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Herein we designed a novel photoelectrochemical sensing platform based on Fe 3+ doped ZnO-Ag photocatalyst (Fe 3+ /ZnO-Ag) for ultrasensitive Hg 2+ detection by using exonuclease III-assisted target recycling and DNAzyme-catalyzed amplification. Firstly, Fe 3+ /ZnO-Ag was synthesized to provide photocurrent under visible light irradiation. Secondly, target Hg 2+ was determined by hairpin DNA probes on the Fe 3+ /ZnO-Ag modified ITO based on T-Hg 2+ -T, and then Hg 2+ was released by the digestion of exonuclease III to double-stranded DNA. Finally, the photocurrent markedly decreased due to catalysis of hemin/G-quadruplex toward 4-chloro-1-naphthol. Under optimal conditions, the photocurrents were linearly related to Hg 2+ concentrations form 0. 5 nM to 100 nM with a detection limit of 0. 1 nM at the 3 S blank criterion. More importantly, the developed biosensor exhibited good selectivity, repeatability, and stability, meanwhile, this analysis platform held great potential for testing real water samples in future. [ABSTRACT FROM AUTHOR]

Mercuric ion (Hg 2+ ) as one kind of environmental pollutants has attracted more and more attentions due to its persistence, mobility and biological enrichment. In this study, a novel photoelectrochemical biosensor for Hg 2+ detection was constructed based on dye sensitization effect induced by Y-shaped DNA transformation as signal amplification strategy. Firstly, graphene oxide-ZnO-CdS nanohybrid (GO-ZnO-CdS) as photoelectric material was synthesized by simple hydrothermal method, and was employed to modify ITO electrode. Secondly, Y-shape DNA was labeled by Au NPs in the solution, and which crosslinked on the surface of GO-ZnO-CdS modified ITO electrode by carbodiimide coupling method, which resulted in the excitation energy transfer (EET) effect between Au NPs and CdS. Finally, in the presence of Hg 2+ , the structure of DNA on the modified electrode changed from Y-shape into hairpin accompanying the proximity of dye molecule based on T-Hg 2+ -T, which eliminated EET effect and triggered dye sensitization effect for enhancing photocurrent response. Under optimal conditions, the photocurrent linearly increased with the increasing of Hg 2+ levels in the range of 5 pM − 500 pM with the detection limit of 1:5 pM(LOD = 3σ blank / s ). More importantly, the developed biosensor showed the advantages of acceptable selectivity, repeatability and stability. [ABSTRACT FROM AUTHOR]

Abstract: A fiber-optic sensor for liquid refractive index measurement based on a Michelson interferometer is described. The interferometer is achieved between the Fresnel reflections from the fiber ends of the coupler. The fiber ends are then in contact with the solvent and solution samples to provide reference and refractive index measurement, respectively. The refractive index of the solution is determined according to the fringe contrast of the interference fringes in the reflective spectrum of the sensor. Its ease of fabrication and low-cost offer the attractive applications in chemical and biological sensing. [Copyright &y& Elsevier]

Abstract: A simple sensor for simultaneous measurement of refractive index and temperature in solutions based on fiber Bragg grating (FBG) is proposed. The sensor contains only a normal FBG with a pigtail fiber. When the FBG is immersed in different liquids of refractive index, the side mode suppression ratio of the FBG varies due to the Fresnel reflection of the pigtail fiber. The sensor is also capable of simultaneous measurement refractive index and temperature combining the thermo-optic effect of the FBG. Its ease of fabrication and low-cost offer the attractive applications in chemical and biological sensing. [Copyright &y& Elsevier]