Portable Photoacoustic System Research Articles

Plasmonic Gold Nanomaterials as Photoacoustic Signal Resonant Enhancers for Cysteine Detection.

The development of photoacoustic systems is important for the real-time detection of cysteine (Cys), a biothiol in biological systems that serves as a significant biomarker for human health. Advanced photoacoustic (PA) signals with colloidal plasmonic Au nanomaterials rely on the efficient conversion of light to energy waves under moderately pulsed laser irradiation. In this study, we synthesized Cys-capped Au nanorods (Au@Cys NRs) and Cys-capped Au nanoparticles (Au@Cys NPs) through a conjugate of three Cys concentrations (10, 100, and 1000 μM). These plasmonic Au nanomaterials can be used as a PA resonance reagent due to their maximum localized surface plasmon resonance (LSPR) absorption bands at 650 nm and 520 nm in Au NRs and Au NPs, respectively. Subsequently, the PA signals were noticeably increased proportionally to the concentrations in the Au@Cys NRs and Au@Cys NPs under 658 nm and 520 nm laser irradiation, respectively, according to our portable photoacoustic system. Furthermore, PA signal amplitudes in Cys detection are boosted by ~233.01% with Au@Cys NRs and ~102.84% with Au@Cys NPs enhancement, compared to free Cys, according to ultrasound transducers at frequencies of 3 MHz.

Measuring the CO2 production from maize‐straw‐amended soil columns— a comparison of four methods

AbstractA soil‐column experiment with maize‐straw application at different depths was carried out to investigate the accuracy of CO2‐measurement systems in a greenhouse experiment with sandy and loamy soils. The classical approach of CO2 absorption in NaOH solution was compared with three other methods using dynamic chambers. These methods were gas chromatography (GC), a portable infrared analyzer (IR), and a portable photo‐acoustic system (PAS). The cumulative CO2 production over the 57‐day incubation period was significantly affected by the method and soil‐specifically by the treatments. The NaOH and GC method always formed a pair of lowest cumulative CO2 production in all treatments with maize‐straw addition. In the treatments with bottom application of the maize straw, IR and PAS methods gave values at identical levels in both soils. In the treatments with top application of the maize straw, the IR method gave significantly highest values in the sandy soil and the PAS method in the loamy soil. The correlation coefficients between the cumulative CO2 production of the three dynamic‐chamber methods (GC, IR, and PAS) and the static NaOH method were all significant, with r values between 0.90 and 0.93. The C balance can be used for testing the plausibility of CO2‐production data. Roughly 102% (NaOH and GC) and 114% (IR and PAS) were recovered, including the CO2‐production data in the C balance of the sandy soil. The respective data were 97% (NaOH and GC) and 104% (IR and PAS) for the loamy soil.