Design of an Integrated Microfluidic Paper-Based Chip and Inspection Machine for the Detection of Mercury in Food with Silver Nanoparticles.

For most of the fast screening test papers for detecting Hg2+, the obtained results are qualitative. This study developed an operation for the µPAD and combined it with the chemical colorimetric method. Silver nanoparticle (AgNP) colloids were adopted as the reactive color reagent to combine and react with the Hg standards on the paper-based chip. Then, the RGB values for the color change were used to establish the standard curve (R2 > 0.99). Subsequently, this detection system was employed for the detection tests of actual samples, and the detected RGB values of the samples were substituted back to the formula to calculate the Hg2+ contents in the food. In this study, the Hg2+ content and recovery rate in commercially available packaged water and edible salts were measured. The research results indicate that a swift, economical, and simple detection method for Hg2+ content in food has been successfully developed.

Process Optimization of Silver Nanoparticle Synthesis and Its Application in Mercury Detection.

Silver nanoparticles (AgNPs) have stable reactivity and excellent optical absorption properties. They can be applied in various industries, such as environmental protection, biochemical engineering, and analyte monitoring. However, synthesizing AgNPs and determining their appropriate dosage as a coloring substance are difficult tasks. In this study, to optimize the process of AgNP synthesis and obtain a simple detection method for trace mercury in the environment, we evaluate several factors-including the reagent addition sequence, reaction temperature, reaction time, the pH of the solution, and reagent concentration-considering the color intensity and purity of AgNPs as the reaction optimization criteria. The optimal process for AgNP synthesis is as follows: Mix 10 mM of silver nitrate with trisodium citrate in a hot water bath for 10 min; then, add 10 mM of sodium borohydride to produce the AgNPs and keep stirring for 2 h; finally, adjust the pH to 12 to obtain the most stable products. For AgNP-based mercury detection, the calibration curve of mercury over the concentration range of 0.1-2 ppb exhibits good linearity (R2 > 0.99). This study provides a stable and excellent AgNP synthesis technique that can improve various applications involving AgNP-mediated reactions and has the potential to be developed as an alternative to using expensive detection equipment and to be applied for the detection of mercury in food.

Host-only solid-state near-infrared light-emitting electrochemical cells based on interferometric spectral tailoring.

Solid-state near-infrared (NIR) light-emitting electrochemical cells (LECs) possess great potential in applications of NIR light sources due to their simple device structure, compatibility with large area and flexible substrates and low operating voltage. However, common host-guest NIR LECs suffer from the problem of significantly enhanced residual host emission upon increasing the bias voltage to achieve a higher NIR light output. A higher NIR light output can only be obtained at the expense of spectral purity in host-guest NIR LECs. To enhance the NIR light output of LECs without sacrificing the spectral purity significantly, a novel approach to generate NIR EL from host-only red-emitting LECs by adjusting the device thickness to modify the microcavity effect is proposed. NIR EL from host-only red-emitting LECs can be realized by adjusting the device thickness to shift the peak wavelength for constructive interference at the NIR spectral region. NIR EL resulting from the microcavity effect is relatively insensitive to bias voltage. Therefore, without losing spectral purity significantly, a 20× enhancement in the NIR output has been obtained in comparison to the previously reported value from host-guest NIR LECs. These results reveal that tailoring the EL spectra of host-only red-emitting LECs via modifying the microcavity effect would be a promising way to generate a higher NIR light output without suffering from the residual host emission problem of host-guest NIR LECs.

Non-doped solid-state white light-emitting electrochemical cells employing the microcavity effect.

Solid-state white light-emitting electrochemical cells (LECs) have attracted research attention owing to their advantages of simple device structure, low operation voltage and compatibility with solution processes. In this work, we demonstrate a simple approach to obtain white electroluminescence (EL) from non-doped LECs based on a blue-emitting complex. With a relatively thicker emissive layer, red emission can be additionally enhanced by the microcavity effect when the recombination zone moves to appropriate positions. Hence, white EL can be harvested by combining blue emission from the complex and red emission from the microcavity effect. These non-doped white LECs show external quantum efficiencies and power efficiencies up to 5% and 12 lm W(-1), respectively. These results show that efficient white EL can be obtained in simple non-doped LECs.

Improving the carrier balance of light-emitting electrochemical cells based on ionic transition metal complexes.

Recently, solid-state light-emitting electrochemical cells (LECs) based on ionic transition metal complexes (iTMCs) have attracted much research interest since they have the advantages of a simple device structure, a low operation voltage and compatibility with air-stable electrodes. These properties enable LECs to be cost-effective, versatile and power-efficient organic light-emitting sources. However, it is generally not easy to modify the molecular structure to achieve balanced carrier mobilities without altering the photoluminescence quantum yield of the iTMC. Furthermore, the carrier balance and the consequent device efficiency of single-layered LECs would not be easy to optimize since no carrier injection and transport layers can be used. In this perspective, some reported techniques to improve carrier balance of LECs based on iTMCs are described and reviewed. The importance and impact of these studies are highlighted. The effects on device lifetime and turn-on time because of employing these techniques to improve the carrier balance are also discussed. This perspective concludes that even with electrochemically doped layers, improving the carrier balance of LECs would be required for realizing efficient electroluminescent emission from simple-structure organic light-emitting sources.