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Query: KEGG:D01931 (TiO2)
 11,320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The solution synthesis of large single crystals of octahedron-like anatase TiO2 is reported, although this novel result is unexpected in the light of reported theoretical calculations. Moreover, systematic control of the crystal growth of rutile nanopins on the microanatase octahedron single crystal results in a nano-micro chestnut-like TiO2 structure. The control of the formation of rutile nanopins on the large single crystals of anatase in the same solution is an interesting and useful technique, based on thermodynamics and surface chemistry.
ACS Nano 2007 Nov
PMID:One-step synthesis of nano-micro chestnut TiO2 with rutile nanopins on the microanatase octahedron. 1920 77

Photoinduced charge transfer events between 3 nm diameter CdSe semiconductor nanocrystals and an electron acceptor, MV2+, have been probed in the subpicosecond-microseconds-seconds time scale by confining the reactants in an AOT/heptane reverse micelle. The probe molecule, methyl viologen (MV2+) interacts with the excited CdSe nanoparticle and quenches its emission effectively. The ultrafast electron transfer to MV2+, as monitored from the exciton bleaching recovery of CdSe and the formation of MV+* radical, is completed with an average rate constant of 2.25x10(10) s(-1). Under steady state irradiation (450 nm) the accumulation of MV+* is seen with a net quantum yield of 0.1. Mediation of the electron transfer through TiO2 nanoparticles is achieved by coupling them with the CdSe-MV2+ system within the reverse micelle. This coupling of two semiconductor nanoparticles increases the quantum yield of MV2+ reduction by a factor of 2. The dual roles of TiO2 as an electron shuttle and a rectifier are elucidated by transient absorption spectroscopy and steady state photolysis. The presence of both TiO2 and MV2+ in the reverse micelle creates a synergistic effect to enhance the electron transfer rate constant by an order of magnitude. The time-resolved events that dictate the production and stabilization of electron transfer product provide an insight into the photocatalytic systems that are potentially important in solar hydrogen production and photocatalytic remediation.
ACS Nano 2009 Mar 24
PMID:Photocatalysis with CdSe nanoparticles in confined media: mapping charge transfer events in the subpicosecond to second timescales. 1922 35

Using a nonhydrolytic solution approach, we demonstrate the bulk synthesis of extremely thin crystalline TiO2 atomic wires in the anatase phase with diameters reaching the atomic limit of a few angstroms (approximately 4-5 A). These nearly monodisperse, atomically thin, and soluble TiO2 wires fill a most important size gap in nanowire fabrication. Preliminary results on photocatalytic activity of the atomic wires are also presented on degradation of methylene blue under visible light. These atomic wires are expected to promote exchanges between theory and experiments in fundamental studies of a one-dimensional (1D) system and provide unique building blocks to construct high-performance devices.
ACS Nano 2009 Apr 28
PMID:Synthesis of angstrom-scale anatase titania atomic wires. 1930 91

We used anionic sulfate surfactants to assist the stabilization of graphene in aqueous solutions and facilitate the self-assembly of in situ grown nanocrystalline TiO2, rutile and anatase, with graphene. These nanostructured TiO2-graphene hybrid materials were used for investigation of Li-ion insertion properties. The hybrid materials showed significantly enhanced Li-ion insertion/extraction in TiO2. The specific capacity was more than doubled at high charge rates, as compared with the pure TiO2 phase. The improved capacity at high charge-discharge rate may be attributed to increased electrode conductivity in the presence of a percolated graphene network embedded into the metal oxide electrodes.
ACS Nano 2009 Apr 28
PMID:Self-assembled TiO2-graphene hybrid nanostructures for enhanced Li-ion insertion. 1932 86

CdSe and CdTe nanocrystals are linked to nanostructured TiO2 films using 3-mercaptopropionic acid as a linker molecule for establishing the mechanistic aspects of interfacial charge transfer processes. Both these quantum dots are energetically capable of sensitizing TiO2 films and generating photocurrents in quantum dot solar cells. These two semiconductor nanocrystals exhibit markedly different external quantum efficiencies ( approximately 70% for CdSe and approximately 0.1% for CdTe at 555 nm). Although CdTe with a more favorable conduction band energy (E(CB) = -1.0 V vs NHE) is capable of injecting electrons into TiO2 faster than CdSe (E(CB) = -0.6 V vs NHE), hole scavenging by a sulfide redox couple remains a major bottleneck. The sulfide ions dissolved in aqueous solutions are capable of scavenging photogenerated holes in photoirradiated CdSe system but not in CdTe. The anodic corrosion and exchange of Te with S dominate the charge transfer at the CdTe interface. Factors that dictate the efficiency and photostability of CdSe and CdTe quantum dots are discussed.
ACS Nano 2009 Jun 23
PMID:Quantum dot sensitized solar cells. A tale of two semiconductor nanocrystals: CdSe and CdTe. 1943 73

At present, nanofilaments are not exclusively based on carbon atoms but can be produced from many inorganic materials in the form of nanotubes and nanowires. It is essential to systematically assess the acute toxicity of these newly synthesized materials since it cannot be predicted from the known toxicity of the same material in another form. Here, the cellular toxicity of TiO2-based nanofilaments was studied in relation to their morphology and surface chemistry. These structures produced by hydrothermal treatment were titanate nanotubes and nanowires with a Na(x)TiO(2+delta) composition. The cytotoxic effect was mainly evaluated by MTT assays combined with direct cell counting and cytopathological analyses of the lung tumor cells. Our work clearly demonstrated that the presence of Na(x)TiO(2+delta) nanofilaments had a strong dose-dependent effect on cell proliferation and cell death. Nanofilament internalization and alterations in cell morphology were observed. Acid treatment performed to substitute Na(+) with H(+) in the Na(x)TiO(2+delta) nanofilaments strongly enhanced the cytotoxic action. This effect was attributed to structural imperfections, which are left by the atom diffusion during the substitution. On the basis of our findings, we conclude that TiO2-based nanofilaments are cytotoxic and thus precautions should be taken during their manipulation.
ACS Nano 2009 Aug 25
PMID:Cellular toxicity of TiO2-based nanofilaments. 1961 Jun 3

Herein, we report a rational method to synthesize a Co3O4 nanobelt array on a conducting substrate and functionalize it in the application of Li-ion battery anodes, which is a novel and facile approach to access the nanobelt array of transition metal oxides. Compared to the previous reports, the as-prepared samples in our experiments exhibited both mesoporosity and single-crystallinity, and meanwhile, good contact with the conducting substrate (via a thin layer of TiO2) provided an express pathway for charge transfer when they were applied in Li-ion batteries without any need to add other ancillary materials (carbon black or binder) to enhance the system's conductivity and stability. Under the condition of high charge-discharge current density of 177 mA/g in Li-ion batteries' testing, the Co3O4 nanobelt array was capable of retaining the specific capacity of 770 mAh/g over 25 cycles. Moreover, even though the charge-discharge rates were increased to 1670 and 3350 mA/g, it still could have reached the stable retention of the specific capacity of 510 and 330 mAh/g beyond 30 cycles, respectively, indicating an obtainable excellent rate capability. More importantly, the improved performance in Li-ion battery testing was definitely ascribed to the unique structures in our samples after elaborate analysis. So the final conclusion would be given that the lab-synthesized Co3O4 nanobelt array potentially could be a highly qualified candidate for Li-ion battery anodes in some practical fields, where high capacity and good capability are strictly required.
ACS Nano 2010 Mar 23
PMID:Excellent performance in lithium-ion battery anodes: rational synthesis of Co(CO3)0.5(OH)0.11H2O nanobelt array and its conversion into mesoporous and single-crystal Co3O4. 2014 55

Thermal annealing of thin films of CdSe/CdS core/shell quantum dots induces superordering of the nanocrystals and a significant reduction of the interparticle spacing. This results in a drastic enhancement of the quantum yield for charge carrier photogeneration and the charge carrier mobility. The mobile electrons have a mobility as high as 0.1 cm(2)/(V x s), which represents an increase of 4 orders of magnitude over non-annealed QD films and exceeds existing literature data on the electron mobility in CdSe quantum dot films. The lifetime of mobile electrons is longer than that of the exciton. A fraction of the mobile electrons gets trapped at levels below the conduction band of the CdSe nanocrystals. These electrons slowly diffuse over 50-300 nm on longer times up to 20 micros and undergo transfer to a TiO2 substrate. The yield for electron injection in TiO2 from both mobile and trapped electrons is found to be >16%.
ACS Nano 2010 Mar 23
PMID:Supercrystals of CdSe quantum dots with high charge mobility and efficient electron transfer to TiO2. 2018 85

A pH-responsive, TiO2-attached sensitizer was prepared based on the adsorption of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) onto TiO2 nanoparticles. This colloidally dispersed TiO2-attached TCPP behaves as a single-phase colloidal sensitizer at pH 1.0-3.3 with quantum yields of singlet oxygen production (Phi(Delta)) between 0.20 and 0.25, as a heterogeneous particle sensitizer at pH 3.5-6.0 with Phi(Delta) between 0.25 and 0.50, and as homogeneous free TCPP molecules in alkaline solutions with Phi(Delta) = 0.53. The changes in Phi(Delta) are fully consistent with pH-dependent adsorption of TCPP onto the TiO2 surface. Recovery yields of 99.8% for TCPP and 98.8% for TiO2 were obtained from 1.4 mM TiO2-attached TCPP. We attribute its photosensitization ability to retaining TCPP solubility on the TiO2 surface and, hence, activity. This novel system shows a potential to bridge the gap between easily recoverable and highly efficient sensitizers.
ACS Appl Mater Interfaces 2009 Aug
PMID:pH-responsive, TiO2-attached porphyrin for singlet oxygen production in an aqueous solution. 2020 36

Dye-sensitized photovoltaic wires (DSPVWs) are developed using anodized Ti wires that contain ordered arrays of TiO2 nanotubes. The prototype DSPVW consists of N719 dye-adsorbed TiO2 nanotube arrays around a Ti wire as a working electrode, a platinum wire as a counter electrode, and an organic electrolyte encased in a capillary glass tube. The effect of length of nanotube arrays on the photovoltaic performance of DSPVWs is studied systematically. A solar-to-electric conversion efficiency of 2.78% is achieved with 55 microm long nanotubes under 98.3 mW/cm(2) AM 1.5 simulated full light. The prototype device is capable of achieving a long distance transport of photocurrent and harvesting all light from any direction in surroundings to generate electricity.
ACS Nano 2010 Apr 27
PMID:Dye-sensitized photovoltaic wires using highly ordered TiO2 nanotube arrays. 2023 17


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