title: Photoelectrochemistry of free-base-porphyrin-functionalized zinc oxide nanoparticles and their applications in biosensing.
abstract: The photoelectrochemical properties of free-base-porphyrin-functionalized zinc oxide nanoparticles were studied. A universal photoelectrochemical biosensing platform was constructed on indium tin oxide (ITO) by using the functional nanohybrid. The nanohybrid was synthesized by means of dentate binding of ZnO nanoparticles with carboxylic groups of 4,4',4'',4'''-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (TCPP), and characterized with scanning electron microscopy, contact angle measurement, and spectral techniques. The nanohybrid-coated ITO electrode showed an efficient photocurrent response under irradiation at a wavelength of 360 nm, which could be greatly improved upon addition of cysteine by its oxidation at +0.3 V. The possible mechanism was that cysteine acts as a sacrificial electron donor to scavenge the photogenerated holes that locate on the excited state of TCPP, which then injects the photoexcitation electrons into the conduction band of ZnO nanoparticles, thereby transferring photoinduced electrons to the ITO electrode. Based on this enhanced photocurrent signal, a novel method for photoelectrochemical detection of cysteine was developed with a linear range of 0.6 to 157 μmol L(-1) in physiological media. The detection limit was 0.2 μmol L(-1) at a signal-to-noise ratio of 3. The novel strategy of cysteine analysis could provide an alternative method for monitoring biomolecules and extend the application of porphyrin-functionalized semiconductor nanoparticles.
authors.affiliation: MOE Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Tu
authors.forename: Jianping
authors.initials: J
authors.lastname: Lei
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Huangxian
authors.initials: H
authors.lastname: Ju
mesh_terms: D015374:Biosensing Techniques; D003545:Cysteine / Q000032:analysis*; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D057230:Limit of Detection; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry; D010084:Oxidation-Reduction; D055668:Photochemical Processes / Q000528:radiation effects; D011166:Porphyrins / Q000737:chemistry*; D045663:Quantum Dots; D012680:Sensitivity and Specificity; D017971:Tin Compounds / Q000737:chemistry; D014466:Ultraviolet Rays; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D017971:Tin Compounds; C018395:tetracarboxyphenylporphine; C109984:indium tin oxide; D003545:Cysteine; D015034:Zinc Oxide