On-Chip Immunoassay for Determination of Urinary Albumin

An immunoassay performed on a portable microfluidic device was evaluated for the determination of urinary albumin. An increase in absorbance at 500 nm resulting from immunoagglutination was monitored directly on the poly(dimethylsiloxane) (PDMS) microchip using a portable miniature fibre-optic spectrometer. A calibration curve was linear up to 10 mg L–1 (r2 = 0.993), with a detection limit of 0.81 mg L–1 (S/N = 3). The proposed system showed good precision, with relative standard deviations (RSDs) of 5.1%, when evaluated with 10 mg L–1 albumin (n = 10). Determination of urinary albumin with the proposed system gave results highly similar to those determined by the conventional spectrophotometric method using immunoturbidimetric detection (r2 = 0.995; n = 15)

Optical H2 sensing properties of vertically aligned Pd/WO3 nanorods thin films deposited via glancing angle rf magnetron sputtering

In this work, the optical H2-sensing properties of Pd/tungsten trioxide (WO3) nanorods prepared by rf magnetron sputtering with glancing-angle deposition (GLAD) technique are investigated. From grazing-incidence X-ray diffraction and field emission scanning electron microscopic characterizations, annealed WO3 structure deposited on a quartz substrate at glancing angle of 85° exhibited polycrystalline monoclinic crystal structure with uniform partially isolated columnar nanorod morphology. The nanorods have the average length, diameter and rod separation of around 400 nm, 50 nm and 20 nm, respectively. The developed sensors show remarkable gasochromic absorbance response when exposed to H2. Cumulative absorbance in 650–1000 nm wavelength range is increased by approximately 51% toward H2 with 0.1% concentration in synthetic air, which is more than an order of magnitude higher than that of WO3 dense film prepared by conventional sputtering method. Moreover, WO3 nanorod based sensor is much more promising for practical use due to its much faster response. Therefore, the developed Pd/WO3 nanorod based optical sensors are highly potential for low H2 concentration sensing with highly sensitivity, fast and stable responses and low operating temperature

Conversion of Carbon Dioxide into Chemical Vapor Deposited Graphene with Controllable Number of Layers via Hydrogen Plasma Pre-Treatment

In this work, we report the conversion of carbon dioxide (CO2) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H2) plasma pre-treatment. The synthesized graphene has been characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show the controllable number of layers (two to six layers) of high-quality graphene by adjusting H2 plasma pre-treatment powers (100–400 W). The number of layers is reduced with increasing H2 plasma pre-treatment powers due to the direct modification of metal catalyst surfaces. Bilayer graphene can be well grown with H2 plasma pre-treatment powers of 400 W while few-layer graphene has been successfully formed under H2 plasma pre-treatment powers ranging from 100 to 300 W. The formation mechanism is highlighted

Violet Laser Treatment of Nitrogen-Doped Reduced Graphene Oxide Electrodes and KOH Electrolytes Containing <i>p</i>‑Phenylenediamine for High-Performance Supercapacitors

The electrical conductivity and capacitive behavior of supercapacitors (SCs) were found to be improved by the synergistic effects of the violet laser treatment (VLT) of nitrogen-doped reduced graphene oxide (N-rGO) as an electrode and 1.5% (w/v) p-phenylenediamine (PPD)-containing KOH as a redox electrolyte. The SC employing VLT treatment on the N-rGO electrode with 2 M KOH (N-rGO-V) represented a greater specific capacitance of up to 263.6 F g–1 compared to N-rGO in the same electrolyte, which was 232.2 F g–1 at 0.25 A g–1. To further improve the charge-storage ability, the SC using the VLT treatment on the N-rGO electrode with the PPD addition into 2 M KOH (N-rGO-V-PPD) revealed the highest specific capacitance, reaching 593.7 F g–1 at 0.25 A g–1 or 28.6% compared to N-rGO in the same redox electrolyte (N-rGO-PPD). Furthermore, the capacitance retention after 10,000 cycles of N-rGO-V-PPD remained at 62% (265 F g–1 at 100 mV s–1), which is still significantly higher than that of other samples, and the VLT technique provided a lower self-discharge rate. According to the physical characterizations, N-rGO-V-PPD has a rougher and larger surface area due to the exfoliated graphene oxide sheets and has a modest increase in the number of quinone/carbonyl functional groups in the graphene material, resulting in better electrical conductivity. All of these could be contributing factors to the performance improvement. Lastly, PPD provides redox mediators such as H+ and e– in the redox electrolyte, which are anticipated to improve the charge storage