Preparation, Structural Characterization, and Application of Reduced Graphene Oxide-Based Hybrid Materials

Department of Energy EngineeringHybrid nanomaterials have the advantages of their individual components while also exhibiting new properties for practical applications. Many approaches have been studied for the synthesis of hybrid materials composed of metals, metal oxides, metal chalcogenides, polymers, and carbon materials. To apply these to practical applications such as field-effect transistors (FET), photovoltaic devices, and sensors, the synthesis of hybrid materials and fundamental study to understand their unexpected properties are very important. In addition, comprehension of the interaction at the interface between the two materials is needed. This paper discussed our approaches to develop new hybrid materials by means of functionalization. This thesis can be divided into two major parts for graphene-based hybrid materials: the functionalization of reduced graphene oxide (rGO) and rGO/TMD hybrid materials. The first part describes functionalization related to graphene oxide (GO) and rGO. Although these are the major applications of graphene, it is worth noting that graphene itself has a zero band-gap as well as chemical inertness, which weaken its competitive strength in the field of semiconductors and sensors. Therefore, tuning the electrical properties of graphene is important. Here, to control the electrical properties, the assembly of rGO and fullerene (C60) into hybrid (rGO/C60) wires was performed by π-π interaction between rGO and C60. Structural characterization and possible applications of the interaction between rGO and C60 will be discussed. In addition, amine-functionalized rGO, which has an n-doping effect in FET, is introduced. The mechanism of the doping effect and a facile method for the fabrication of rGO FET with self-assembled monolayers (SAMs) will also be discussed. The second part focuses on the synthesis of transition-metal dichalcogenide (TMD)-functionalized rGO and its electrocatalytic activity in the hydrogen evolution reaction (HER). Relatively, little is known about the synthesis of hybrid materials with TMD and rGO. In addition, the application of bulk TMDs for hydrogen evolution has been ignored for a long time owing to their poor activity. However, these materials, in particular 2D MoS2 and WS2 nanosheets, are starting to gain attention for use as catalysts in HER, alongside the explosive interest in graphene and other 2D materials. Therefore, synthesis of WS2/rGO hybrid sheets and their electrocatalytic activity levels have been demonstrated. Furthermore, we report the synthesis of a hybrid of CoS2/rGO, which has not been reported, and its electrocatalytic activity in HER.ope

Multilayer Heterojunction Anodes for Saline Wastewater Treatment: Design Strategies and Reactive Species Generation Mechanisms

Multilayer heterojunction SbSn/CoTi/Ir anodes, which consist of Ir_(0.7)Ta_(0.3)O_2 bottom layers coated onto a titanium base, Co-TiO_2 interlayers, and overcoated discrete Sb-SnO_2 islands, were prepared by spray pyrolysis. The Ir_(0.7)Ta_(0.3)O_2 bottom layer serves as an Ohmic contact to facilitate electron transfer from semiconductor layers to the Ti base. The Co-TiO_2 interlayer and overcoated Sb-SnO_2 islands enhance the evolution of reactive chlorine. The surficial Sb-SnO_2 islands also serve as the reactive sites for free radical generation. Experiments coupled with computational kinetic simulations show that while ·OH and Cl· are initially produced on the SbSn/CoTi/Ir anode surface, the dominant radical formed in solution is the dichlorine radical anion, Cl_2·–. The steady-state concentration of reactive radicals is 10 orders of magnitude lower than that of reactive chlorine. The SbSn/CoTi/Ir anode was applied to electrochemically treat human wastewater. These test results show that COD and NH_4^+ can be removed after 2 h of electrolysis with minimal energy consumption (370 kWh/kg COD and 383 kWh/kg NH_4^+). Although free radical species contribute to COD removal, anodes designed to enhance reactive chlorine production are more effective than those designed to enhance free radical production

Selective synthesis of pure cobalt disulfide on reduced graphene oxide sheets and its high electrocatalytic activity for hydrogen evolution reaction

We synthesized single-phase CoS2 on a large scale by adding graphene oxide of sufficient quantity via the hydrothermal method using cobalt acetate and thioacetamide as precursors; this produced the hybrid of CoS2 with reduced graphene oxide which exhibited high electrocatalytic activity in the hydrogen evolution reaction.ope

Wavelength-selective silencing of photocurrent in Au-coated C-60 wire hybrid

A Au-coated C-60 wire device showed wavelength-selective silencing of photocurrent on illumination with 532 nm light.close6

Influence of the molecular structure of metal-phthalocyanine on electrocatalytic reactions

The demand for new catalysts for renewable energy production has become crucial. As an alternative to metal catalysts for electrocatalysis to produce energy sources, metal-phthalocyanine (MPc) electrocatalysts have shown potential. Their physicochemical and electrochemical properties depend on the chemical structure of the MPc and the central metal atom. Recent reviews of MPcs focused on their electrochemical performance in specific catalytic reactions, such as oxygen reduction reaction and CO2 reduction reaction. However, understanding the structure of MPcs in depth is important, since their electrochemical catalytic activity is affected by structural modifications of MPcs. Therefore, this minireview focuses on how the molecular structure of MPcs affects electrochemical catalysis

Generation of mice with a conditional allele for the p75 NTR neurotrophin receptor gene

The p75 NTR neurotrophin receptor has been implicated in multiple biological and pathological processes. While significant advances have recently been made in understanding the physiologic role of p75 NTR , many details and aspects remain to be determined. This is in part because the two existing knockout mouse models (Exons 3 or 4 deleted, respectively), both display features that defy definitive conclusions. Here we describe the generation of mice that carry a conditional p75 NTR (p75 NTR‐FX ) allele made by flanking Exons 4–6, which encode the transmembrane and all cytoplasmic domains, by loxP sites. To validate this novel conditional allele, both neural crest‐specific p75 NTR /Wnt1‐Cre mutants and conventional p75 NTR null mutants were generated. Both mutants displayed abnormal hind limb reflexes, implying that loss of p75 NTR in neural crest‐derived cells causes a peripheral neuropathy similar to that seen in conventional p75 NTR mutants. This novel conditional p75 NTR allele will offer new opportunities to investigate the role of p75 NTR in specific tissues and cells. genesis 49:862–869, 2011. © 2011 Wiley‐Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/88029/1/20747_ftp.pd

Signaling Heterogeneity is Defined by Pathway Architecture and Intercellular Variability in Protein Expression.

Insulin's activation of PI3K/Akt signaling, stimulates glucose uptake by enhancing delivery of GLUT4 to the cell surface. Here we examined the origins of intercellular heterogeneity in insulin signaling. Akt activation alone accounted for ~25% of the variance in GLUT4, indicating that additional sources of variance exist. The Akt and GLUT4 responses were highly reproducible within the same cell, suggesting the variance is between cells (extrinsic) and not within cells (intrinsic). Generalized mechanistic models (supported by experimental observations) demonstrated that the correlation between the steady-state levels of two measured signaling processes decreases with increasing distance from each other and that intercellular variation in protein expression (as an example of extrinsic variance) is sufficient to account for the variance in and between Akt and GLUT4. Thus, the response of a population to insulin signaling is underpinned by considerable single-cell heterogeneity that is largely driven by variance in gene/protein expression between cells

The dopamine analogue CA140 alleviates AD pathology, neuroinflammation, and rescues synaptic/cognitive functions by modulating DRD1 signaling or directly binding to Abeta.

BACKGROUND: We recently reported that the dopamine (DA) analogue CA140 modulates neuroinflammatory responses in lipopolysaccharide-injected wild-type (WT) mice and in 3-month-old 5xFAD mice, a model of Alzheimers disease (AD). However, the effects of CA140 on Aβ/tau pathology and synaptic/cognitive function and its molecular mechanisms of action are unknown. METHODS: To investigate the effects of CA140 on cognitive and synaptic function and AD pathology, 3-month-old WT mice or 8-month-old (aged) 5xFAD mice were injected with vehicle (10% DMSO) or CA140 (30 mg/kg, i.p.) daily for 10, 14, or 17 days. Behavioral tests, ELISA, electrophysiology, RNA sequencing, real-time PCR, Golgi staining, immunofluorescence staining, and western blotting were conducted. RESULTS: In aged 5xFAD mice, a model of AD pathology, CA140 treatment significantly reduced Aβ/tau fibrillation, Aβ plaque number, tau hyperphosphorylation, and neuroinflammation by inhibiting NLRP3 activation. In addition, CA140 treatment downregulated the expression of cxcl10, a marker of AD-associated reactive astrocytes (RAs), and c1qa, a marker of the interaction of RAs with disease-associated microglia (DAMs) in 5xFAD mice. CA140 treatment also suppressed the mRNA levels of s100β and cxcl10, markers of AD-associated RAs, in primary astrocytes from 5xFAD mice. In primary microglial cells from 5xFAD mice, CA140 treatment increased the mRNA levels of markers of homeostatic microglia (cx3cr1 and p2ry12) and decreased the mRNA levels of a marker of proliferative region-associated microglia (gpnmb) and a marker of lipid-droplet-accumulating microglia (cln3). Importantly, CA140 treatment rescued scopolamine (SCO)-mediated deficits in long-term memory, dendritic spine number, and LTP impairment. In aged 5xFAD mice, these effects of CA140 treatment on cognitive/synaptic function and AD pathology were regulated by dopamine D1 receptor (DRD1)/Elk1 signaling. In primary hippocampal neurons and WT mice, CA140 treatment promoted long-term memory and dendritic spine formation via effects on DRD1/CaMKIIα and/or ERK signaling. CONCLUSIONS: Our results indicate that CA140 improves neuronal/synaptic/cognitive function and ameliorates Aβ/tau pathology and neuroinflammation by modulating DRD1 signaling in primary hippocampal neurons, primary astrocytes/microglia, WT mice, and aged 5xFAD mice