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The combination of a tunable quantum cascade laser (QCL) and plasmonic mid-infrared (MIR) metasurface is a powerful tool enabling high-content microscopy of hydrated cells using the vibrational contrast of their constituent biomolecules. While the QCL provides a high-brightness source whose frequency can be rapidly tuned to that of the relevant molecular vibration, the metasurface is used to overcome water absorption of MIR light. Here we employ the resulting metasurface-enabled inverted reflected-light infrared absorption microscopy (MIRIAM) tool for non-destructive monitoring of the vital process of lipogenesis (DNL), by which fat tissue cells (adipocytes) synthesize fatty acids from glucose and store them inside lipid droplets. Using C-labeled glucose as a metabolic probe, we produce spatially- and temporally-resolved images of C incorporation into lipids and proteins, observed as red-shifted vibrational peaks in the MIR spectra. These findings demonstrate MIRIAM’s capability for studying metabolic pathways with molecular specificity, offering a powerful platform for metabolic imaging.

Carbon dots (CDs) have attracted significant interest as one of the most emerging photoluminescence (PL) nanomaterials. However, the realization of CDs with dominant near‐infrared (NIR) absorption/emission peaks in aqueous solution remains a great challenge. Herein, CDs with both main NIR absorption bands at 720 nm and NIR emission bands at 745 nm in an aqueous solution are fabricated for the first time by fusing large conjugated perylene derivatives under solvothermal treatment. With post‐surface engineering, the polyethyleneimine modified CDs (PEI‐CDs) exhibit enhanced PL quantum yields (PLQY) up to 8.3% and 18.8% in bovine serum albumin aqueous and DMF solutions, which is the highest PLQY of CDs in NIR region under NIR excitation. Density functional theory calculations support the strategy of fusing large conjugated perylene derivatives to achieve NIR emissions from CDs. Compared to the commercial NIR dye Indocyanine green, PEI‐CDs exhibit excellent photostability and much lower cost. Furthermore, the obtained PEI‐CDs illustrate the advantages of remarkable two‐photon NIR angiography and in vivo NIR fluorescence bioimaging. This work demonstrates a promising strategy of fusing large conjugated molecules for preparing CDs with strong NIR absorption/emission to promote their bioimaging applications. Carbon dots with both main near‐infrared (NIR) absorption and emission bands in aqueous solution are fabricated through solvothermal fusion of large conjugated perylene derivatives. After post‐surface modification with polyethyleneimine, high photoluminescence quantum yields in NIR region up to 8.3% and 18.8% are obtained in their bovine serum albumin aqueous and DMF solutions, respectively.

Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful technique that overcomes the issue of low molecular absorption cross-sections in infrared spectroscopy. Due to the collective oscillations of electrons in the infrared regime, SEIRA using resonant metamaterial provides greatly enhanced (up to 10 7 ) electromagnetic fields extending up to tens of nanometers from the metamaterial. The enhanced near-field enables spectroscopic analysis and ultrasensitive on-chip sensing of molecules. This interesting characteristic has aroused widespread attention from researchers to SEIRA technology, and various SEIRA-based sensing applications have been continuously emerging. Optimization of the signal enhancement to obtain high sensing performance is the developing main thread of SEIRA technology. In this Review, we provide a basic understanding of SEIRA's sensing mechanism and theoretical model. With this background, several SEIRA optimizing methods are discussed, ranging from design, materials to algorithms. Additionally, perspectives about the future development trends of SEIRA technologies are discussed.

The development of efficient non-precious metal catalysts is important for the large-scale application of alkaline hydrogen evolution reaction (HER). Here, we synthesized a composite catalyst of Cu and Mo 2 C (Cu/Mo 2 C) using Anderson-type polyoxometalates (POMs) synthesized by the facile soaking method as precursors. The electronic interaction between Cu and Mo 2 C drives the positive charge of Cu, alleviating the strong adsorption of hydrogen at the Mo site by modulating the d-band center of Mo 2 C. By studying the interfacial water structure using in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), we determined that the positively charged Cu crystals have the function of activating water molecules and optimizing the interfacial water structure. The interfacial water of Cu/Mo 2 C contains a large amount of free water, which could facilitate the transport of reaction intermediates. Due to activated water molecules and optimized interfacial water structure and hydrogen adsorption energy, the overpotential of Cu/Mo 2 C is 24 mV at a current density of 10 mA·cm −2 and 178 mV at a current density of 1000 mA·cm −2 . This work improves catalyst performance in terms of interfacial water structure optimization and deepens the understanding of water-mediated catalysis.

In this study, eight types of bacteria were cultivated, including Staphylococcus aureus. The infrared absorption spectra of the gas surrounding cultured bacteria were recorded at a resolution of 0.5 cm−1 over the wavenumber range of 7500–500 cm−1. From these spectra, we searched for the infrared wavenumbers at which characteristic absorptions of the gas surrounding Staphylococcus aureus could be measured. This paper reports two wavenumber regions, 6516–6506 cm−1 and 2166–2158 cm−1. A decision tree–based machine learning algorithm was used to search for these wavenumber regions. The peak intensity or the absorbance difference was calculated for each region, and the ratio between them was obtained. When these ratios were used as training data, decision trees were created to classify the gas surrounding Staphylococcus aureus and the gas surrounding other bacteria into different groups. These decision trees show the potential effectiveness of using absorbance measurement at two wavenumber regions in finding Staphylococcus aureus.

Simultaneous on‐chip sensing of multiple greenhouse gases in a complex gas environment is highly desirable in industry, agriculture, and meteorology, but remains challenging due to their ultralow concentrations and mutual interference. Porous microstructure and extremely high surface areas in metal–organic frameworks (MOFs) provide both excellent adsorption selectivity and high gases affinity for multigas sensing. Herein, it is described that integrating MOFs into a multiresonant surface‐enhanced infrared absorption (SEIRA) platform can overcome the shortcomings of poor selectivity in multigas sensing and enable simultaneous on‐chip sensing of greenhouse gases with ultralow concentrations. The strategy leverages the near‐field intensity enhancement (over 1500‐fold) of multiresonant SEIRA technique and the outstanding gas selectivity and affinity of MOFs. It is experimentally demonstrated that the MOF–SEIRA platform achieves simultaneous on‐chip sensing of CO2 and CH4 with fast response time (<60 s), high accuracy (CO2: 1.1%, CH4: 0.4%), small footprint (100 × 100 µm2), and excellent linearity in wide concentration range (0–2.5 × 104 ppm). Additionally, the excellent scalability to detect more gases is explored. This work opens up exciting possibilities for the implementation of all‐in‐one, real‐time, and on‐chip multigas detection as well as provides a valuable toolkit for greenhouse gas sensing applications. Porous metal–organic frameworks are provided with excellent gas adsorption selectivity due to their extremely high surface areas. Integrating it into the multiresonant surface‐enhanced infrared absorption platform overcomes the shortcomings of poor selectivity in gas sensing and enables simultaneous on‐chip sensing of greenhouse gases. Importantly, the strategy shows a competitive advantage in terms of response time, accuracy, footprint, and linearity.

Through interface engineering and content control strategy, a PdBi bimetallic interface structure was constructed for the first time to selectively convert CO 2 to formate with a remarkably high Faraday efficiency (FE formate ) of 94% and a partial current density ( j formate ) of 34 mA·cm − 2 at −0.8 V vs. reversible hydrogen electrode (RHE) in an H-cell. Moreover, the PdBi interface electrocatalyst even exhibited a high current density of 180 mA·cm − 2 with formate selectivity up to 92% in a flow cell and could steadily operate for at least 20 h. Electrochemical in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) confirmed that the PdBi interface could greatly weaken the adsorption of *CO intermediates due to electronic and geometric effects. Density functional theory (DFT) calculations also established that the PdBi interface regulated the CO 2 -to-formate pathway by reducing the energy barrier toward HCOOH and largely weakening the adsorption of *CO intermediates on the catalyst surface. This study reveals that the unique PdBi bimetallic interface can provide a novel platform to study the reaction mechanism through combining in-situ ATR-SEIRAS and DFT calculations.

MicroRNAs play an important role in early development, cell proliferation, apoptosis, and cell death, and are aberrantly expressed in many types of cancers. To understand their function and diagnose cancer at an early stage, it is crucial to quantitatively detect microRNA without invasive labels. Here, a plasmonic biosensor based on surface‐enhanced infrared absorption (SEIRA) for rapid, label‐free, and ultrasensitive detection of miR‐155 is reported. This technology leverages metamaterial perfect absorbers stimulating the SEIRA effect to provide up to 1000‐fold near‐field intensity enhancement over the microRNA fingerprint spectral bands. Additionally, it is discovered that the limit of detection (LOD) of the biosensor can be greatly improved by using tetrahedral DNA nanostructure (TDN) as carriers. By using near‐field enhancement of SEIRA and specific binding of TDN, the biosensor achieves label‐free detection of miR‐155 with a high sensitivity of 1.162% pm−1 and an excellent LOD of 100 × 10−15 m. The LOD is about 5000 times lower than that using DNA single strand as probes and about 100 times lower than that of the fluorescence detection method. This work can not only provide a powerful diagnosis tool for the microRNAs detection but also gain new insights into the field of label‐free and ultrasensitive SEIRA‐based biosensing. The detection of diagnostic and prognostic biomarkers for cancer is of great significance in clinical medicine. A plasmonic biosensor based on surface‐enhanced infrared absorption is demonstrated for rapid, label‐free, and ultrasensitive detection of cancer biomarker miR‐155. It is discovered that the limit of detection of the biosensor can be greatly broken by using tetrahedral DNA nanostructure as carriers.

DNA-wrapped single-walled carbon nanotubes (DNA-SWCNTs) in stable dispersion are expected to be used as biosensors in the future, because they have the property of absorption of light in the near infrared (NIR) region, which is safe for the human body. However, this practical application requires the understanding of the DNA-SWCNTs’ detailed response characteristics. The purpose of this study is to predict, in detail, the response characteristics of the absorption spectra that result when the antioxidant catechin is added to oxidized DNA-SWCNTs, from a small amount of experimental data. Therefore, in the present study, we predicted the characteristics of the absorption spectra of DNA-SWCNTs using the Bayesian regularization backpropagation neural network (BRBPNN) model. The BRBPNN model was trained with the catechin concentration and initial absorption peaks as inputs and the absorption spectra after catechin addition as outputs. The accuracy of the predicted absorption peaks and wavelengths after the addition of catechin, as predicted by the BRBPNN model, was within 1% of the error of the experimental data. By inputting the catechin concentrations under hundreds of conditions into this BRBPNN model, we were able to obtain detailed prediction curves for the absorption peaks. This method has the potential to help to reduce the experimental costs and improve the efficiency of investigating the properties of high-cost materials such as SWCNTs.

Silicate minerals are essential bricks of solid planets, which have been studied deeply by infrared absorption spectroscopy. Along with the rapid development of planetary exploration, infrared emission spectroscopy and corresponding radiation properties of minerals have been receiving attention. However, systematic research on silicate minerals using infrared emission spectroscopy has been absent so far. In this work, various silicate minerals (totally ten in five series included nesosilicates, eyclosilicates, inosilicates, phyllosilicates and tectosilicates) were investigated infrared spectral characteristics and infrared radiation properties using X-ray diffraction, X-ray fluorescence, and infrared spectroscopy (absorption and emission spectroscopy). Results indicated that the assignment of each band in infrared emission spectra of all samples could be obtainable referring to the well-known infrared absorption spectra, presenting a dominant absorption band near 1000 cm −1 related with the stretching of Si–O bonds and several weak bending-driven absorption bands in the range of 400–650 cm −1 . A good linear relationship (coefficient of determination R 2  = 0.996) between two corresponding wavenumbers suggested emission bands of silicate minerals have great correspondence with their absorption bands. Both vibrational stretching and bending of Si–O bonds in both spectra regularly shifted to higher frequencies as the increase of Si/O from 0.25 for nesosilicates and 0.50 for tectosilicates. The average emissivity of silicates, obtained from radiation energy spectra from 400 to 2000 cm −1 in the temperature range of 50–140 °C, showed all silicate minerals presented relatively higher emissivity (> 0.910) and displayed a remarkable reduction from nesosilicates (e.g., 0.981 for forsterite) to tectosilicates minerals (e.g., 0.913 for quartz). It was thus concluded that higher emissivity of silicates was attributed to the decrease of polymerization degree of SiO 4 tetrahedron ( R 2  = 0.86), vibrational frequency and range for Si–O stretching ( R 2  = 0.88, 0.92, respectively), and vibrational range for Si–O bending ( R 2  = 0.85). This work gets insight into the relationship among spectral characteristics, crystal chemistry, and radiation properties of silicate minerals, and would help accurately identify and distinguish various silicate minerals in remote sensing analysis for understanding the composition of planetary surfaces and their evolutionary path.