A novel fluorescence turn-on sensor for Cr3+ based on fluorescence resonance energy transfer between gold nanoparticles and rhodamine B

Abstract

Up to now, “Turn-on” fluorescence sensor exhibits promising potential toward the detection of heavy metal ions, anions, drugs, organic dyes, DNA, pesticides, and other amino acids due to their simple, quick detection, and high sensitivity and selectivity. Herein, a novel fluorescence method of detecting Cr3+ in an aqueous solution was described based on the fluorescence resonance energy transfer between rhodamine B (RhB) and gold nanoparticles (AuNPs). The fluorescence of RhB solution could be obviously quenched (“off” state) with the presence of citrate-stabilized AuNPs. However, upon addition of Cr3+ to AuNPs@RhB system, the fluorescence of AuNPs was recovered owing to the strong interaction between Cr3+ and the specific groups on the surface of citrate-stabilized AuNPs, which will lead to the aggregation of AuNPs (“on” state). At this point, the color of the reaction solution turned to black. Under optimal conditions, the limit of detection (LOD) for Cr3+ was 0.95 nM (signal-to-noise ratio, S/N = 3) with a linear range of 0.164 nM to 3.270 μM. Furthermore, the proposed method exhibits excellent performances, such as rapid analysis, high sensitivity, extraordinary selectivity, easy preparation, switch-on fluorescence response, and non-time consuming.

1. Introduction

Recently, owing to the rapid development of industries such as textile, plastic, paper, leather, and food processing, various pollutants like antibiotics, toxic dyes [1–4], and heavy metal ions were released into the ecosystem and threatened the survival of human [5–7]. Among them, heavy metal ions like trivalent chromium ion (Cr3+) have received significant attention [8–10]. We all known that chromium ion (Cr3+), which is an essential trace element, plays a significant role in environment and biological process [11–12]. This important metal ion is closely related with the physiological activities of cells such as metabolism of fats, carbohydrates, and proteins [13–14]. Nevertheless, an overdose of Cr3+ can cause the genotoxic effect and malignant cancer [15–16]. Conversely, Cr3+ deficiency may lead to nervous system disorder, diabetes, and cardiovascular diseases [17–18]. Consequently, it is critical to develop a rapid, efficient, and highly selective analysis method to monitor of Cr3+ for environmental and human health.

Until now, several in vitro and in vivo analytical methods have been reported for detecting Cr3+, including high-performance liquid chromatography (HPLC), atomic absorption spectrometry (AAS), ion-coupled plasma-mass spectroscopy (ICP-MS), electrochemical analysis [19], colorimetric sensor [20–21], and liquid chromatography with ultraviolet detection (LC-UV). Despite the mentioned methods were widely used in the field of food and drug analysis, they have major disadvantages such as most of them are usually require extensive sample purification, expensive instrumentation, poor interference immunity, complexity, and the need for special equipment. In contrast, fluorescence analysis is a promising method for detection of Cr3+ due to its advantages of low-cost, real-time detection, simplicity, and high sensitivity.

Interestingly, nanoparticles, especially gold nanoparticles (AuNPs), have been broadly utilized to the fields of molecular recognition, sensor [22–23], photocatalysis [24], electrochemiluminescence (ECL), and fluorescence analysis, due to its unique advantages of instinct optical properties, extremely high extinction coefficient, strong surface plasmon resonance (SPR), and color-tunable optical properties [25–27]. Furthermore, the easy-to-modify surfaces of AuNPs have been successfully utilized as color reporters for colorimetric cartap sensing a large variety of targets. Therefore, AuNPs have been used as ideal color reporters for colorimetric sensors.