UV-ozone Treatment Research Articles

Surface disinfection of wheat kernels using gas phase hydroxyl-radical processes: Effect on germination characteristics, microbial load, and functional properties.

Wheat kernels harbor a diverse microflora that can negatively affect the suitability of the grains for further processing. To reduce surface microflora, a kernel disinfection method is required that does not affect grain functionality. Three different versions of gas phase hydroxyl-radical processes were compared with the common method for grain disinfection, that is, a bleach treatment. The gas phase hydroxyl-radicals are generated by the UV-C mediated degradation of hydrogen peroxide and/or ozone in a near water-free process. It was found that treating kernels with a bleach solution could reduce total aerobic count (TAC) and fungal count to below the level of enumeration. In comparison, the gas phase hydroxyl-radical treatment, that is, H2 O2 -UV-ozone treatment, could support a 1.3 log count reduction (LCR) in TAC and a 1.1 LCR in fungal count. The microbial load reduction for the wholemeal samples was less pronounced as endophytic microorganisms were less affected by all treatments, hinting at a limited penetration depth of the treatments. Despite reducing the microbial load on the kernel surface through the bleach and H2 O2 -UV-ozone treatments, none of these treatments resulted in a reduced microbial count on grains that underwent sprouting after the treatments. No negative effect on germination power or development of the seedling was observed for any of the treatments. The gluten aggregation behavior and xylanase activity of the wholemeal also remained unchanged after the gas phase hydroxyl-radical treatments. Our findings suggest that UV-H2 O2 -ozone treatment shows promise for dry-kernel disinfection, but further optimization of the processing parameters is required.

The Influence of UV-Ozone, O2 Plasma, and CF4 Plasma Treatment on the Droplet-Based Deposition of Diamond Nanoparticles.

Surface treatment is critical for homogeneous coating over a large area and high-resolution patterning of nanodiamond (ND) particles. To optimize the interaction between the surface of a substrate and the colloid of ND particles, it is essential to remove hydrocarbon contamination by surface treatment and to increase the surface energy of the substrate, hence improving the diamond film homogeneity upon its deposition. However, the impact of substrate surface treatment on the properties of coatings and patterns is not fully understood. This study explores the impact of UV-ozone, O2 plasma, and CF4 plasma treatments on the wetting properties of the fused silica glass substrate surface. We identify the optimal time interval between the treatment and subsequent ND coating/patterning processes, which were conducted using inkjet printing and ultrasonic spray coating techniques. Our results showed that UV-ozone and O2 plasma resulted in hydrophilic surfaces, while CF4 plasma treatment resulted in hydrophobic surfaces. We demonstrate the use of CF4 plasma treatment before inkjet printing to generate high-resolution patterns with dots as small as 30 μm in diameter. Ultrasonic spray coating showed homogeneous coatings after using UV-ozone and O2 plasma treatment. The findings of this study provide valuable insights into the hydrocarbon airborne contamination on cleaned surfaces over time even in clean-room environments and have a notable impact on the performance of liquid coatings and patterns. We highlight the importance of timing between the surface treatment and printing in achieving high resolution or homogeneity.

III–V gain region/Si waveguide hybrid lasers by chip-on-wafer hydrophilic bonding process using UV-ozone treatment

The direct bonding process of InP chips on a silicon-on-insulator (SOI) wafer is investigated using surface hydrophilization by UV-ozone treatment. The influence of the treatment on surface roughness is observed by atomic force microscopy, and found to be negligibly small. A high-quality III–V/Si bonding interface without crystal defects is verified in a scanning transmission electron microscope observation. The III–V layers remaining on the SOI wafer after the removal process of the InP substrate show uniform photoluminescence intensity over the whole region of the chip, indicating a bonding interface without the influence of lateral etching and peeling-off. From this bonding process, Fabry–Perot lasers with III–V gain and Si waveguide regions are fabricated, and cw operation is successfully achieved at a stage temperature from 20 °C to 85 °C. Stable operation is also confirmed from the changes of threshold current in the aging test (200 mA at 85 °C) after 2000 h.

Addressable and stable physically unclonable functions based on cross-linked poly(2-vinylpyridine)

Counterfeiting poses a significant threat to global trade and public health. Effectively combating counterfeiting involves benefiting from stochastic physical processes to build physically unclonable functions (PUFs). Polymers, as low-cost materials with a wide range of functionalities, hold huge potential for PUF applications. In this context, while there are ongoing applications and studies related to PUF systems today, the development of PUF systems that provide high stochastic characteristics and robustness through simple and low-cost production methods remains critically important. In this regard, we propose stable and addressable polymer PUFs, utilizing a cross-linkable poly(2-vinylpyridine) (P2VP). The Rayleigh instability phenomenon occurring in electrohydrodynamic processes is used to fabricate randomized polymeric features. A brief thermal annealing process enhances adhesion with the substrate, while UV-ozone treatment cross-links P2VP. When applied through stencil masks, UV-ozone treatment results in localized cross-linking, yielding addressable randomized features. Structural and chemical analysis is employed to examine the cross-linked polymer features. Adjusting the conditions of electrospraying and cross-linking leads to PUFs with outstanding stability against solvents, oxygen plasma, and thermal heating. The randomized response of polymer features is evaluated through various statistical criteria. Feature matching algorithms enable direct authentication of images captured under different rotations and lighting conditions. This study demonstrates a versatile strategy for creating polymer-based PUFs with remarkable stability and addressability, enabled by a cross-linkable polymer system.

Parabens and Methylisotiazolinone (MIT): Preservatives with Different Behaviors When Subjected to Ozone and Ultraviolet Light Treatments

The influence that contaminants exert on the degradation of other substances commonly found in the same water bodies drives this study, which aims to investigate the simultaneous degradation of preservatives such as parabens and methylisothiazolinone (MIT). Mixtures of five parabens, MIT solutions, and mixtures of all five parabens plus MIT (each at 5 mg/L) were treated using 254 nm UV light, ozone treatments, and simultaneous ozone and UV light treatments at three different pH levels (3, 5, and 9). Regardless of pH, UV light is inefficient in degrading parabens, whereas MIT is efficiently degraded under this radiation. On the other hand, ozone treatments rapidly degrade the paraben mixture at any pH, with a basic pH resulting in faster degradation due to the predominance of the indirect mechanism. MIT, due to its structural characteristics, reacts minimally with ozone, and the process is enhanced at basic pH when hydroxyl radicals are involved. The simultaneous treatment with ozone and UV light proves to be the fastest method for eliminating both parabens and MIT at any pH. However, when treating joint mixtures of parabens and MIT, behaviors change notably, particularly for processes involving UV light due to the interfering effect of MIT. Both parabens and MIT require more time to degrade, except at an acidic pH. Only MIT reduces its ozone treatment time when treated alongside parabens due to the distinct degradation mechanisms that each type of contaminant has in the presence of ozone.

Modulating the Properties of SnO2 Thin Film by Post-Deposition UV-Ozone Treatment

AbstractTin(IV) oxide (SnO2) is a metal oxide renowned for its excellent optoelectronic properties. With the use of simple post-processing methods, the characteristics of SnO2 may be easily modified. In the current work, SnO2 thin films were prepared using the spray pyrolysis technique and were subjected to post-UV-ozone (UVO) treatment for different durations. Characterization techniques including x-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, UV–visible spectroscopy, and photoluminescence spectroscopy were employed to assess the effects of UVO treatment. It was found that UVO treatment had no significant impact on the film's structural characteristics. However, after exposure to UVO, the bandgap was seen to decrease from 3.04 eV to 2.84 eV. Also, photoluminescence investigations revealed that UVO treatment increased the defects in the films with a decrease in the ratio between band-to-band emission and defect emissions. The results indicate that UVO treatment is an effective strategy for tuning the optical properties of SnO2 thin films by precisely managing the bandgap.

Evaluation of Conventional Treated and UV-Ozone Treatment Water Processes for Organic Pollutants from Shendam Dam in Plateau State, Nigeria

The use of contaminated water makes human populations to suffer from water borne diseases. The potential application of ultraviolet-ozone synergy for the removal of organic pollutants in raw water source from Shendam in Plateau state, Nigeria was undertaken. The conventional and uv-ozone treated water samples were extracted with dichloromethane and screened with GC-MS for organic pollutants. GC-MS chromatogram for the conventional treated water yielded 18 different organic pollutants while the uv-ozone treated water yielded 8 different organic compounds. GC-MS of the solvent blank (dichloromethane) used as the control showed similar profile of organic compounds detected as those of uv-ozone treated water. The profile obtained indicated reduction in the number of the organic pollutants because most of the organic compounds detected in the conventional treated water were not detected in the uv-ozone treated water. The results obtained during the evaluation period indicated that the conventional treatment system is highly vulnerable to passing on contaminated treated water to the end user. Uv-ozone treatment system, therefore, can represent an alternative drinking water treatment option. The use of the uv-ozone treatment process could be integrated in a drinking water flow sheet to replace the conventional disinfection processes because it is effective and environmentally friendly.

Mechanical and thermal properties of high volume‐fraction carbon nanotube/epoxy composites, and property enhancement byUVozone treatment of carbon nanotubes

AbstractA new method to fabricate carbon nanotube/epoxy composites, consisting of well dispersed and highly concentrated CNTs in an epoxy resin, has been developed. In this method, multiwalled carbon nanotubes (MWNTs) were dispersed into water with the assistance of cationic polymers to form a MWNT sheet by filtration. An epoxy resin was impregnated into the MWNT sheet by vacuum assisted impregnation using a filtration system, followed by autoclave cure, resulting in a MWNT/epoxy composite with a MWNT content of 33 wt%. It was revealed that the composite has a tensile modulus of 8.37 GPa and a tensile strength of 130 MPa. An application of a UV ozone (UV/O3) treatment to the MWNTs increased the XPS O/C ratio from 0.03 to 0.10, resulting in the improvement of the tensile strength to 171 MPa. These results indicate the effectiveness of the UV/O3treated MWTNs for mechanical property enhancement.

Highly Efficient HTM-Free Tin Perovskite Solar Cells with Outstanding Stability Exceeding 10000 h.

The bottleneck in the rapid development of tin-based perovskite solar cells (TPSCs) is the inherent chemical instability. Although this is being addressed continuously, the device performance has not improved further due to the use of PEDOT:PSS as the hole-transport material (HTM), which has poor long-term stability. Herein we have applied commercial ITO nanoparticles over ITO glass substrates and altered the surface chemistry of the ITO electrode via a simple two-step thermal annealing, followed by a UV-ozone treatment. These surface-modified ITO electrodes display promising interfacial characteristics, such as a suitable band alignment owing to significantly reduced surface carbon contamination, increased In-O bonding, and reduced oxygen vacancies, that enabled fabrication of an HTM-free TPSC device according to a two-step method. The fabricated device possessed an outstanding power conversion efficiency (PCE) of 9.7%, along with a superior long-term stability by retaining over 90% of the initial PCE upon shelf storage in a glovebox for a period of over 10000 h. The application of ITO nanoparticles led to effective interfacial passivation, whose impacts on the long-term durability were assessed using electrochemical impedance spectroscopy, time-resolved photoluminescence decay profiles, and femtosecond transient absorption spectroscopy techniques.

Solvent engineering of SnO2 electron transport layer for high-performance perovskite solar cells

Perovskite solar cells (PSCs) show great potential as industrial photovoltaic devices due to their low fabrication cost and high power conversion efficiency. Owing to high electron conductivity and good energy level matching with perovskites, SnO2 is widely used as electron transport layers (ETLs) for PSCs. However, the agglomeration of SnO2 nanoparticles makes them have poor contact with the glass substrate and it is easy to produce defects on the film surface. Herein, acetonitrile (ACN) is used to optimize the conventional solvent of commercial SnO2 colloid to solve these problems. The addition of ACN in solvent resulted in better-performing SnO2 ETLs, thus eliminating the need for long-time ultraviolet ozone (UV-ozone) treatment of the glass substrate, which undoubtedly greatly simplified the fabrication process. The subsequent vacuum treatment of SnO2 films before annealing further improves morphology of the ETLs film and performance of the overall device. Finally, the best devices after the above solvent engineering treatment achieved an efficiency of 22.28%, increased by 16% with respect to the control device fabricated by conventional method. In addition, the long-term stability of devices was also apparently improved. This solvent engineering strategy provides a simple route to prepare high-quality SnO2 ETL for high-performance PSCs.

Reconstruction of the Indium Tin Oxide Surface Enhances the Adsorption of High‐Density Self‐Assembled Monolayer for Perovskite/Silicon Tandem Solar Cells

AbstractSelf‐assembled monolayers (SAMs) are widely used as carrier transport interlayers for enabling high‐efficiency perovskite solar cells (PSCs). However, achieving uniform and pinhole‐free monolayers on metal oxide (e.g., indium tin oxide, ITO) surfaces is still challenging due to the sensitivity of SAM adsorption to the complex oxide's surface chemistry. Here, the hydrofluoric acid and the subsequent UV–ozone treatment are employed to reconstruct the ITO surface by selectively removing the undesired terminal hydroxyl and hydrolysis product. This can significantly increase the ITO surface activity and area, thus facilitating the adsorption of high‐density SAMs. The resultant fluorinated surface can also prevent the direct contact of ITO with the perovskite active layer and passivate the perovskite bottom interface. Benefiting from the synergistically improved perovskite film formation, charge extraction, energy level alignment, and interfacial chemical stability, the corresponding PSC achieves a greatly enhanced power conversion efficiency of 21.3%, along with an enhanced long‐term stability as compared to the control counterpart. Furthermore, a semitransparent PSC with a certified efficiency of 19.0% (with a record fill factor of 84.1%) and a four‐terminal perovskite/silicon tandem with an efficiency of 28.4% are also demonstrated.

Nano sized gallium oxide surface features for enhanced antimicrobial and osteo-integrative responses

Gallium oxide has known beneficial osteo-integrative properties. This may have importance for improving the osteointegration of orthopedic implants. At high concentrations gallium is cytotoxic. Therefore, integration of gallium into implant devices must be carefully controlled to limit its concentration and release. A strategy based on surface doping of gallium although challenging seems an appropriate approach to limit dose amounts to minimize cytotoxicity and maximize osteointegration benefits. In this work we develop a novel form of patterned surface doping via a block copolymer-based surface chemistry that enables very low gallium content but enhanced osteointegration as proven by comprehensive bioassays. Polystyrene-b-poly 4vinyl pyridine (PS-b-P4VP) BCP (block copolymer) films were produced on surfaces. Selective infiltration of the BCP pattern with a gallium salt precursor solution and subsequent UV-ozone treatment produced a surface pattern of gallium oxide nanodots as evidenced by atomic force and scanning electron microscopy. A comprehensive study of the bioactivity was carried out, including antimicrobial and sterility testing, gallium ion release kinetics and the interaction with human marrow mesenchymal stomal cells and mononuclear cells. Comparing the data from osteogenesis media assay tests with osteoclastogenesis tests demonstrated the potential for the gallium oxide nanodot doping to improve osteointegration properties of a surface.

Quantification, Exchange, and Removal of Surface Ligands on Noble-Metal Nanocrystals.

ConspectusSurface ligands are vital to the colloidal synthesis of noble-metal nanocrystals with well-controlled sizes and shapes for various applications. The surface ligands not only dictate the formation of nanocrystals with diverse shapes but also serve as a colloidal stabilizer to prevent the suspended nanocrystals from aggregation during their synthesis or storage. By leveraging the facet selectivity of some surface ligands, one can further control the sites for growth or galvanic replacement to transform presynthesized nanocrystals into complex structures that are otherwise difficult to fabricate using conventional methods. Furthermore, the presence of surface ligands on nanocrystals also facilitates their applications in areas such as sensing, imaging, nanomedicine, and self-assembly. Despite their popular use in enhancing the properties of nanocrystals and thus optimizing their performance in a wide variety of applications, it remains a major challenge to quantitatively determine the coverage density of ligand molecules, not to mention the difficulty of substituting or removing them without compromising the surface structure and aggregation state of the nanocrystals.In this Account, we recapitulate our efforts in developing methods capable of qualitatively or quantitatively measuring, exchanging, and removing the surface ligands adsorbed on noble-metal nanocrystals. We begin with an introduction to the typical interactions between ligand molecules and surface atoms, followed by a discussion of the Langmuir model that can be used to describe the adsorption of surface ligands. It is also emphasized that the adsorption process may become very complex in the case of a polymeric ligand due to the variations in binding configuration and chain conformation. We then highlight the capabilities of various spectroscopy methods to analyze the adsorbed ligands qualitatively or quantitatively. Specifically, surface-enhanced Raman scattering, Fourier transform infrared, and X-ray photoelectron spectroscopy are three examples of qualitative methods that can be used to confirm the absence or presence of a surface ligand. On the other hand, ultraviolet-visible spectroscopy and inductively coupled plasma mass spectrometry can be used for quantitative measurements. Additionally, the coverage density of a ligand can be derived by analyzing the morphological changes during nanocrystal growth. We then discuss how the ligands present on the surface of metal nanocrystals can be exchanged directly or indirectly to meet the requirements of different applications. The former can be done using a ligand with stronger binding, whereas the latter is achieved by introducing a sacrificial shell to the surface of the nanocrystals. Furthermore, we highlight three additional strategies besides simple washing to remove the surface ligands, including calcination, heating in a solution, and UV-ozone treatment. Finally, we showcase three applications of metal nanocrystals in nanomedicine, tumor targeting, and self-assembly by taking advantage of the diversity of surface ligands bearing different functional groups. We also offer perspectives on the challenges and opportunities in realizing the full potential of surface ligands.

Nickel(II) Nitrate Hole-Transporting Layers for Single-Junction Bulk Heterojunction Organic Solar Cells with a Record 19.02 % Efficiency.

A facile strategy was developed here to improve the film quality of nickel-based hole transporting layer (HTL) for efficient organic solar cell (OSC) applications. To prevent the agglomeration of Ni(NO3 )2 during film deposition, acetylacetonate was added into the precursor solution, which led to the formation of an amorphous and glass-like state. After thermal annealing (TA) treatment, the film-forming ability could be further improved. The additional UV-ozone (UVO) treatment continuously improved the film quality and increased the work function and conductivity of such HTL. The resulting TA & UVO modified Ni(NO3 )2 & Hacac HTL produced highly efficient organic solar cells with exciting power conversion efficiencies of 18.42 % and 19.02 % for PM6 : BTP-eC9 and D18 : BTP-Th devices, respectively, much higher than the control PEDOT : PSS devices.

Optoelectronic Synaptic Memtransistor Based on 2D SnSe/MoS2 van der Waals Heterostructure under UV-Ozone Treatment.

Memristive switching devices with electrically and optically invoked synaptic behaviors show great promise in constructing an artificial biological visual system. Through rational design and integration, 2D materials and their van der Waals (vdW) heterostructures can be applied to realize multifunctional optoelectronic devices. Here, a multifunctional optoelectronic synaptic memtransistor based on a SnSe/MoS2 vdW p-n heterojunction to simulate the human biological visual system is reported. By employing simple mild UV-ozone treatment, the device exhibits reversible resistive switching (RS) behavior with switching ratio up to 103 . The retina-like selective response to different input light wavelengths is activated, as well as programmable multilevel resistance states and long-term synaptic plasticity. Moreover, memory and logic functions analogous to those found in the visual cortex of the brain are performed by controlling the optical and electrical input signals. This work proposes a feasible strategy to modulate RS in vdW heterostructures for memristive devices, which show significant potential for neuromorphic processing.

The Effect of Post Deposition Treatment on Properties of ALD Al-Doped ZnO Films

In this paper, aluminum-doped zinc oxide (ZnO:Al or AZO) thin films are grown using atomic layer deposition (ALD) and the influence of postdeposition UV-ozone and thermal annealing treatments on the films' properties are investigated. X-ray diffraction (XRD) revealed a polycrystalline wurtzite structure with a preferable (100) orientation. The crystal size increase after the thermal annealing is observed while UV-ozone exposure led to no significant change in crystallinity. The results of the X-ray photoelectron spectroscopy (XPS) analyses show that a higher amount of oxygen vacancies exists in the ZnO:Al after UV-ozone treatment, and that the ZnO:Al, after annealing, has a lower amount of oxygen vacancies. Important and practical applications of ZnO:Al (such as transparent conductive oxide layer) were found, and its electrical and optical properties demonstrate high tunability after postdeposition treatment, particularly after UV-Ozone exposure, offers a noninvasive and easy way to lower the sheet resistance values. At the same time, UV-Ozone treatment did not cause any significant changes to the polycrystalline structure, surface morphology, or optical properties of the AZO films.

Effect of substrate surface on the wide bandgap SnO2 thin films grown by spin coating

Tin (IV) oxide (SnO2) sols have been synthesized from SnCl2·2H2O precursor solution by applying two different processing conditions. The prepared sols were then deposited on UV-Ozone-treated quartz and soda lime glass (SLG) substrates by spin coating. The as-synthesized film was soft baked at about 100 °C for 10 min. This process was repeated 5 times to get a compact film, followed by air annealing at 250 °C for 2 h. The pristine and annealed films were characterized by UV–Vis–NIR spectroscopy, Grazing Incident X-Ray Diffraction (GIXRD), and Field Emission Scanning Electron Microscope (FESEM). The effect of the substrate surface was investigated by measuring the contact angles with De-Ionized (DI) water. UV-Ozone treatment of substrate provides a cleaner surface to grow a homogeneous film. The electrical resistivity of annealed thin films was carried out by a four-point collinear probe employing the current reversal technique and found in the range of ~ 2 × 103 to 3 × 103 Ω·cm. Film thickness was found in the range of ~ 137–285 nm, measured by a stylus profilometer. UV–Vis–NIR transmission data revealed that all the thin-film samples showed maximum (82–89) % transmission in the visible range. The optical bandgap of the thin films was estimated to be ~ 3.75–4.00 eV and ~ 3.78–4.35 eV for the films grown on SLG and quartz substrates, respectively.

UV ozone treatment for oxidization of spiro-OMeTAD hole transport layer.

For practical application of perovskite photovoltaic devices, it is vital to choose an appropriate carrier extraction material with high mobility, high conductivity, and appropriate molecular energy levels. One of the most frequently used hole transport materials, spiro-OMeTAD, is known to show an improvement in its electrical properties after the oxidation reaction. However, this oxidation reaction is generally accomplished by simple atmospheric exposure, often taking one or more nights under atmospheric conditions, and thus the development of a rapid oxidation strategy without the degradation of device performance is strongly required. Here, we propose a rapid and reproducible oxidation route employing a UV ozone treatment process that enables quick oxidation of spiro-OMeTAD in solution, as short as 30 seconds. Optical and electrical characterization reveals that this method modifies the highest occupied molecular orbital energy level of spiro-OMeTAD to reduce the voltage loss, and also improves the conductivity and mobility, leading to the enhancement in the photovoltaic properties. This finding will provide useful insights into the further development of spiro-OMeTAD-based perovskite solar cell devices.

Graphitic Carbon Nitride Nanosheets: Dual Functional Charge Selective Cathode/Anode Interface Layer for Polymer Solar Cells

Here, we report a systematic study proposing the utilization of graphitic carbon nitride nanosheets (g-C3N4 NS) thin film as a charge-selective cathode/anode interface layer for inverted as well as conventional polymer solar cells. The pristine ITO/g-C3N4 NS thin film-based electrodes were found to have a work function value of approximately 4.43 eV making them a potential candidate as a cathode interface layer for inverted devices. The work function value increased to ∼5.25 eV after UV-ozone treatment, befitting as an anode interface layer for conventional PSCs. The device with g-C3N4 NS as the interface layer exhibited similar short circuit current density for both inverted and conventional device architecture. This confirms the dual functionality of the g-C3N4 NS thin film in terms of charge-selectivity for efficient carrier collection. The overall power conversion efficiency for the two devices was approximately 5.60% and 6.05%, respectively. The UV-ozone treatment seems to alter the work function of g-C3N4 NS thin film by inducing surface dipoles due to the incorporation of oxygen atoms. This results in switching from electron-extracting behavior to hole extraction. Our results demonstrate the dual functional nature of g-C3N4 NS as an interface layer (CIL/AIL) for solution-processable polymer solar cells.

The Effect of UV–Ozone Treatment on Structural, Optical, and Dielectric Properties of Thermally Evaporated Graphitic Carbon Nitride Thin Film

The Effect of UV–Ozone Treatment on Structural, Optical, and Dielectric Properties of Thermally Evaporated Graphitic Carbon Nitride Thin Film