Luyi Chen

Facile synthesis of ultrahigh-surface-area hollow carbon nanospheres for enhanced adsorption and energy storage

Exceptionally large surface area and well-defined nanostructure are both critical in the field of nanoporous carbons for challenging energy and environmental issues. The pursuit of ultrahigh surface area while maintaining definite nanostructure remains a formidable challenge because extensive creation of pores will undoubtedly give rise to the damage of nanostructures, especially below 100 nm. Here we report that high surface area of up to 3,022 m2 g−1 can be achieved for hollow carbon nanospheres with an outer diameter of 69 nm by a simple carbonization procedure with carefully selected carbon precursors and carbonization conditions. The tailor-made pore structure of hollow carbon nanospheres enables target-oriented applications, as exemplified by their enhanced adsorption capability towards organic vapours, and electrochemical performances as electrodes for supercapacitors and sulphur host materials for lithium–sulphur batteries. The facile approach may open the doors for preparation of highly porous carbons with desired nanostructure for numerous applications.

Water-Dispersible, Responsive, and Carbonizable Hairy Microporous Polymeric Nanospheres.

Multifunctionalization of microporous polymers is highly desirable but remains a significant challenge, considering that the current microporous polymers are generally hydrophobic and nonresponsive to different environmental stimuli and difficult to be carbonized without damage of their well-defined nanomorphology. Herein, we demonstrate a facile and versatile method to fabricate water-dispersible, pH/temperature responsive and readily carbonizable hairy microporous polymeric nanospheres based on combination of the hyper-cross-linking chemistry with the surface-initiated atom transfer radical polymerization (SI-ATRP). The hyper-cross-linking creates a highly microporous core, whereas the SI-ATRP provides diverse functionalities by surface grafting of hairy functional blocks. The as-prepared materials present multifunctional properties, including sensitive response to pH/temperature, high adsorption capacity toward adsorbates from aqueous solution, and valuable transformation into well-defined microporous carbon nanospheres because of hybrid of carbonizable core and thermo-decomposable protection shell. We hope this strategy could promote the development of both functional microporous polymers and advanced hairy nanoparticles for multipurpose applications.

Outcomes and risk factors for hepatitis B virus (HBV) reactivation after kidney transplantation in occult HBV carriers

The purpose of this study was to explore the outcomes and risk factors for hepatitis B virus (HBV) reactivation after kidney transplantation in occult HBV carriers, who are hepatitis B surface antigen (HBsAg) seronegative and hepatitis B core antibody (HBcAb) seropositive before kidney transplantation.

Superhierarchical Cobalt‐Embedded Nitrogen‐Doped Porous Carbon Nanosheets as Two‐in‐One Hosts for High‐Performance Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries, based on the redox reaction between elemental sulfur and lithium metal, have attracted great interest because of their inherently high theoretical energy density. However, the severe polysulfide shuttle effect and sluggish reaction kinetics in sulfur cathodes, as well as dendrite growth in lithium-metal anodes are great obstacles for their practical application. Herein, a two-in-one approach with superhierarchical cobalt-embedded nitrogen-doped porous carbon nanosheets (Co/N-PCNSs) as stable hosts for both elemental sulfur and metallic lithium to improve their performance simultaneously is reported. Experimental and theoretical results reveal that stable Co nanoparticles, elaborately encapsulated by N-doped graphitic carbon, can work synergistically with N heteroatoms to reserve the soluble polysulfides and promote the redox reaction kinetics of sulfur cathodes. Moreover, the high-surface-area pore structure and the Co-enhanced lithiophilic N heteroatoms in Co/N-PCNSs can regulate metallic lithium plating and successfully suppress lithium dendrite growth in the anodes. As a result, a full lithium-sulfur cell constructed with Co/N-PCNSs as two-in-one hosts demonstrates excellent capacity retention with stable Coulombic efficiency.

Stepwise Crosslinking: A Facile Yet Versatile Conceptual Strategy to Nanomorphology-Persistent Porous Organic Polymers

Both high surface areas and well-orchestrated nanomorphologies are important for porous organic polymers (POPs). However, the two key characteristics are generally difficult to be satisfied simultaneously, because the common pore-making procedures usually produce ill-defined nanomorphologies or give rise to damage of precustomized nanomorphologies. Herein, a facile yet versatile stepwise crosslinking strategy for fabrication of POPs with an unusual nanomorphology-persistent characteristic during pore-making is reported. Polystyrene nanofibers and poly(styrene-co-divinylbenzene) nanosphere arrays are utilized as building blocks, and then transformed into nanofibrillar morphology-persistent and ordered array morphology-persistent POPs via stepwise crosslinking, respectively. The stepwise crosslinking strategy includes pre-crosslinking and hypercrosslinking; the pre-crosslinking in a carefully selected poor solvent of polystyrene forms a lowly crosslinked structure, which guarantees the stability of nanomorphology during the subsequent pore-making via hypercrosslinking. The as-obtained POPs can be used as precursors for novel well-defined hyperporous carbon nanofibers and ordered carbon nanosphere arrays with excellent adsorption performances.

Synthesis and adsorption properties of highly monodisperse hollow microporous polystyrene nanospheres

Hollow polymer nanospheres (HPNSs) have received an increased level of attention, not only for their fundamental scientific interest, but also for technological applications. Despite a great deal of research effort, most of the current HPNSs are suffering from a poor polydispersity as well as a particle size larger than 500 nm. Here, we report the synthesis of highly monodisperse hollow microporous polystyrene nanospheres (MHMPNSs) with diameters as low as 120 nm based on a facile hypercrosslinking strategy. We utilize the rapid formation of an almost unreactive crosslinked polystyrene outer skin during the initial hypercrosslinking process, to minimize the undesired inter-sphere crosslinking. Due to the intra-sphere hypercrosslinking, the resulting MHMPNSs possess a well-developed microporous shell structure. The MHMPNSs are able to be used as potential absorbents toward organic vapors, because of their unique hollow core and microporous shell characteristics.

Multi-dimensional construction of a novel active yolk@conductive shell nanofiber web as a self-standing anode for high-performance lithium-ion batteries

A novel active yolk@conductive shell nanofiber web with a unique synergistic advantage of various hierarchical nanodimensional objects including the 0D monodisperse SiO2 yolks, the 1D continuous carbon shell and the 3D interconnected non-woven fabric web has been developed by an innovative multi-dimensional construction method, and thus demonstrates excellent electrochemical properties as a self-standing LIB anode.

Fabrication and electrochemical performance of novel hollow microporous carbon nanospheres

Development of facile synthetic procedures for the fabrication of well-defined hollow carbon nanospheres with a highly porous shell structure is still a very important but really challenging issue. Herein, we report a facile hypercrosslinking strategy to prepare hollow microporous carbon nanospheres with a BET surface area as high as 1166 m2 g−1. SiO2@polystyrene core–shell nanospheres were first prepared, and then were treated through a hypercrosslinking reaction to provide the polystyrene shell with well-developed microporosity. Moreover, the as-constructed hypercrosslinked shell structure ensures a good framework carbonizability and nanostructure inheritability during the high-temperature carbonization process. The porous structure and morphology of the resulting hollow microporous carbon nanospheres can be easily tailored by varying the hypercrosslinking and carbonization conditions. Due to the rational integration of a highly microporous shell structure and a well-defined hollow spherical morphology in the nanometer range, the hollow microporous carbon nanospheres prepared here show good electrochemical performances as active electrodes of lithium ion batteries and supercapacitors.

Donor Factors Predictive for Poor Outcomes of Living Donor Kidney Transplantation

INTRODUCTION The aim of this study was to explore donor risk factors that predict the poor outcomes after living donor kidney transplantation. METHODS We retrospectively analyzed our 219 living donor kidney transplantations collecting donor age and gender, graft glomeular filtration rate (GFR), human leukocyte antigen (HLA) typing, recipient age and gender, acute rejection episodes chronic rejection, and 1-year serum creatinine level. Patient and graft survivals were calculated using the Kaplan-Meier analysis. Independent donor risk factors affecting graft survival and 1-year serum creatinine level were analyzed using Cox regression and logistic regression. RESULTS One-, 3-, 5-year patient and graft survivals were 98.6%, 98.1%, and 97.4% and 97.7%, 95.0%, and 92.2%, respectively. Acute rejection rate was 12.8%, and chronic rejection, 4.1%. If donor age was over 50 years, there were significantly increased incidences of acute and chronic rejection (χ(2) were 5.385 and 5.039; P < .05). Univariate analysis showed donor age > 50 years, graft GFR < 35 mL/min, female to male, HLA mismatch > 3 loci to be risk factors for an abnormal 1-year serum creatinine. Logistic multivariate regression revealed donor age > 50 years, female to male, and graft GFR before transplant < 35 mL/min to be independent risk factors for an abnormal 1-year serum creatinine level (odds ratio values 5.928, 2.489, and 6.993, respectively; P < .05). Cox multivariate regression demonstrated that graft GFR before transplant < 35 mL/min was an independent risk factor for long-term graft survival (relative risk value = 6.984; P = .004). CONCLUSION Older donor, female to male, and insufficient graft GFR before transplantation are predictive factors for poor outcomes of living donor kidney transplantations.

Long-term effects of conversion from cyclosporine to rapamycin on testicular function and morphology in a rat transplantation model.

PURPOSE The purpose of this study was to investigate the long-term effects of conversion from cyclosporine (CsA) to rapamycin on testicular function and morphology in a rat transplantation model compared with the continuous administration of CsA. METHODS Fisher 344 kidneys were orthotopically transplanted into Lewis recipients. Four Fisher 344 to Lewis allograft groups were treated posttransplantation as follows: Group 1, CsA treatment to week 8 followed by rapamycin from week 8-24; Group 2, CsA from transplantation to week 24; Group 3, CsA from transplantation to week 8 then vehicle from weeks 8-24, and Group 4, control vehicle from transplantation to week 24. A fifth group (Group 5) underwent syngeneic isografts (Lewis to Lewis) with no drug treatment. At 24 week, we measured serum creatinine and sex hormones and harvested the right testis for histological analysis. RESULTS All rats showed normal serum creatinine levels. Testosterone was significantly lower in Group 1 versus Group 5 (0.85 ± 0.09 vs 1.05 ± 0.17 ng/mL; P = .008). Groups 2, 3 and 4 displayed higher testosterone values than Group 1 but lower than Group 5. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were also higher in Group 1 versus the other groups, but the differences were not significant. The histological damage score was significantly higher in Groups 1, 2, 3, and 4 versus Group 5 (1.8 ± 0.8), but the highest one was observed in Group 1 (8.3 ± 1.6). Electron microscopy showed more severe testicular ultrastructural damage in Group 1. CONCLUSION Conversion from CsA to rapamycin resulted in more severe damage to testicular function and structure than the continuous use of CsA in a rat kidney transplantation model.