Publications

JTD Keywords: copper, emissions, ethanol productions, greenhouse gases, solar energy, sustainable catalysts, Environmental pollution, Reduction

Van der Waals layered ferroelectrics, such as CuInP2S6 (CIPS), offer a versatile platform for miniaturization of ferroelectric device technologies. Control of the targeted composition and kinetics of CIPS synthesis enables the formation of stable self-assembled heterostructures of ferroelectric CIPS and nonferroelectric In4/3P2S6 (IPS). Here, we use quantitative scanning probe microscopy methods combined with density functional theory (DFT) to explore in detail the nanoscale variability in dynamic functional properties of the CIPS-IPS heterostructure. We report evidence of fast ionic transport which mediates an appreciable out-of-plane electromechanical response of the CIPS surface in the paraelectric phase. Further, we map the nanoscale dielectric and ionic conductivity properties as we thermally stimulate the ferroelectric-paraelectric phase transition, recovering the local dielectric behavior during this phase transition. Finally, aided by DFT, we reveal a substantial and tunable conductivity enhancement at the CIPS/IPS interface, indicating the possibility of engineering its interfacial properties for next generation device applications.

JTD Keywords: copper indium thiophosphate, diffusion, elastic band method, ferroelectrics, ionic conductor, migration, nanoscale, phase transition, piezoresponse force microscopy, scanning dielectric microscopy, transition, Copper indium thiophosphate, Initio molecular-dynamics, Scanning dielectric microscopy

Effective inhibition of sperm motility using a spermicide can be a promising approach in developing non-invasive male contraceptive agents. Copper is known to have contraceptive properties and has been used clinically for decades as intrauterine contraceptive devices (IUDs) for contraception in females. Beyond that, the spermicidal use of copper is not explored much further, even though its use can also subdue the harmful effects caused by the hormonal female contraceptive agents on the environment. Herein, the size, concentration, and time-dependent in vitro inhibition of bovine spermatozoa by copper microparticles are studied. The effectivity in inhibiting sperm motility is correlated with the amount of Cu2+ ions released by the particles during incubation. The copper particles cause direct suppression of sperm motility and viability upon incubation and thereby show potential as sperm-inhibiting, hormone-free candidate for male contraception. In addition, biocompatibility tests using a cervical cell line help optimizing the size and concentration of the copper particles for the best spermicidal action while avoiding toxicity to the surrounding tissue.

JTD Keywords: Bovine spermatozoa, Clinical-trial, Copper, Human-spermatozoa, Ions, Male contraception, Metallic copper, Microparticles, Progestins, Sperm motility, Sperm viability, Spermicide, Viability

Permanently polarized hydroxyapatite is a new material with electrical enhanced properties. This review discusses the advances in this material in terms of structure, properties and catalytic activity of green processes.

JTD Keywords: ammonia, bone, copper hydroxyapatite, electrophotosynthesis, nanoparticles, oxidation, phase-transition, reduction, Amino-acids

In the recent decades, zinc (Zn) and its alloys have been drawing attention as promising candidates for bioresorbable cardiovascular stents due to its degradation rate more suitable than magnesium (Mg) and iron (Fe) alloys. However, its mechanical properties need to be improved in order to meet the criteria for vascular stents. This work investigates the mechanical properties, biodegradability and biocompatibility of Zn-Mg and Zn-Cu alloys in order to determine a proper alloy composition for optimal stent performance. Nanoindentation measurements are performed to characterize the mechanical properties at the nanoscale as a function of the Zn microstructure variations induced by alloying. The biodegradation mechanisms are discussed and correlated to microstructure, mechanical performance and bacterial/cell response. Addition of Mg or Cu alloying elements refined the microstructure of Zn and enhanced yield strength (YS) and ultimate tensile strength (UTS) proportional to the volume fraction of secondary phases. Zn-1Mg showed the higher YS and UTS and better performance in terms of degradation stability in Hanks’ solution. Zn-Cu alloys presented an antibacterial effect for S. aureus controlled by diffusion mechanisms and by contact. Biocompatibility was dependent on the degradation rate and the nature of the corrosion products.

JTD Keywords: behavior, biocompatibility, biodegradable metals, bioresorbable metals, bioresorbable scaffold, copper, corrosion properties, elastic-modulus, galvanic corrosion, microstructure, nanoindentation, redox homeostasis, zinc, Biocompatibility, Bioresorbable metals, Galvanic corrosion, Nanoindentation, Room-temperature superplasticity, Zinc alloys

Here, we present a flexible and low-cost inkjet printed electrochemical sensor for enzyme-free glucose analysis. Versatility, short fabrication time and low cost make inkjet printing a valuable alternative to traditional sensor manufacturing techniques. We fabricated electro-chemical glucose sensors by inkjet printing electrodes on a flexible polyethylene terephthalate substrate. CuO microparticles were used to modify our electrodes, leading to a sensitive, stable and cost-effective platform for non-enzymatic detection of glucose. Selectivity, reproducibility, and life-time provided by the CuO functionalization demonstrated that these sensors are reliable tools for personalized diagnostics and self-assessment of an individual's health. The detection of glucose at concentrations matching that of tear fluid allows us to envisage applications in ocular diagnostics, where painless and non-invasive monitoring of diabetes can be achieved by analyzing glucose contained in tears.

JTD Keywords: Inkjet printing, Non-enzymatic sensor, Glucose, Copper oxide, Tear analysis

We present a method to measure directly and at the single-molecule level the distance decay constant that characterizes the rate of electron transfer (ET) in redox proteins. Using an electrochemical tunneling microscope under bipotentiostatic control, we obtained current-distance spectroscopic recordings of individual redox proteins confined within a nanometric tunneling gap at a well-defined molecular orientation. The tunneling current decays exponentially, and the corresponding decay constant (β) strongly supports a two-step tunneling ET mechanism. Statistical analysis of decay constant measurements reveals differences between the reduced and oxidized states that may be relevant to the control of ET rates in enzymes and biological electron transport chains.

JTD Keywords: Long-range electron transfer (LRET), Distance decay constant, Single-molecule electrochemistry, Redox enzyme, Metalloprotein, Blue copper protein, Azurin, Electrochemical scanning tunneling microscopy and spectroscopy, Nanoelectrodes, Debye length, Electrochemical charge screening

In this work we successfully prepared p-type semiconducting Cu2-xTe layers on Cu substrates by applying a potential multistep signal. Spontaneously deposited tellurium layers were reduced in a single cathodic sweep. The X-ray diffraction characterization showed the presence of single-phased, crystalline Cu2-xTe in the weissite form. A further anodization step allows crystallization of several phases such as CU1.75Te, Cu0.664Te0.336 and CU7Te4. This type of sample was found to be photoactive. The prepared films are p-type and have carrier concentrations in the order of 10(21) CM-3, suitable for CdTe-CU2-xTe contacts.

JTD Keywords: Copper telluride, Electrochemical signal, XRD, Morphology, EIS, Photocurrent, Telluride thin-films, Solar cells, Deposition, Cu