Multifunctional tunable Cu2O and CuInS2 quantum dots on TiO2 nanotubes for efficient chemical oxidation of cholesterol and ibuprofen.

In this study, a CuInS2/Cu2O/TiO2 nanotube (TNT) heterojunction-based hybrid material is reported for the selective detection of cholesterol and ibuprofen. Anodic TNTs were co-decorated with Cu2O and CuInS2 quantum dots (QDs) using a modified chemical bath deposition (CBD) method. QDs help trigger the chemical oxidation of cholesterol by cathodically generating hydroxyl radicals (˙OH). The small size of QDs can be used to tune the energy levels of electrode materials to the effective redox potential of redox species, resulting in highly improved sensing characteristics. Under optimal conditions, CuInS2/Cu2O/TNTs show the highest sensitivity (∼12 530 µA mM-1 cm-2, i.e. up to 11-fold increase compared to pristine TNTs) for cholesterol detection with a low detection limit (0.013 µM) and a fast response time (1.3 s). The proposed biosensor was successfully employed for the detection of cholesterol in real blood samples. In addition, fast (4 s) and reliable detection of ibuprofen (with a sensitivity of ∼1293 µA mM-1 cm-2) as a water contaminant was achieved using CuInS2/Cu2O/TNTs. The long-term stability and favourable reproducibility of CuInS2/Cu2O/TNTs illustrate a unique concept for the rational design of a stable and high-performance multi-purpose electrochemical sensor.

Tin Oxide/Vertically Aligned Graphene Hybrid Electrodes Prepared by Sonication-Assisted Sequential Chemical Bath Deposition for High-Performance Supercapacitors.

Hybrid electrodes comprising metal oxides and vertically aligned graphene (VAG) are promising for high-performance supercapacitor applications because they enhance the synergistic effect owing to the large contact area between the two constituent materials. However, it is difficult to form metal oxides (MOs) up to the inner surface of a VAG electrode with a narrow inlet using conventional synthesis methods. Herein, we report a facile approach to fabricate SnO2 nanoparticle-decorated VAG electrodes (SnO2@VAG) with excellent areal capacitance and cyclic stability using sonication-assisted sequential chemical bath deposition (S-SCBD). The sonication treatment during the MO decoration process induced a cavitation effect at the narrow inlet of the VAG electrode, allowing the precursor solution to reach the inside of the VAG surface. Furthermore, the sonication treatment promoted MO nucleation on the entire VAG surface. Thus, the SnO2 nanoparticles uniformly covered the entire electrode surface after the S-SCBD process. SnO2@VAG exhibited an outstanding areal capacitance (4.40 F cm-2) up to 58% higher than that of VAG electrodes. The symmetric supercapacitor with SnO2@VAG electrodes showed an excellent areal capacitance (2.13 F cm-2) and a cyclic stability of 90% after 2000 cycles. These results suggest a new avenue for sonication-assisted fabrication of hybrid electrodes in the field of energy storage.

Anodic SnO2 Nanoporous Structure Decorated with Cu2O Nanoparticles for Sensitive Detection of Creatinine: Experimental and DFT Study.

Advanced anodic SnO2 nanoporous structures decorated with Cu2O nanoparticles (NPs) were employed for creatinine detection. Anodization of electropolished Sn sheets in 0.3 M aqueous oxalic acid electrolyte under continuous stirring produced complete open top, crack-free, and smooth SnO2 nanoporous structures. Structural analyses confirm the high purity of rutile SnO2 with successful functionalization of Cu2O NPs. Morphological studies revealed the formation of self-organized and highly-ordered SnO2 nanopores, homogeneously decorated with Cu2O NPs. The average diameter of nanopores is ∼35 nm, while the average Cu2O particle size is ∼23 nm. Density functional theory results showed that SnO2@Cu2O hybrid nanostructures are energetically favorable for creatinine detection. The hybrid nanostructure electrode exhibited an ultra-high sensitivity of around 24343 µA mM-1 cm-2 with an extremely lower detection limit of ∼0.0023 µM, a fast response time (less than 2 s), and wide linear detection ranges of 2.5-45 µM and 100 µM to 15 mM toward creatinine. This is ascribed to the creation of highly active surface sites as a result of Cu2O NP functionalization, SnO2 band gap diminution, and the formation of heterojunction and Cu(1)/Cu(ll)-creatinine complexes through secondary amines which occur in the creatinine structure. The real-time analysis of creatinine in blood serum by the fabricated electrode evinces the practicability and accuracy of the biosensor with reference to the commercially existing creatinine sensor. The proposed biosensor demonstrated excellent stability, reproducibility, and selectivity, which reflects that the SnO2@Cu2O nanostructure is a promising candidate for the non-enzymatic detection of creatinine.

A Transparent Nano-Polycrystalline ZnWO4 Thin-Film Scintillator for High-Resolution X-ray Imaging.

Facile approaches for creating thin-film scintillators with high spatial resolutions and variable shapes are required to broaden the applicability of high-resolution X-ray imaging. In this study, a transparent nano-polycrystalline ZnWO4 thin-film scintillator was fabricated by thermal evaporation for high-resolution X-ray imaging. The scintillator is composed of nano-sized grains smaller than the optical wavelength range to minimize optical scattering. The high transparency of the scintillators affords a sufficiently high spatial resolution to resolve the 2 µm line and space patterns when used in a high-resolution X-ray imaging system with an effective pixel size of 650 nm. The thermal evaporation method is a convenient approach for depositing thin and uniform films on complex substrates. ZnWO4 thin-film scintillators with various shapes, such as pixelated and curved, were fabricated via thermal evaporation. The results show that the transparent nano-polycrystalline ZnWO4 thin-film scintillator deposited through thermal evaporation has a potential for use in various high-resolution X-ray imaging applications.

Wetting Property Modification of Al2O3 by Helium Ion Irradiation: Effects of Beam Energy and Fluence on Contact Angle.

In imparting wetting properties, a fabrication process without the addition of new compounds and deposition of coating layers would be the most desirable because it does not introduce additional complexities. Hence, the ion beam irradiation technique is used as it enables the chemistry of materials to be modified through simple adjustments of irradiation parameters such as the type of accelerated particles, beam energy, and fluence. In this study, the hydrophilicity of alumina surfaces was weakened by irradiating He ion beams of different energy levels (200 keV and 20 MeV). These transitions become more pronounced as the total beam fluence increases. In low-energy irradiation, the effect of irradiation is predominant near the surface, and hydrophilicity is weakened by the increase in carbon adsorption and suppression of dissociative adsorption of water molecules owing to the introduction of oxygen vacancies. In contrast, nuclear transmutations are induced by irradiation with high-energy beams. Consequently, fluorine is generated, and hydrophobic functional groups are formed on the surface. By varying the beam conditions, the wetting properties of the target ceramic can be controlled to the desired level, which is required in various industries, via appropriate adjustments of the beam parameters. In addition, the beam irradiation technique may be applicable to all ceramic materials, including lattice oxygen and alumina.

Lasing from MEH-PPV with a refractive index tunable by electron irradiation.

A simple one-step approach to producing a distributed feedback (DFB) laser through selective irradiation of the gain medium, MEH-PPV, is presented. Electron irradiation alters the refractive index of MEH-PPV, thus, direct patterning by electron irradiation can be applied to create a periodic diffraction grating. The non-irradiated regions of MEH-PPV serve as the primary gain medium, while the irradiated regions of MEH-PPV provide the refractive index difference required to fabricate a DFB laser. This method was successfully applied to achieve lasing with a relatively low lasing threshold of 3 kW/cm2or 1.8 µJ/cm2 (pulse width: 600 ps). Furthermore, the lasing wavelength can be finely tuned by simply adjusting the grating period. In stark contrast to the simple one-step process described in this work, conventional procedures for the fabrication of DFB lasers involve multiple steps of varying complexity, including mold creation and careful coating of the substrate with the gain medium.

Effects of Electron Beam Irradiation on Mechanical and Thermal Shrinkage Properties of Boehmite/HDPE Nanocomposite Film.

Nanocomposites comprising high-density polyethylene (HDPE) and boehmite (BA) nanoparticles were prepared by melt blending and subsequently irradiated with electrons. Electron irradiation of HDPE causes crosslinking and, in the presence of BA, generates ketone functional groups. The functional groups can then form hydrogen bonds with the hydroxyl groups on the surface of the BA. Additionally, if the BA is surface modified by vinyltrimethoxysilane (vBA), it can covalently bond with the HDPE by irradiation-induced radical grafting. The strong covalent bonds generated by electron beam irradiation allow the desirable properties of the nanofiller to be transferred to the rest of the nanocomposite. Since EB irradiation produces a great number of strong covalent bonds between vBA nanoparticles and HDPE, the modulus of elasticity, yield strength, and resistance to thermal shrinkage are enhanced by electron irradiation.

Improvement of Corrosion Resistance of Stainless Steel Welded Joint Using a Nanostructured Oxide Layer.

In this study, we fabricated a nanoporous oxide layer by anodization to improve corrosion resistance of type 304 stainless steel (SS) gas tungsten arc weld (GTAW). Subsequent heat treatment was performed to eliminate any existing fluorine in the nanoporous oxide layer. Uniform structures and compositions were analyzed with field emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD) measurements. The corrosion resistance of the treated SS was evaluated by applying a potentiodynamic polarization (PDP) technique and electrochemical impedance spectroscopy (EIS). Surface morphologies of welded SS with and without treatment were examined to compare their corrosion behaviors. All results indicate that corrosion resistance was enhanced, making the treatment process highly promising.

In situtailoring the morphology of In(OH)3nanostructures via surfactants during anodization and their transformation into In2O3nanoparticles.

The present work reports the effect of various surfactants on the morphology of In(OH)3nanostructures prepared via anodization. In-sheets were anodized in an environmentally benign electrolyte containing a small quantity of CTAB, CTAC, and PDDA surfactants at room temperature. The produced nanostructures were characterized using XRD, HRTEM, SAED, and EDAX. The morphology of indium hydroxide (In(OH)3) nanostructures was successfully tailoredin situwith the help of surfactants in 1 M KCl aqueous electrolyte. XRD results confirmed the formation of In(OH)3and indium oxyhydroxide (InOOH) nanostructures in the pristine form which were transformed into single-phase cubic In2O3nanoparticles (NPs) after calcination. HRTEM analyses showed that the morphology and size of the In(OH)3nanostructures can be tuned to form nanorods, nanosheets and nanostrips using different surfactants. The results revealed that CTAC and PDDA surfactants have a profound effect on the morphology of In(OH)3nanostructure compared to CTAB due to the higher concentration of Cl-ion. The possible mechanism of surfactants effect on the morphology is proposed. Furthermore, annealing converted the In(OH)3nanostructures into spherical In2O3NPs with uniform and homogeneous size. We anticipate that the morphology of other metal-oxides nanostructure can be tuned using this simple, facile and rapid technique. In2O3NPs prepared without and with CTAB surfactant were further explored for the non-enzymatic detection of hydrogen peroxide (H2O2). Electrochemical measurements showed enhanced electrocatalytic performance with fast electron transfer (∼2s) between the redox centers of H2O2and electrode surface. The In2O3NPs prepared using CTAB/Au electrode exhibited about 4-fold increase in sensitivity compared to the bare Au electrode. The biosensor also demonstrated good reproducibility, higher selectivity, and increased shelf life.

Voltage-Switchable Biosensor with Gold Nanoparticles on TiO2 Nanotubes Decorated with CdS Quantum Dots for the Detection of Cholesterol and H2O2.

A thin layer of gold nanoparticles (Au NPs) sputtered on cadmium sulfide quantum dots (CdS QDs) decorated anodic titanium dioxide nanotubes (TNTs) (Au/CdS QDs/TNTs) was fabricated and explored for the nonenzymatic detection of cholesterol and hydrogen peroxide (H2O2). Morphological studies of the sensor revealed the formation of uniform nanotubes decorated with a homogeneously dispersed CdS QDs and Au NPs layer. The electrochemical measurements showed an enhanced electrocatalytic performance with a fast electron transfer (∼2 s) between the redox centers of each analyte and electrode surface. The hybrid nanostructure (Au/CdS QDs/TNTs) electrode exhibited about a 6-fold increase in sensitivity for both cholesterol (10,790 µA mM-1 cm-2) and H2O2 (78,833 µA mM-1 cm-2) in analyses compared to the pristine samples. The hybrid electrode utilized different operational potentials for both analytes, which may lead to a voltage-switchable dual-analyte biosensor with a higher selectivity. The biosensor also demonstrated a good reproducibility, thermal stability, and increased shelf life. In addition, the clinical significance of the biosensor was tested for cholesterol and H2O2 in real blood samples, which showed maximum relative standard deviations of 1.8 and 2.3%, respectively. These results indicate that a Au/CdS QDs/TNTs-based hybrid nanostructure is a promising choice for an enzyme-free biosensor due to its suitable band gap alignment and higher electrocatalytic activities.

Hydrophilicity Improvement of Polymer Surfaces Induced by Simultaneous Nuclear Transmutation and Oxidation Effects Using High-Energy and Low-Fluence Helium Ion Beam Irradiation.

Two commodity polymers, polystyrene (PS) and high-density polyethylene (HDPE), were irradiated by high-energy He ion beams at low fluence to examine the wettability changes at different fluences. The water contact angles of the PS and HDPE surfaces were reduced from 78.3° to 46.7° and 81.5° to 58.5°, respectively, upon increasing the fluence from 0 to 1 × 1013 He2+/cm2 for irradiation durations ≤4 min. Surface analyses were performed to investigate these wettability changes. Surface texture evaluations via scanning electron and atomic force microscopies indicated non-remarkable changes by irradiation. However, the chemical structures of the irradiated polymer surfaces were notable. The high-energy He ions induced nuclear transmutation of C to N, leading to C-N bond formation in the polymer chains. Further, C-O and C=O bonds were formed during irradiation in air because of polymer oxidation. Finally, amide and ester groups were generated by irradiation. These polar groups improved hydrophilicity by increasing surface energies. Experiments with other polymers can further elucidate the correlation between polymer structure and surface wettability changes due to high-energy low-fluence He ion irradiation. This method can realize simple and effective utilization of commercial cyclotrons to tailor polymer surfaces without compromising surface texture and mechanical integrity.

Oxygen Content-Controllable Synthesis of Non-Stoichiometric Silicon Suboxide Nanoparticles by Electrochemical Anodization.

A facile route to producing non-stoichiometric silicon suboxide nanoparticles (SiOx NPs, 0 < x < 1) with an adjustable oxygen content is proposed. The process is based on electrochemical anodization involving the application of a strong electric field near the surface of a Si electrode to directly convert the Si electrode into SiOx NPs. The difference in ion mobility between oxygen species (O2- and OH-), formed during anodization, causes the production of non-stoichiometric SiOx on the surface of the Si while, simultaneously, fluoride ions in the electrolyte solution etch the formed SiOx layer, generating NPs under the intense electric field. The adjustment of the applied voltage and anodization temperature alters the oxygen content and the size of the SiOx NPs, respectively, allowing the characteristics of the NPs to be readily controlled. The proposed approach can be applied for mass production of SiOx NPs and is highly promising in the field of batteries and optoelectronics.

ZnWO4 Nanoparticle Scintillators for High Resolution X-ray Imaging.

The effect of scintillator particle size on high-resolution X-ray imaging was studied using zinc tungstate (ZnWO4) particles. The ZnWO4 particles were fabricated through a solid-state reaction between zinc oxide and tungsten oxide at various temperatures, producing particles with average sizes of 176.4 nm, 626.7 nm, and 2.127 µm; the zinc oxide and tungsten oxide were created using anodization. The spatial resolutions of high-resolution X-ray images, obtained from utilizing the fabricated particles, were determined: particles with the average size of 176.4 nm produced the highest spatial resolution. The results demonstrate that high spatial resolution can be obtained from ZnWO4 nanoparticle scintillators that minimize optical diffusion by having a particle size that is smaller than the emission wavelength.

Development of a high resolution x-ray inspection system using a carbon nanotube based miniature x-ray tube.

A new concept for a non-destructive testing device using a novel carbon nanotube (CNT) based miniature x-ray tube is proposed. The device can be used for small-scale internal inspection of objects. To investigate the effectiveness of the proposed concept, the device was fabricated and its performance was systematically analyzed. The non-destructive testing device consists of a CNT based miniature x-ray tube, a scintillator, an optical lens, and a detector. The size of the focal spot needed to identify objects as small as 5 µm was calculated through simulation. An electron optics simulation software, E-GUN, was used to optimize the geometries of both the focusing cup and the x-ray target to achieve the desired focal spot size of the x-ray tube. The CNT based miniature x-ray tube was fabricated using the brazing process, and an NdFeB focusing lens was used to further reduce the focal spot size. XR images were obtained using the fabricated device and the spatial resolutions of the images were evaluated using the modulation transfer function (MTF). The fields of view (FOVs) per probe are 7.1 mm2 and 1.8 mm2 when using a 5× optical lens and a 10× optical lens, respectively. The FOV can be increased by increasing the number of probes incorporated into the device. MTF10 values were determined to be 105 lp/mm and 230 lp/mm when using the 5× optical lens and 10× optical lens, respectively. By using an optical lens to enlarge the XR images, the effect of focal spot was minimized and clear XR images were obtained.

Formation of a self-organized nanoporous structure with open-top morphology on 304L austenitic stainless steel.

A novel and simple method is reported for producing a self-organized nanoporous structure on austenitic stainless steel (SUS-304L) with open-top morphology. Uniform nanopores with a quasi-hexagonal arrangement were obtained on a very large scale with no crack formation by using single-step anodization. Electropolishing of SUS-304L in ethylene glycol monobutyl ether and perchloric acid electrolyte prior to anodization was the key factor to obtain self-organized and regularly ordered nanopores. Under optimized electropolishing conditions, a honeycomb-like patterned morphology of shallow nanopores was developed on the surface of SUS-304L. Anodization of the patterned morphology in ethylene glycol-based electrolyte generated self-organized and ordered nanopores. Morphology, structure and chemical analyses of the samples were carried-out using FESEM, EDAX, XRD, XPS and ToF-SIMS. FESEM images revealed the formation of hexagonal and ordered nanopores with uniform diameter. EDAX analysis confirmed that the nanoporous oxide layer is composed of iron, chromium, nickel and oxygen. A blue energy shift in the XPS spectra was observed after annealing, which is attributed to the absence of F-species. ToF-SIMS depth profile analysis confirmed the high content of chromium oxide on the surface of the nanoporous oxide layer. The hexagonal nanoporous ordered morphology is useful in anti-corrosion and decoration applications.

A Novel Route to High-Quality Graphene Quantum Dots by Hydrogen-Assisted Pyrolysis of Silicon Carbide.

Graphene quantum dots (GQDs) can be highly beneficial in various fields due to their unique properties, such as having an effective charge transfer and quantum confinement. However, defects on GQDs hinder these properties, and only a few studies have reported fabricating high-quality GQDs with high crystallinity and few impurities. In this study, we present a novel yet simple approach to synthesizing high-quality GQDs that involves annealing silicon carbide (SiC) under low vacuum while introducing hydrogen (H) etching gas; no harmful chemicals are required in the process. The fabricated GQDs are composed of a few graphene layers and possess high crystallinity, few defects and high purity, while being free from oxygen functional groups. The edges of the GQDs are hydrogen-terminated. High-quality GQDs form on the etched SiC when the etching rates of Si and C atoms are monitored. The size of the fabricated GQDs and the surface morphology of SiC can be altered by changing the operating conditions. Collectively, a novel route to high-quality GQDs will be highly applicable in fields involving sensors and detectors.

Ductilization of Nanoporous Ceramics by Crystallinity Control.

Synthesizing ceramic materials with a significant amount of deformability is one of the most important engineering pursuits. In this study, we demonstrate the emergence of metal-like plasticity through the crystallinity control in the monolithic zirconia with the vertically aligned honeycomb-like periodic nanopore structures fabricated using the anodizing technique. The crystalline orders of the nanoporous zirconia films vary between monoclinic, tetragonal, and amorphous phases after the heat treatment and/or proton irradiation, whereas the vertical pore structures are maintained. The micropillar compression tests on those samples reveal a large amount of plasticity, more than 20% of total stains, in the as-anodized and proton-irradiated samples, both of which contain the amorphous phase. In contrast, the fully crystallized zirconia that resulted from annealing at 500 °C shows the brittle failure, the typical characteristic of conventional ceramic foams. These results offer a new opportunity for the nanoporous ceramic materials to be used in various applications, benefited from the tunable structural stability.

Biocompatible UV-absorbing polymer nanoparticles prepared by electron irradiation for application in sunscreen.

We present a novel approach to preparing non-toxic sunscreen active ingredients by electron irradiation of poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanoparticles (NPs). Electron irradiation modifies the molecular structure of the polymers, generating conjugated aliphatic carbon-carbon double bonds in PMMA and conjugated aromatic rings in PS. The conjugation length increases as the electron fluence increases, leading to hyperchromic and bathochromic shifts in the UV-vis absorption spectra of the irradiated polymer NPs. Consequently, the irradiated polymer NPs become capable of UV absorption and the UV-absorbing properties are improved with increasing electron fluence. The UV-screening performance of the electron-irradiated polymer NPs are found to be superior to those of commercially available sunscreen ingredients. In addition, in vitro cytotoxicity and phototoxicity test results show that the irradiated polymer NPs exhibit excellent biocompatibility.

Three-dimensional-printed vaginal applicators for electronic brachytherapy of endometrial cancers.

PURPOSE: Vaginal applicators for a novel miniature x-ray tube were developed using three-dimensional (3D) printing to be used in brachytherapy of endometrial cancers. METHODS: Cylindrical vaginal applicators with various diameters, lengths, and infill percentages (IFPs) were fabricated using a 3D printer. X-ray dose distributions and depth-dose profiles were calculated using a Monte Carlo simulation. The performances of the applicators were evaluated by measuring and analyzing the dosimetric characteristics of x rays generated from the miniature x-ray tube equipped with the applicators. RESULTS: Quite uniform dose distributions around the applicators were achieved by optimizing the dwell positions and the dwell times of the miniature x-ray tube inside the applicators. In addition, identical absolute dose and depth-dose profiles were obtained through the control of the IFP values even though different-sized applicators are used. CONCLUSION: The presented 3D printing technique provides an efficient approach to provide vaginal applicators with optimal IFPs that allow consistent treatment time for patients of varying vaginal canal size.

A novel route to the formation of 3D nanoflower-like hierarchical iron oxide nanostructure.

The present work reports the formation of 3D nanoflower-like morphology of iron alkoxide via the anodization of Fe sheet in ethylene glycol (EG) electrolyte. XRD, FESEM, EDX, XPS, Raman and FTIR are applied to characterize the samples. SEM results show that the as-anodized sample is composed of 3D nanoflowers with hierarchical nanosheets beneath it. The average width of the nanoflower petal is ∼25 nm and the length is about 1 µm. The 3D nanoflowers are transformed into spherical nanoparticles (NPs) with uniform size when calcined at elevated temperature. XRD and Raman results indicate that the 3D nanoflowers consist of akaganeite, which transforms into magnetite and hematite by annealing. XPS and FTIR results confirm that the nanoflowers contain significant amounts of F, C and OH, which are drastically decreased after annealing. The formation of 3D nanoflower-like morphology can be attributed to EG. A possible formation mechanism of 3D nanoflowers and their transformation into NPs is proposed. We showed that the morphology of the as-anodized iron oxide can be tailored simply by changing the electrolyte. The anodization of Fe sheet in glycerol-based electrolyte under identical conditions produced nanotubes.