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SnS2 as the promising anode for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) still encounters the undesirable rate performance and cycle stability. Herein, a unique stable structure is developed, where the SnS2 nanocrystals (NCs) are sturdily encapsulated by carbon shells anchored on a reduced graphene oxide (rGO) via the one-pot solvothermal process. The well-controlled carbon shells provide the enduring protection for SnS2 NCs through C-S covalent bonds from the corrosion of electrolyte and pulverization of structure. Moreover, both experimental results and density functional theory (DFT) calculations demonstrate that the carbon protective shell effectively enhances the structure stability and conductivity of the resulting materials. Interestingly, the size of SnS2 NCs and the thickness of carbon shells are accurately controlled by regulating the content of glucose. Aided by the advanced electron/ion transfer kinetics and structure stability, the SnS2-based electrode exhibits desired lithium/sodium storage performance and unprecedented long-term cycling stability (capacity retention of 74.7% after 1000 cycles at 2 A g-1 for LIBs and 102% after 200 cycles at 500 mA g-1 for SIBs). This work develops a method for promoting the practical applications and large-scale production of SnS2 composites for energy storage devices.

To reveal a new structure-property relationship regarding the nonlinear optical (NLO) properties of fullerenes that are associated with gamma (γ) density, fullerenes I (C40, C50, C60 and C70), whose heights range from 4.83 to 7.96 Å, and II (C24, C36, C48 and C72), whose widths range from 4.45 to 8.22 Å, have been the research objects. Calculation of their geometric and electronic structures, absorption spectra, and the second hyperpolarizability (γ) and the γ density analysis have been performed. It is found that the electronic spatial extent and the polarizability (α) value increase linearly as the fullerenes increase by every 12 carbon atoms. Similarly, the γ values are also proportional to the fullerene size. It is worth noting that the relative magnitude of γ xxxx and γ zzzz was exactly consistent with that of the width and height of fullerenes. The analysis of γ density provides the essential reason for this result, that is, the magnitude of the contribution to γ values associated with γ densities is proportional to the density amplitudes multiplied by the distance between them. Larger fullerenes possess larger density amplitudes and longer distances, resulting in larger γ values with respect to smaller fullerenes. This work presents a new structure-property interplay between the width and height of the fullerenes and their second hyperpolarizability γ. Moreover, the γ density analysis provides a new insight to explore the nature of the relationship between the structure and the NLO properties.

The effect of graphene lateral size on the electrochemical performance of lithium-sulfur (Li-S) batteries is often ignored. In this study, the thermally exfoliated large lateral-sized graphene (denoted LTG) was employed as the conductive matrix to support sulfur, and its performance was then compared with that of a smaller lateral-sized graphene (denoted STG) for Li-S batteries. The results showed that the LTG-S composite exhibited much higher capacity retention (53%) versus the STG-S (29%) and better rate capabilities. Because they were both identical in morphology, in terms of sulfur content and sulfur distribution, the improved properties probably resulted from the potential prevention of polysulfide diffusion upon cycling due to the larger graphene-based network and higher aspect ratio of the LTG matrix, referred as better polysulfide reservoirs. To further improve the cell performance, a reduced graphene oxide-coated carbon fiber paper (RCF) was inserted between the LTG-S cathode and the separator by a simple drop-coat method, which provided an increased conductive surface area for polysulfides to be oxidized/reduced and buffered volume expansion. As expected, the discharge capacities of 1143 and 622 mA h g(-1) at first use and after 100th cycles were obtained with an average Coulombic efficiency of 99.7%, which were higher than 847 and 455 mA h g(-1) for the cathode without the RCF, respectively. This study highlights the significance of large graphene sheets and interlayers on the inhibition of polysulfide diffusion and offers a new way to solve the problems of Li-S batteries.

Stimulated by the preparation and characterization of the isolated pentagon rule (IPR) violating chlorofullerene: C(60)Cl(8) (Nat. Mater. 2008, 7, 790-794), we have performed a systematic investigation on the structural stabilities, electronic and optical properties of the IPR-violating C(60)X(8) (X = H, F, and Cl) fullerene compounds via density functional theory. The large energy gaps between the highest occupied and the lowest unoccupied molecular orbitals provide a clear indication of high chemical stabilities of C(60)X(8) derivatives, and moreover, the C(60)X(8) molecules present great aromatic character with the negative nucleus independent chemical shift values. In the addition reactions of C(60) (C(2v)) + 4X(2) → C(60)X(8), a series of exothermic processes are involved, with high reaction energies ranging from -71.97 to -233.16 kcal mol(-1). An investigation on the electronic property shows that C(60)F(8) and C(60)Cl(8) could be excellent electron acceptors as a consequence of large vertical electron affinities. The density of state analysis suggests that the frontier molecular orbitals of C(60)X(8) are mainly from the carbon orbitals of two separate annulene subunits, and the influence from X atoms is secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C(60)X(8) are calculated by means of time-dependent density functional theory and a finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <γ> of C(60)X(8) increase greatly compared to those of C(60).

A nanoparticle-based strategy has been demonstrated using structurally-tailored tert-butylcalixarenes immobilized on gold nanoparticles to tune the guest access to the calixarene cone cavity for cationic recognition. This strategy exploits the interparticle charge-induced aggregation upon selective capture of metal cations into the nanoparticle-immobilized tert-butylcalixarenes, which produces calorimetric changes for the detection. A possible pathway for the binding of M(n+) into the t-BCA structure and the interparticle interaction is proposed for the formation of an electric double layer inducing the interparticle association responsible for the red-shifted surface plasmon resonance band of the nanoparticles. The value of this class of calorimetric nanoprobes will be in the area of designing advanced host-guest probes using a variety of calixarene ligands for ionic recognition in a simplistic detection format.