Design And Applications Of Gold Nanorods Based Non-aggregation Colorimetric Sensors

Nanomaterials show unique properties in physics and chemistry due to the characteristicsof quantum size effect, surface effect, small size effect and tunneling effect and so on. As aspecial nanomaterial, gold nanorods （AuNRs） possess unique transverse surface plasmonresonance （TSPR） and longitudinal surface plasmon resonance （LSPR） because of theiranisotropism. Based on the correlation between the LSPR absorption peaks of AuNRs andtheir corresponding absorbance with analyte, a series of high-performance colorimetricsensors have been developed at home and abroad and successfully applied to thedetermination of ions, small molecules, proteins, amino acids and other bioactive substances.In this paper, AuNRs were firstly synthesized through a seed-mediated method and then threenovel colorimetric sensors were designed according to the changes of LSPR absorption peaksof AuNRs induced by the catalytic or inhibiting effect of analyte on AuNRs dissolution.（1） In HCl medium, I^-could catalyze Fe³⁺oxidizing etching AuNRs along the longitudinalaxis, resulting in the LSPR absorption peaks of AuNRs blue shifting, the aspect ratio and theabsorbance decreasing accompanied with the color of the solution distinctly changing. Thus, anovel catalytic oxidizing of AuNRs based non-aggregation colorimetric sensor for thedetermination of I^-has been established. Meanwhile, the morphological changes of AuNRsunder the process of I^-catalyzing Fe³⁺oxidizing AuNRs were characterized by highresolution transmission electron microscopy （HRTEM） and the sensing mechanism for the I^-determination was also discussed.（2） In the presence of S₂O₃^2-, Cu²⁺can catalyze leaching of AuNRs induced by dissolveoxygen along the longitudinal axis, causing the aspect ratio decreasing, LSPR absorptionpeaks of AuNRs blue shifting as well as the distinctly changes of the solution color. Basis onthis phenomenon, a non-aggregation colorimetric sensor for rapid determining Cu²⁺has beendesigned. This highly sensitive and selective colorimetric sensor has been utilized todetermine Cu²⁺in tap water samples with the results agreeing well with those of inductively coupled plasma-mass spectroscopy （ICP-MS）. Meanwhile, the morphological changes ofAuNRs were characterized by HRTEM and the sensing mechanism for the determination ofCu²⁺was also discussed.（3） Vitamine C （Vc） can reduce Hg²⁺to Hg0, and the latter would react with Au at the tipsof AuNRs to form gold amalgamation （AuHg2（L））, causing the LSPR absorption peaks ofAuNRs blue shifting. However, the strong coordination between hydrosulfide group （–SH） incysteine （Cys） and Hg²⁺would effectively inhibit the formation of AuHg2（L）, further inhibitthe LSPR absorption peaks of AuNRs blue shifting, resulted in the obviously color changingof the solution. Thus, a responsive, sensitive and simple AuNRs colorimetric sensor for thedetermination of Cys has been developed. The proposed sensor has been utilized to determineCys in human urine samples, and the results were consistent with those obtained by ICP-MS.Furthermore, the morphological changes of AuNRs at each etching stages were measuredusing HRTEM and the sensing mechanism for the determination of Cys was also discussed.