A novel photoelectrochemical biosensor incorporating nanosized CdS semiconductor crystals with enzyme to enhance photochemical reaction has been investigated. CdS nanoparticles were synthe-sized by using dendrimer PAMAM as inner templates. The CdS nanoparticles and glucose oxidase (GOD) were immobilized on Pt electrode via layer-by-layer (LbL) technique to fabricate a biological-inorganic hybrid system. Under ultraviolet light,the photo-effect of the CdS nanoparticles showed enhancement of the biosensor to detect glucose. Pt nanoparticles were mixed into the Nafion film to immobilize the CdS/enzyme composites and to improve the charge transfer of the hybrid. Experimental results demon-strate the desirable characteristics of this biosensing system,e.g. a sensitivity of 1.83 A/(mM cm2),lower detection limit (1 M),and acceptable reproducibility and stability.
Two types of photoluminescent carbon dots(CDs)-embedded polyelectrolyte(PE) microcapsules were successfully prepared via the layer-by-layer(LbL) assembly approach on sacrificial templates.For the first type,the PE microcapsules with CDs embedded in the cavity were produced from assembly of five pairs of poly(sodium 4-styrensulfonate)(PSS) and poly(allylamine hydrochloride)(PAH) on CDs-pre-loaded meso-porous silica.For the second type,the PE microcapsules with CDs embedded in the wall were made of CDs and PAH,which were derived from SiO_2 particles as templates.Microscope images confirmed the introduction of CDs into the two CDs-embedded microcapsules.These two microcapsules also retained the optical properties of free CDs.Photoluminescence spectra revealed that the two types of microcapsules had excitation-dependent photoluminescence behavior.When the excitation wavelength changed from280 to 340 nm,photoluminescence emission peak of the PE microcapsules with CDs embedded in the cavity shifts from 369 to 377 nm,while for microcapsules with CDs embedded in the wall,emission peak shifts from 367 to 390 nm.Due to low toxicity,good hydrophilicity and photoluminescence properties of CDs,these two kinds of photo-luminescent microcapsules have competitive potential for application in carriers for imaging,drug delivery and biosensors.
