藉修飾螢光試劑於金奈米粒子開發比色法及螢光變化雙特性之高靈敏、高選擇性、廣測定範圍氰化物偵測器

Abstract

在眾多探討離子對於環境汙染研究報告中，氰化物是目前被受關注的離子之一。其具有強烈毒性及致死性，中毒時氰離子會進入粒線體並抑制電子傳遞鏈進行，此作用可在數分鐘之內造成人類死亡。雖然氰化物會造成嚴重的環境污染，且對人體健康有不良影響，但目前仍被廣泛應用於電鍍、冶金、採礦以及其它工業。隨著工業廢水排放，在不同水域中會有不同程度污染，例如地下水、湖水、河水、海水等。因此，開發一套具有高靈敏與選擇性之氰化物偵測系統是迫切被需要的，且為了實際應用於不同水域之偵測，此系統應具有廣泛的偵測範圍才能適於監控各種程度的環境污染。 為達到此目標，本研究將開發一套系統用於定量分析氰化物之濃度，此方法選用金奈米粒子作為基本材料，利用其獨特之光學和螢光特性，可廣泛地偵測各種水域之氰化物含量。在本實驗中，我們選用Tween-20 (T-20) 分子作為穩定劑，而Fluorescein isothiocyanate (FITC) 分子作為螢光染料，將分子修飾於金奈米粒子表面後，T-20可保護粒子，避免其在高鹽類溶液中聚集；而FITC分子之螢光會被金奈米粒子吸收，使其螢光強度降低。由於氰化物會與金奈米粒子表面反應形成化合物，此作用會造成修飾分子脫離奈米粒子表面，當FITC分子離開表面時，利用其螢光回復之能力可偵測至濃度較低之汙染樣品；當氰化物濃度高於150 □M時，會造成穩定劑T-20大量脫離，此時溶液將從酒紅色轉為紫色，利用金奈米粒子聚集特性之比色法可偵測到較高濃度之汙染範圍。此氰化物偵測器，最低偵測極限可達100 nM，此濃度遠低於World Health Organization (WHO) 所規範飲用水之容許濃度2.7 □M，而其最高可偵測至數百micro molar等級，此涵蓋範圍將可應用於偵測各種不同水域之汙染。此新穎奈米金粒子偵測器具有容易製備、高選擇性、高靈敏性、低成本、廣偵測範圍等優點，在未來分析氰化物之環保議題中將會被廣泛應用。

Cyanide is one of the most-concerning anions in the environment, the toxicity of which is known because it can inhibit the electron transport chain in mitochondria and directly lead to the death of human beings in several minutes. Although this toxic anion act as severe environmental pollutants and have adverse health effects, it is still widely used in electroplating, gold mining and other fields. As a consequence, accidental cyanide release from those industries could cause different levels of contamination in various water resources (e.g., groundwater, lake, river, and stream). From the viewpoint of practical applications, it is desirable to develop a highly sensitive and selective sensing system with wide detection range of cyanide for the environmental monitoring in various water bodies. Towards achieving this aim, herein, we present a new analytic method for the determination of cyanide in a wide concentration range, which relies on the unique optical and fluorescence quenching properties of gold nanoparticles (AuNPs). In this work, Tween-20 (T-20; stabilizer) and Fluorescein isothiocyanate (FITC; fluoresce dye) molecules were both modified on the surface of AuNPs. The T-20 can protect the AuNPs from aggregation in the salinity solutions and FITC were severely quenched as they were attached to the surface of AuNPs. At a lower concentration of cyanide, it was capable of etching AuNPs to form gold cyanidation, thereby removal of fluoresce dye from the surface. The liberated fluoresce dyes were then restored to their original fluorescence intensity. When the concentration of sample over 150 □M, the stabilizer of T-20 was detached from AuNPs surface, enabled the system of AuNPs lost its stability and assemble in the high-slat solution. In this detection range, colorimetric strategies can be used to effectively determine the concentration of cyanide, based on distinguishable color changes from red to violet upon aggregation. With this sensor, the lowest concentration to quantify cyanide ions could be down to 100 nM, which is approximately 27 times lower than the maximum level (2.7 □M) of cyanide in drinking water permitted by the World Health Organization (WHO); the highest concentration can reach at hundreds micro molar level, which can be used as a suitable tool for industrial sewage monitoring. The AuNPs-based sensor provides a number of advantages, including easy preparation, selectivity, sensitivity, low cost, and wide detection range. The demand of cyanide analysis in environmental applications requires parallel analytical strategies; our designed method gives a great potential for reliable detection of cyanide in various water samples.