Room Temperature Electrochemical Synthesis of Crystalline GaOOH Nanoparticles from Expanding Liquid Metals

Gallium oxyhydroxide (GaOOH) is a wide band gap semiconductor of interest for a variety of applications in electronics and catalysis where the synthesis of the crystalline form is usually achieved via hydrothermal routes. Here we synthesize GaOOH via the electrochemical oxidation of gallium based liquid metals in solutions of 0.1 M NaNO3 electrolyte with pH adjusted over the range of 7–8.4 with NaOH. This electrochemical approach employed under ambient conditions results in the formation of crystalline oblong shaped α-GaOOH nanoparticles from both liquid gallium and liquid galinstan which is a eutectic based on Ga, In, and Sn. The size and shape of the GaOOH particles could be controlled by the solution pH. The product is characterized with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–visible spectroscopy, and photoluminescence spectroscopy. During the electrochemical oxidation process, the liquid metal drop was found to expand significantly in the case of galinstan due to a constant electrowetting effect which resulted in the continuous expulsion of nanomaterial from the expanding liquid metal droplet. This electrochemical approach may be applicable to other liquid metals for the fabrication of metal oxide nanomaterials and also demonstrates that significant chemical reactions may be occurring at the surface of liquid metals that are actuated under an applied electric field in aqueous electrolytes

Electrochemical restructuring of Gold electrodes with redox active species to create electrocatalytically active nanostructured surfaces

Electrochemical potential cycling of gold electrodes in commonly used redox active species to produce a nanostructured surface is introduced. A commercially available gold electrode when cycled in three redox active species including hexaammine ruthenium chloride, ferrocene methanol and ferricyanide shows rapid conversion of the surface into a nanostructured form within 50 cycles which usually requires hundreds of cycles in their absence. The active gold nanostructured electrode was characterized by cyclic voltammetry in acidic and alkaline electrolyte indicating the presence of different basal sites depending on the redox species employed. In addition, the active gold nanostructured surface shows higher electrocatalytic activity than the pristine polycrystalline gold electrode for glucose and ascorbic acid oxidation in alkaline media.</p

Chemical reactivity of Ga-based liquid metals with redox active species and its influence on electrochemical processes

Room temperature liquid metals based on gallium demonstrate interesting physical and chemical properties when placed in electrochemical environments. In this work we explore the applicability of hanging liquid metal droplets as electrode materials for simple surface insensitive and surface sensitive electron transfer reactions, namely the electrochemical reduction of [Ru(NH3)6]3+ and [Fe(CN)6]3− ions in solution. Significantly we found that for both redox species the electron transfer process was impeded at galinstan (68.5% Ga, 22.5% In and 10% Sn). This is related to the chemical reactivity of the Ga component which is oxidised when exposed to aqueous solutions of [Ru(NH3)6]3+ and [Fe(CN)6]3− to generate the reduced form of the redox mediator. For the former this results in the production of Ru-red and Ru-brown cationic trimers in solution as well as gallium oxide on the surface of the liquid metal, and in the latter case the formation of solid Prussian Blue

Utilising solution dispersed platinum nanoparticles to direct the growth of electrodeposited platinum nanostructures and its influence on the electrocatalytic oxidation of small organic molecules

Highlights - The presence of Pt nanoparticles in solution influences the electrodeposition of Pt. - Nanostructured Pt with different exposed crystal facets are formed in the presence of Pt nanoparticles. - Enhanced electrocatalytic activity is found for nanostructures created using Pt nanoparticles in solution. Abstract The electrodeposition of platinum nanostructures on glassy carbon electrodes in the absence and presence of platinum nanoparticles in the electrolyte is reported. It is found that the presence of platinum nanoparticles has a significant influence of the morphology of the platinum electrodeposited onto the electrode surface. Even though the morphology of the materials is affected, the overall surface area is similar. The electrochemical behaviour of the platinum nanostructures is investigated in 1 M H2SO4 where distinct differences are observed in the exposed surface sites for platinum electrodeposited in the presence of nanoparticles. The influence of these surface sites is then studied for a variety of electrocatalytic reactions such as methanol and ethylene glycol oxidation and the hydrogen evolution reaction. In the case of organic molecule oxidation reactions, the platinum structures created using platinum nanoparticles in the electrodeposition solution exhibited earlier onset potentials and increased current densities compared to those that were electrodeposited in their absence

Directing nanostructure formation of gold via the in situ under potential deposition of a secondary metal for the detection of nitrite ions

In this work the underpotential deposition of metals such as copper and lead during the electrochemical deposition of gold is investigated to understand the influence that the incorporation of a second metal has on the morphology of gold nanostructures. The incorporation of Pb or Cu, even at concentrations as low as 0.2 %, significantly influence the morphology of the deposit where the formation of elongated structures from a central gold structure is favoured. These nanostructures are characterised by cyclic voltammetry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) and tested for their suitability as a sensing layer for the electrochemical detection of nitrite ions in aqueous solution. A limit of detection of 0.3 µM is achieved with a linear range up to 1 mM which is adequate for the determination of nitrite contained within food products

Molecularly Imprinted Polymer-Amyloid Fibril-Based Electrochemical Biosensor for Ultrasensitive Detection of Tryptophan

A tryptophan (Trp) sensor was investigated based on electrochemical impedance spectroscopy (EIS) of a molecularly imprinted polymer on a lysozyme amyloid fibril (MIP-AF). The MIP-AF was composed of aniline as a monomer chemically polymerized in the presence of a Trp template molecule onto the AF surface. After extracting the template molecule, the MIP-AF had cavities with a high affinity for the Trp molecules. The obtained MIP-AF demonstrated rapid Trp adsorption and substantial binding capacity (50 &micro;M mg&minus;1). Trp determination was studied using non-Faradaic EIS by drop drying the MIP-AF on the working electrode of a screen-printed electrode. The MIP-AF provided a large linear range (10 pM&ndash;80 &micro;M), a low detection limit (8 pM), and high selectivity for Trp determination. Furthermore, the proposed method also indicates that the MIP-AF can be used to determine Trp in real samples such as milk and cancer cell media

Room Temperature Electrochemical Synthesis of Crystalline GaOOH Nanoparticles from Expanding Liquid Metals

Gallium oxyhydroxide (GaOOH) is a wide band gap semiconductor of interest for a variety of applications in electronics and catalysis where the synthesis of the crystalline form is usually achieved via hydrothermal routes. Here we synthesize GaOOH via the electrochemical oxidation of gallium based liquid metals in solutions of 0.1 M NaNO₃ electrolyte with pH adjusted over the range of 7–8.4 with NaOH. This electrochemical approach employed under ambient conditions results in the formation of crystalline oblong shaped α-GaOOH nanoparticles from both liquid gallium and liquid galinstan which is a eutectic based on Ga, In, and Sn. The size and shape of the GaOOH particles could be controlled by the solution pH. The product is characterized with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–visible spectroscopy, and photoluminescence spectroscopy. During the electrochemical oxidation process, the liquid metal drop was found to expand significantly in the case of galinstan due to a constant electrowetting effect which resulted in the continuous expulsion of nanomaterial from the expanding liquid metal droplet. This electrochemical approach may be applicable to other liquid metals for the fabrication of metal oxide nanomaterials and also demonstrates that significant chemical reactions may be occurring at the surface of liquid metals that are actuated under an applied electric field in aqueous electrolytes

Fingerprinting green curry:An electrochemical approach to food quality control

The detection and identification of multiple components in a complex sample such as food in a cost-effective way is an ongoing challenge. The development of on-site and rapid detection methods to ensure food quality and composition is of significant interest to the food industry. Here we report that an electrochemical method can be used with an unmodified glassy carbon electrode for the identification of the key ingredients found within Thai green curries. It was found that green curry presents a fingerprint electrochemical response that contains four distinct peaks when differential pulse voltammetry is performed. The reproducibility of the sensor is excellent as no surface modification is required and therefore storage is not an issue. By employing particle swarm optimization algorithms the identification of ingredients within a green curry could be obtained. In addition, the quality and freshness of the sample could be monitored by detecting a change in the intensity of the peaks in the fingerprint response.</p

Simple, sensitive, and cost-effective detection of wAlbB Wolbachia in Aedes mosquitoes, using loop mediated isothermal amplification combined with the electrochemical biosensing method.

BackgroundWolbachia is an endosymbiont bacterium generally found in about 40% of insects, including mosquitoes, but it is absent in Aedes aegypti which is an important vector of several arboviral diseases. The evidence that Wolbachia trans-infected Ae. aegypti mosquitoes lost their vectorial competence and became less capable of transmitting arboviruses to human hosts highlights the potential of using Wolbachia-based approaches for prevention and control of arboviral diseases. Recently, release of Wolbachia trans-infected Ae. aegypti has been deployed widely in many countries for the control of mosquito-borne viral diseases. Field surveillance and monitoring of Wolbachia presence in released mosquitoes is important for the success of these control programs. So far, a number of studies have reported the development of loop mediated isothermal amplification (LAMP) assays to detect Wolbachia in mosquitoes, but the methods still have some specificity and cost issues.Methodology/principal findingsWe describe here the development of a LAMP assay combined with the DNA strand displacement-based electrochemical sensor (BIOSENSOR) method to detect wAlbB Wolbachia in trans-infected Ae. aegypti. Our developed LAMP primers used a low-cost dye detecting system and 4 oligo nucleotide primers which can reduce the cost of analysis while the specificity is comparable to the previous methods. The detection capacity of our LAMP technique was 1.4 nM and the detection limit reduced to 2.2 fM when combined with the BIOSENSOR. Our study demonstrates that a BIOSENSOR can also be applied as a stand-alone method for detecting Wolbachia; and it showed high sensitivity when used with the crude DNA extracts of macerated mosquito samples without DNA purification.Conclusions/significanceOur results suggest that both LAMP and BIOSENSOR, either used in combination or stand-alone, are robust and sensitive. The methods have good potential for routine detection of Wolbachia in mosquitoes during field surveillance and monitoring of Wolbachia-based release programs, especially in countries with limited resources

Using H2O2 as a green oxidant to produce fluorescent GaOOH nanomaterials from a liquid metal

We report a simple and rapid method for the synthesis of fluorescent gallium oxyhydroxide (GaOOH) nanoparticles from liquid Ga by a probe sonication method in the presence of H2O2 as an oxidant. The aspect ratio of the GaOOH nanoparticles is determined by the concentration of H2O2 and solution pH, as well as the probe energy and sonication time. Further surface modification with cyclodextrin to achieve biocompatibility for potential biomedical applications is reported where an example of cell uptake and fluorescence imaging is shown.</p