UV-ozone Irradiation Research Articles

Printer toner-assisted immobilization of antibodies on PET for genuinely-2D, flexible ELISA spot arrays

The application of laser printing on a transparent poly(ethylene terephthalate) (PET) foil for toner-assisted immobilization of antibodies is employed for the first time in the preparation of two-dimensional arrays for high throughput ELISA. Two protocols for rapid microfabrication of single- and multi-layer immunoassay substrates with spatially controlled wettability are demonstrated, which include essential steps of laser Printing, UV-ozone Irradiation, and ultrasonically assisted toner Delamination (PID). This study demonstrates the potential of laser toner as an effective and easily removable protectant of PET against permanent hydrophilization by UV irradiation. To prove the feasibility and analytical performance of this novel immunosensing platform, an indirect sandwich immunoassay for human C-reactive protein (hCRP) was selected as a model. Dynamic range, covering CRP levels between 10 ng∙mL−1 and 5.62 µg∙mL−1, with a detection limit of 0.656 ng∙mL−1, as well as excellent signal recovery in human serum (97.3 - 104.5%), confirms clinical suitability of the assay in the analysis of real samples. Thanks to the design and fabrication simplicity, use of commonly available materials and up-scalability, presented methodologies can be successfully applied in the production of substrates for high-throughput immunodiagnostics and flexible microfluidics in Lab-on-a-Foil technology.

Improvement of hole injection characteristics in wet-processed organic field-effect transistor based on oxidation of silver electrode surface

Source–drain electrodes for organic field-effect transistors (OFETs) were fabricated with Ag nanoink on a Si wafer with a 300 nm thick oxide layer using the repellent patterning method, and a depth-profile analysis of the composition and physical properties of the electrode surface was performed once the electrode was oxidized by UV–ozone irradiation. Additionally, OFETs with a wet-processed electrode and 9,10-diphenylanthracene layer were fabricated, and their electrical characteristics were measured. The chemical composition of the Ag electrode surface changed to silver oxide (Ag2O or AgO) due to the longer oxidation treatment time, and the work function value increased. In the OFET with the electrode oxidized for 600 s, increased drain current ∣I D∣ was observed around a gate voltage of 0 V. Furthermore, good OFET characteristics were obtained [maximum ∣I D∣ = 326.2 μA, mobility μ = 0.91 cm2V −1·s−1], which were similar to those of the OFETs manufactured using a dry process.

Platinum in-situ catalytic oleylamine combustion removal process for carbon supported platinum nanoparticles

Abstract Colloidal synthesis method such as oleylamine (OAm)-stabilized process is of great interest for obtaining uniform and highly dispersed platinum nanoparticle catalysts, yet the ligand may unavoidably inhibit their electro-catalytic performance. Thus, fully removing these ligands is critical to activate catalyst surface. Previous research of OAm removal process pointed that thermal annealing was the most effective way in comparison with other methods such as chemical washing, UV–Ozone irradiation and cyclic voltammetry sweeping, but generally resulting in undesired growth of platinum nanoparticle. Few studies concerning a more efficient ligand removal process have been published yet. In this work we proposed a platinum in-situ catalytic OAm combustion strategy to elucidate the removal mechanism of OAm ligands in thermal process and the key experimental parameters were also optimized. In addition, heat flow signal based on differential scanning calorimetry (DSC) measurement as a sensitive indicator, is suggested to reveal the ligand removal efficiency, which is much more reliable than the traditional spectroscopy. In comparison with commercial Pt/C sample, such a surface clean Pt/C electrocatalyst has shown an enhanced specific activity for oxygen reduction reaction. Our removal strategy and the evaluation method are highly instructive to efficient removal of different organic ligands.

Structural, Thermal and Optical Modifications of Chitosan due to UV-Ozone Irradiation

The present work focused on modifying the chitosan structure which has noticeable places in advanced research. The effect of UV-ozone irradiation with different exposure doses (9.68 x 10-14, 19.35 x 10-14, 29.03 x 10-14 and 38.75 x 10-14 J/m2) on the microstructural, thermal stability and optical properties of chitosan was studied. X-ray diffraction (XRD), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), optical parameters techniques as well as Differential thermal analysis (DTA) and thermogravimetric analysis (TGA and DTG), were performed. The obtained results indicated that, effects on semi-crystalline structures have occurred. Detected variations in XRD, SAED, HRTEM, DTA and TGA analyses under investigation may be attributed to the different degrees of crystallinity, induction of structural changes and molecular configuration of chitosan upon exposure to UV-ozone. The results confirmed that the UV-ozone irradiation plays a role in refining the microstructure and changes occurring in chitosan matrix for future biomedical applications.

Control of positive and negative threshold voltage shifts using ultraviolet and ultraviolet-ozone irradiation

The precise control of the threshold voltage (Vth) required to turn a metal-oxide semiconductor field-effect transistor on/off at the designed voltage was important to ensure that the Vth was constant for all the transistors in the circuit. In this study, Vth was adjusted in both the negative and positive directions by manipulating the number of O vacancies on the surface of an oxide nanowire channel using ultraviolet (UV) and UV-ozone (UVO) irradiation. UV irradiation shifted the Vth in the negative direction by an amount that increased with increasing exposure time (−0.96 V at 1 min, −1.42 V at 2 min, and −1.70 V at 3 min), whereas UVO irradiation shifted the Vth in the positive direction by an amount that increased with increasing exposure time (+0.37 V at 3 min, +0.69 V at 5 min, and +1.07 V at 10 min). The shifted values of Vth were maintained by passivating the channel region of the oxide nanowire with an octadecylphosphonic acid self-assembled monolayer.

Polyester hydrophobicity enhancement via UV-Ozone irradiation, chemical pre-treatment and fluorocarbon finishing combination

Abstract Enhancement in polyester substrates hydrophobicity was carried out by surface modification via chemical pre-treatment, UV-Ozone irradiation and fluorocarbon finishing combinations, which are referred to as CUF-process in this paper. Polyester fabrics were impregnated with different chemicals (Na 2 CO 3 , H 2 O 2 , H 2 O 2 /Na 2 SiO 3 , NaOH and CH 3 NH 2 ) before UV-Ozone gases exposure to investigate the effects of these precursor surface pre-impregnation on the effectiveness of UV-Ozone modification and final superhydrophobicity formation. The changes in substrate properties were by measuring 3 M water repellency (Water/Alcohol Drop Test), water sliding angle (WSA), water contact angle (WCA), wash and abrasion fastness, air permeability, tensile strength and visual appearance of treated fiber surfaces via SEM. The results indicated the usefulness of UV-Ozone treatment for creating proper surface roughness to improve the hydrophobicity of polyester fabrics after fluorocarbon finishing, especially when the fabric was pre-treated with NaOH and H 2 O 2 solutions. The lowest WSA value of 7.9° and the highest WCA of 142.2° were achieved on polyester fabrics using pre-treatment with 60 g/l NaOH and 42 ml/l H 2 O 2 CUF-treatments. Also, the obtained highest water repellency levels and the best air permeability properties led to significant increase in the substrate hydrophobicity did not show any adverse effect on tensile properties and strength deterioration.

Effects of UV-ozone irradiation on copper doped nickel acetate and its applicability to perovskite solar cells.

The effects of UV-ozone (UVO) irradiation on copper-doped nickel acetate and its applicability to perovskite solar cells were investigated. UVO irradiation of copper-doped nickel acetate significantly increased the electrical conductivity (from 4.28 × 10(-4) S cm(-1) to 5.66 × 10(-2) S cm(-1)), which is due to the increased carrier concentration (from 3.53 × 10(13) cm(-3) to 2.41 × 10(16) cm(-3)), and the charge extraction efficiency was enhanced, leading to better compatibility with the hole transport layer. By UVO irradiation, the work function was increased from 4.95 eV to 5.33 eV by the surface dipole formation, which effectively reduced the interface barrier between the hole transport layer and the MAPbI3 light absorbing layer. UVO Irradiation of the underlying layer also allows the MAPbI3 precursors to form better morphology with highly arranged crystallinity. Compared to the cells using non-irradiated copper doped nickel acetate, UVO-irradiated copper-doped nickel acetate devices showed an enhanced open-circuit voltage (3% increase), short circuit current (16% increase), fill factor (5% increase), showing an enhanced power conversion efficiency of 12.2% (21% increase).

Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer.

Enhanced physical properties of poly(vinyl alcohol)-based single-walled carbon nanotube nanocomposites through ozone treatment of single-walled carbon nanotubes

Single-walled carbon nanotubes were treated with ozone through the UV-ozone irradiation to improve their dispersion in poly(vinyl alcohol) matrix. The untreated single-walled carbon nanotubes-poly(vinyl alcohol) and ozone-treated single-walled carbon nanotubes-poly(vinyl alcohol) nanocomposites were prepared at 1% single-walled carbon nanotubes by weight to evaluate the effect of ozone treatment on the rheological, electrical, and thermal properties of poly(vinyl alcohol)-based single-walled carbon nanotube nanocomposites. Rheological results such as storage modulus, loss modulus and loss tangent indicated that incorporation of ozone-treated single-walled carbon nanotubes into poly(vinyl alcohol) up to 1% (by wt.) significantly improved the interfacial bonding between carbon nanotubes and polymer. Electrical results revealed that ozone treatment of single-walled carbon nanotubes improved the dispersion of single-walled carbon nanotubes in neat poly(vinyl alcohol) and reduced the distance between carbon nanotubes in carbon nanotubes-polymer network and as a result the electrical conductivity increased up to four orders of magnitude compared with neat poly(vinyl alcohol). Differential scanning calorimetric results showed that combining ozone-treated single-walled carbon nanotubes (1% by wt.) with poly(vinyl alcohol) enhanced the melting temperature and degree of crystallinity of the neat poly(vinyl alcohol).

High-performance low-temperature solution-processed InGaZnO thin-film transistors via ultraviolet-ozone photo-annealing

Ultraviolet (UV)-ozone photo-annealing was applied to fabricate low-temperature high-performance solution-processed thin-film transistors (TFTs). With UV-ozone treatment at the optimal temperature of 300 °C, TFT devices showed an improved field-effect mobility of 1.73 cm2 V−1 s−1, a subthreshold slope (S) of 0.32 V dec−1, an on/off-current ratio greater than 1.3 × 107, and good operational bias-stress stability compared to those of InGaZnO TFT devices fabricated with only a conventional thermal-annealing process. The results of X-ray photoelectron spectroscopy and the maximum density of the surface states (Ns) confirm that the device improvement originates from reduced oxygen-related defects and improved electron trapping due to UV-ozone irradiation.

Electrical, optical, and rheological properties of ozone-treated multiwalled carbon nanotubes–polystyrene nanocomposites

The functionalization of multiwalled carbon nanotubes was performed through the treatment of multiwalled carbon nanotubes with ozone using UV-ozone irradiation to improve their dispersion in polystyrene matrix. Multiwalled carbon nanotubes–polystyrene nanocomposites were prepared at different multiwalled carbon nanotubes weight ratios to investigate the effect of multiwalled carbon nanotubes loadings on the electrical, optical, and rheological properties of polystyrene matrix. The obtained results revealed that incorporation of functionalized multiwalled carbon nanotubes into polystyrene improved the electrical, optical, and rheological properties of neat polystyrene which indicated that multiwalled carbon nanotubes were well dispersed in the polymer matrix. Results obtained from DC and AC electrical measurements revealed that the percolation threshold was around 0.8 wt% multiwalled carbon nanotubes and incorporation of 3% multiwalled carbon nanotubes into polystyrene increased polystyrene electrical conductivity up to six orders of magnitude. Besides, increasing of multiwalled carbon nanotubes loadings increased the relative dielectric permittivity, dielectric loss, and loss tangent while decreased the total impedance of polystyrene matrix. Rheological results indicated that incorporation of multiwalled carbon nanotubes into polystyrene elevated the magnitudes of storage modulus and loss modulus up to two orders of magnitude with increasing of multiwalled carbon nanotubes loadings up to 3 wt%. Finally, the addition of multiwalled carbon nanotubes to polystyrene matrix enhanced the UV/visible absorption of polystyrene and decreased the optical energy gap with a total reduction ratio of 5.8% compared to neat polystyrene with increasing multiwalled carbon nanotubes loadings up to 2 wt%.

Surfactant Removal for Colloidal Nanoparticles from Solution Synthesis: The Effect on Catalytic Performance

Colloidal nanoparticles prepared by solution synthesis with robust control over particle size, shape, composition, and structure have shown great potential for catalytic applications. However, such colloidal nanoparticles are usually capped with organic ligands (as surfactants) and cannot be directly used as catalyst. We have studied the effect of surfactant removal on the electrocatalytic performance of Pt nanoparticles made by organic solution synthesis. Various methods were applied to remove the oleylamine surfactant, which included thermal annealing, acetic acid washing, and UV-Ozone irradiation, and the treated nanoparticles were applied as electrocatalysts for the oxygen reduction reaction. It was found that the electrocatalytic performance, including electrochemically active surface area and catalytic activity, was strongly dependent on the pretreatment. Among the methods studied here, low-temperature thermal annealing (∼185 °C) in air was found to be the most effective for surface cleaning without...

Device Performance and Lifetime of Polymer:Fullerene Solar Cells with UV-Ozone-Irradiated Hole-Collecting Buffer Layers

We report the influence of UV-ozone irradiation of the hole-collecting buffer layers on the performance and lifetime of polymer:fullerene solar cells. UV-ozone irradiation was targeted at the surface of the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layers by varying the irradiation time up to 600 s. The change of the surface characteristics in the PEDOT:PSS after UV-ozone irradiation was measured by employing optical absorption spectroscopy, photoelectron yield spectroscopy, and contact angle measurements, while Raman and X-ray photoelectron spectroscopy techniques were introduced for more microscopic analysis. Results showed that the UV-ozone irradiation changed the chemical structure/composition of the surface of the PEDOT:PSS layers leading to the gradual increase of ionization potential with irradiation time in the presence of up-and-down variations in the contact angle (polarity). This surface property change was attributed to the formation of oxidative components, as evidenced by XPS and Auger electron images, which affected the sheet resistance of the PEDOT:PSS layers. Interestingly, device performance was slightly improved by short irradiation (up to 10 s), whereas it was gradually decreased by further irradiation. The short-duration illumination test showed that the lifetime of solar cells with the UV-ozone irradiated PEDOT:PSS layer was improved due to the protective role of the oxidative components formed upon UV-ozone irradiation against the attack of sulfonic acid groups in the PEDOT:PSS layer to the active layer.

In situ GISAXS monitoring of Langmuir nanoparticle multilayer degradation processes induced by UV photolysis

AbstractIn continuation of our previous studies on Langmuir nanoparticle films we prepared well‐ordered bilayer film on the air–water interface in the Langmuir–Blodgett trough. The distance of neighboring nanoparticles was adjustable by shortening the carbon chain length by UV–ozone irradiation. Kinetics of the nanoparticle reassembly in multilayer structure was monitored in time by grazing‐incidence small angle X‐ray scattering (GISAXS) technique. The interparticle distance determined from the first lateral peak positions decayed exponentially with characteristic time of 102 ± 13 s. The final GISAXS pattern proves nanoparticle multilayer collapse and multilayer agglomeration at the end of the UV exposition.

Ligand-Assisted Fabrication of Small Mesopores in Semi-Crystalline Titanium Oxide Films for High Loading of Ru(II) Dyes

Small mesoporous (2-3 nm) and optically uniform titania films with high surface areas were fabricated by employing the ligand-assisted templating approach using designed surfactants that contain strong N-donor sites around the hydrophilic headgroup. Two N atoms, located in a pyridine ring and in the attached alkyl chain, can strongly interact with one Ti atom via covalent ligation and reduce the reactivity (hydrolysis and condensation) of soluble Ti species. The as-made films were treated with UV-ozone irradiation, before calcination to crystallize the titania frameworks. Condensation of the titania frameworks proceeded during the UV-ozone treatment that also destroyed the binding sites between the designed surfactants and Ti atoms with partial decomposition of the surfactants. The titania surfaces were then covered with resultant charred organic species and stabilized, which was helpful for the retention of the mesostructures even after partial crystallization of the titania frameworks during calcination at 400 °C. The small mesopores were more useful for effective accommodation of Ru(II) bipyridyl dyes (∼1 nm) than were common mesopores (∼10 nm). Almost 2 times higher dye loadings were achieved over the small mesoporous titania films than other porous titania films due to the high surface areas, and consequently a high density of the photosensitive dye molecules was achieved even in the thin film fabricated in one pot.

Mechanical properties of mesoporous silica thin films: Effect of the surfactant removal processes

Mechanical properties including hardness and Young's modulus of ordered mesostructured silica thin films are characterized by nanoindentation measurements. PE6800 and CTAB are used as templating agents. Emphasis is given on the effect of the template removal by thermal treatment, solvent extraction or UV-Ozone irradiation. The mechanical properties of the film are intimately correlated to the microstructure of the silica network and the film porosity as studied by IR, X-ray diffraction and N 2 adsorption. Particularly, the position and shape of the longitudinal optic mode of the Si–O–Si asymmetric stretch are correlated to the mechanical response as a function of the treatments. A contrasted behaviour is observed between PE6800 templated films which present low initial condensation state and high network contraction after post-synthesis treatments, and CTAB templated films which exhibit higher initial silica condensation degree but lower compressibility after template removal. These distinct behaviours are correlated to the strengthening of the silica structure and the decrease of the film porosity during template removal, which evolve differently according to the nature of the template and the template removal processing.