Kinetic study of DNA/DNA hybridization with electrochemical impedance spectroscopy

The hybridization of immobilized oligonucleotides probe strands with solution phase targets is the underlying principle of microarraybased techniques for the analysis of DNA variation. To study the kinetics of DNA/DNA hybridization, target DNA is often prior labeled with markers. A label-free method of electrochemical impedance spectra (EIS) for study the hybridization in process was reported. The Langmuir model was used to determine the association rate constant (K-on), the dissociation rate constant (K-off) and the affinity rate constant (K-A), for perfect matched DNA hybridization. The results show that, EIS is a successful technique possessing high effectivity and sensitivity to study DNA/DNA hybridization kinetics. This work can provide another view on EIS for the studying of DNA/DNA hybridization.

Structure and electrochemical characteristics of TiV1.1Mn0.9Nix (x=0.1-0.7) alloys

The structure and electrochemical properties of TiV1.1Mn0.9Nix (x = 0.1-0.7) solid solution electrode alloys have been investigated. It is found that these alloys mainly consist of a solid solution phase with body centered cubic (bcc) structure and a C14 Laves secondary phase. The solid solution alloys show easy activation behavior, high temperature dischargeability, high discharge capacity and favorable high-rate dischargeability as a negative electrode material in Ni-MH battery. The maximum discharge capacity is 502 mAh g(-1) at 303 K when x = 0.4. Electrochemical impedance spectroscopy (EIS) test shows that the charge-transfer resistance at the surface of the alloy electrodes decreases obviously with increasing Ni content.

Microstructure and some dynamic performances of Ti0.17Zr0.08V0.34RE0.01Cr0.1Ni0.3 (RE = Ce, Dy) hydrogen storage electrode alloys

Microstructure and some dynamic performances of Ti0.17Zr0.08V0.34RE0.01Cr0.1Ni0.3 (RE=Ce, Dy) hydrogen storage electrode alloys have been investigated using XRD, FESEM-EDS, ICP-MS and EIS measurements. The alloy is composed of V-based solid solution phase with a dendritic shape and a continuous C14 Laves phase with a network shape surrounding the dendrite. Pressure-composition isotherm curves indicate that the alloy with Dy addition has a lower equilibrium hydrogen pressure and a wider plateau region. The alloy electrode with Dy addition has higher discharge capacity, while the alloy electrode with Ce addition has better activation and higher cycle stability. The alloy electrode with Ce addition has better electrochemical activity with higher exchange current density (127.5 mA g(-1)), lower charge transfer resistance (1.37 Omega) and lower apparent activation energy (30.5 kJ mol(-1)). The capacity degradation behavior for the alloy electrode is attributed to two main factors: one is the dissolutions of V and Zr element to KOH solution, and another is the larger charge transfer resistance which increases with increasing cycle number.

Effect of cerium on microstructure and electrochemical performance of Ti-V-Cr-Ni electrode alloy

Effect of cerium on the microstructure and electrochemical performance of the Ti0.25V0.35-xCexCr0.1Ni0.3 (x = 0, 0.005) electrode alloy was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy/energy dispersive X-ray spectrometry (FESEM-EDS), and electrochemical impedance spectroscopy (EIS) measurements. On the basis of XRD and FESEM-EDS analysis, the alloy was mainly composed of V-based solid solution with body-centered-cubic structure and TiNi-based secondary phase. Ce did not exist in two phases, instead, it existed as Ce-rich small white particles, with irregular edges, distributed near the grain boundaries of the V-based solid solution phase. Discharge capacity, cycle stability, and high-rate discharge ability of the alloy electrode were effectively improved with the addition of Ce at 293 K. It was very surprising that the charge retention was abnormal with larger discharge capacity after standing at the open circuit for 24 h. EIS indicated that addition of Ce improved the dynamic performance, which caused the charge transfer resistance (R-T) to decrease and exchange current density (I-0) to increase markedly. The exchange current density of the electrochemical reaction on the alloy surface with Ce addition was about 2.07 and 3.10 times larger than that of the alloy without Ce at 303 and 343 K, respectively.

Analytical applications of the electrochemiluminescence of tris (2.2 '-bipyridyl) ruthenium and its derivatives

This article presents the state of the art of analytical applications of the electrochemiluminescence (ECL) of tris (2,2'-bipyridyl) ruthenium (Ru(bpy)(3)(2+)) and its derivatives. in the last seven years, Ru(bpy)(3)(2+) ECL has attracted much interest from analysts and been successfully exploited as a detector of flow injection analysis (FIA), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and micro total analysis systems (TAS). Immobilization of Ru(bPY)(3)(2+) on a solid surface provides several advantages over the solution-phase ECL procedure, such as the simplicity of experimental design and cost-effectiveness. After a brief discussion of the mechanism of Ru(bpy)(3)(2+) ECL, we discuss its applications in FIA, HPLC, CE and TAS and give special attention to the design of Ru(bpy)(3)(2+) ECL cells and some immobilization techniques of Ru(bpy)(3)(2+); we focus on papers published after 1997.

Characterization of non-covalent complexes of rutin with cyclodextrins by electrospray ionization tandem mass spectrometry

Electrospray ionization tandem mass spectrometry (ESI-MSn) and the phase solubility method were used to characterize the gas-phase and solution-phase non-covalent complexes between rutin (R) and alpha-, beta- and gamma-cyclodextrins (CDs). The direct correlation between mass spectrometric results and solution-phase behavior is thus revealed. The order of the 1:1 association constants (K-c) of the complexes between R and the three CDs in solution calculated from solubility diagrams is in good agreement with the order of their relative peak intensities and relative collision-induced dissociation (CID) energies of the complexes under the same ESI-MSn condition in both the positive and negative ion modes. Not only the binding stoichiometry but also the relative stabilities and even binding sites of the CD-R complexes can be elucidated by ESI-MSn. The diagnostic fragmentation of CD-R complexes, with a significant contribution of covalent fragmentation of rutin leaving the quercetin (Q) moiety attached to the CDs, provides convincing evidence for the formation of inclusion complexes between R and CDs. The diagnostic fragment ions can be partly confirmed by the complexes between Q and CDs. The gas-phase stability order of the deprotonated CD-R complexes is beta-CD-R > alpha-CD-R > gamma-CD/R; beta-CD seems to bind R more strongly than the other CDs.

Semiconductor "nano-onions" with multifold alternating CdS/CdSe or CdSe/CdS structure

"Nano-onions" with multifold alternating CdS/CdSe or CdSe/CdS structure have been synthesized via a two-phase approach. The influences of shell on photoluminescence (PL) quantum yields (QYs) and PL lifetimes are investigated and discussed. It is found that the outmost shell plays an important role in the PL QYs and PL lifetimes of the multishells "onion-like" nanocrystals. The PL QYs and PL lifetimes fluctuate regularly with CdSe and CdS shells. The PL QY increases when the nanocrystals have an outmost CdS shell; however, it decreases dramatically with the outmost CdSe shell. The trend of the change of PL lifetimes is consistent with that of the QYs. The crystal structure and composition of the novel nano-onions are characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectra techniques.

Seed-mediated synthesis of branched gold nanoparticles with the assistance of citrate and their surface-enhanced Raman scattering properties

We report an easy synthesis of highly branched gold particles through a seed-mediated growth approach in the presence of citrate. The addition of citrate in the growth solution is found to be crucial for the formation of these branched gold particles. Their size can be varied from 47 to 185 nm. The length of the thumb-like branch is estimated to be between about 5 and 20 nm, and changes slightly as the particle size increases. Owing to these obtuse and short branches, their surface plasmon resonance displays a marked red-shift with respect to the normal spherical particles. These branched gold particles exhibit stronger SERS activity than the non-branched ones, which is most likely related to these unique branching features.

Structures and electrochemical characteristics of several kinds of alloys

The structures and the electrochemical characteristics of La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1-0.5) alloy, Ti0.25-xZrxV0.35Cr0.1Ni0.3 (x = 0.05-0.15) alloy and AB(3

Microstructures and properties of melt-spun and as-cast Mg-20Gd binary alloy

Mg-20Gd(%, mass fraction) samples were prepared using melt-spinning and copper mold casting techniques. Microstructures and properties of the Mg-20Gd were investigated. Results show that the melt-spun ribbon is mainly composed of supersaturated alpha-Mg solid solution phase and the as-east ingot mainly contains alpha-Mg solid solution and Mg5Gd phase. The differential scanning calorimeter (DSC) curve of the ribbon exhibits a small exothermic peak in the temperature range from 630 to 680 K, which indicates that the ribbon contains a metastable phase (amorphous). Tensile strength at room temperature of the melt-spun ribbon and as-cast specimen are 308 and 254 MPa, respectively. The elongations of the two samples are less than 2%. The fracture surfaces demonstrate that the fracture mode of the as-cast Mg-20Gd is a typical cleavage fracture and that of the melt-spun sample is a combination of brittle fracture and ductile fracture.

Studies on the non-covalent complexes between oleanolic acid and cyclodextrins using electrospray ionization tandem mass spectrometry

Non-covalent inclusion complexes formed between an anti-inflammatory drug, oleanolic acid (OA), and alpha-, beta- and gamma-cyclodextrins (CDs) were investigated by means of solubility studies and electrospray ionization tandem mass spectrometry (ESI-MSn). The order of calculated association constants (K-1:1) of complexes between OA and different CDs in solution is in good agreement with the order of their relative peak intensities and the relative CID energies of the complexes under the same ESI-MSn conditions. These results indicate a direct correlation between the behaviors of solution- and gas-phase complexes. ESI-MS can thus be used to evaluate solution-phase non-covalent complexes successfully. The experimental results show that the most stable 1:1 inclusion complexes between three CDs and OA can be formed, but 2:1 CD-OA complexes can be formed with beta- and gamma-CDs. Multi-component complexes of alpha-CD-OA-beta-CD (1:1:1), alpha-CD-OA-gamma-CD (1:1:1) and beta-CD-OA-gamma-CD (1:1:1) were found in equimolar CD mixtures with excess OA. The formation of 2:1 and multi-component 1:1:1 non-covalent CD-OA complexes indicates that beta- and gamma-CD are able to form sandwich-type inclusion non-covalent complexes with OA. The above results can be partly supported by the relative sizes of OA and CD cavities by molecular modeling calculations.

Synthesis, characterisation and applications of group IV nanocrystals

Group IV materials such as silicon nanocrystals (Si NCs) and carbon quantum dots (CQDs) have received great attention as new functional materials with unique physical/chemical properties that are not found in the bulk material. This thesis reports the synthesis and characterisation of both types of nanocrystal and their application as fluorescence probes for the detection of metal ions. In chapter 2, a simple method is described for the size controlled synthesis of Si NCs within inverse micelles having well defined core diameters ranging from 2 to 6 nm using inert atmospheric synthetic methods. In addition, ligands with different molecular structures were utilised to reduce inter-nanocrystal attraction forces and improve the stability of the NC dispersions in water and a variety of organic solvents. Regulation of the Si NCs size is achieved by variation of the surfactants and addition rates, resulting high quality NCs with standard deviations (σ = Δd/d) of less than 10 %. Large scale production of highly mondisperse Si NC was also successfully demonstrated. In chapter 3, a simple solution phase synthesis of size monodisperse carbon quantum dots (CQDs) using a room temperature microemulsion strategy is demonstrated. The CQDs are synthesized in reverse micelles via the reduction of carbon tetrachloride using a hydride reducing agent. CQDs may be functionalised with covalently attached alkyl or amine monolayers, rendering the CQDs dispersible in wide range of polar or non-polar solvents. Regulation of the CQDs size was achieved by utilizing hydride reducing agents of different strengths. The CQDs possess a high photoluminescence quantum yield in the visible region and exhibit excellent photostability. In chapter 4, a simple and rapid assay for detection of Fe3+ ions was developed, based on quenching of the strong blue-green Si NC photoluminescence. The detection method showed a high selectivity, with only Fe3+ resulting in strong quenching of the fluorescence signal. No quenching of the fluorescence signal was induced by Fe2+ ions, allowing for solution phase discrimination between the same ion in different charge states. The optimised sensor system showed a sensitive detection range from 25- 900 μM and a limit of detection of 20.8 μM

Photoelectrocatalysis: Principles, nanoemitter applications and routes to bio-inspired systems

An overview on processes that are relevant in light-induced fuel generation, such as water photoelectrolysis or carbon dioxide reduction, is given. Considered processes encompass the photophysics of light absorption, excitation energy transfer to catalytically active sites and interfacial reactions at the catalyst/solution phase boundary. The two major routes envisaged for realization of photoelectrocatalytic systems, e.g. bio-inspired single photon catalysis and multiple photon inorganic or hybrid tandem cells, are outlined. For development of efficient tandem cell structures that are based on non-oxidic semiconductors, stabilization strategies are presented. Physical surface passivation is described using the recently introduced nanoemitter concept which is also applicable in photovoltaic (solid state or electrochemical) solar cells and first results with p-Si and p-InP thin films are presented. Solar-to-hydrogen efficiencies reach 12.1% for homoepitaxial InP thin films covered with Rh nanoislands. In the pursuit to develop biologically inspired systems, enzyme adsorption onto electrochemically nanostructured silicon surfaces is presented and tapping mode atomic force microscopy images of heterodimeric enzymes are shown. An outlook towards future envisaged systems is given. © 2010 The Royal Society of Chemistry.

Raman spectroscopy in pharmaceutical analysis

A wide and versatile range of analytical techniques are routinely used, indeed are necessary, in pharmaceutical analysis. Over the past decade Raman spectroscopy has increasingly come to the fore as a valuable member of the arsenal of methods used, from both a fundamental and applied perspective, for the interrogation of solid, liquid and solution phase samples. Advances have occurred not only in instrumentation but also in fundamental techniques and applications. The method holds substantial potential for the investigation of, what are normally considered, problematic or challenging areas of analysis. The aforementioned areas include – but are, definitely not limited too reaction kinetics, pharmaceutical drug discovery, detection of counterfeit/adulterated/illegal drugs, trace analysis and uses for on-line pharmaceutical process manufacturing. This, the first of several articles on the use of Raman spectroscopic techniques in pharmaceutical analysis, provides an introductory overview of the theory of the technique.