household and industrial applications can cause human-to-human cross-infection by residual bacteria attached to their surfaces. In particular, for fabrics used in the medical and healthcare sectors, it is vital to use highly antibacterial fabrics to prevent secondary infections caused by body fluids. In this work, antibacterial fabrics with strong water repellency were developed by electrophoretic deposition (EPD) of zinc oxide (ZnO) and hydrophobic silicon dioxide (SiO2) nanoparticles. The top layer of hydrophobic SiO2 nanoparticles prevents direct adhesion of bacterial droplets, while the bottom layer of hydrophilic ZnO nanoparticles provides antibacterial properties against the residual bacteria on the fabric. As a result, the developed fabrics can simultaneously reduce droplet adhesion and bacteria viability, effectively lowering the risk of bacterial infection. The ability to express these opposing wettabilities can be achieved by our EPD process, which can deposit various nanoparticles in porous form using electric fields on a non-conductive substrate. We expect that the fabrics developed in this work can be applied to various fields that require both antibacterial and antiwetting properties.

Magnetic properties optimization of an iron-based soft magnetic composite coated by nano-ZnO and boron oxide

Double-layered soft magnetic composite (SMC) based on pure iron powder coated by a first layer of zinc oxide nanoparticles (nano-ZnO) and a second layer of boron oxide (B2O3) has demonstrated superior magnetic performance when compared to SMCs prepared with only one of these insulating compounds. The investigation reported in this manuscript focused on improving the properties of such double-layered SMC even further by finding optimal processing conditions through a Response Surface Model evaluation using a central composite design of experiments. Mixing time of iron powder with nano-ZnO suspension, mass fraction of boron oxide precursor (boric acid - H3BO3), and heat treatment maximum temperature were investigated to achieve the condition of minimum total losses in frequencies up to 1 kHz. The discussion on the total losses is accompanied by the study of static and dynamic losses coefficients, relative magnetic permeability, electrical resistivity, and electronic microscopy of the samples. While the optimal mixing time was observed to be that of 1 h regardless of the intended operation condition, the heat treatment temperature and H3BO3 mass fraction proved to be sensible factors in order to optimize the losses for distinct levels of frequency and magnetic induction.

Tapered Optical Fiber-Based LSPR Biosensor for Ascorbic Acid Detection

The ascorbic acid (AA) is a biomarker that can be used to detect the symptoms of severe disorders such as scurvy, Parkinson’s, Alzheimer’s, and cardiovascular diseases. In this work, a simple and effective sensor model is developed to diagnose the presence of AA samples. To develop the sensor, a tapered single-mode optical fiber has been used with the well-known phenomenon of localized surface plasmon resonance (LSPR). For LSPR, the tapered region is immobilized with synthesized gold nanoparticles (AuNPs) and zinc oxide nanoparticles (ZnO-NPs) whose absorbance peak wavelengths appear at 519nm and 370nm, respectively. On the basis of nanoparticles (NPs) configurations, two different biosensor probes are developed. In the first one, the sensing region is immobilized with AuNPs and named Probe I. In the second probe, the immobilized layer of AuNPs is further coated with a layer of ZnO-NPs, and a resultant probe is termed as Probe II. The characterizations of synthesized AuNPs and developed fiber probes are done by the ultraviolet-visible (UV-vis) spectrophotometer, high-resolution transmission electron microscope (HR-TEM), atomic force microscopy (AFM), and scanning electron microscope (SEM). To enhance the selectivity, a sensing region of probes is functionalized with ascorbate oxidase enzyme that oxidizes the AA in the presence of oxygen. The response of developed sensor probes is authenticated by sensing the samples of AA in the range from 500 nM to 1 mM, which covers the range of AA found in human bodies, i.e., 40µM–120µM. The performance analysis of the developed sensor probes has been done in terms of their stability, reproducibility, reusability, and selectivity. To observe the stability of AA, a pH-test has also been done that results in a better solubility of AA molecules in phosphate-buffered saline (PBS) solution.

Improving Performance of Inverted Blue Quantum‐Dot Light‐Emitting Diodes by Adopting Organic/Inorganic Double Electron Transport Layers

Colloidal quantum dots (QDs) have many advantages in optoelectronic applications such as light‐emitting diodes (LEDs), solar cells, and photocatalysts because of their superb optical and electrical properties that can be tuned by changing the shapes and sizes of the QDs. The efficiency of QD‐LEDs is significantly improved as inorganic metal oxide nanoparticles (NPs) are adopted for electron transport layers (ETLs) because of the high electron mobility of the NPs. However, there are two significant drawbacks of the ETLs with metal oxide NPs that hinder device performance and stability: low compactness of the metal oxide NP films that generate a massive leakage current pathway and charge imbalance caused by spontaneous electron injection from metal oxide ETLs into the QDs. To address these drawbacks, an organic/inorganic double ETL is introduced consisting of 1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene (TPBi) and zinc oxide (ZnO) NPs. By depositing TPBi on the ZnO NP ETL, the pinholes and cracks present in the ZnO NP layer are filled successfully, preventing the leakage current pathway. Furthermore, TPBi also works as a “charge balancer” by suppressing spontaneous electron injection from the ETL into the QDs. As a result, twice the external quantum efficiency and three times the lifetime are obtained with the blue QD‐LEDs.

Sustainable, Fluorine-Free, Low Cost and Easily Processable Materials for Hydrophobic Coatings on Flexible Plastic Substrates.

Zinc oxide nanoparticles (ZnONPs) and stearic acid are herein used for the preparation of hydrophobic coatings with good moisture barrier property on flexible plastic substrates. Fast, high throughput, mild and easy-to-run processing techniques, like airbrushing and gravure printing, are applied for thin films deposition of these materials. The results of this study indicated that the best hydrophobic coating in terms of water contact angle (115°) is obtained through a two-steps printing deposition of a ZnONPs layer followed by a stearic acid layer. All the deposition procedures proved to be effective in terms of water vapor barrier properties, reaching values of 0.89 g/m2/day, with a 45% reduction with respect to the bare substrate. These preliminary data are very encouraging in the perspective of a low cost and green approach for the realization of functional coatings for packaging applications.

Uncooled Short-Wave Infrared Sensor Based on PbS Quantum Dots Using ZnO NPs.

Shortwave infrared (SWIR) sensors have attracted interest due to their usefulness in applications like military and medical equipment. SWIR sensors based on various materials are currently being studied. However, most SWIR detectors need additional optical filters and cooling systems to detect specific wavelengths. In order to overcome these limitations, we proposed a solution processed SWIR sensor that can operate at room temperature using lead chloride (PbS) QDs as a photoactive layer. Additionally, we adapted zinc oxide (ZnO) nanoparticles (NPs) as an electron transport layer (ETL) to improve the sensitivity of a PbS SWIR sensor. In this study, PbS SWIR sensors with and without a ZnO NPs layer were fabricated and their current–voltage (I–V) characteristics were measured. The on/off ratio of the PbS SWIR sensor with ZnO NPs was 2.87 times higher than that of the PbS SWIR sensor without ZnO NPs at the maximum current difference. The PbS SWIR sensor with ZnO NPs showed more stable current characteristics than that without ZnO NPs because of the ZnO NPs’ high electron mobility and proper lowest unoccupied molecular orbital (LUMO) level.

Poly(3-hydroxybutyrate) Modified by Nanocellulose and Plasma Treatment for Packaging Applications.

In this work, a new eco-friendly method for the treatment of poly(3-hydroxybutyrate) (PHB) as a candidate for food packaging applications is proposed. Poly(3-hydroxybutyrate) was modified by bacterial cellulose nanofibers (BC) using a melt compounding technique and by plasma treatment or zinc oxide (ZnO) nanoparticle plasma coating for better properties and antibacterial activity. Plasma treatment preserved the thermal stability, crystallinity and melting behavior of PHB‒BC nanocomposites, regardless of the amount of BC nanofibers. However, a remarkable increase of stiffness and strength and an increase of the antibacterial activity were noted. After the plasma treatment, the storage modulus of PHB having 2 wt % BC increases by 19% at room temperature and by 43% at 100 °C. The tensile strength increases as well by 21%. In addition, plasma treatment also inhibits the growth of Staphylococcus aureus and Escherichia coli by 44% and 63%, respectively. The ZnO plasma coating led to important changes in the thermal and mechanical behavior of PHB‒BC nanocomposite as well as in the surface structure and morphology. Strong chemical bonding of the metal nanoparticles on PHB surface following ZnO plasma coating was highlighted by infrared spectroscopy. Moreover, the presence of a continuous layer of self-aggregated ZnO nanoparticles was demonstrated by scanning electron microscopy, ZnO plasma treatment completely inhibiting growth of Staphylococcus aureus. A plasma-treated PHB‒BC nanocomposite is proposed as a green solution for the food packaging industry.

(Invited) Hydrothermal Growth of Zinc Oxide (ZnO) Nanorods and Structural and Optical Studies for Soil pH Measurement Applications

Zinc Oxide (ZnO) nanorods (NRs) are developed by a hydrothermal growing method using zinc acetate as the precursor material. The synthesized ZnO particle solution deposited on the Aluminum and Glass substrate by using a spin coating and thermal evaporation method. ZnO nanoparticle layer is treated for hydrothermal growing procedure and further annealing at high temperature to obtain uniform ZnO NRs. The structural and optical properties of the ZnO NRs are examined with field emission scanning electron microscopy with Energy Dispersive Spectrometer, X-ray diffraction meter and UV visible spectrometer. The crystal qualities, grain size, diameter, and optical bandgap of the ZnO NRs were affected by the type of solvent and substrates used. The developed ZnO NRs thin film structure has high potential application in soil pH measurement. Keywords: ZnO NRs; Spin Coating; Thermal Evaporation; FESEM/EDS; XRD; UV Visible spectrometer Figure 1

Performance Enhancement by ZnO Nanoparticle Layer in Hybrid Ionic Transition Metal Complex‐Light‐Emitting Electrochemical Cells (iTMC‐LECs)

Light‐emitting electrochemical cells (LECs) are solution processable solid‐state light sources comprising in their simplest architecture an ionic emissive layer in between of two electrodes. Although LECs possess several advantages that make them promising candidates for future large‐area low‐cost lighting technologies, their device wall‐plug efficacies remain so far moderate on the order of a few lumens per watt. One of the reasons therefore is considered to be the charge imbalance within the device. Here, a hybrid LEC device concept is introduced, whereby an additional layer of zinc oxide (ZnO) nanoparticles at the cathode side supports electron injection into the active light‐emitting layer and boosts the performance of the Ir‐based ionic transition metal complex LEC (iTMC‐LEC). The brightness and efficacy of the devices can be increased in average by more than 70% by the implementation of the additional inorganic layer. The time to reach the maximum brightness can be reduced in average by a factor of 7, which is attributed to an improved electron/hole balance in the device due to enhanced electron injection into the active iTMC layer.

Ultraviolet Sensor Based on Organic/Inorganic Heterojunction between PEDOT:PSS and ZnO Nanoparticles Thin Films

In this work, the ultraviolet (UV) sensors based on heterojunction between layer of zinc oxide nanoparticles (ZnO NPs) and poly (3,4-ethylenedioxythiophene):poly (styrenesulfonic acid) (PEDOT:PSS) were fabricated, characterized and studied in the electrical response to UV 365 nm. The ZnO NPs layer was solution-based coated on the top of PEDOT:PSS film on the patterned indium tin oxide (ITO) coated on glass. Aluminum was deposited as the top electrode of the device. The current-voltage (I-V) characteristic shows the rectifying behavior in the dark field. With the UV irradiation, the reverse bias current can be found and the forward bias current also highly increases. The current-voltage data fitting with the thermionic emission model shows that the potential barrier height at the heterojunction decreases with illuminating by UV light. Relative high photoresponse of the device exhibits the potential to UV detector application.

Fiber optic hydrogen sulfide gas sensors utilizing ZnO thin film/ZnO nanoparticles: A comparison of surface plasmon resonance and lossy mode resonance

Fabrication and characterization of fiber optic sensors employing surface plasmon resonance (SPR) and lossy mode resonance (LMR) for the detection of hydrogen sulfide gas have been carried out. Three kinds of probes, two utilizing LMR technique and the one utilizing SPR technique, have been fabricated over unclad core of the fiber using zinc oxide (ZnO). The first LMR probe, named as LMR 1, has been fabricated by coating ZnO thin film with an over layer of ZnO nanoparticles while the second LMR probe, named as LMR 2, has a layer of ZnO nanoparticles over the unclad core of the fiber. The third probe, named as SPR probe, has been fabricated by coating silver film and a thin over layer of ZnO over unclad core of the fiber. The variation of peak absorbance/resonance wavelength with the concentration of the hydrogen sulfide gas has been used to calibrate all the three sensors having different platforms. The results show the maximum sensitivity to H2S gas for LMR 1 probe while the minimum for the SPR probe. In addition, the LMR 1 probe is highly selective to hydrogen sulfide gas in comparison to other two probes. This has been confirmed by performing experiments using different gases. The LMR 1 sensor probe has number of advantages, in addition to high sensitivity and selectivity, such as low cost, miniaturized probe, fast response, reusability of the probe, capability of online monitoring and remote sensing.

High-performance semitransparent perovskite solar cells with solution-processed silver nanowires as top electrodes

In this work, we report efficient semitransparent perovskite solar cells using solution-processed silver nanowires (AgNWs) as top electrodes. A thin layer of zinc oxide nanoparticles is introduced beneath the AgNWs, which fulfills two essential functionalities: it ensures ohmic contact between the PC60BM and the AgNWs and it serves as a physical foundation that enables the solution-deposition of AgNWs without causing damage to the underlying perovskite. The as-fabricated semitransparent perovskite cells show a high fill factor of 66.8%, Voc = 0.964 V, Jsc = 13.18 mA cm(-2), yielding an overall efficiency of 8.49% which corresponds to 80% of the reference devices with reflective opaque electrodes.

Fully solution-processing route toward highly transparent polymer solar cells.

We report highly transparent polymer solar cells using metallic silver nanowires (AgNWs) as both the electron- and hole-collecting electrodes. The entire stack of the devices is processed from solution using a doctor blading technique. A thin layer of zinc oxide nanoparticles is introduced between photoactive layer and top AgNW electrode which plays decisive roles in device functionality: it serves as a mechanical foundation which allows the solution-deposition of top AgNWs, and more importantly it facilitates charge carriers extraction due to the better energy level alignment and the formation of ohmic contacts between the active layer/ZnO and ZnO/AgNWs. The resulting semitransparent polymer:fullerene solar cells showed a power conversion efficiency of 2.9%, which is 72% of the efficiency of an opaque reference device. Moreover, an average transmittance of 41% in the wavelength range of 400-800 nm is achieved, which is of particular interest for applications in transparent architectures.

Sensitivity improvement of the surface acoustic wave ultraviolet sensor based on zinc oxide nanoparticle layer with an ultrathin gold layer

In this study, we demonstrate the improvement in the sensitivity of surface acoustic wave (SAW) ultraviolet (UV) sensor with a UV-sensitive zinc oxide nanoparticles (ZnO NPs) layer and an ultrathin gold layer. The additional gold layer plays an important role in the enhancement of photoresponse by increasing the overall sheet conductivity of the ZnO/Au layer, thereby improving the sensitivity of SAW UV sensor. The SAW sensor fabricated in this study consists of UV-sensitive ZnO NPs layer deposited onto a 41°Y–X LiNbO3 substrate that can propagate shear-horizontal (S-H) waves. The sheet conductivity of the film was calculated by transmission line method, using which the sensitivity of the sensor was estimated. The morphological and structural properties of ZnO NPs were evaluated by using scanning electron microscope (SEM) and X-ray diffraction (XRD). In addition, the effect of Au/ZnO bilayer on the UV absorption of the device was analyzed by using spectrophotometer. The device was irradiated with a commercial UV lamp, the intensity of which was assessed by a UV meter. In addition, the current–voltage characteristics and time responses of the device were determined by using a semiconductor parameter analyzer, in order to investigate the effects of annealing conditions and the additional deposition of an ultrathin gold metal layer. The improvement in the sensitivity of the SAW UV sensor with the gold layer was verified by the phase shift of S21 from 55° to 198°.