Search

Redox and acid-base chemistry of 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF4), and their mono- and di-anions in acetonitrile in the presence or absence of trifluoroacetic acid (TFA) have been studied systematically. In acetonitrile containing supporting electrolyte, both compounds undergo two electrochemically and chemically reversible one-electron reduction steps. The reversible formal potentials associated with these reductions of TCNQF4 are 0.36 and 0.37 V more positive than those for TCNQ. This result is consistent with the higher electron affinity of TCNQF4 than TCNQ due to the strong electron withdrawing effect of the fluorine atoms. The underlying mechanisms for the electrochemistry and the acid-base chemistry of TCNQ, TCNQF4 and their anions have been proposed and supported by digital simulations. A wealth of thermodynamic and kinetic parameters has been revealed from the experimental and simulated data. A comparison of the redox and acid-base chemistry between TCNQ and TCNQF4 as well as their anions also has been discussed. Studies of chemical and electrochemical synthesis of new materials based on TCNQF4 in combination with Li+, Pr4N+, Ag+, Cu+, Co2+ and Ni2+ have been undertaken. In acetonitrile, I- (as the I- salt) reduces TCNQF4 to TCNQF4•- or TCNQF4(2-) depending on the reaction conditions. At low temperature (0 oC) and using the molar ratio I-:TCNQF4 < 3:2, TCNQF4 is reduced to the TCNQF4•- monoanion. In contrast, at higher temperatures (50-60 oC) and using the molar ratio > 3:1, the major product is the TCNQF4(2-) dianion. The LiTCNQF4 and Li2TCNQF4 thus generated were used to chemically synthesize Pr4NTCNQF4 and (Pr4N)2TCNQF4. TCNQF4 can also be electrochemically reduced in acetonitrile to afford either TCNQF4•- or TCNQF4(2-) by applying different potentials. This electrosynthetic approach has, therefore, been applied to crystallize a family of charge-transfer, semiconducting materials, including AgTCNQF4, Ag2TCNQF4, CuTCNQF4, Cu2TCNQF4, CoTCNQF4 and NiTCNQF4 onto an electrode surface. The electrodeposition of these compounds has been monitored using cyclic voltammetry, surface plasmon resonance and electrochemical quartz crystal microbalance. The solubility of these compounds has been determined in acetonitrile in the presence or absence of 0.1 M Bu4NPF6 supporting electrolyte and found to increase in the presence of the supporting electrolyte as a result of ion pairing between ions from the electrolyte and the complexes. These metal-organic charge-transfer complexes also have been chemically synthesized from acetonitrile solutions of the corresponding TCNQF4 anion and metal cation. A wide range of microscopic and spectroscopic techniques has been applied to characterize the newly generated compounds. Besides synthesis of TCNQF4-based compounds in acetonitrile, a new complex Ni(TCNQF4)2(H2O)2 has been electrochemically synthesized in aqueous media via the reduction of TCNQF4 solid immobilized onto an electrode surface and placed in contact with a Ni2+(aq) solution. The solid-solid state transformation TCNQF4/Ni(TCNQF4)2(H2O)2 has been explored via cyclic voltammetry and chronoamperometry. The electrosynthesis involves a one-electron reduction of TCNQF4 to TCNQF4•-, accompanied with the ingress of Ni2+(aq) from the bulk solution. This transformation is governed by a nucleation and growth mechanism, and is independent of the electrode material and the identity of Ni2+(aq) counter anion, but strongly dependent on Ni2+(aq) concentration and scan rate. The composition, structure, magnetic and conducting properties of the Ni(TCNQF4)2(H2O)2 complex have been determined. The disproportionation reaction of TCNQF4•- and TCNQ•- (both designated as TCNQ(F4)•-) in the presence of Zn2+ is reported. Acetonitrile solutions containing TCNQ(F4)•- and Zn2+ form dissolved TCNQ(F4) and ZnTCNQ(F4) precipitates. The neutral TCNQ(F4) dissolved in acetonitrile was detected using UV-vis spectroscopy and steady-state voltammetry, whilst the presence of TCNQ(F4)2- in the precipitates was confirmed by infrared spectroscopy, and also by showing that the precipitates reacts with TCNQ(F4) in the presence of water to form TCNQ(F4)•-. Interestingly, the extent of the disproportionation decreases upon addition of water; > 3% (v/v) of water results in no disproportionation. A mechanism for the disproportionation has been proposed and is attributed to the precipitation of ZnTCNQ(F4), which shifts the equilibrium 2TCNQ(F4)•- TCNQ(F4) + TCNQ(F4)2- to the right-hand side. However, the solubility of ZnTCNQ(F4) in water is higher than in acetonitrile, and hence the disproportionation is less favored in the presence of water. Electrochemical and spectroscopic identification of TCNQF4 redox levels are reviewed. Steady-state voltammetry and UV-vis spectroscopy are simple and powerful techniques for the qualitative and quantitative detection of TCNQF4 and its anions (TCNQF4•- and TCNQF4(2-)) since each species has a characteristic fingerprint. Infrared spectroscopy has been applied extensively and successfully in the qualitative determination of the redox levels of TCNQF4 in a range of compounds. Predominately, the frequency of the CN triple bond stretch is diagnostic of the redox level. Raman vibration modes for the CN triple bond and C=C ring stretches also are sensitive to the TCNQF4 redox levels.

Introduction: Global health agencies and the Vietnam Ministry of Health have identified pediatric emergency care and health information technology as high priority goals. Clinical decision support (CDS) software provides physicians with access to current literature to answer clinical queries, but there is limited impact data in developing countries. We hypothesized that Vietnamese physicians will demonstrate improved test performance on common pediatric emergencies using CDS technologies despite being in English. Methods: This multicenter, prospective, pretest-posttest study was conducted in 11 Vietnamese hospitals enrolled a convenience sample of physicians who attended an 80-minute software training on a pediatric CDS software (PEMSoft). Two multiple-choice exams (A, B) were administered before and after the session. Participants, who received Test A as a pretest, received Test B as a posttest, and vice versa. Participants used the CDS software for the posttest. The primary outcome measure was the mean percentage difference in physician scores between the pretest and posttest, as calculated by a paired, two-tailed t-test. Results: For the 203 participants, the mean pretest, posttest, and improvement scores were 37% (95% CI: 35-38%), 70% (95% CI: 68-72%), and 33% (95% CI: 30-36%), respectively, with p

Vietnam is a developing country with tropical climate where infectious diseases, especially encephalitis are common. Every year, in National Hospital of Pediatrics from 200 to 300 encephalitis patients are hospitalized due to encephalitis. A rapid assessment of consciousness level in encephalitis is of importance in treatment and prognosis for patients. Two scales are usually used in assessment of consciousness level, The Alert Verbal Painful Unresponsiveness (AVPU) scale and the Glasgow Coma Scale (GCS). The GCS score is one of the most commonly used methods. AVPU scale is a simple method for assessment of consciousness. We conducted this study to determine how the AVPU responsive scale corresponds with the GCS in children who have encephalitis.

During an outbreak of severe acute respiratory infections in 2 orphanages, Vietnam, 7/12 hospitalized children died. All hospitalized children and 26/43 children from outbreak orphanages tested positive for rhinovirus versus 9/40 control children (p = 0.0005). Outbreak rhinoviruses formed a distinct genetic cluster. Human rhinovirus is an underappreciated cause of severe pneumonia in vulnerable groups.

Background. Infections with community-acquired methicillin-resistant Staphyloccus aureus (CA-MRSA) are emerging worldwide. We investigated an outbreak of severe CA-MRSA infections in children following out-patient vaccination. Methods and Findings. We carried out a field investigation after adverse events following immunization (AEFI) were reported. We reviewed the clinical data from all cases. S. aureus recovered from skin infections and from nasal and throat swabs were analyzed by pulse-field gel electrophoresis, multi locus sequence typing, PCR and microarray. In May 2006, nine children presented with AEFI, ranging from fatal toxic shock syndrome, necrotizing soft tissue infection, purulent abscesses, to fever with rash. All had received a vaccination injection in different health centres in one District of Ho Chi Minh City. Eight children had been vaccinated by the same health care worker (HCW). Deficiencies in vaccine quality, storage practices, or preparation and delivery were not found. Infection control practices were insufficient. CA-MRSA was cultured in four children and from nasal and throat swabs from the HCW. Strains from children and HCW were indistinguishable. All carried the Panton-Valentine leukocidine (PVL), the staphylococcal enterotoxin B gene, the gene complex for staphylococcal-cassette-chromosome mectype V, and were sequence type 59. Strain HCM3A is epidemiologically unrelated to a strain of ST59 prevalent in the USA, although they belong to the same lineage. Conclusions. We describe an outbreak of infections with CA-MRSA in children, transmitted by an asymptomatic colonized HCW during immunization injection. Consistent adherence to injection practice guidelines is needed to prevent CA-MRSA transmission in both in- and outpatient settings. © 2007 Chi Thuong et al.

Within the framework of the macroscopic dielectric continuum model the longitudinal optical (LO) phonon modes are derived for a cylindrical semiconductor quantum wire made of semiconductor 1 (well material) embedded in another finite semiconductor 2 (barrier material). The phonon states of modes are given by solving the generalized Born-Huang equation. It is shown that there may exist four types of longitudinal optical phonon modes according to the concrete materials forming the wire. The dispersion equations for phonon frequencies with wave-vector components parallel to the wire are obtained. After having quantized the phonon field we derive the Fröhlich Hamiltonian describing the electron--LO-phonon interaction. The influence of the thickness of the barrier layer as well as the thin metallic shell on the phonon frequencies and their interaction with electrons is studied.

We propose a novel image fusion scheme based on indppendent component analysis in which image / information is fused aimed at information maximizutian. In the scheme, a novel algorithm is presented which, bused on speciJic fusing images, determines aduptivery a speci$c weight for linear fusion of images using ICA. The scheme is established on the ICA maximum iHfomation principles and ofem an eflcieflt and adaptive huge fusiola process with the robustness under various fusion situations.

Graphene, a single-atom-thick and two-dimensional sp2 carbon networking materials, has attracted a great deal of interest owing to its remarkable electrical, mechanical, and thermal properties. These excellent properties make it more suitable for use in transparent and flexible electrodes. The successful implementation of graphene films for various applications requires high quality and high resolution patterning at defined positions, with large-scale control of location and orientation. The plasma etching technique is one of the patterning techniques, which has been used widely for the surface activation of various materials, as well as for removal of carbon-based organic material from substrate surfaces [1]. This method has several advantages over other patterning techniques: (1) it can be scaled-up to produce large quantities for commercial use; (2) it results in high feature resolutions and sharp pattern edges; (3) the processing time is short; and (4) it offers good reproducibility and reliability. Herein, we report a simple patterning method for the production of graphene films on flexible, transparent plastic substrates such as poly(ethylene terephthalate) PET using an O2-plasma technique in a CCP system [2]. For the preparation of graphene, graphene oxide suspension was reduced at 85°C for 24h by employing L-ascorbic acid as a reducing agent. L-ascorbic acid is non-toxic, so this method is eco-friendly compared to other reducing agents [3]. To apply the homogeneous graphene films in a large area, flexible and transparent graphene films were fabricated by vacuum filtration method and then patterned by conventional photolithography and subsequent O2-plasma treatment. Figure 1 (a) The effect of O2-plasma treatment on the resistivity and transparency of graphene films. Graphene films were treated with O2-plasma under a power ranging from 200 to 500 W between 1 and 5 min. (b) The changes of resistivity and transparency according to plasma treatment time at a power of 200 W. Figure 1 shows the effect of O2-plasma treatment on the resistivity and transparency of graphene films. The resistivity increased as the plasma power increased. When graphene films were treated at 100 W for 5 min and at 200 W over 3 min, it was impossible to measure resistivity as it was above the measurement range of the instrument (~100 MΩ). In addition, the transparency of graphene films increased as the power increased. As the results, an applied power of 200 W for 5 min was optimal for the patterning of graphene films. Figure 2Optimal images of the patterned graphene films under 200 W for 5 min. The scale bar represent 1 mm. The optical microscope images of the patterned graphene films on the PET flexible substrate are shown in Figure 2. The area patterned by O2-plasma treatment is more transparent than the area protected with the photoresist polymer. The clear patterns demonstrated the effectiveness of graphene patterning by this method. For a more detailed characterization, the morphological change of graphene films was investigated by scanning electronmicroscope (SEM) and atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used for the investingation of chemical property changes of graphene films. An electrochemiluminescence (ECL) reaction was carried out the patterned graphene films to confirm that it could function as a transparent electrode. For the ECL reaction, three electrode configuration was employed, consisting of the patterned graphene film serving as a working electrode, Ag/AgCl (3M NaCl) (a reference electrode), and platinum wire (a counter electrode). Red light is emitted on the graphene electrode surface without leakage, as shown in the line-scan of the chemiluminescent signal in Figure 3. This experiment indicates that the O2-plasma treatment can be successfully applied to pattern a graphene transparent electrode. We expect that this simple and versatile patterning technique will facilitate the fabrication of graphene film-based electronic of optoelectronic devices. Figure 3 (a) Luminescence image of the patterned graphene electrodes after the ECL reaction. The scale represents 300µm. (b) ECL line scan at the location indicated by the white line. References Tingting Feng et al., Materials Letters, 72 (2012) 187-189 Kwi Nam Han et al., Langmuir, 26 (2009) 598-602 Juali Zhang et al., ChemComm, 46 (2010) 1112-1114