Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems

Transition metal oxides possessing two kinds of metals (denoted as A_xB_3−xO₄, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe,etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs).

Nanoporous carbon tubes from fullerene crystals as the π-electron carbon source

Here we report the thermal conversion of one-dimensional (1D) fullerene (C60) single-crystal nanorods and nanotubes to nanoporous carbon materials with retention of the initial 1D morphology. The 1D C60 crystals are heated directly at very high temperature (up to 2000 °C) in vacuum, yielding a new family of nanoporous carbons having π-electron conjugation within the sp(2)-carbon robust frameworks. These new nanoporous carbon materials show excellent electrochemical capacitance and superior sensing properties for aromatic compounds compared to commercial activated carbons.

Platinum-free counter electrode comprised of metal-organic-framework (MOF)-derived cobalt sulfide nanoparticles for efficient dye-sensitized solar cells (DSSCs)

We fabricated a highly efficient (with a solar-to-electricity conversion efficiency (η) of 8.1%) Pt-free dye-sensitized solar cell (DSSC). The counter electrode was made of cobalt sulfide (CoS) nanoparticles synthesized via surfactant-assisted preparation of a metal organic framework, ZIF-67, with controllable particle sizes (50 to 320 nm) and subsequent oxidation and sulfide conversion. In contrast to conventional Pt counter electrodes, the synthesized CoS nanoparticles exhibited higher external surface areas and roughness factors, as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) element mapping, and electrochemical analysis. Incident photon-to-current conversion efficiency (IPCE) results showed an increase in the open circuit voltage (V_OC) and a decrease in the short-circuit photocurrent density (Jsc) for CoS-based DSSCs compared to Pt-based DSSCs, resulting in a similar power conversion efficiency. The CoS-based DSSC fabricated in the study show great potential for economically friendly production of Pt-free DSSCs.

Rapid exchange between atmospheric CO2 and carbonate anion intercalated within magnesium rich layered double hydroxide

The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2 under ambient conditions. (Ishihara et al., J. Am. Chem. Soc. 2013, 135, 18040-18043). The use of (13)C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2 within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2 can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2 storage and/or separation.

Increasing testicular temperature by exposure to elevated ambient temperatures restores spermatogenesis in adult Utp14b (jsd) mutant (jsd) mice

Because mutations in the human UTP14C gene are associated with male infertility, we sought to develop a method for fertility restoration in azoospermic mice with a mutation in the orthologous Utp14b(jsd) (jsd) gene that have spermatogonial arrest. The method is based on our observation that elevation of testicular temperatures restores spermatogonial differentiation in jsd mutant mice. To non-surgically raise intrascrotal temperatures we placed these mice in incubators at different elevated ambient temperatures. Exposure of jsd/jsd mice to ambient temperatures of 34.5 °C or 35.5 °C for 24 days increased the proportion of tubules with spermatocytes from 0% in untreated controls to over 80%. As those higher temperatures interfere with spermatid differentiation, the mice were then transferred to incubators at 32-32.5 °C for the next 24 days. These environments allowed differentiation to progress, resulting in up to 42% of tubules having late spermatids and about half of the mutant mice having spermatozoa in testicular suspensions. When these spermatozoa were used in intracytoplasmic sperm injection, all gave rise to viable healthy offspring with normal weight gain and fertility. The successful restoration of fertility in Utp14b mutant mice suggests that transient testicular warming might also be useful for spermatogenesis recovery in infertile men with UTP14C gene mutations.

Mesoporous silica particles as topologically crosslinking fillers for poly(N-isopropylacrylamide) hydrogels

Here it is demonstrated that mesoporous silicas (MPSs) can be used as effective "topological crosslinkers" for poly(N-isopropylacrylamide) (PNIPA) hydrogels to improve the mechanical property. Three-dimensional bicontinuous mesporous silica is found to effectively reinforce the PNIPA hydrogels, as compared to nonporous silica and two-dimensional hexagonally ordered mesoporous silica.

Nanoarchitectured graphene-based supercapacitors for next-generation energy-storage applications

Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high-energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy-storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double-layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene-based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene-based asymmetric supercapacitors. The challenges and prospects of graphene-based supercapacitors are also discussed.

Chemical preparation of ferroelectric mesoporous barium titanate thin films: drastic enhancement of Curie temperature induced by mesopore-derived strain

Mesoporous barium titanate (BT) thin films are synthesized by a surfactant-assisted sol-gel method. The obtained mesoporous BT thin films show enhanced ferroelectricity due to the effective strains induced by mesopores. The Curie temperature (T(c)) of the mesoporous BT reaches approximately 470 °C.

Evaluating the antibacterial property of gold-coated hydroxyapatite: a molecular biological approach

Hydroxyapatite nanoparticles (HAP NPs) are one of the widely used biocompatible materials. However, information about the reaction between HAP NPs and microorganisms is insufficient. This paper aims to understand the antibacterial property of a new nanocomposite consisting of gold-coated HAP and alginate polymer (namely, Au-HAP@Alg NPs). To the best of our knowledge, we reported the first information regarding to MIC (25mg/mL), DIZ (no visible zone), and IC50 (0.5mg/mL) of Au-HAP@Alg NPs toward the microorganism Escherichia coli TOP10. The real-time gene expression levels of polA, polB, cyd, mdoG, GAPDH, and 16S rRNA were maintained at stable levels up until conditions of 2.5mg/mL Au-HAP@Alg NPs. The results showed that 16S rRNA can be a good reference under these conditions. The expressions of GAPDH, cyd, and mdoG were inhibited obviously under condition of 10mg/mL of Au-HAP@Alg NPs. Our results indicated that the possible antibacterial mechanism of Au-HAP@Alg was through the interaction with these carbohydrate and cell wall-related genes. This novel biocompatible and antibacterial material can potentially be applied in medical and environmental fields.