Disposable Paper-Based Analytical Device for Visual Speciation Analysis of Ag(I) and Silver Nanoparticles (AgNPs)

Abstract

A disposable, instrument-free, height readout paper-based analytical device (HR-PAD) based on a paper strip inkjet-printed with CdTe quantum dots (QDs) was developed for the sensitive speciation analysis of Ag + and silver nanoparticles (AgNPs). When the paper strip is immersed into a sample solution, capillary action draws it through the surface and any Ag + in the solution quenches the fluorescence of CdTe QDs via a cation exchange reaction between Ag + and the CdTe QDs, with the height of the quenched band being proportional to the concentration of Ag + . In contrast, fluorescence quenching cannot be observed when only AgNPs are present in solution. Thus, the concentration of AgNPs can be obtained by subtracting the Ag + content from the total silver determined by the HR-PAD after digestion with HNO 3 . Under optimized conditions, the methodology provides high selectivity, sensitivity, and accuracy for the detection of Ag + or AgNPs in various samples, even at concentrations as low as 0.05 mg L −1 . Precisions of 4.5% and 2.2% RSDs were achieved at concentrations of 1 mg L −1 and 7 mg L −1 of Ag + , respectively. Compared to conventional methods, this approach is inexpensive and user-friendly and eliminates the need for expensive and sophisticated detection instruments. The practicality of the method was demonstrated via the speciation analysis of AgNPs and Ag + in river water and 12 commercial products with satisfactory results.

Fabrication and Applications of Microfluidic Devices: A Review

“…Since 2007, paper-based microfluidics has been explored as an alternative to expensive materials for microfluidic applications [34,39]. Paper-based systems benefit from simplicity [40], accessibility [29], significant low costs [29,[39][40][41], high porosity [2,29], high physical absorption [24], ease of manipulation and sterilization [29], potential for chemical or biological modifications [29], similarity to the native ECM [29], bio-affinity [24], biocompatibility [29], light weights [41], and the ability to operate without supporting equipment [39,41]. What makes paper so special is the surface tension of a fluid and its contact angle with cellulose fibers [33].…”

“…Paper-based systems are attractive for rapid point-of-care diagnostic testing and medical screening in the developing world [39,41,42], being mostly used together with a colorimetric or an electrochemical readout for detecting target biomolecules [24,42]. Besides, paper microfluidic systems can be directly and in situ operated, even in the absence of technical infrastructure and trained experts, making these devices a promising solution for field analysis or testing at home [40]. However, paper-based systems are limited by their poor mechanical strength in a wet state and thickness requirements for achieving transparency [29].…”

Desktop Fabrication of Lab-On-Chip Devices on Flexible Substrates: A Brief Review

“…When paper strips were dipped in the solutions containing silver ions, it would quench the fluorescence of CdTe quantum dots. The concentration of silver ions present in the sample was directly related to the height of the fluorescent band to get calibration curve, as shown in the Figure 7 [45]. There are numerous advantages of inkjet printing including mask-less technique, time efficient, has good reproducibility, and has high spatial resolution.…”

Recent Advances and Applications in Paper-Based Devices for Point-of-Care Testing

“…Through selection of electrode material and electrochemical technique, electrochemical detection was realized with fast response and high sensitivity [29]. Nowadays, to enrich these detection methods and achieve sensitive and accurate signal out-put, various micro-and nano-materials with different signal transduction mechanisms, such as metal nanoparticles [30,31], metal oxide [32,33], graphene or graphene oxide [34,35], quantum dots [36,37], hybrid materials [38,39] and metal-organic frameworks [40][41][42] have brought new breakthroughs in the design of new paper-based sensors. In addition, signal readers tend to be miniaturized.…”