Redox active hexacyanoferrate (HCF) was immobilized on CdS-graphene (CdS-G) electrode to study the photovoltammetric behavior of p-phenylenediamine (PPD). Under visible light illumination, the immobilized HCF could quickly consume photogenerated carriers on CdS-G electrode and mediate the photoelectrocatalytic oxidation of PPD, leading to an enhanced anodic limiting current response. The HCF/CdS-G electrode fabricated with 1% graphene content in CdS-G composites and 0.3 mmol·L−1 K4[Fe(CN)6] was found to show the optimum photovoltammetric response to PPD. The fabricated HCF/CdS-G electrode was explored for photovoltammetric determination of PPD, which showed a current response linearly proportional to PPD concentration from 1.0 × 10−7 to 1.0 × 10−5 mol·L−1. The detection limit (3S/N) was 4.7 × 10−8 mol·L−1. Moreover, the HCF/CdS-G electrode displayed good reproducibility and high stability. The developed photovoltammetric method was successfully applied to the determination of PPD in environmental water samples.
Kong Weisu,Tan Qingqing,Guo Haiyu,Sun Han,Qin Xia,Qu Fengli
A method is described for photoelectrochemical determination of the activity of alkaline phosphatase (ALP). It employs an indium tin oxide (ITO) electrode modified a CdS quantum dots@graphene (CdS@GR) composite and hexagonal cobalt oxyhydroxide (CoOOH) nanosheets. The CdS@GR nanocomposite was synthesized by assembling the CdS quantum dots onto a GO film to receive a basic photocurrent response of the ITO. This is further improved by covering it with CoOOH nanosheets. Secondly, 2-phospho-L-ascorbic acid (AAP) is added as a substrate for ALP. Its hydrolysis yields ascorbic acid which reduces CoOOH to form cobalt(II) ion. As a result, the CoOOH nanosheets decompose. This is accompanied by a reduction of the photocurrent. The effect was used to design a selective and sensitive assay of determination of the activity of ALP. Under the optimized experimental conditions, response is linear in the 10 to 300 U·L −1 ALP activity range. The detection limit is 1.5 U·L −1 at a signal-to-noise ratio of 3.
Indium tin oxide (ITO) was coted with CdS@graphene and CoOOH to obtain a material with superior photoelectrochemical properties. The detection of alkaline phosphatase (ALP) was accomplished by using 2-phospho-L-ascorbic acid (AAP) which is hydrolyzed by ALP to release ascorbic acid (AA) which reduces CoOOH to Co 2+ .
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