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We demonstrate the deposition of films of the conducting charge transfer complex TTF-TCNQ from solution by spray-coating. The benefit of spray-coating is the ability to process large volumes of solution, therefore allowing the utilisation of compounds with very low solubility. The sheet resistance in the TTF-TCNQ film is similar to that of the commonly used organic PEDOT:PSS electrodes, with the added benefit of room temperature deposition and no additional thermal treatments. Spray-coated TTF-TCNQ is used as source and drain electrodes for transistors based on the organic semiconductor C8-BTBT, achieving similar performances in terms of mobility and turn-on voltage than when conventional contacts of MoO x /Au are used, whilst exhibiting a slight improvement in the linearity of the output characteristics. [ABSTRACT FROM AUTHOR]

Organic charge-transfer complex tetrathiofluorene-7,7,8,8-tetroquinolinedimethane (TTF-TCNQ) is applied as cathode material in aqueous zinc ion battery (AZIBs). Ionic storage behavior of TTF–TCNQ complex is systematically investigated from 25 ℃ to −40 ℃. Due to the high conductivity, TTF-TCNQ complex shows much better rate and cycle performance than each single-moiety counterpart. [Display omitted] • TTF-TCNQ is applied as a novel organic electrode material in aqueous zinc ion batteries. • TTF-TCNQ complexes exhibit higher ionic diffusivity than each single-moiety counterpart in zinc storage systems, especially at low temperatures. • TTF-TCNQ//Zn battery shows high cycle stability of capacity retention rate of 74% at a current density of 1A g−1 after 500 cycles and excellent rate performance of specific capacity of 123.3 mAh/g at a current density of 3A g−1 at −20℃. • Advanced characterizations find that N C- and C S groups are the reaction centers and morphology and crystal structure of TTF-TCNQ are highly reversible. Charge-transfer organic materials are molecular metallic materials with high electronic conductivity, but their potential in rechargeable batteries, especially at low temperatures, has not been investigated. In this work, micro-structured organic charge-transfer complex tetrathiofluorene-7,7,8,8-tetroquinolinedimethane (TTF-TCNQ) is applied as cathode material in aqueous zinc-ion batteries (AZIBs). Ionic storage behavior of TTF–TCNQ complex is systematically investigated from 25 ℃ to −40 ℃. Owing to higher electrical conductivity and higher ionic diffusivity in ionic storage, smaller charge transfer resistance, and lower activation energy, TTF-TCNQ shows much superior rate and cycling performance than each single-moiety counterpart, especially at low temperatures. Reaction mechanism is explored by ex-situ X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier Transform infrared spectroscopy (FT-IR) and in-situ Raman technologies, confirming that C N and C S groups are the redox centers and the redox reaction is highly reversible. Our research not only provides a new type of choice for AZIBs at low temperatures, but also greatly broads the application field of charge-transfer complexes. [ABSTRACT FROM AUTHOR]

Pressure is a powerful tool to unveil the profound nature of electronic properties in a variety of organic conductors. Starting from technology of high pressure, we plan to review what kind of physics or phenomena have previously been discussed.

A conducting thin layer of aligned fibrous nano-crystallites of tetrathiafulvalene–7,7,8,8,-tetracyanoquinodimethane (TTF–TCNQ) is fabricated directly on semiconducting organic crystals under ambient conditions. The widths of the crystallites are 50–100 nm. Their growth direction is governed by the direction of the intermolecular charge transfer interactions in the substrate crystal. The carrier transport in the film is metallic between 150 K and 300 K, reflecting the uniform alignment of the TTF–TCNQ nano-crystallites on the substrate crystal. [ABSTRACT FROM AUTHOR]

We present results on the formation of thin films of the charge transfer salts tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) prepared by physical vapor deposition on several substrates in a high vacuum. We mainly investigate the influence of the substrate materials and surface structures on the surface morphology of the thin films. The obtained results show that the surface structure of the substrate has a stronger influence on the film morphology than that of the material. In particular, we report the influence of surface nano-structure on the growth mode of TTF–TCNQ. The flat TTF–TCNQ thin films were continuously grown on both 2° off-SiO2/Si(111) and NaCl(100) substrates. The maximum conductivities of the films grown on 2° off-SiO2/Si(111) and NaCl(100) were 0.4 and 4Ω−1 cm−1, respectively. With a CaF2 substrate, a large number of TTF–TCNQ nano-scale ribbon-like crystals grew on the as-deposited CaF2/CaF2(110) substrate. This indicates that we could realize a TTF–TCNQ adsorption site by depositing CaF2. [ABSTRACT FROM AUTHOR]

Tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) single crystal was prepared by a solution technique and studied by Raman spectra in the aspects of temperature dependence, polarised Raman spectra and the polarised Raman scattering anisotropy. Raman properties of TTF-TCNQ depend strongly on the temperature as the intensities of Raman scattering increase significantly with the decreasing of the temperature. Highly polarised Raman scattering anisotropy was found in the TTF-TCNQ single crystal, and this is caused by the dielectric properties of the crystal. The dielectric circumstance of the crystal leads to the reduction in the parallel field component inside the crystal; thus, the A(z) mode cannot be excited when the incident light polarised parallel to the b axis of the TTF-TCNQ single crystal. [ABSTRACT FROM AUTHOR]

We herein report on the electrocatalytic activity towards the oxidation of NADH of a PVC/TTF-TCNQ composite electrode modified with gold nanoparticles. This electrocatalytic property allows proposing this system as a new alternative for amperometric determination of NADH, without need to add another mediator. The sensor shows a linear response to NADH over a concentration range from 5.0×10−6 M up to 5.0×10−4 M, with a sensitivity of 11.22±0.5 mA M−1 and a detection limit ( S/N=3) of 4.0×10−6 M for measurements in batch and similar data in FIA. [ABSTRACT FROM AUTHOR]

Abstract: The electron transfer mechanism in enzymatic electrodes employing tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) complex is despite of numerous publications, still a matter of controversy. To clarify this issue, enzymatic electrodes based on TTF, TCNQ and TTF–TCNQ have been prepared in an identical manner and their electrochemical behavior and activity have been tested. The enzymatic electrodes containing the respective mediator, glucose oxidase and Vulcan nanoparticles dispersed in a gelatin matrix show high activity for glucose oxidation in terms of both currents and oxidation onset potential. The observed electrochemical features, supported by infrared spectroscopy measurements, indicate that the activity of the TTF–TCNQ electrodes can be ascribed to TTF and TCNQ species released from the organic salt. The two mediators are active in different potential regions, implying an alternating electron transfer mechanism. TTF is active at more negative potentials and generates higher current densities, while TCNQ exhibits activity only at potentials more positive than 0V vs. SCE. This work analyzes and summarizes different aspects of the most recent electron transfer hypotheses by providing the respective experimental evidences in an effort for better understanding of this puzzling bioelectrochemical system. [Copyright &y& Elsevier]

Pressure is a powerful tool to unveil the profound nature of electronic properties in a variety of organic conductors. Starting from technology of high pressure, we plan to review what kind of physics or phenomena have previously been discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we investigate the influence of the substrate material and film thickness on the Peierls transition temperature in tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) thin films, grown by physical vapor deposition. Our analysis shows that the substrate material and the growth conditions strongly influence the film morphology. In particular, we demonstrate that the Peierls transition temperature in thin films is lower than in TTF–TCNQ single crystals. We argue that this effect arises due to defects, which emerge in TTF–TCNQ thin films during the growth process. [Copyright &y& Elsevier]

Abstract: Thin films of tetrathiofulvalene–tetracyanoquinodimethane (TTF–TCNQ), a typical organic material of charge transfer salts, were prepared on glass substrates by evaporation using TTF–TCNQ powder. The rubbing effect on the surface morphology and thermoelectric properties was studied. TTF–TCNQ films exhibited a bush-like disordered growth on the as-received glass substrate, whereas those on the rubbed glass substrate had extremely flat surfaces tiled with small rectangular TTF–TCNQ single crystals. Due to the ordered alignment of TTF–TCNQ tiles, improvement in the electrical conductivity and enhancement of the Seebeck coefficient were achieved. [Copyright &y& Elsevier]

Abstract: A comparison of the analytical performances of several enzyme biosensor designs, based on the use of different tailored gold nanoparticle-modified composite PVC/TTF-TCNQ electrodes, is discussed. The analytical characteristics of glucose calibration plots and kinetic parameters of the enzyme reaction were compared for the biosensors tested: Aucoll +GOx, GOx+Aucoll, Mixed GOx+Aucoll and PVC/TTF-TCNQ-Aucoll. The presence of this nanomaterial enhances the analytical performance with respect to the precursor biosensor without Au. The proposed biosensor can be applied in batch (response linear up to 2.0mM, sensitivity of 45±0.5mAM−1 with a limit of detection, s/n =3, of 6.2×10−6 M) and in FIA systems (linear range between 0.1 and 8mM, sensitivity of 3.67±0.3mAM−1 with a limit of detection, s/n =3, of 1.9×10−5 M). [Copyright &y& Elsevier]

Abstract: A simple and effective amperometric biosensor based on PVC/TTF–TCNQ composite electrode is proposed for glucose determination. Glucose oxidase (GOx) was immobilized by crosslinking with glutaraldehyde. The TTF–TCNQ salt acts as a conducting phase and as a redox mediator, without needing the addition of any other substance. The biosensor can be applied in batch (response linear up to 5.0mM, with a limit of detection, s/n =3, of 8.5×10−6 M) and in FIA systems (linear range between 0.1 and 8.0mM, with a limit of detection, s/n =3, of 1.9×10−5 M). It is also proposed a simple procedure that allows glucose and ascorbic acid to be simultaneously determined. [Copyright &y& Elsevier]

A derivative of EDT-TTF (ethylenedithio-tetrathiafulvalene) with decylphosphonic acid was prepared and formed as its self-assembled monolayer (SAM) on the surface of indium-tin oxide (ITO) glass. The formation of the SAM was characterized by UV–vis and micro-Raman spectroscopies, cyclic voltammetry and atomic force microscopy. Cyclic voltammetry of the surface-modified ITO (SM-ITO) electrode showed two reversible peaks at E1/21 = 0.658V and E1/22 = due to the redox processes of EDT-TTF moiety on the SAM. Cyclic voltammogram of TCNQ (7,7,8,8-tetracyanoquinodimethane) with the SM-ITO electrode shows two redox couples, one at E1/21 = 0.287V corresponding to the TCNQ/TCNQ·- process and the other at E1/22 = 0.963V corresponding to the [EDT-TTF]/[EDT-TTF]·+ one. [Copyright &y& Elsevier]

An amperometric biosensor has been developed for measurement of Umami, or the taste based on the amount of l-glutamate, in tomato foods. The biosensor is based on an enzyme-mediator system in which l-glutamate oxidase is used for biochemical oxidation of l-glutamate and a tetrafulvalene-tetracyanoquinodimethane (TTF-TCNQ) paste, prepared from the mixture of TTF-TCNQ salt, graphite powder, and silicone oil, serves as the mediator. The limit of detection, calculated by use of a four-parameter logistic model, was 0.05 mmol L−1, and the limit of quantification was 0.15 mmol L−1. The correlation coefficient ( R 2) was 0.990 and the relative standard deviation was no more than 1% ( n=5). The response time ( τ 95) was 20–50 s, depending on concentration. The repeatability of the sensor was better than 5% ( n=10). The sensor developed was stable for more than ten days. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Background: GSH has a relevant role in human metabolism as an indicator of disease risks. An amperometric sensor for glutathione (GSH) determination is described as an alternative method featuring simple construction procedure and short time analysis. Method: The developed sensor was used to determine glutathione at low potential using a TTF–TCNQ complex. Results: The sensor exhibits a linear response range from 5 to 340 μmol/l under applied potential of 200 mV vs. SCE. The sensitivity and detection limit were 90.1 μA l/mmol cm2 and 0.3 μmol/l, respectively. Conclusion: When the sensor was tested in hemolysed erythrocyte samples for GSH determination, a good correlation in results was observed between the sensor and the spectrophotometric method. The sensor showed recovery values between 98% and 102%. [Copyright &y& Elsevier]

The elastic response of molecular organic materials to external mechanical nanoindentations in the nano- and low micronewton force range can be characterized using ultrasharp cantilever tips of an Atomic Force Microscope (AFM). Because clear distinction between elastic and plastic deformation is achieved, the maximal accumulated elastic energy can be directly determined from the force vs. penetration curves, giving an estimate of the characteristic energies of the materials. [ABSTRACT FROM AUTHOR]

The development of an amperometric sensor for the determination of reduced glutathione (GSH) is described. The sensor is based on tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) incorporated into the graphite powder/Nujol oil matrix. The electrooxidation of GSH was monitored amperometrically at 200 mV versus SCE (saturated calomel electrode). The amperometric response of the sensor was linearly proportional to the GSH concentration between 20 and 300 μmol l-1, in 0.1 mol l-1 phosphate buffer (pH 8.0), containing 0.1 mol l-1 KCl and 0.5 mmol l-1 Na2H2EDTA, as supporting electrolyte.The detection limit, considering signal/noise ratio equal three, was 4.2 μmol l-1 for GSH and the repeatability obtained as relative standard deviation was of 5.1% for a series of 10 successive measurements. [Copyright &y& Elsevier]

TTF–TCNQ is a one-dimensional charge transfer compound. Charge density wave (CDW) transition occurs at 54 K in TTF–TCNQ, and CDW presents three phases: high temperature commensurate phase (T>49 K; 2a×3.39b); inter-mediated incommensurate phase (T=38–49 K; μa×3.39b) and low temperature commensurate phase (T<38 K; 4a×3.39b). In this report, we present our experimental result on cleaved (0 0 1) surfaces of TTF–TCNQ with UHV–LT–STM (Omicron LTSTM). For a broad temperature range (33–100 K), molecular resolution of TTF–TCNQ has been obtained. Below 54 K an additional two-dimensional superstructure of CDW appears in our images. The ordering of CDW modulation both along a and b direction are first revealed by our STM measurement. Our result shows that, on (0 0 1) surface of TTF–TCNQ, C–I–C CDW phase transition persists in nanometer scale and C–I–C transition is homogeneous. The determination of local CDW phase shift will be presented in this report too. At high temperature (60–280 K), we observed a v-shape pseudo-gap. The pseudo-gap and Peierls-gap co-exist at low temperature. [Copyright &y& Elsevier]

We present recent results on the characterization of highly ordered polycrystalline thin films of the charge transfer salt TTF–TCNQ (TTF=tetrathiafulvalene, TCNQ=tetracyanoquinodimethane) prepared by thermal sublimation in high vacuum under different conditions. The increase in orientation and microcrystal size as a function of substrate and annealing temperatures is addressed. A consequence of such an increase is the reduction of the conductivity activation energy, which eventually leads to the observation of the Peierls transition by resistivity measurements. X-ray absorption near edge spectroscopy studies performed with synchrotron radiation reveal directly the influence of charge transfer on unoccupied states near the Fermi level. [Copyright &y& Elsevier]

A format for a disposable screen-printed biosensor was investigated for monitoring formaldehyde. The screen-printed sensor format comprised a working electrode (WE) modified with platinised carbon, a new lipophilic tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) salt as mediator, a plasticised polyurethane membrane (TECOFLEX SG80, PU) with anionic sites and the enzyme (formaldehyde dehydrogenase FOH) and co-factor (β-NAD+). The new lipophilic TTF-TCNQ salt gave a smooth, robust electrode surface rather than microcrystalline deposits of the salt observed with TTF-TCNQ salts. Entrapment of the enzyme and co-factor behind a plastcised PU membrane with anionic sites enhanced the sensitivity and stability of the sensor. A linear response between 10−3 and 10−4 mol dm−3 was observed. To demonstrate the feasibility of the use of the screen-printed sensor to monitoring formaldehyde in ambient air, preliminary experiments were carried out in the vicinity of a local medium density fibreboard factory and its performance compared to that of a biosensor made from the same platinised carbon and enzyme system, but without the lipophilic TTF-TCNQ and membrane, using a commercial ‘Rank’ cell. Samples were collected using a Molspin ‘Super-sniffer’. [Copyright &y& Elsevier]

Abstract: Temperature dependence of the resistivity of TTF–TCNQ along the b-(1D)- and a-axes was studied under hydrostatic pressure up to 8GPa. A striking contrast was seen between the b-(1D)- and a-axes in the power-law dependence of resistivity ρ=ρ 0 T α in the metallic region as well as the activation energy in the charge density wave (CDW) insulating state. We note that the careful terminal configuration is essentially important to obtain these properties. [Copyright &y& Elsevier]