Pt nanoparticles-assisted electroless deposition of Prussian blue on the electrode: Detection of H2O2 with tunable sensitivity

In this communication, electroless deposition of Prussian blue (PB) on the electrode promoted by Pt nanoparticles (Pt_nano) is proposed for detecting H₂O₂ with adjustable sensitivity. Pt_nano/carbon nanotubes hybrid was initially used to modify the working electrode, followed by immersing it into the Fe³⁺[Fe^III(CN)₆] aqueous solution for electroless deposition of PB through a simple chemical reaction, which was catalyzed by Pt_nano. The amount of PB deposit was controllable through varying the deposition time or the Pt_nano amount on carbon nanotubes. Detection of H₂O₂ was successfully realized, sensitivity being dependent upon the amount of PB in the system. This work first demonstrates the feasibility of controlling the sensitivity of PB-based amperometric sensors through nanoparticles-assisted chemical deposition of PB, offering new insight into the development of electrochemical sensors using PB as the transducer.     

pH-dependent electrochemical behavior of proteins with different isoelectric points on the nanostructured TiO2 surface

Nanostructured materials are widely employed for facilitating electron transfer of proteins, and then constructing the third-generation biosensors. For further understanding the mechanism that nanomaterials facilitate electron transfer of proteins, nanostructured titanium dioxide (TiO₂) film was prepared as an example for investigating the interaction between proteins and electrode surfaces. The TiO₂ film was characterized by electrochemical methods, and the point of zero charge (pzc) was determined to be ∼6.27. On the other hand, cytochrome c (cyt. c) and superoxide dismutase (SOD) were raised as model proteins because they have different isoelectric points of 10.5 and 4.9, respectively. Direct electron transfer of cyt. c and SOD was achieved at the nanostructured TiO₂ surfaces at pH 7.0 and the proteins were verified to be stably immobilized onto the TiO₂ films. Furthermore, electrochemical behavior of cyt. c and SOD modified on nanostructured TiO₂ film was investigated in a series of different pH PBS solutions based on cyclic voltammetry. It was found that electron transfer of proteins strongly depended on pH of solutions, i.e., the surface charge of TiO₂ film. This observation could be ascribed to the electrostatic interaction between proteins and surfaces. This is the first report to provide the insight in the relationship between electron transfer of proteins and interaction of surfaces charge.     

牙科修复用CuO掺杂纳米二氧化钛的制备与表征

目的 通过氧化铜掺杂,制备改性氧化铜纳米二氧化钛光催化剂,检测氧化铜掺杂对CuO/TiO₂复合光催化剂吸收光谱的影响,为研制口腔临床修复功能性材料提供依据。方法 采用共沉淀法制备CuO/TiO₂（CuO掺杂纳米二氧化钛）,通过X射线衍射仪（XRD）、扫描电镜（SEM）和紫外-可见光吸收光谱（UV-vis谱）对其形态、结构、组成和性质进行表征。结果 成功制备了CuO/TiO₂复合光催化剂,不同CuO掺杂比的TiO₂的形貌基本不变,CuO掺杂使CuO/TiO₂吸收光谱发生红移,增加了可见光的吸收边界,提高可见光响应。结论 掺杂CuO后的光催化剂有效地提高其可见光响应能力,减少了空穴和电子复合,提高了可见光响应的性能。本研究对解决口腔临床修复对抗菌抑菌自洁特性材料的需求具有参考意义。     

Preparation and characterization of TiO2-NTs/SnO2-Sb electrodes by electrodeposition

The novel Sb-doped SnO₂ electrodes (TiO₂-NTs/SnO₂-Sb) have been prepared by anodization, electrodeposition and annealing. TiO₂ nanotubes (TiO₂-NTs) after Sb and Sn electrodeposited were characterized using field-emission scanning electron microscopy (FE-SEM). In contrast with the traditional Sb-doped SnO₂ coating prepared by thermal decomposition, the Sb-doped SnO₂ coating prepared by electrodeposition processes show more compact. X-ray diffraction (XRD) analysis indicates that the Sb-doped SnO₂ coating prepared by electrodeposition processes are firmly combined with the TiO₂-NTs formed on the Ti substrate. Accelerated service life tests reveal that the electrodeposition processes enhance the electrochemical stability of the Sb-doped SnO₂ electrode. The cyclic voltammetry analysis shows that TiO₂-NTs/SnO₂-Sb electrodes have higher overpotential for oxygen evolution and higher electrochemical porosity. Besides, the enhanced stabilization mechanism of the TiO₂-NTs/SnO₂-Sb electrode prepared by electrodeposition processes has been studied.     

The effect of doping Mg on the structure and electrochemical properties of Li3V2(PO4)3 cathode materials for lithium-ion batteries

The Mg-doped Li₃V_2−xMg_x(PO₄)₃ (x = 0.00, 0.01, 0.02, 0.05, 0.10, 0.20, 0.30, 0.33, 0.50, 1.00 and 1.33) compounds have been prepared by a sol–gel method in reducing atmosphere (70%Ar + 30%H₂) using citric acid as a chelating agent and a carbon source coated on the samples. The Mg-doped effects on the structural and electrochemical performance of Li₃V₂(PO₄)₃ are investigated by X-ray diffraction, galvanostatic, charge/discharge and four-point probe measurement method. The Li₃V_2−xMg_x(PO₄)₃ solid solution phase can exist stable in the composition range between x = 0.00 and 0.27. The simple improve mechanism of the electrochemical performance for Mg-doped Li₃V_2−xMg_x(PO₄)₃ system is discussed too. In the Mg-doped Li₃V_2−xMg_x(PO₄)₃ system, at a lower charge/discharge rate (0.1C), the cycle performance has no much improvement with the increasing Mg doping content. However, at higher rates, there has an excited improvement in both cycle performance and rate capability due to the increase of electrical conductivity (more than one order of magnitude). At 5C charge/discharge rate, for the Li₃V_1.95Mg_0.05(PO₄)₃ sample, the discharge capacities for the 1st and 100th cycle were 138.9 and 123.3 mAh g⁻¹. The discharge capacity retention reached to 89% (more than 51% for undoped Li₃V₂(PO₄)₃ system). More important is that, except for the first 15 cycles, the discharge capacities kept almost a constant. Based on the excellent electrochemical performance, Li₃V_1.95Mg_0.05(PO₄)₃ will be a promising cathode material for rechargeable lithium-ion batteries.     

Electrocatalytic oxidation and reduction of H2O2 on vertically aligned Co3O4 nanowalls electrode: Toward H2O2 detection

Single crystal and vertically aligned cobalt oxide (Co₃O₄) nanowalls were synthesized by directly heating Co foil on a hot-plate under ambient conditions. The vertically aligned Co₃O₄ nanowalls grown on the plate show excellent mechanical property and were facilely attached to the surface of a glassy carbon (GC) electrode using conductive silver paint. The prepared Co₃O₄ nanowalls electrode was then applied to study the electrocatalytic oxidation and reduction of hydrogen peroxide (H₂O₂) in 0.01 M pH 7.4 phosphate buffer medium. Upon the addition of H₂O₂, the Co₃O₄ nanowalls electrode exhibits significant oxidation and reduction of H₂O₂ starting around +0.25 V (vs. Ag/AgCl), while no obvious redox activity is observed at a bare GC electrode over most of the potential range. The superior electrocatalytic response to H₂O₂ is mainly attributed to the large surface area, minimized diffusion resistance, high surface energy, and enhanced electron transfer of the as-synthesized Co₃O₄ nanowalls. The same Co₃O₄ nanowalls electrode was also applied for the amperometric detection of H₂O₂ and showed a fast response and high sensitivity at applied potentials of +0.8 V and −0.2 V (vs. Ag/AgCl), respectively. The results also demonstrate that Co₃O₄ nanowalls have great potential in sensor and biosensor applications.     

牙科修复用BiOIO3/g-C3N4复合纳米光催化剂的制备与表征

目的 研究不同剂量NaOH条件对制备BiOIO3/g-C3N4复合纳米光催化剂的结构形貌及其可吸收光谱的影响,为研制适用于口腔修复纳米光催化功能性材料提供依据.方法 水热法制备BiOIO3/g-C3N4,通过XRD(X射线衍射仪)、SEM(扫描电镜图)和UV-vis(紫外-可见光吸收光谱)对其形貌、结构、分子组成和理化...     

EQCM study of electrochemical modification of Bi2S3 films in the Zn-containing electrolyte

The electrochemical behavior of Bi₂S₃ as-deposited on Au using the successive ionic layer adsorption and reaction method has been investigated in the Zn²⁺-free background and Zn²⁺-containing electrolytes at different pH by electrochemical quartz crystal microbalance coupled with cyclic voltammetry and X-ray photoelectron spectroscopy. It has been shown that when the Bi₂S₃ film is reduced in the Zn²⁺-containing electrolyte Zn²⁺ ions are involved in electrochemical bismuth sulfide reduction and are partially reduced together with the bismuth sulfide film. The bismuth sulfide film initiates the adsorbed Zn²⁺ ions reduction prior to the traditional overpotential deposition of it. Reduction of Zn²⁺ ions prior to the overpotential deposition of Zn depends on solution pH: at pH 5 it occurs at more negative potential values and the observed mass changes due to Zn electrodeposition are greater than at solution pH 3. After bismuth sulfide film reduction in the Zn²⁺-containing electrolyte, Zn was detected as ZnO and metallic Zn at pH 5, while at pH 3 only ZnO was detected.     

Effects of sodium sulfamate on electrodeposition of Cu(In,Ga)Se2 thin film

Cu(In,Ga)Se₂ thin films have been prepared by electrodeposition from chloride electrolytes using sodium sulfamate as a complexing agent. Cyclic voltammograms indicate that sodium sulfamate can inhibit the reduction of Cu²⁺, Cu⁺ and H₂SeO₃, and accordingly hinder the formation of copper selenides. EDS analysis reveals that with the increase of sodium sulfamate concentration in the bath, atom ratio (Cu + Se)/(In + Ga) decreases while gallium content increases, and the film composition transforms from Cu-rich to Cu-poor. SEM and Raman spectra also show that copper selenides phases in electrodeposited films diminish with the increase of sodium sulfamate concentration.     

Spectroelectrochemical investigation of MnO2 electro-generation and electro-reduction in acidic media

Spectroscopic investigations of Mn²⁺ electro-oxidation and MnO₂ electro-reduction in acidic media (0.5–2 M H₂SO₄) have been performed using optically transparent electrodes (OTE). Reticulated vitreous carbon (RVC) has been used as the electrode material. Our results show that in the first step of Mn²⁺ ions electro-oxidation the unstable in aqueous media Mn³⁺ ions are formed. In the next step Mn³⁺ ions can hydrolyse to MnOOH and/or disproportionate to Mn²⁺ and Mn⁴⁺ ions. Contrary to the electro-oxidation of Mn²⁺ to MnO₂, the electro-reduction of MnO₂ proceeds in two steps. The first step is strictly connected with electro-generation of MnOOH and the next with regeneration of Mn²⁺ ions.     

不同浓度的过氧化氢对银汞合金表面性能的影响

目的研究不同浓度过氧化氢对银汞合金表面性能的影响。方法采用表面轮廓仪和扫描电镜对0 wt%、3.6 wt%、10 wt%和30 wt%四种浓度过氧化氢浸泡112 h后的牙科银汞合金的表面粗糙度、表面形貌进行比较,并运用光电子能谱仪分析0%和30%两种浓度过氧化氢浸泡后银汞合金的表面腐蚀产物。结果过氧化氢浸泡112 h后,不同银汞合金表面粗糙度的Ra和Rz的大小顺序均为0 wt%<3.6 wt%<10 wt%<30 wt%;且表面均有不同程度的腐蚀,主要表现为分布不均匀、孔径大小不一的点蚀,其中以30wt%过氧化氢浸泡组的腐蚀最明显;此外,0 wt%和30 wt%过氧化氢浸泡后,银汞合金表面分别检测到Cu、Sn、Hg、Ag、O元素,表面氧化物主要为SnO₂,与0 wt%过氧化氢相比,30 wt%过氧化氢浸泡后,银汞合金表面Ag、Hg、O元素含量明显下降,而Sn、Cu元素含量则升高。结论随着过氧化氢浓度的升高,银汞合金表面粗糙度增加,表面形貌有不同程度腐蚀,表面腐蚀产物成分有所改变,氧化程度减弱。     

Synthesis and electrochemical characterizations of nano size Ce doped LiMn2O4 cathode materials for rechargeable lithium batteries

LiCe_xMn_2−xO₄ (x = 0.00–0.10) cathode materials for rechargeable lithium-ion batteries were synthesized by simple sol–gel technique using aqueous solutions of metal nitrates and succinic acid as the chelating agent. The gel precursors of metal succinates were dried in vacuum oven for 10 h at 120 °C. After drying, the gel precursors were ground and heated at 900 °C. The structural characterization was carried out by X-ray powder diffraction and X-ray photoelectron spectroscopy to identify the valence state of Mn and Ce in the synthesized materials. The sample exhibited a well defined spinel structure and the lattice parameter linearly increased with increasing the cerium contents in LiCe_xMn_2−xO₄. Surface morphology and particle size of the synthesized materials were determined by scanning electron microscopy and transmittance electron microscopy respectively. Electrochemical properties were characterized for assembled Li/LiCe_xMn_2−xO₄ coin type cells using galvanostatic charge/discharge studies at 0.5C rate and cyclic voltammetry in the potential range between 2.75 and 4.5 V at a scan rate of 0.1 mV s⁻¹. Among them cerium doped spinel LiCe_0.05Mn_1.90O₄ has improved structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries.     

Effects of Ag-photodeposition on photocurrent of an ITO electrode modified by a hybrid film of TiO2 nanosheets

We performed the photodeposition of Ag clusters onto a TiO₂ nanosheet hybridized with an amphiphlic Ru(II) complex (denoted by TiO₂–Ru/Ag). Firstly a floating monolayer of [Ru(phen)₂(dC18bpy)](ClO₄)₂ (phen = 1,10-phenanthroline, dC18bpy = 4,4^′-dioctadecyl-2,2^′-bipyridyl) was formed on an aqueous dispersion of exfoliated layered titanate, (TBAOH)_xTi_2?x/4□_x/4O₄ · H₂O (x～0.7;□, vacancy; TBAOH = tetrabutylammonium hydroxide) (denoted as TiO₂ nanosheet). The monolayer acted as the organic part for the hybridization of TiO₂ particles in an aqueous phase. A hybrid film of TiO₂ nanosheet and an amphiphilic metal complex (denoted by TiO₂–Ru) was transferred onto an indium tin oxide substrate by the vertical dipping method. Thereafter the electrode was immersed in 1.0 M AgNO₃ for 10 min and rinsed with water. The electrode was irradiated for 30 min by a Xe-lamp (150 W). Atomic force microscope, X-ray photoelectron spectra and cyclic voltammometry showed the formation of silver nanoparticles with a radius of 20–150 nm. The photocurrent response was measured in the potential range of 0.2–1.2 V (vs. Ag|AgCl|KCl(sat)) under the illumination of light (>350 nm). The current increased 1.7 times when the layer number of hybrid films increased from one to two. It should be emphasized that such an increase of photocurrent with a layer number was not observed in the absence of Ag particles.     

Biomechanical properties of nano-TiO2 addition to a medical silicone elastomer: The effect of artificial ageing

Objectives

The aim of this study was to evaluate the effect of TiO₂ nanoparticles on the mechanical and anti-ageing properties of a medical silicone elastomer and to assess the biocompatibility of this novel combination.

Methods

TiO₂ (P25, Degussa, Germany) nanoparticles were mixed with the silicone elastomer (MDX4-4210, Dow Corning, USA) at 2%, 4%, and 6% (w/w) using silicone fluid as diluent (Q7-9180, Dow Corning, USA). Blank silicone elastomer served as the control material. The physical properties and biocompatibility of the composites were examined. The tensile strength was tested for 0% and 6% (w/w) before and after artificial ageing. SEM analysis was performed.

Results

TiO₂ nanoparticles improved the tensile strength and Shore A hardness of the silicone elastomer (P < 0.05). However, a decrease in the elongation at break and tear strength was found for the 6% (w/w) composite (P < 0.05). All the ageing methods had no effect on the tensile strength of the 6% (w/w) composite (P > 0.05), but thermal ageing significantly decreased the tensile strength of the control group (P < 0.05). Cellular viability assays indicated that the composite exhibited biocompatibility.

Conclusions

We obtained a promising restorative material which yields favourable physical and anti-ageing properties and is biocompatible in our in vitro cellular studies.     

Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study

Objectives: The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO₂) laser that was designed for soft tissue surgery.Methods: Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO₂ irradiation conditions used were: wave length 10.6 μm; 1.2–2.6 J/cm² fluence per pulse; repetition rate 120–1000 Hz; 100–200 ms pulse duration; and cumulative fluences ranging from 14 to 2200 J/cm². Each window was irradiated with a 0.3 mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0 s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM).Results: The pulp chamber temperature rise ranged from 0.5 to 19° C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40 J/cm², 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel.Conclusions: These results indicate there are threshold conditions above which pulsed CO₂ laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.     

Electrodeposition of submicron/nanoscale Cu2O/Cu junctions in an ultrathin CuSO4 solution layer

The electrodeposition experiments were carried out in an ultrathin CuSO₄ solution layer under lower growth driving forces and the structure of electrodeposits were characterized by FESEM, chemical etching, EDS and DC conducting measurement. It was found that the Cu₂O crystallites distributed over the entire sample surface and formed submicron/nanoscale Cu₂O/Cu junctions. Meanwhile, the abnormal growth of Cu₂O crystallites in the electrodeposit front area was found for the first time. In the study, we present the obvious evidences for clarifying the relationship between the morphology and the compositional distribution of electrodeposits at grain size level. This result may be helpful for us to prepare the electrodeposits with controlled surface morphology at micro–nanoscale.