Time-resolved in situ vibrational spectroscopy for electrocatalysis: challenge and opportunity.

Understanding the structure-activity relationship of catalysts and the reaction pathway is crucial for designing efficient, selective, and stable electrocatalytic systems. In situ vibrational spectroscopy provides a unique tool for decoding molecular-level factors involved in electrocatalytic reactions. Typically, spectra are recorded when the system reaches steady states under set potentials, known as steady-state measurements, providing static pictures of electrode properties at specific potentials. However, transient information that is crucial for understanding the dynamic of electrocatalytic reactions remains elusive. Thus, time-resolved in situ vibrational spectroscopies are developed. This mini review summarizes time-resolved in situ infrared and Raman techniques and discusses their application in electrocatalytic research. With different time resolutions, these time-resolved techniques can capture unique dynamic processes of electrocatalytic reactions, short-lived intermediates, and the surface structure revolution that would be missed in steady-state measurements alone. Therefore, they are essential for understanding complex reaction mechanisms and can help unravel important molecular-level information hidden in steady states. Additionally, improving spectral time resolution, exploring low/ultralow frequency detection, and developing operando time-resolved devices are proposed as areas for advancing time-resolved techniques and their further applications in electrocatalytic research.

Revealing protein binding affinity on metal surfaces: an electrochemical approach.

Revealing the binding affinity between viruses and surfaces of environmental matrices is crucial to evaluate the bioactivity of an immobilized virus and accompanying indirect virus-related infection pathways. The understanding for SARS-CoV-2 remaining infective for even days on stainless steel but only hours on copper is still unclear. Electrochemical chronoamperometry, ultrasensitive to interfacial capacitance on surface species, was used to investigate the binding affinity of SARS-CoV-2 on metal surfaces. SRBD, the surrogate of SARS-CoV-2, shows the highest adsorption capacity on a gold surface, followed by Cu, but lowest on a stainless steel surface. The strong binding of SRBD on copper is a result of the naturally grown Cu2O under ambient conditions. Measurement of electrochemical capacitance provides a simple strategy to explore and evaluate the potential risk of an indirect virus-related infection pathway through conductive environmental matrices.

Deep Learning for Biospectroscopy and Biospectral Imaging: State-of-the-Art and Perspectives.

With the advances in instrumentation and sampling techniques, there is an explosive growth of data from molecular and cellular samples. The call to extract more information from the large data sets has greatly challenged the conventional chemometrics method. Deep learning, which utilizes very large data sets for finding hidden features therein and for making accurate predictions for a wide range of applications, has been applied in an unbelievable pace in biospectroscopy and biospectral imaging in the recent 3 years. In this Feature, we first introduce the background and basic knowledge of deep learning. We then focus on the emerging applications of deep learning in the data preprocessing, feature detection, and modeling of the biological samples for spectral analysis and spectroscopic imaging. Finally, we highlight the challenges and limitations in deep learning and the outlook for future directions.

Surface-enhanced Raman spectroscopy: benefits, trade-offs and future developments.

Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopy technique with sensitivity down to the single molecule level that provides fine molecular fingerprints, allowing for direct identification of target analytes. Extensive theoretical and experimental research, together with continuous development of nanotechnology, has significantly broadened the scope of SERS and made it a hot research field in chemistry, physics, materials, biomedicine, and so on. However, SERS has not been developed into a routine analytical technique, and continuous efforts have been made to address the problems preventing its real-world application. The present minireview focuses on analyzing current and potential strategies to tackle problems and realize the SERS performance necessary for translation to practical applications.

DNA Hydrogels and Microgels for Biosensing and Biomedical Applications.

DNA hydrogels, which take advantage of the unique properties of functional DNA motifs, such as specific molecular recognition, programmable and high-precision assembly, multifunctionality, and excellent biocompatibility, have attracted increasing research interest in the past two decades in diverse fields, especially in biosensing and biomedical applications. The responsiveness of smart DNA hydrogels to external stimuli by changing their swelling volume, crosslinking density, and optical or mechanical properties has facilitated the development of DNA-hydrogel-based in vitro biosensing systems and actuators. Furthermore, reducing the sizes of DNA hydrogels to the micro- and nanoscale leads to better responsiveness and delivery capacity, thereby making them excellent candidates for rapid detection, in vivo real-time sensing, and drug release applications. Here, the recent progress in the development of smart DNA hydrogels and DNA microgels for biosensing and biomedical applications is summarized, and the current challenges as well as future prospects are also discussed.

Cationic-Polyelectrolyte-Modified Fluorescent DNA-Silver Nanoclusters with Enhanced Emission and Higher Stability for Rapid Bioimaging.

DNA-templated silver nanoclusters (DNA-Ag NCs) have shown great potential in various bioanalysis and bioimaging applications, owing to their facile synthesis and ultrasmall sizes and especially their programmable fluorescence emission depending on the sequences of DNA templates. However, the bioimaging applications of DNA-Ag NCs are severely limited by their poor stability in physiological environments and their poor cell permeability, resulting from the highly negatively charged DNA backbones. In this paper, cationic polyelectrolytes were used to modify fluorescent DNA-Ag NCs via electrostatic interactions between the positive polymer backbones and the negatively charged phosphate groups of the DNA strands. The fluorescence properties of a typical single-stranded-DNA (ssDNA)-templated Ag NC changed dramatically after incorporation with the cationic polyelectrolyte caused by conformational changes in the DNA, with a 3-fold fluorescence-emission enhancement of the Ag NCs observed after incorporation with a typical cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA), whereas the fluorescence of double-stranded-DNA (dsDNA)-templated Ag NCs changed little after incorporation. Moreover, the modification with PDDA greatly prolonged the stability of both ssDNA- and dsDNA-stabilized Ag NCs against nuclease digestion and enhanced the cell uptake of the DNA-Ag NCs. Rapid cell imaging was demonstrated using NIH/3T3 cells as a model system.

Reversible modulation of CsPbBr3 perovskite nanocrystal/gold nanoparticle heterostructures.

A facile strategy is illustrated to reversibly modulate CsPbBr3 perovskite nanocrystal/Au nanoparticle heterostructures with the reversible formation and fragmentation of gold nanoparticles anchored to the corners and surface of CsPbBr3 perovskite nanocrystals. The modulation process was performed under ambient conditions and could be conducted for cycles.

Liposome Crosslinked Polyacrylamide/DNA Hydrogel: a Smart Controlled-Release System for Small Molecular Payloads.

A novel stimuli-responsive hydrogel system with liposomes serving as both noncovalent crosslinkers and functional small molecules carriers for controlled-release is developed. Liposomes can crosslink polyacrylamide copolymers functionalized with cholesterol-modified DNA motifs to yield a DNA hydrogel system, due to the hydrophobic interaction between cholesteryl groups and the lipid bilayer of liposomes. Functional information encoded DNA motifs on the polymer backbones endow the hydrogel with programmable smart responsive properties. In a model system, the hydrogel exhibits stimuli-responsive gel-to-sol transformation triggered by the opening of DNA motifs upon the presence of a restriction endonuclease enzyme, EcoR I, or temperature change, realizing the controlled-release of liposomes which are highly efficient carriers of active small molecules payloads. Two active molecules, 1,1-dioctadecyl-3,3,3,3-tetramethylindodicarbocyanine perchlorate (DiIC18(5)) and calcein, are chosen as the hydrophobic and hydrophilic model payloads, respectively, to address the feasibility of the releasing strategy. Moreover, the hydrogel exhibits injectable property as well as self-recovery behaviors.

Fabrication of aluminum terephthalate metal-organic framework incorporated polymer monolith for the microextraction of non-steroidal anti-inflammatory drugs in water and urine samples.

Polymer monolith microextraction (PMME) based on capillary monolithic column is an effective and useful technique to preconcentrate trace analytes from environmental and biological samples. Here, we report the fabrication of a novel aluminum terephthalate metal-organic framework (MIL-53(Al)) incorporated capillary monolithic column via in situ polymerization for the PMME of non-steroidal anti-inflammatory drugs (NSAIDs) (ketoprofen, fenbufen and ibuprofen) in water and urine samples. The fabricated MIL-53(Al) incorporated monolith was characterized by X-ray powder diffractometry, scanning electron microscopy, Fourier transform infrared spectrometry, and nitrogen adsorption experiment. The MIL-53(Al) incorporated monolith gave larger surface area than the neat polymer monolith. A 2-cm long MIL-53(Al) incorporated capillary monolith was applied for PMME coupled with high-performance liquid chromatography for the determination of the NSAIDs. Potential factors affecting the PMME were studied in detail. Under the optimized conditions, the developed method gave the enhancement factors of 46-51, the linear range of 0.40-200µgL(-1), the detection limits (S/N=3) of 0.12-0.24µgL(-1), and the quantification limits (S/N=10) of 0.40-0.85µgL(-1). The recoveries for spiked NSAIDs (20µgL(-1)) in water and urine samples were in the range of 77.3-104%. Besides, the MIL-53(Al) incorporated monolith was stable enough for 120 extraction cycles without significant loss of extraction efficiency. The developed method was successfully applied to the determination of NSAIDs in water and urine samples.