Redox properties of inorganic nanoparticles

The redox potentials E°(M₁₄₇) (M = Au, Cu) were calculated on the basis of the shell model with inclusion of hybridized electronic configurations of atoms. The prospects for studying E°(M _N ) for nanoparticles of other d metals were outlined.     

Electropolymerizing polyaniline on undoped 100 nm diamond powder and its electrochemical characteristics

Conductive polyaniline (PANI) was electropolymerized on undoped 100 nm diamond powders in sulphuric acid solution containing aniline to improve the conductivity and the electrochemistry of the nano- or submicro-scaled diamond particles. Cyclic voltammetry (CV) experiment was carried out at an upper potential of 1.1 V in initial sweeps and a potential range of ?0.2–0.9 V for the growth of PANI on a diamond powder electrode. Field emission-scanning electron microscope (FESEM) result reveals that the diamond particles were well coated by PANI films with globular or fibroid surface morphology. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were employed to investigate the electrochemical properties of the PANI/diamond composite electrode. It presents lower resistance and better capacitance than the pristine diamond powder.     

Synthetic diamond electrodes: Photoelectrochemical behavior of vacuum-annealed undoped polycrystalline diamond films

The photocurrent and photopotential for undoped polycrystalline diamond film electrodes prepared by chemical vapor deposition and annealed in vacuum at 1500–1640°C are measured. The metal-like samples (annealed at 1630°C) have a negligible photosensitivity. Judging from the positive sign of the photopotential and the cathodic direction of the photocurrent, the material under study formally behaves as a p-type semiconductor. The photoeffects are presumably caused by structure defects, in particular, the dislocations in diamond crystallites formed close to intercrystalline boundaries during the high-temperature annealing.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 343–349.Original Russian Text Copyright © 2005 by Pleskov, Krotova, Ralchenko, Khomich, Khmelnitskii.     

Synthesis,textural and magnetic properties of doped and undoped CuO nanoparticles

We have fabricated undoped CuO, Co_0.1Ni_0.07Zn_0.04Cu_0.79O and Co_0.08Ni_0.07Zn_0.04Mg_0.03Cu_0.78O nanoparticles through thermal decomposition of their respective inorganic copper creatinate hydrazinate and mixed metal doped copper creatinate hydrazinate precursors which were prepared by the co-precipitation method and characterized through EDS, ICP-AES, IR, and TG-DTA analysis. Techniques such as EDS, ICP-AES, FT-IR, XRD, XPS, TEM, SEM, BET, and VSM analysis were employed to characterize the composition, structural phase, chemical state, morphological, textural, and magnetic properties of the nanoparticles.     

Comparison of the hole mobility in undoped and boron-doped polycrystalline CVD diamond films

The drift mobility of nonequilibrium holes injected in undoped polycrystalline diamond films was determined, by a transit-time technique, as ca. 10⁻³ cm²/(V s). This hole mobility is three orders of magnitude lower than the “equilibrium” mobility in boron-doped diamond films [0.1–1 cm²/(V s)], determined from the films' dc conductivity. This difference is explained by the effect of a nonequilibrium charge carrier trapping during the carrier transport in polycrystalline diamond. Received: 3 December 1997 / Accepted: 9 April 1998     

Preparation and antibacterial activities of undoped and palladium doped titania nanoparticles

Undoped and palladium doped titania nanoparticles have been prepared by sol–gel method using isopropyl alcohol as solvent. The products have been characterized through XRD, FESEM, TEM, HRTEM, FTIR, specific surface area analysis and ICPOES technologies. The antibacterial activities of the products against Escherichia coli (E. Coli) have been investigated by microcalorimetric method and antibacterial circle method, respectively. The process of E. Coli growth and metabolism affected by nanoparticles has been monitored using a Thermal Activity Monitor (TAM) Air Isothermal Calorimeter by microcalorimetric method. The results indicate that undoped and palladium doped titania nanoparticles present better antibacterial activities. Among them, 3 mol% Pd doped titania nanoparticles exhibit the best antibacterial activity due to the lowest value of minimum inhibitory concentration (MIC). This result is in accordance with that of the antibacterial circle method. This work provides a general analytic technology to quantification study antibacterial activity of nanomaterials against various bacteria by microcalorimetric method, which could be a potential application in the future.     

Direct electrochemistry and electrocatalysis of hemoglobin on undoped nanocrystalline diamond modified glassy carbon electrode

Direct electrochemistry of hemoglobin (Hb) was observed at glassy carbon electrode (GCE) modified with undoped nanocrystalline diamond (UND) and Hb multilayer films via layer-by-layer assembly. UV-VIS absorbance spectroscopy, electrochemical impedance spectroscopy and cyclic voltammograms were employed to characterize the film. The results showed that the UND had the effect of enhancing the electron transfer between Hb and the electrode surface. Hb in the multilayer films maintained its bioactivity and structure. It also exhibited a good catalytic activity towards the reduction of H(2)O(2). The reciprocal of catalytic current showed a linear dependence on the reciprocal of H(2)O(2) concentration ranging from 0.5 microM to 0.25 mM with a detection limit of 0.4 microM. The apparent Michaelis-Menten constant was estimated to be 0.019 mM.     

Nanomolar hydrogen peroxide detection using horseradish peroxidase covalently linked to undoped nanocrystalline diamond surfaces

In this article, we report on the low-level detection of hydrogen peroxide, a key player in the redox signaling pathway and a toxic product in the cellular system, using a colorimetric solution assay. Amine-terminated undoped nanocrystalline diamond thin films were grown on glass using a linear-antenna microwave plasma CVD process. The diamond surface consists mainly of -NH(2) termination. The aminated diamond surface was decorated with horseradish peroxidase (HRP) enzyme using carbodiimide coupling chemistry. The success of the HRP immobilization was confirmed by X-ray photoelectron spectroscopy (XPS). The enzymatic activity of immobilized HRP was determined with a colorimetric test based on the HRP-catalyzed oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sufonic acid (ABTS) in the presence of hydrogen peroxide. The surface coverage of active HRP was estimated to be Γ = 7.3 × 10(13) molecules cm(-2). The use of the functionalized diamond surface as an optical sensor for the detection of hydrogen peroxide with a detection limit of 35 nM was demonstrated.     

On diamond D5

Diamond D₅ is a hyperdiamond structured as coalesced C₂₀ and C₂₈ small fullerenes, in the ratio 2:1, and having up to 90?% pentagonal rings while the others being hexagonal. Design of several precursors, intermediates, and crystal networks was performed using our original software programs CVNet and Nano-Studio. Energetic data, calculated at DFT and DFTB levels of theory revealed a stability of these structures close to that of classical diamond. A lonsdaleite-like structure is also discussed. The topology of these networks is described in terms of the net parameters and the net characteristics in crystallographic terms.     

Electrical and thermoelectric properties of undoped MnO single crystals

The electrical resistivity and Seebeck coefficients of pure MnO single crystals have been measured above the Néel temperature. The material is p type in this temperature range. The results are interpreted on the basis of small-polaron hopping involving charge carriers in one or more sets of transport levels.     

Value-added anticancer reactivity of sub-5 nm Ag-drug nanoparticles derived from organosilver(I) MOF

Science China Chemistry - A totally structure-determined organosilver(I) metal-oganic framework (MOF) of [{Ag18(CF3COO)18(H2O)2}{Ag4(erlotinib)4}]n•7nCH3OH•3nH2O (1) was first...     

Water photodissociation in free ice nanoparticles at 243 nm and 193 nm

The photolysis of (H(2)O)(n) nanoparticles of various mean sizes between 85 and 670 has been studied in a molecular beam experiment. At the dissociation wavelength 243 nm (5.10 eV), a two-photon absorption leads to H-atom production. The measured kinetic energy distributions of H-fragments exhibit a peak of slow fragments below 0.4 eV with maximum at approximately 0.05 eV, and a tail of faster fragments extending to 1.5 eV. The dependence on the cluster size suggests that the former fragments originate from the photodissociation of an H(2)O molecule in the cluster interior leading to the H-fragment caging and eventually generation of a hydronium H(3)O molecule. The photolysis of surface molecules yields the faster fragments. At 193 nm (6.42 eV) a single photon process leads to a small signal from molecules directly photolyzed on the cluster surface. The two photon processes at this wavelength may lead to cluster ionization competing with its photodissociation, as suggested by the lack of H-fragment signal increase. The experimental findings are complemented by theoretical calculations.     

Redox properties of self-assembled gold nanoclusters

The redox properties of a monolayer of alkanethiolate-protected gold nanoclusters (MPCs) constructed on a gold slide electrode was studied in 1,2-dichloroethane (DCE) electrolyte solutions. The influence of the electrostatic interaction between attached MPCs and the substrate electrode on the absolute standard redox potential of MPCs was theoretically considered and studied experimentally.     

Redox properties of rhodium diene-cyclopentadienyl complexes

The electrochemical behavior of rhodium sandwich complexes containing η⁴-pentamethylcyclopentadiene or tetramethylfulvene fragments has been studied by cyclic voltammetry. The complexes undergo one-electron oxidation to give unstable 17-electron radical cations which are converted into rhodocenium salts as a result of elimination or uptake of hydrogen or C-C bond cleavage. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1802–1805, October, 1993.     

Playing the surface game-Diels-Alder reactions on diamond nanoparticles

Stable covalent C-C bonding of aromatic moieties has been achieved using Diels-Alder reactions on surface-annealed nanodiamond. Subsequent functionalisation leads to tunable surface properties and molecule-like behaviour.     

Crystal-face-selective adsorption of Au nanoparticles onto polycrystalline diamond surfaces

Crystal-face-selective adsorption of Au nanoparticles (AuNPs) was achieved on polycrystalline boron-doped diamond (BDD) surface via the self-assembly method combined with a UV/ozone treatment. To the best of our knowledge, this is the first report of crystal-face-selective adsorption on an inorganic solid surface. Hydrogen-plasma-treated BDD samples and those followed by UV/ozone treatment for 2 min or longer showed almost no adsorption of AuNP after immersion in the AuNP solution prepared by the citrate reduction method. However, the samples treated by UV/ozone for 10 s showed AuNP adsorption on their (111) facets selectively after the immersion. Moreover, the sample treated with UV/ozone for 40-60 s showed AuNP adsorption on the whole surface. These results indicate that the AuNP adsorption behavior can be controlled by UV/ozone treatment time. This phenomenon was highly reproducible and was applied to a two-step adsorption method, where AuNPs from different batches were adsorbed on the (111) and (100) surface in this order. Our findings may be of great value for the fabrication of advanced nanoparticle-based functional materials via bottom-up approaches with simple macroscale procedures.     

Synthesis and optical characterizations of undoped and rare-earth-doped CaF2 nanoparticles

The synthesis of undoped as well as Yb or Er-doped CaF₂ nanocrystals using a reverse micelle method is reported. X-ray powder diffraction and transmission electron microscopy analysis showed that the products were single phased and rather monodispersed with an average particles size around 20 nm. The emission spectra and fluorescence decay times of both Yb³⁺ and Er³⁺ rare earths (RE) ions in CaF₂ nanoparticles are presented. The particles size is increased by heating the as-obtained nanoparticles at different temperatures. The effect of annealing on the optical properties of the two RE ions in CaF₂ is also investigated.     

Redox indicator properties of some substituted chrysoidins

Indicator properties of eleven substituted chrysoidins have been studied. Conditional reduction potentials of the three appreciably reversible indicators in this group were obtained by classical approaches and by use of a potentiopoised standard solution procedure. Chemical and electrochemical observations lead to the conclusion that the other eight indicators act irreversibly in their oxidation. Hence, only transition potential ranges can be reported for these. Substitution in other than the 4-position induces greater irreversibility, while the hydroxy group in the 4-position produces a greater degree of reversibility than does either the methoxy or ethoxy group, 4-Hydroxychrysoidin appears to be the best of the group for bromate titrations.     

Semiconductor properties of nanocrystalline diamond electrodes

The semiconductor properties of nitrogenated nanocrystalline diamond electrodes and their corrosion transformations caused by electrochemical experiment in indifferent electrolyte (1 M K₂SO₄) were studied by the electrochemical impedance spectroscopy method. It was shown that after electrochemical measurements a narrow diamond peak at 1335.7 cm^?1 appears in the Raman spectrum; formerly the peak was hidden at a background of the intense signal inherent to graphite-like carbon. It was suggested that the corrosion damage caused by the exposure to electrochemical experiment resulted in a decrease of relative amount of nondiamond (graphite-like) carbon in the subsurface layer in the nanocrystalline diamond. By using Mott-Schottky plots, the nanocrystalline diamond was shown having n-type conductance. Within the bounds of the “effective medium” approach, the nanocrystalline diamond’s flat-band potential in aqueous solution and the noncompensated donor apparent concentration were estimated.