ACS Sensors最新文献

The successful application of fluorescence immunoassays for clinical diagnosis requires stable photoluminescent materials and highly efficient signal amplification strategies. In this work, the magnetism-functionalized lanthanide MOF-on-MOF (Fe₃O₄@SiO₂@MOF-on-MOF) was synthesized through intermolecular (van der Waals) interaction-assisted growth and further homogeneous epitaxial growth, which significantly improved the fluorescence performances and uncovered the underlying mechanism. The quantum chemical theory calculation and experimental studies revealed that the introduced magnetic Fe₃O₄@SiO₂ not only endowed magnetic separation capability but also promoted fluorescence performances, which increased the energy transfer of the intersystem crossing process and suppressed the luminescence of ligands and aggregation-induced quenching. Furthermore, the plasmonic Ag/Au nanocages were developed as highly efficient fluorescence quenchers to improve the sensitivity of the fluorescence immunoassay. On the basis of the proposed differential signal amplification (DSA) strategy, the immunoassay displayed superior detection ability, with a limit of detection of 0.13 pg·mL^-1 for severe acute respiratory syndrome coronavirus 2 nucleocapsid protein. The designed magnetic lanthanide MOF-on-MOF and proposed DSA strategy give new insights into ultrasensitive fluorescence immunoassays.

The evaluation of selectivity/cross-sensitivity is one of the most important tests for gas sensor development, particularly that based on chemiresistive technology. It is known that chemiresistive gas sensors suffer from low selectivity when they provide sensitivity to several analytes. Typically, selectivity testing involves independently assessing a sensor's response to a specific gas. However, there is a growing need to evaluate performance with interfering gases or gas mixtures since gas sensors are always exposed to gas mixtures in practice. Despite the great importance of selectivity characterization, currently, there are no standard methods of selectivity tests at conditions when target gas coexists with interfering gas compounds, which mimics real conditions. We outlined the four main methods researchers use to evaluate the cross-sensitivity of gas sensors. It highlights key aspects of selectivity test performance, assessment methodologies, and procedure features, attempting to classify them by their distinct characteristics. This review covers the essentials of gas properties, adsorption and desorption processes, and gas molecule interactions. Finally, we tried to address the lack of standardized protocols for evaluating chemiresistive gas sensors' cross-sensitivity to interfering gases and guide researchers.

Hyperpolarized (HP) ¹³C-labeled probes are emerging as promising agents to noninvasively image pH in vivo. HP [1,5-¹³C₂]Z-OMPD (Z-4-methyl-2-oxopent-3-enedioic acid) in particular has recently been used to simultaneously report on kidney perfusion, filtration, and pH homeostasis, in addition to the ability to detect local tumor acidification. In previous studies, dissolution dynamic nuclear polarization was used to hyperpolarize Z-OMPD. Here, we pioneered the hyperpolarization of [1,5-¹³C₂]Z-OMPD via SABRE-SHEATH (signal amplification by reversible exchange in shield enabling alignment transfer to heteronuclei), which is relatively simple and fast and promises to be highly scalable. With SABRE-SHEATH, we achieve enhancement values of ∼3950 and ∼2400 at 1.1 T (P_13C = 0.4 and 0.25%) on the labeled C-1 and C-5 positions of Z-OMPD. Density functional theory calculations at the B3LYP level of theory were used to investigate possible binding modes of Z-OMPD on the iridium-based polarization transfer catalyst. The experimental and theoretical results suggest that the equatorial binding mode to the catalyst, where Z-OMPD binds to the catalyst at both C-1 and C-5 carboxylate positions, is the most stable complex. The HP signals were used to measure the Z-OMPD chemical shift as a function of pH showing an ∼3 ppm shift across pH 4-11. This work lays a foundation for the development of a simple, low-cost hyperpolarization technique to image pH.

Ionic conductive hydrogel-based temperature sensors have emerged as promising candidates due to their good stretchability and biocompatibility. However, the unsatisfactory sensitivity, sluggish response/recovery speed, and poor environmental stability limit their applications for accurate long-term health monitoring and robot perception, especially in extreme environments. To address these concerns, here, the stretchable temperature sensors based on a double-side elastomer-encapsulated thin-film organohydrogel (DETO) architecture are proposed with impressive performance. It is found that the water-polyol binary solvent, organohydrogel film, and sandwiched device structure play important roles in the temperature sensing performance. By modifying the composition of binary solvent and thicknesses of organohydrogel and elastomer films, the DETO microsensors realize a thickness of only 380 μm, unprecedented temperature sensitivity (37.96%/°C), fast response time (6.01 s) and recovery time (10.53 s), wide detection range (25-95.7 °C), and good stretchability (40% strain), which are superior to those of conventional hydrogel-based sensors. Furthermore, the device displays good environmental stability with negligible dehydration and prolonged operation duration. With these attributes, the wearable sensor is exploited for the real-time monitoring of various physiological signals such as human skin temperature and respiration patterns as well as temperature perception for robots.