An up-conversion test paper based on "switch-off" of fluorescence is constructed to sensitively and selectively detect cancer-causing dye Sudan III in lipstick.

Cancer-causing dye Sudan III is banned adding to cosmetics, so a method for detecting trace Sudan III in cosmetics is established. A single dispersed up-conversion molecularly imprinted fluorescent nanoprobe is constructed and coated on the filter paper. The mechanism for detecting Sudan III by this composite fluorescent nanoprobes-paper is systematically analyzed. The fluorescent response (max emission peak is at 541 nm) is linearly related to 10-1000 nM Sudan III, and Sudan III can be selectively recognized (imprinting factor increased to 4.1). The limit of detection and quantitation are further reduced to 2.89 nM and 9.63 nM, respectively. The recoveries of Sudan III in lipstick samples are between 93.18 and 108.3%, and relative standard deviation is less than or equal to 4.6%. Trace Sudan III in cosmetics are detected accurately and sensitively by this method due to up-conversion nanoparticles with little interference of background fluorescence and molecularly imprinted polymers with selective enrichment.

Highly Sensitive and Durable Sea-Urchin-Shaped Silver Nanoparticles Strain Sensors for Human-Activity Monitoring.

High-performance strain sensors, composed of various artificial sensing materials on/in stretchable substrates, show great promise for applications in flexible electronic devices. Here, we demonstrated a highly sensitive and durable strain sensor consisting of a ribbon of close-packed sea-urchin-shaped silver nanoparticles (SUSNs) sandwiched between two layers of poly(dimethylsiloxane) (PDMS). Each of SUSNs possesses high-density and spherically distributed sharp spines over the body, which promotes electron transduction and further improves signal detection. This SUSN-based sensor possesses a desirable integration of high sensitivity (a gauge factor of 60) and large stretchability (up to 25%) at tensile sensing, broadening its application in wearable devices. Moreover, it also shows fast response (48 ms), good reproducibility, and long-term stability (>2500 cycles at 20% strain). It can also be used to detect compressing (sensitivity up to 31.5) and folding-type bending deformations. The sensing mechanism, the resistance of the sensors varying as the deformation load, results from the inter-spine contacts change and the microcracks evolution caused by variation in the gap between SUSNs. The sensor's sensitivity at different degrees of strain was also achieved by controlling the width of the close-packed SUSNs ribbon. For practical demonstration, the SUSN-based sensors could be used as wearable devices for monitoring human activities ranging from subtle deformations to substantial movements.