Flexible Transparent Electrodes Formed from Template-Patterned Thin-Film Silver.

Template-patterned, flexible transparent electrodes (TEs) formed from an ultrathin silver film on top of a commercial optical adhesive - Norland Optical Adhesive 63 (NOA63) - are reported. NOA63 is shown to be an effective base-layer for ultrathin silver films that advantageously prevents coalescence of vapor-deposited silver atoms into large, isolated islands (Volmer-Weber growth), and so aids the formation of ultrasmooth continuous films. 12 nm silver films on top of free-standing NOA63 combine high, haze-free visible-light transparency (T ≈ 60% at 550 nm) with low sheet-resistance ( R s ${\mathcal{R}}_s$ ≈ 16 Ω sq-1 ), and exhibit excellent resilience to bending, making them attractive candidates for flexible TEs. Etching the NOA63 base-layer with an oxygen plasma before silver deposition causes the silver to laterally segregate into isolated pillars, resulting in a much higher sheet resistance ( R s ${\mathcal{R}}_{s}$  > 8 × 106 Ω sq-1 ) than silver grown on pristine NOA63 . Hence, by selectively etching NOA63 before metal deposition, insulating regions may be defined within an otherwise conducting silver film, resulting in a differentially conductive film that can serve as a patterned TE for flexible devices. Transmittance may be increased (to 79% at 550 nm) by depositing an antireflective layer of Al2 O3 on the Ag layer at the cost of reduced flexibility.

Identification of Poly(ethylene terephthalate) Nanoplastics in Commercially Bottled Drinking Water Using Surface-Enhanced Raman Spectroscopy.

Micro/nanoplastics have emerged as global contaminants of serious concern to human and ecosystem health. However, identification and visualization of microplastics and particularly nanoplastics have remained elusive due to the lack of feasible and reliable analytical approaches, particularly for trace nanoplastics. Here, an efficient surface-enhanced Raman spectroscopy (SERS)-active substrate with triangular cavity arrays is reported. The fabricated substrate exhibited high SERS performance for standard polystyrene (PS) nanoplastic detection with size down to 50 nm and a detection limit of 0.001% (1.5 × 1011 particles/mL). Poly(ethylene terephthalate) (PET) nanoplastics collected from commercially bottled drinking water were detected with an average mean size of ∼88.2 nm. Furthermore, the concentration of the collected sample was estimated to be about 108 particles/mL by nanoparticle tracking analysis (NTA), and the annual nanoplastic consumption of human beings through bottled drinking water was also estimated to be about 1014 particles, assuming water consumption of 2 L/day for adults. The facile and highly sensitive SERS substrate provides more possibilities for detecting trace nanoplastics in an aquatic environment with high sensitivity and reliability.

Large Area Patterning of Highly Reproducible and Sensitive SERS Sensors Based on 10-nm Annular Gap Arrays.

Applicable surface-enhanced Raman scattering (SERS) active substrates typically require low-cost patterning methodology, high reproducibility, and a high enhancement factor (EF) over a large area. However, the lack of reproducible, reliable fabrication for large area SERS substrates in a low-cost manner remains a challenge. Here, a patterning method based on nanosphere lithography and adhesion lithography is reported that allows massively parallel fabrication of 10-nm annular gap arrays on large areas. The arrays exhibit excellent reproducibility and high SERS performance, with an EF of up to 107. An effective wearable SERS contact lens for glucose detection is further demonstrated. The technique described here extends the range of SERS-active substrates that can be fabricated over large areas, and holds exciting potential for SERS-based chemical and biomedical detection.