A smartphone-integrated aptasensor for pesticide detection using gold-decorated microparticles.

The increasing incidence of environmental concerns related to excessive use of pesticides, such as imidacloprid and carbendazim, poses risks to pollinators, water bodies, and human health, prompting regulatory scrutiny and bans in developed countries. In this study, we propose a portable smartphone-based biosensor for rapid and label-free colorimetric detection by using the gold-decorated polystyrene microparticles (Ps-AuNP) functionalized with specific aptamers to imidacloprid and carbendazim on a microfluidic paper-based analytical device (µ-PAD). Four aptamers were selected for the detection of these pesticides and their sensitivity and selectivity performance was evaluated. The sensitivity results show a detection limit for imidacloprid of 3.12 ppm and 1.56 ppm for carbendazim. The aptamers also exhibited high selectivity performance against other pesticides, such as thiamethoxam, fenamiphos, isoproturon, and atrazine. However, the platform presented cross-selectivity when detecting imidacloprid, carbendazim, and linuron, which is discussed herein. Overall, we present a promising platform for simple, on-site, and rapid colorimetric screening of specific pesticides, while highlighting the challenges of aptasensors in achieving selectivity amidst diverse molecular structures.

Harnessing Acoustic Dispersions in YX-LN/SiO2/Si SH-SAW Resonators for Electromechanical Coupling Optimization and Rayleigh Mode Suppression.

In this study, we investigate the dispersive behavior of the electromechanical coupling coefficient ( [Formula: see text]) for shear-horizontal (SH) and Rayleigh surface acoustic wave (SAW) modes in a YX-LiNbO3 (LN)/SiO2/Si substrate across various wavelengths. Due to the difference in velocity dispersion between the SH and Rayleigh modes, mode coupling can be observed when these two modes operate at closely proximate frequencies, leading to a notable variation in their [Formula: see text]. With a careful design, SH and Rayleigh modes can be tuned to achieve a mode-decoupling state for enhancing [Formula: see text] of the SH-SAW and suppressing the presence of the Rayleigh mode in YX-LN/SiO2/Si. Consequently, a series of proof-of-concept SH-SAW resonators with wavelengths ( λ ) ranging from 1.6 to [Formula: see text] are fabricated. The optimized resonator with a λ of [Formula: see text] exhibits a resonant frequency of 1.064 GHz, an effective [Formula: see text] of 47.7%, a maximum Bode- Q of around 900, and an 18-dB rejection of spurious modes spanning from 0.5 to 3 GHz, without the presence of the Rayleigh mode.