An electrically switched ion exchange film with molecular coupling synergistically-driven ability for the selective recovery of Ag + ions is developed by coupling a conducting polypyrrole (PPy) with a 2, 2ʹ-dithiosalicylic acid (DTSA) at molecular scale. The rapid and selective uptake/release of Ag + ions by this hybrid film was found to be realized by the electrochemical circulation of the PPy ↔ PPy n+ as well as the disulfide ↔ dithiolate and the recognition ability of the carboxyl groups and disulfide bonds of DTSA. As a result, the recovery of Ag + ions can be handily achieved by adjusting the operating potential applied on the hybrid film coated electrode. The electrochemical quartz crystal microbalance measurements combined with the cyclic voltammetric technique, X-ray photoelectron spectroscopy and density functional theory computations were performed to identify the uptake/release mechanism of the hybrid film. Furthermore, the uptake capacity of the hybrid film maintained almost invariable after 10 consecutive uptake/release cycles, and the regeneration rate of Ag + ions remained over 80% in each cycle. It is expected that such an electroactive hybrid film can be applied for the recovery of Ag + ions from various industrial discharges.
Qiang Niu,Jiarui Hu,Han Hao,Rong Zhao,Guling Zhang,Jinfeng Zhu,Yuping Yang
Enhancing the interaction between light and matter, especially at the terahertz band, is pivotal for achieving ultra-broadband trace molecular fingerprint detection. Here, an efficient scheme featuring multiple Fabry–Pérot modes with equal intervals and uniform intensity is presented to implement a resonance interaction enhancement of molecular fingerprints with long-awaited precision and flexibility. This technique constructs uniform resonant probes across the entire spectral range to reveal molecular coupling effects via frequency-selective amplitude attenuation, enabling both qualitative and quantitative detection of L-tyrosine with a detection limit of 0.11 µg mm −2 . This is an inaugural experimental achievement of quantitative THz trace fingerprint detection with dual capabilities of achieving ultra-broadband and high-efficiency. Significantly, the technology enables direct identification of molecular absorption signatures from the transmitted multiple Fabry–Pérot modes using wavelet denoising algorithms, eliminating cumbersome data postprocessing and redundant testing procedures. This advancement heralds a new, accessible era in terahertz fingerprint spectroscopy.
Rong Chen,Linlong Tang,Guowei Li,Peng Luo,Yipei Wang,Xiaoqin Wu,Jinpeng Nong,Wei Wei
Chemically synthesized gold nanoantennas possess easy processability, low cost, and suitability for large-area fabrication, making them advantageous for surface-enhanced infrared (SEIRA) biosensing. Nevertheless, current gold nanoantennas face challenges with limited enhancement of biomolecular signals that hinder their practical applications. Here, we demonstrate that the coupling rate between antennas and molecules critically impacts the enhancement of molecular signals based on temporal coupled mode theory. To improve this coupling rate, we synthesized gold nanonails with sharp tips, significantly amplifying the localized electric fields of antenna resonance modes. Modulating the nanonail aspect ratio allows us to tailor antenna resonance frequencies to match molecular vibrational frequencies. Additionally, we introduced specific aptamers on antenna surfaces through solution exchange methods to control the antenna–molecule distances. These combined strategies enabled noninvasive, label-free detection with high sensitivity for the biomarker cortisol. Experiments revealed 3 orders of magnitude enhancement in cortisol detection levels upon increasing coupling efficiency, achieving a detection limit of 0.1 ng/mL, notably lower than the normal cortisol concentration in human saliva (0.398 ng/mL). In addition to demonstrating a novel strategy for cortisol detection, this study provides a viable approach to biomarker detection for future applications in disease diagnosis and human health monitoring.
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