A simple sensor for pH determination is reported using unmodified edge plane pyrolytic graphite (EPPG) electrodes. The analysis is based on the electro-reduction of surface quinone groups on the EPPG which was characterised using cyclic voltammetry (CV) and optimised with square-wave voltammetry (SWV). Under optimised conditions, a linear response is observed between the peak potential and pH with a gradient of ∼59 mV per pH (at 25 °C), which corresponds well with Nernstian behaviour based on a 2 proton, 2 electron system over the aqueous pH range 1.0 to 13.0. As such, an EPPG is suggested as a reagent free and robust pH sensing material.

Developing and building on recent work based on a simple sensor for pH determination using unmodified edge plane pyrolytic graphite (EPPG) electrodes, we present a voltammetric method for pH determination using a bare unmodified glassy carbon (GC) electrode. By exploiting the pH sensitive nature of quinones present on carbon edge-plane like sites within the GC, we show how GC electrodes can be used to measure pH. The electro-reduction of surface quinone groups on the glassy carbon electrode was characterised using cyclic voltammetry (CV) and optimised with square-wave voltammetry (SWV) at 298 K and 310 K. At both temperatures, a linear correlation was observed, corresponding to a 2 electron, 2 proton Nernstian response over the aqueous pH range 1.0 to 13.1. As such, unmodified glassy carbon electrodes are seen to be pH dependent, and the Nernstian response suggests its facile use for pH sensing. Given the widespread use of glassy carbon electrodes in electroanalysis, the approach offers a method for the near-simultaneous measurement and monitoring of pH during such analyses.

A novel high-efficiency silicon-chip-to-fiber grating coupler is investigated here. By introducing a dual layer grating structure with an inter-layer lateral shift to mimic 45° tilted mirror behavior, perfectly vertical coupling is successfully demonstrated. Our numerical results show that a peak silicon-chip-to-fiber coupling efficiency about 70% is possible near 1550 nm. Meanwhile, for the entire telecom C-band, i.e. wavelengths from 1530 nm to 1565 nm, the coupling efficiency is > 50% and the back reflection is less than < 1%. Our proposed high-performance silicon perfectly vertical coupling structure is suitable for interfacing with multi-core fiber platform, which may play an important role in the future CMOS photonic integration technology.

BACKGROUND:The emergence of microfluidic immunosensors has provided a promising tool for improving clinical diagnoses. We developed an electrochemical immunoassay for the simultaneous detection of cardiac troponin I (cTnI) and C-reactive protein (CRP), based on microfluidic chips.

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We report the sensitive simultaneous detection of cadmium(II) and lead(II) using an unmodified edge plane pyrolytic graphite (EPPG) electrode via linear sweep anodic stripping voltammetry (LSASV). Simultaneous additions of the heavy metals gave two well separated stripping peaks observed over two linear ranges, 20 to 200 mg L À1 and 2 to 20 mg L À1. These gave detection limits of 0.3 mg L À1 and 0.2 mg L À1 for cadmium(II) and lead(II), respectively. The use of unmodified EPPG electrodes shows comparable performance to bismuth and mercury modified electrodes, and offers a simple and effective alternative to modified systems.

Iron is an abundant element in the environment which plays an important role in environmental and biological systems. In particular, its essential function in photosynthesis has been seen as a limiting factor for phytoplanktons in ocean waters. Thus, sensitive speciation and determination of iron is of major interest, and many techniques have been established for analytical purposes. Electrochemical methods have been commonly explored due to their inexpensive, simple and rapid nature, with adsorptive stripping voltammetry (AdSV) being widely used due to its ability to complex and preconcentrate iron ions for ultrasensitive detection. This paper aims to present a review of recent determinations of trace iron using electrochemical methods.

Fe 2 O 3 /γ-Al 2 O 3 catalysts were prepared using the wet impregnation method and characterized by Xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption-desorption. The continuous catalytic wet hydrogen peroxide oxidation of an aqueous phenol solution over Fe 2 O 3 /γ-Al 2 O 3 was studied in a fixedbed reactor. The effects of several factors, such as the weight hourly space velocity (WHSV), particle size, reaction temperature, H 2 O 2 concentration, and initial pH, were studied to optimize the operation conditions for phenol mineralization. For a 1 g L −1 phenolic aqueous solution, the phenol was nearly completely removed and chemical oxygen demand (COD) removal was approximately 92 % at steady-state conditions with a WHSV of 2.4×10 −2 g PhOH h −1 g cat −1 at 80°C with 5.1 g L −1 H 2 O 2 . The long-term stability of the Fe 2 O 3 / γ-Al 2 O 3 catalyst was also investigated for the continuous treatment of phenolic water. The removal of phenol and COD exhibited a slowly decreasing trend, which was primarily due to the complexation of active sites with acid organic compounds and the adsorption of intermediate products. The deposition of organic carbon and Fe leached from the catalyst had a small role in the partial deactivation of the catalyst. The Fe leached from the catalyst partially contributed to the phenol removal during a short run. However, this contribution could be neglected after 36 h because the Fe leached from the catalyst decreased to approximately 5 mg L −1 .