In this study, a portable silver ion (Ag + ) sensor was fabricated based on a dual signal output system using black phosphorus quantum dots (BPQDs) as probes. It is the first work for Ag + detection using paper test strip based on BPQDs. The color change of BPQDs paper sensor for the determination of Ag + was easily identified by naked eye. BPQDs were synthesized from bulk black phosphorus (BP) by mechanical exfoliation combined with a solvothermal method. BPQDs exhibited blue fluorescence with a quantum yield of 8.82 %. The fluorescence of BPQDs can be quenched by Ag + , and the absorbance of BPQDs is increased with increasing Ag + concentration. The mechanism of the interaction between BPQDs and Ag + involving fluorescence quenching and bonding was investigated by experimental and computational methods. The detection limit of Ag + was 1.56 μg/mL and 0.19 μg/mL using fluorometry and colorimetry methods, respectively. A portable visual sensor based on paper test strip was constructed for Ag + detection using the colorimetric approach. The strategy was employed to determine Ag + successfully in drinking water samples. Therefore, the proposed portable Ag + sensor can be potentially utilized for the lab-free analysis of drinking water and even dietary samples.
Liu Yaqing,Lin Xiaodong,Ji Xiangyi,Hao Zhe,Tao Zhanhui
A novel fluorescence strategy based on the outstanding catalytic capability of CuS nanoparticles (CuS NPs ) has been developed for highly sensitive and specific determination of o,o-dimethyl-o-2,2-dichlorovinyl phosphate (DDVP) under enzyme-free and hydrogen peroxide (H 2 O 2 )-free conditions. In the presence of DDVP, CuS NPs can catalyze non-fluorescence substratum of Amplex red (AR) into resorufin, which exhibits fluorescence emission at 584 nm under excitation at 540 nm. The sensing system exhibits outstanding specificity and only responds to DDVP and no other organophosphorus pesticides (OPs). A wide linear range is obtained from 0.0001 to 0.1 μg/mL, and the limit of detection (LOD) is 0.1 ng/mL. Furthermore, paper-based test strips have been constructed for visual detection of DDVP under ultraviolet light irradiation. By integrating a smartphone installed with Color Picker APP, point-of-care detection with quantitative determination is realized, demonstrating substantial potential applications of the as-developed assay for in situ detection.
Graphical abstract
Ti 3 C 2 MXene quantum dots (Ti 3 C 2 MQDs) are recognized as promising new nanomaterial recently, while the majority of the Ti 3 C 2 MQDs manifest limited maximum emission in the blue-light range. Herein, the green fluorescence nitrogen, phosphorus-doped Ti 3 C 2 MQDs (N, P-Ti 3 C 2 MQDs) were synthesized via facile microwave-assisted method, which greatly reduces the reaction time. The as-prepared N, P-Ti 3 C 2 MQDs showed excitation-dependent photoluminescence , anti-photobleaching, and favorable dispersibility . Interestingly, the fluorescence of N, P-Ti 3 C 2 MQDs can be quenched by 1,10-phenanthroline-Fe (II) complex (Phen-Fe 2+ ) via inner filter effect (IFE), accompanied by the increased orange color. After introduction of nitrite (NO 2 - ), owing to the redox reaction between NO 2 - and Fe 2+ , the fluorescence will be recovered and the color varies from orange to colorless gradually. Therefore, a colorimetric/fluorometric dual-modal recognition of NO 2 - was fabricated based on N, P-Ti 3 C 2 MQDs and Phen-Fe 2+ complex. Moreover, paper-based test trips were facilely made by the N, P-Ti 3 C 2 MQDs/Phen-Fe 2+ sensing system in response to ultrafast-response, real-time detection of NO 2 - with the assistant of smartphone. This study tendered a novel dual-channel method for real-time visual assay of NO 2 - as well as provided insightful research into functionalized Ti 3 C 2 MQDs regarding in food analysis.
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