HAuCl4 Solution Research Articles

Au/ZnO hybrid nanocomposites and their optical and photocatalytic properties

Au decorated zinc oxide nanorods have been synthesized by adopting a multistep chemical method. Initially the surface of synthesized nanorods have been functionalized by dipping the sample in potassium iodide solution and then Au nanoparticles were decorated on these rods by subsequent dipping in HAuCl4 solution. The size of Au particles and covering of ZnO nanorods by these particles were studied as a function of reaction time in the HAuCl4 solution. The photoluminescence spectra exhibit two emission bands at 371 and 575 that corresponds to the band edge emission and defect related emissions, respectively. The photocatalytic activity of the nanostructures that are prepared on the substrate has been tested for degradation of RhB by the illumination of ultra violet light on the nanostructures produced by commercially available lower power UV lamp.

Blood-brain barrier amenable gold nanoparticles biofabrication in aged cell culture medium.

Green fabrication of nanoscale materials is highly desirable because of associated adverse effects with conventional nanomaterial biomedical applications. Moreover, the higher selective nature of the blood-brain barrier (BBB) limits the brain ailments treatment through conventional chemotherapy, thus providing room for nanotechnology-based modalities for BBB traversing. In this contribution, we have biosynthesized gold nanoparticles from the HAuCl4 solution in the aged cells culture medium. This approach is highly facile without any other chemical utilization. The cell culture medium age and cell number can tune the Au nanoparticles (AuNPs) size from 2 to several hundred nm. The 24 h MTT assay and cell uptake studies in vitro and murine models' vital organs (liver, kidney, spleen, lung, and heart) study up to 48 h demonstrated that biosynthesized AuNPs were biocompatible and BBB amenable. Interestingly, the transferrin and cell culture medium isolated proteins were found factors responsible for HAuCl4 solution biomineralization and size control. Moreover, the protein corona on biosynthesized AuNPs could help them traverse BBB both in vitro and in vivo, suggesting their potential applications for brain disease theranostics. In conclusion, the biosynthesis of AuNPs from aged cells medium is highly facile, green, and biocompatible for brain disease theranostics.

Direct Investigation of Synthesis of Gold Nanoparticles Using Polyscias scutellaria Leaf Extract in the Hexane-Water System Using the Centrifugal Liquid Membrane-Spectrophotometry Method

The Centrifugal liquid Membrane (CLM) method, which provides an ultra-thin two-phase liquid membrane system in a rotating glass cell, was successfully applied to Green Synthesis from Polyscias scutellaria (PS) capped gold nanoparticles (AuNPs-PS) using a Mangkokan leaf (Polyscias scutellaria) extract as a reducing agent and stabilizer in the hexane-water system. PS extract in hexane fraction as the organic phase has a UV absorption spectrum at the maximum wavelength, λmax of 220 nm, while the precursor of HAuCl4 solution as an aqueous phase has an λmax of 214 nm. Investigation of AuNPs-PS formation was carried out at various concentrations of Mangkokan leaf extract concentration; i.e., 0.001 0.003; 0.005; 0.007 and 0.009%, while the reaction was carried out at various rotational speeds of 5,000-9,000 rpm. The formation and stability of AuNPs-PS were observed from the phenomenon of surface plasmon resonance (SPR) and absorbance changes as measured by a UV-Vis spectrophotometer. The results of measurements using CLM-Spectrophotometry shows the formation of AuNPs-PS in the hexane-water system at λmax of 534 nm.

Synthesis and Characterization of Gold Nanoparticles Using Trisodium Citrate as a Reductant

This research is an experimental study that aims to determine the characteristics of gold nanoparticles (Au-NPs) synthesized using trisodium citrate as a reducing agent. 0.4 mM HAuCl4 solution was synthesized using Na3C6H5O7 to convert Au3+ to Au0 with several variations of the reducing agent concentration, 3.5%; 5%; 6.5% and 8%. Determination of reaction time was measured using a UV-Vis spectrophotometer with time variations of 1, 5, 15, 30 and 45 minutes. Characterization of the size and lattice of Au-NPs crystals using X-Ray Difraction (XRD) and morphological characterization using Scanning Electron Microscopy (SEM). The results of the characterization, Au-NPs were produced blackish brown in color, and yields were 66.13%, 89%, 59.63% and 50.30% respectively for trisodium citrate reductant concentrations of 3.5%; 5%; 6.5% and 8%, with an average Au-NPs size of 46.97; 19.06; 50.03 and 39.68 nm, Face Centered Cubic (FCC) Crystal lattice and have a homogeneous morphology.

BIOSYNTHESIS AND CHARACTERIZATION OF GOLD NANOPARTICLES AND THEIR INTERACTION STUDY WITH METFORMIN

BIOSYNTHESIS AND CHARACTERIZATION OF GOLD NANOPARTICLES AND THEIR INTERACTION STUDY WITH METFORMIN. Synthesis of gold nanoparticles successfully carried using Imperata cylindrica L leaf extract. In this study, the approach used through green synthesis method is a reaction betwen of the HAuCl4 solution (concentration variation as 3; 5; 7 x 10-4 M) with Imperata cylindrica L leaf extract. Results of UV-Vis showed of gold nanoparticles has a maximum wavelength at 530 nm with absorbance value of 1.4. Results of FTIR shows a shift the absorption peak at wavenumber of 3392 cm-1 to 3404 cm-1. PSA and PZC showed the distribution of gold nanoparticles was 48.84 nm with a charge of 20.5 mV. Gold nanoparticles has a spherical shape and an average particle size of 20 nm which can be seen from the results of the characterization using TEM. XRD showed crystalize size average of gold nanoparticles as 20.47 nm. The interaction between of gold nanoparticles with metformin can be seen in the absorbance decrease of 0.38 at a wavelength of 531 nm and the results of PSA shows an average particle size of AuNPs@metformin is 122 nm. From the characterization data can be concluded the gold nanoparticles were successfully synthesized using natural bioreductors by utilizing secondary metabolites from Imperata cylindrica L leaf extract.

Preparation and Catalytic Property of Au-decorated Titanium Dioxide Dendritic Nanofibers

To remove organic pollutants from industrial wastewater, the Au-decorated titanium dioxide dendritic nanofibers (Au-Ti DNFs) were synthesized through in situ decoration of gold (Au) nanoparticles on the titanium dioxide dendritic nanofibers (Ti DNFs). The electrospun Ti NFs were firstly prepared by sol-gel method combined with electrospinning technology, then in situ converted to Ti DNFs in the NaOH solution via a hydrothermal route, and finally treated in the solution of HAuCl4.4H2O to produce Au-DTi NFs. SEM and TEM analyses showed that the Au-Ti DNFs had the dendritic and fibrous morphology and consisted of a large number of Au-Ti nanowires. 4-Nitrophenol was used as the model organic material to test the catalytic performance of Au-Ti DNFs. The results showed that Au-Ti DNFs catalytically reduced 4-nitrphenol to 4-amonphenol and their catalytic performance was higher than that of Ti DNFs due to the decoration of Au nanoparticles.

Gold Nanohelices: A New Synthesis Route, Characterization, and Plasmonic E-Field Enhancement.

Gold nanohelices (AuNHs) are synthesized using surfactant-assisted seed-mediated growth in an aqueous solution. AuNHs with diameters and lengths of 30–150 nm and several micrometers, respectively, are grown in a reaction carried out at 15 °C for 20 h by adding poly(ethylene glycol)(12)tridecyl ether, polyvinylpyrrolidone, and cetyltrimethylammonium bromide as the capping agents in an HAuCl4(aq) solution. With the addition of gold nanoparticles (AuNPs) in the reaction, the yield of the helical products is considerably increased, which indicates that AuNPs behave as the seeds for AuNH growth. The growth routes of AuNHs in the system are investigated by transmission electron microscopy measurements. Finite-difference time-domain (FDTD) simulations show that total extinction of the AuNH at 660 and 570 nm is dominantly influenced by strong e-field enhancement and the scattering of light incidence. In a practical application, surface-enhanced Raman scattering (SERS) measurements are conducted using AuNHs as the substrates and 4-mercaptobenzoic acid as the probe. A detection limit of 20 ppb is acquired using a micro-Raman spectrometer using a 633 nm He–Ne laser with a power of 3.35 mW which corresponds with the FDTD simulation results and reveals that AuNHs are superior SERS templates with resonance tuning ability in consequence of their unique helical architectures.

Synthesis of highly oriented WO3 nanowire bundles decorated with Au for gas sensing application

This study demonstrates the synthesis of self-assembled hexagonal WO3 nanowire bundles, with both ordered and random structures in the presence of SO42− ions, by a simple but efficient solvent-thermal method. The as-synthesized products are composed of hierarchical bundles with assembled ultrathin nanowire subunits. The growth and assembly mechanisms, regarding WO3 nanowire bundles, may be elucidated through oriented attachment or Ostwald ripening growth, based on a synergistic effect from both oxalic acid and ethylene glycol in dehydrating WO3·xH2O to WO3 nanocrystals and in controlling segregation behavior, along with high surface areas (18.4 m2 g-1 for ordered structures while 11.6 m2 g-1 disordered ones), which makes WO3 bundles great potential for gas sensing. To further enhance gas sensing, gold nanoparticles were chosen to deposit on the surface of WO3 nanowire bundles by acting with amino groups linked with WO3 bundles in the HAuCl4 solution with further oxidation. The Au-WO3 composites were examined towards various reducing gases, with exemplary sensitivities of (S = 127, 82), (S = 72, 52) towards n-butanol and acetone, respectively. The sensing mechanisms of such WO3 bundle structures are further understood in detail. This work will make the unique WO3 bundle nanostructures highly potential for gas sensing applications.

Rosin-based chiral wormlike Micelles: Rheological behavior and its application in preparing ultrasmall gold nanoparticles

Innovations in surfactant structures are a feasible way to prepare unique molecular aggregates with interesting properties. Herein, taking dehydroabietic acid as the starting material, a new amine oxide surfactant, abbreviated as R-8-AO, was synthesized. Cryogenic transmission electron microscopy (cryo-TEM) images and circular dichroism (CD) spectra reveal that at suitable concentrations, R-8-AO molecules form rarely discovered right-handed chiral wormlike micelles, which have a cross-sectional diameter of 5–6 nm. The overlap concentration of R-8-AO is approximately 8 mM, above which the wormlike micelles began to entangle in solutions. Due to the strong van der Waals forces between R-8-AO molecules, the scaling law gives an exponent of 7.88, which is higher than the theory predicted value. Gold nanoparticles were synthesized in-situ by irradiating mixed solutions of HAuCl4 and wormlike micelles formed by R-8-AO with UV light. These ultrasmall spherical gold nanoparticles, which are located at the surface of wormlike micelles, have a uniform particle size of 3 ± 1 nm, as observed by TEM. In addition, the gold nanoparticles form a worm-like morphology induced by the wormlike micelles, showing soft-aggregate-directed nanoparticle assembly. This work is first to reveal the effectiveness of preparing ultrasmall gold nanoparticles with new morphological wormlike micelles as soft templates. The resulting organic-inorganic hybrid aggregates are also expected to find applications in catalysis and electronic fields.

Experimental Investigations on Behaviour of Rhamnolipid Biosurfactant as a Green Stabilizer for the Biological Synthesis of Gold Nanoparticles

Use of biosurfactant as a stabilizer for the biological synthesis of gold nanoparticles (AuNPs) is now emerging as a nontoxic and environmentally acceptable green chemistry procedure. Stability of AuNPs at different pHs is very important because our body has different pHs. This paper addresses this issue. In this work, first P. aeruginosa PTCC 13401 was used to produce rhamnolipid biosurfactant. The highest rhamnolipid production occurred at 120 h, achieving a value of 3.1 g/L. The thin layer chromatography (TLC) indicated that the crude product is a mixture of mono-rhamnolipid and di-rhamnolipid with retardation factor (Rf) value of about 0.35 and 0.78, respectively. Moreover, rhamnolipid solutions with different pHs were added to HAuCl4 solution and incubated for 24 h at 37 oC and 150 rpm. The formation of spherical AuNPs was monitored using a UV–vis spectrophotometer and verified by TEM. Our results showed that the formation of AuNPs occurred just for pH values between 7.0 -8.0. Measurement of the surface tension of the solution at different pH values was performed to find out the reason for this observation. Our results showed that the surface tension was also stable only between pH 7.0-8.0. This was inferred from precipitation of rhamnolipid at higher and lower pH values. The results of this work may help pharmacists to have a good prediction of behavior of rhamnolipid biosurfactants as a stabilizer for biomedical applications including tissue engineering and drug delivery.

Bio fabrication of gold nanoparticles and their combination with chemotherapy and ultrasound for effective treatment of tumors

Chemotherapy is one of the important medical option for the cancer therapy, but still new combination of therapeutic treatment methods are needed to achieve efficient anti tumor activity. In this work, Pueraria lobata leaf extract was utilized as a bio reductant for the fabrication of the Gold nanoparticles (Au-NPs) by an ecological approach without using any harmful chemical. This work also evaluates whether the combined effect of chemotherapy along with Au-NPs and Ultrasound (US) is effective over the tumors or not. About 10 mL of plant extract was added to 1mM of HAuCl4 solution (20.0 mL) and pH was maintained at 12 and allowed for stirring for half an hour. The change in solution color from yellow to purple signified the Au-NPs formation. XRD results and TEM images confirmed the formation of crystalline Au-NPs with sizes ranging from 23-30 nm. Further, biological studies revealed that the combination of Au-NPs and US along with chemotherapy improved the impact of anti-cancer drug. In conclusion, Pueraria lobata leaf extract mediated synthesis of Au-NPs by an eco-friendly approach was reported in this work. The plant biomolecules of the extract were involved in the reduction and capping of the Au-NPs formed. The major conclusion is that addition of Au-NPs with chemotherapy and ultrasound has shown more effective anti-tumor activity.

A Smart Phosphine–Diyne Polymer Displays “Turn-On” Emission with a High Selectivity for Gold(I/III) Ions

A polymeric phosphine sensor is reported that exhibits bright blue fluorescence in the presence of gold(I/III) ions but is nonemissive with other metal ions. Specifically, solutions of a poly(p-arylenediethynylene phosphine) copolymer are 35 or 94 times more emissive when treated with solutions of (tht)AuCl or HAuCl4·3H2O, respectively. Model compound studies confirm phosphine coordination to metals, including gold(I/III) and rhodium(I), and the selective "turn-on" fluorescence was investigated using time-dependent density functional theory calculations.

Albumin-stabilized fluorescent metal nanoclusters: fabrication, physico-chemical properties and cytotoxicity

Fluorophores with a wide excitation range and the possibility of multicolor fluorescence are required for different applications such as sensing or multiplex analysis. Here we report about fluorescent Au, Cd and bimetallic Au-Cd nanoclusters (NCs) with sizes less than 1.6 nm fabricated and stabilized with bovine serum albumin (BSA). Based on mass spectrometry (MS) and energy-dispersive X-ray spectroscopy (EDX) data the average number of metal atoms per each BSA molecule was estimated to be 15 for BSA-Au NCs; 40 for BSA-Cd NCs; 9 atoms of Au and 26 of Cd for bi-metallic Au-Cd NCs. The NCs demonstrated large Stokes shifts of more than 130 nm. Fluorescence emission maxima for Au NCs at excitation wavelength of 325 nm were at 410 nm and 650 nm; for Cd NCs excitation at 370 nm resulted in the maximal emission at 500 nm, whereas for mixed Au-Cd NCs two peaks of emission were observed at 440 and 640 nm after excitation at 365–380 nm. For human cell lines HEp-2 and L41 both Au and Cd NCs in complex with BSA were less toxic compared to highly toxic original CdCl2 and HAuCl4 solutions. Protein nanoparticles (NPs) fabricated from BSA with metal NCs retained fluorescent properties.

Incorporation of Reduced Graphene Oxides for Enhancing the Gas Sensing Characteristics

Incorporation of Reduced Graphene Oxides for Enhancing the Gas Sensing Characteristics

Deposition of Gold Nano-Micro Islands on Electrochemically Reduced Graphene Oxide to Use in Combination with Molecularly Imprinted Polymers

Molecularly imprinted polymers (MIPs) are known as an alternative for antibodies in immunosensors with high stability and low production cost. MIP approach relies on polymerization in the presence of a template molecule and subsequent template removal. In this process, the template molecule is exactly the same as the target molecule leading to a good selectivity for the biomimetic sensor [1]. The integration of MIPs with nanomaterials enables ultrasensitive sensors for various analytes. Besides, nanomaterials with uniform distribution and suitable morphology provide a wide linear range of detection for the sensor [1]. In particular, the controlled electrodeposition of gold can supply gold nano-micro islands (NMIs) with remarkable electrochemical behavior and high active surface area [2, 3]. However, it is found that the modification of an electrode surface using electrochemically reduced graphene oxide (ERGO), as a facile and fast method, not only increases the surface area but also improves its electrochemical behavior [4]. Herein, we describe a surface modification strategy based on indium tin oxide (ITO) electrode coated with ERGO to increase the surface active sites for nucleation and deposition of NMI. For this aim, we electrochemically reduced graphene oxide (GO) by one cycle in cyclic voltammetry (CV) with a scan rate of 100 mV s-1 in the range of -0.6 to -2 VAg/AgCl. The succeed of the electrochemical reduction was confirmed through ID/IG ratio in Raman spectroscopy and observing the enhanced electrochemical behavior in CV and electrochemical impedance spectroscopy (EIS) tests. The gold layers were deposited at 0 and -0.4 VAg/AgCl in 5, 50 and 100 mM HAuCl4 solutions for 50 and 300 s. The surface area of the resulted structures was also determined by integrating the reduction peak in CV tests in 50 mM H2SO4 solution [2]. The results showed that the gold structure deposited from 100 mM HAuCl4 at 0 VAg/AgCl for 50 s provided a significant surface area (0.47 cm2) on the electrode surface of 1 mm diameter, while this value for gold nanoparticles, as the common form of gold nanostructure in electrochemical biosensing, was determined only 0.063 cm2. This noticeable increase in surface area can result in a wide linear range of detection as well as excellent electrochemical behavior in biosensing applications. Scanning electron microscopy (SEM) of NMI structures deposited on both ITO and ERGO/ITO electrodes indicated a shrub-like structure because of the concentration polarization governed during gold deposition. Transmission scanning electron microscopy (TEM) of the NMI displayed Au (113) as the main crystalline plane. Based on the chronoamperometry plots, the gold deposition mechanism on the surface of both electrodes was according to the instantaneous deposition mode [2]. However, the electrode background surface indicated that the ERGO/ITO was uniformly covered by gold. This was attributed to the higher nucleation sites on the ERGO-modified electrode, which was confirmed by the increase of double-layer formation time (tmax). Accordingly, several nucleation stages on the chronoamperometry plot during NMI deposition on the ERGO/ITO electrode, were related to the formation of gold shrub-like structures with more needle-shaped structures. Finally, electropolymerization of a thin layer of o-phenylenediamine in the presence of Heart-fatty acid binding protein (H-FABP) as the template molecule and its subsequent removal was applied to make a biomimetic sensor. In this study, we demonstrated that the biomimetic developed electrode with high surface area, low production cost, and facile and fast synthesis method is acceptably selective to H-FABP against other cardiac biomarkers and serum proteins.KEYWORDS: Electrodeposition; Electrochemically reduced graphene oxide; Electrochemical sensors; Gold nano-micro islands; Molecularly imprinted polymers.

Green synthesis of non-spherical gold nanoparticles using Solidago canadensis L. extract

In the present article, we reported the application of the extract of leaves from Solidago canadensis L. for the green synthesis of triangular and hexagonal gold nanoparticles (AuNPs). The phytochemical characterization, by reaction with HAuCl4 solutions, showed that the extract of Solidago canadensis L. contained the secondary metabolites that can act both as reducing and as stabilizing agents. For the synthesis of AuNPs, the effects of the HAuCl4 concentration (0.25–0.975 mM) and the reaction time (10–180 min) were investigated. The formation of AuNPs is confirmed by the color change from yellowish to purple-red. Photoluminescence measurements of Au nanocolloids showed a continuous emission band ranging from violet to red. UV–Vis characterization of AuNPs in the prepared nanocolloids showed surface plasmon resonance peaks at 530 and > 870 nm. TEM revealed that the AuNPs are in the range of 8–200 nm, they have spherical, triangular, and hexagonal forms of varying sizes. AFM and STM showed a non-ideal relief of large triangular and hexagonal gold nanoprisms. The EDX analysis, XRD and SAED patterns confirmed the face-center cubic structure of AuNPs.

The morphology regulation and plasmonic spectral properties of Au@AuAg yolk-shell nanorods with controlled interior gap.

Au@AuAg yolk-shell nanorods with tunable and uniform interior gap were synthesized through galvanic replacement reaction, where Au@Ag core-shell nanorods served as sacrificial templates and HAuCl4 solution served as reductant. The effects of HAuCl4, Ag shell thickness and aspect ratio (AR) of Au nanorods on the morphology of Au@AuAg yolk-shell nanorods had been investigated systemically. The results clearly indicated that AuAg alloy shell thickness of Au@AuAg yolk-shell nanorods could be increased from 3.6 to 10.0nm by varying the amount of HAuCl4. Meanwhile, the shape of AuAg alloy shell could be tuned by changing the shape of Ag coating. With the increasing of Ag coating thickness, the interior gap could be finely tuned in the range from 2.6 to 8.1nm. The uniformity of interior gap could be improved by increasing the AR of Au nanorods. All these tunable geometries can further affect the plasmonic spectral properties of Au@AuAg yolk-shell nanorods. Because of the appearance of interior gap, the longitudinal localized surface plasmon resonance (LSPR) peak of Au@AuAg yolk-shell nanorods was located between that of bare Au nanorods and Au@Ag core-shell nanorods without interior gap. The increase of outer AuAg shell thickness can weaken the coupling between the inner and outer surface of the AuAg shell and lead to the decrease of AR, so the transverse and longitudinal LSPR bands gather together. The decrease of Ag coating thickness can enhance the coupling between inner Au nanorod and outer AuAg shell, which results in the red shift of the longitudinal LSPR band. This paper provides a method for studying the plasmonic coupling between two metal surfaces with a metal layer or a dielectric layer, which is also a new approach for regulating the plasmonic spectral properties of bimetallic nanoparticles. The controllability of Au@AuAg yolk-shell nanorods in both the interior gap and outer alloy shells makes them have potential applications in biomedicine, catalysis, nanoreactors, and energy storage.

Gold Nanoparticle Functionalized Mesoporous Silica-Chitosan as Efficient and Recyclable Catalyst for the Green One-Pot Synthesis of 4H-pyran Derivatives in Aqueous Medium

Gold nanoparticle functionalized mesoporous silica-chitosan (Au NPs/silica-chitosan) as an environmentally benign and heterogeneous nanocatalyst was prepared and its properties were characterized using field emission scanning electron microscopy (FE-SEM) and fourier transform infrared (FT-IR). The catalytic activity of Au NPs/silica-chitosan was studied in the synthesis of biologically important 4H-pyran derivatives. In these reactions, efficient and green syntheses of 4H-pyrans were carried out using isatins or aldehydes, active methylene compounds, and 1,3-dicarbonyl compounds in the presence of a catalytic amount of Au NPs/silica-chitosan in water in excellent yields. Au NPs/silica-chitosan can be recovered easily and reused without any significant loss of the catalytic activity. 4H-pyran derivatives were synthesized using Au NPs/silica-chitosan as catalyst in three component reaction of isatins/aldehydes, active methylene, and 1,3-dicarbonyl compounds in water. Au NPs/Silica-Chitosan was prepared by reaction of aqueous solution of HAuCl4 (1 wt.%) and solution chitosan in deionized water and acetic acid with tetraethyl ortho silicate (TEOS) at 100ºC for 24 h. Gold nanoparticle functionalized mesoporous silica-chitosan was prepared and its catalytic activity was investigated for forming 4H-pyran derivatives. In this study, active methylene and 1,3-dicarbonyl compounds reacted with various isatins and aldehydes which afforded the corresponding spirooxindoles with 88-98% yields. This method includes the environmentally friendly reaction conditions, short reaction time, simple work-up, excellent yield, broad scope of usable substrates, recovery and reusability of heterogeneous catalyst.

Citrate-driven modification of gold on titanium wire electrodes by the treatment in aqueous solutions of HAuCl4

The modification of titanium (Ti) wire with gold was explored using a simple treatment of Ti wire in aqueous solutions of HAuCl4. Just immersing Ti wire in the solutions of HAuCl4 could not modify Au on Ti, which was confirmed by observing cyclic voltammograms (CVs) of ferrocyanide using the treated Ti wire as a working electrode. However, the addition of trisodium citrate into aqueous solution of HAuCl4 was found to promote the Au modification of Ti wire showing sigmoidal CV responses of ferrocyanide. The modified states of Au on Ti were discussed based on the electrochemical responses. While our trial was initiated seeking possibilities of easier preparations, the pre-etching of Ti wire with HCl was clarified to be effective to promote the modification of Au on Ti. Consequently, we could observe the electrocatalytic properties for the oxidations of uric acid, ethanol and glucose depending on the degrees of Au modification of Ti. Because unmodified Ti wire electrodes were electrochemically silent for these species, the simple treatments of Ti wire in aqueous solutions containing both HAuCl4 and trisodium citrate were clarified to be effective for the preparation of Au nano-elecctrode ensembles and Au-like electrodes on Ti wire bases.

Doped Poly(3-hexylthiophene) Coatings onto Chitosan: A Novel Approach for Developing a Bio-Based Flexible Electronic.

Conductive and flexible bio-based materials consisting of chitosan films coated with conductive poly(3-hexylthiophene) (P3HT) were prepared. Thermal, optical, mechanical, morphological, wettability, and conductive properties were analyzed. In a very simple and effective method of chitosan film modification, a controlled volume of a P3HT solution was deposited onto a previously formed chitosan film, assisted by the spin coating method. Later, P3HT-coated chitosan films were doped by simple contact with an aqueous solution of HAuCl4. The use of HAuCl4 becomes attractive because the reports on the doping process in this type of material using this reagent are still scarce and recent to date. In addition, since this acid is a well-known metal nanoparticle precursor, its use opens new future perspectives for these materials into new applications. The effect of P3HT concentration and doping times on film properties was studied. Attenuated total reflectance spectroscopy and UV-Vis spectroscopy allowed us to demonstrate that the presence of the P3HT coating and its doping induce significant changes in the vibrational modes and optoelectronic properties of samples. Additionally, the images obtained by scanning electron microscopy showed a well-distributed and homogeneous coating on the surface of chitosan films. Measured conductivity values of doped film samples fall in the range from 821.3 to 2017.4 S/m, representing, to the best of our knowledge, the highest values reported in the literature for chitosan/chitin-based materials. Indeed, these values are around or even higher than those obtained for some materials purely consisting of conductive polymers.