Optical constants of animal and plant tissues were measured over a wide spectral range using an integrating sphere spectrophotometer. The data were analyzed with two formulations of the 1-D diffusion approximation differing in the phase function. The accuracy of the similarity transformation was examined with tissue phantoms incorporating known chromophores in light scattering media.

A yolk–double shell cube-like SnS@N–S codoped carbon (YDSC-SnS@NSC) was delicately tailored by a self-templated and selective etching method as well as a self-assembly strategy. Herein, the ZnSn­(OH)6 (ZHS) solid nanocubes were used as templates for the formation of a thin carbon shell that encapsulated the active material, thereby preventing the aggregation and maintaining the uniformity. ZHS is then converted into an intermediate ZnS–SnS2 hybrid by a facile thermal sulfidation process. Because SnS2 is insoluble in acidic condition, it is easy to create a yolk–shell architecture by selectively removing the ZnS component. Further heat treatment promoted the melting of SnS2 and resulted in the decomposition of SnS2 into SnS, which is simultaneously accompanied with a heat- and capillary-driven self-assembly to form a SnS inner core and SnS/C double shell. Such nanostructures with an inner void space and robust double shells are useful in buffering the volume expansion of SnS during lithiation and sodiation. Furthermore, N and S atoms doped into the carbon shell can enhance the electrical conductivity, which is beneficial to the fast charge-transfer kinetics. Because of these advantages, YDSC-SnS@NSC as the anode for Li-ion batteries exhibits improved electrochemical properties. Especially, the YDSC-SnS@NSC anode for Na-ion batteries shows an outstanding rate capability of 257 mA h g–1 at 8 A g–1 and an ultrastable long-term cyclic performance at a current density of 1 A g–1 with a capacity retention of 83.5% (340 mA h g–1 at the first cycle and ultimately reached 284 mA h g–1) and only 0.012% capacity decay per cycle for over 1500 cycles. Such superior electrochemical performance demonstrated that this rationally designed anode is promising for application in both Li- and Na-ion storages.

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Tremendous efforts have been made toward the development of lithium–sulfur (Li–S) batteries as one of the most reasonable solutions to the rapidly increasing demand for portable electronic devices and electric vehicles, owing to their high cost-efficiency and theoretical energy density. However, the shuttle effect caused by soluble polysulfides is generally considered to be an insurmountable challenge, which can significantly reduce the battery lifecycle and sulfur utilization. Here, we report a lignin nanoparticle-coated Celgard (LC) separator to alleviate this problem. The LC separator enables abundant electron-donating groups and is expected to induce chemical binding of polysulfides to hinder the shuttle effect. When a sulfur-containing commercially available acetylene black (approximately 73.8 wt% sulfur content) was used as the cathode without modification, the Li–S battery with the LC separator presented much enhanced cycling stability over that with the Celgard separator for over 500 cycles at a current density of 1 C. The strategy demonstrated in this study is expected to provide more possibilities for the utilization of low-cost biomass-derived nanomaterials as separators for high-performance Li–S batteries.

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Considering the sharp increase in energy demand, Si-based composites have shown promise as high-performance anodes for lithium-ion batteries during the last few years. However, a significant volume change of Si during repetitive cycles may cause technical and security problems that limit the particular application. Here, an optimized reduced graphene oxide/silicon (RGO/Si) composite with excellent stability has been fabricated via a facile templated self-assembly strategy. The active silicon nanoparticles were uniformly supported by graphene that can further form a three-dimensional network to buffer the volume change of Si and produce a stable solid-electrolyte interphase film due to the increased specific surface area and enhanced intermolecular interaction, resulting in an increase of electrical conductivity and structural stability. As the anode electrode material of lithium-ion batteries, the optimized 10RGO/Si-600 composite showed a reversible high capacity of 2317 mA h/g with an initial efficiency of 93.2% and a quite high capacity retention of 85% after 100 cycles at 0.1 A/g rate. Especially, it still displayed a specific capacity of 728 mA h/g after 100 cycles at a reasonably high current density of 2 A/g. This study has proposed the optimized method for developing advanced graphene/Si nanocomposites for enhanced cycling stability lithium-ion batteries.

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Flux density distributions were measured in large tissue sections illuminated with 633- and 1064-nm laser radiation delivered by an optical fiber. The results were modeled by solving the 2-D diffusion approximation for an incident Gaussian beam and fitting the data with nonlinear regression. It is shown that the radial average flux density is exponentially attenuated for an arbitrary incident irradiance profile.