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Spectral imaging is a technology that integrates conventional imaging and spectroscopy to get both spatial and spectral information from an object. Although this technology was originally developed for remote sensing, it has been extended to the biomedical engineering field as a powerful analytical tool for biological and biomedical research. This review introduces the basics of spectral imaging, imaging methods, current equipment, and recent advances in biomedical applications. The performance and analytical capabilities of spectral imaging systems for biological and biomedical imaging are discussed. In particular, the current achievements and limitations of this technology in biomedical engineering are presented. The benefits and development trends of biomedical spectral imaging are highlighted to provide the reader with an insight into the current technological advances and its potential for biomedical research.

Anion-exchange membrane fuel cells hold promise to greatly reduce cost by employing nonprecious metal cathode catalysts. More efficient anode catalysts are needed, however, to improve the sluggish hydrogen oxidation reaction in alkaline electrolytes. We report that BCC-phased PdCu alloy nanoparticles, synthesized via a wet-chemistry method with a critical thermal treatment, exhibit up to 20-fold HOR improvement in both mass and specific activities, compared with the FCC-phased PdCu counterparts. HOR activity of the BCC-phased PdCu is 4 times or 2 times that of Pd/C or Pt/C, respectively, in the same alkaline electrolyte. In situ HE-XRD measurements reveal that the transformation of PdCu crystalline structure favors, at low annealing temperature (<300 °C), the formation of FCC structure. At higher annealing temperatures (300−500 °C), a BCC structure dominates the PdCu NPs. Density functional theory (DFT) computations unravel a similar H binding strength and a much stronger OH binding of the PdCu BCC surface (cf. FCC surface), both of which are simultaneously close to those of Pt surfaces. The synergistic optimization of both H and OH binding strengths is responsible for the enhancement of HOR activity on BCC-phased PdCu, which could serve as an efficient anode catalyst for anion-exchange membrane fuel cells. This work might open a new route to develop efficient HOR catalysts from the perspective of crystalline structure transformation.

An investigation of the electrochemical and structural properties of layered P2–Na0.62Mn0.75Ni0.25O2 is presented. The effect of changing the Mn/Ni ratio (3:1) from what is found in Na0.67Mn0.67Ni0.33O2 (2:1) and consequently the introduction of a third metal center (Mn3+) was investigated. X-ray powder diffraction (in situ and ex situ) revealed the lack of Na+-ion/vacancy ordering at the relevant sodium contents (x = 0.33, 0.5, and 0.67). Mn3+ in Na0.62Mn0.75Ni0.25O2 introduces defects into the Ni–Mn interplane charge order that in turn disrupts the ordering within the Na-plane. The material underwent P2–O2 and P2–P2′ phase transitions at high (4.2 V) and low (∼1.85 V) voltages, respectively. The material was tested at several different voltage ranges to understand the effect of the phase transitions on the capacity retention. Interestingly, the inclusion of both phase transitions demonstrated comparable cycling performance to when both phase transitions were excluded. Last, excellent rate performance was demonstrated between 4.3 and 1.5 V with a specific capacity of 120 mA h/g delivered at 500 mA/g current density.

Sulfide-based Na-ion conductors are promising electrolytes for all-solid-state sodium batteries (ASSSBs) because of high ionic conductivity and favorable formability. However, no effective strategy has been reported for longduration Na cycling with sulfide-based electrolytes because of interfacial challenges. Here we demonstrate that a cellulose− poly(ethylene oxide) (CPEO) interlayer can stabilize the interface between sulfide electrolyte (Na 3 SbS 4 ) and Na by shutting off the electron pathway of the electrolyte decomposition reaction. As a result, we achieved stable Na plating/stripping for 800 cycles at 0.1 mA cm −2 in all-solidstate devices at 60 °C.

The unique physical property of negative thermal expansion (NTE) is not only interesting for scientific research but also important for practical applications. Chemical modification generally tends to weaken NTE. It remains a challenge to obtain enhanced NTE from currently available materials. Herein, we successfully achieve enhanced NTE in Pb(TiV)O by improving its ferroelectricity. With the chemical substitution of vanadium, lattice tetragonality (c/a) is highly promoted, which is attributed to strong spontaneous polarization, evidenced by the enhanced covalent interaction in the V/Ti-O and Pb-O2 bonds from first-principles calculations. As a consequence, Pb(TiV)O exhibits a nonlinear and much stronger NTE over a wide temperature range with a volumetric coefficient of thermal expansion α = -3.76 × 10/°C (25-550 °C). Interestingly, an intrinsic giant volume contraction (∼3.7%) was obtained at the composition of Pb(TiV)O during the ferroelectric-to-paraelectric phase transition, which represents the highest value ever reported. Such volume contraction is well correlated to the effect of spontaneous volume ferroelectrostriction. The present study extends the scope of the NTE family and provides an effective approach to explore new materials with large NTE, such as through adjusting the NTE-related ferroelectric property in the family of ferroelectrics.

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Because of the low cost and high abundance of sodium, room-temperature sodium-ion batteries have recently been considered as an alternative power source to lithium-ion batteries. In contrast to the electrochemical performance of the batteries, safety has been paid much less attention, but safety is a critical consideration because sodium-ion batteries are intended for large-scale electrochemical energy storage applications. Herein, we have reported a NaNi 1/3 Fe 1/3 Mn 1/3 O 2 /hard carbon full cell with a good cycling performance and high Coulombic efficiency. The energy density of this pouch cell is close to 95 Wh/kg, and the capacity retention of the NFM full cell attained at 92.6% after 100 cycle numbers. Moreover, we have further used accelerating rate calorimetry, scanning electron microscopy, and operando synchrotron high-energy X-ray diffraction to investigate the thermal/chemical stability of charged Na x Ni 1/3 Fe 1/3 Mn 1/3 O 2 cathode material at both cell and component level. It is found that the thermal decomposition of desodiated Na x Ni 1/3 Fe 1/3 Mn 1/3 O 2 is a redox reaction that can be facilitated with the presence of either a reductive environment, such as electrolytes, or a strong oxidative environment that can result from a higher degree of desodiation. The findings presented in this work can guide future development of advanced sodium-ion batteries for practical application.