An electrochemical study on the effect of metal chelation and reactive oxygen species on a synthetic neuromelanin model

Neuromelanin is present in the cathecolaminergic neuron cells of the substantia nigra and locus coeruleus of the midbrain of primates. Neuromelanin plays a role in Parkinson's disease (PD). Literature reports that neuromelanin features, among others, antioxidant properties by metal ion chelation and free radical scavenging. The pigment has been reported to have prooxidant properties too, in certain experimental conditions. We propose an explorative electrochemical study of the effect of the presence of metal ions and reactive oxygen species (ROS) on the cyclic voltammograms of a synthetic model of neuromelanin. Our work improves the current understanding on experimental conditions where neuromelanin plays an antioxidant or prooxidant behavior, thus possibly contributing to shed light on factors promoting the appearance of PD

Biodegradation of bio-sourced and synthetic organic electronic materials towards green organic electronics

Ubiquitous use of electronic devices has led to an unprecedented increase in related waste as well as the worldwide depletion of reserves of key chemical elements required in their manufacturing. The use of biodegradable and abundant organic (carbon-based) electronic materials can contribute to alleviate the environmental impact of the electronic industry. The pigment eumelanin is a bio-sourced candidate for environmentally benign (green) organic electronics. The biodegradation of eumelanin extracted from cuttlefish ink is studied both at 25 °C (mesophilic conditions) and 58 °C (thermophilic conditions) following ASTM D5338 and comparatively evaluated with the biodegradation of two synthetic organic electronic materials, namely copper (II) phthalocyanine (Cu–Pc) and polyphenylene sulfide (PPS). Eumelanin biodegradation reaches 4.1% (25 °C) in 97 days and 37% (58 °C) in 98 days, and residual material is found to be without phytotoxic effects. The two synthetic materials, Cu–Pc and PPS, do not biodegrade; Cu–Pc brings about the inhibition of microbial respiration in the compost. PPS appears to be potentially phytotoxic. Finally, some considerations regarding the biodegradation test as well as the disambiguation of “biodegradability” and “bioresorbability” are highlighted

An electrochemical study of natural and chemically controlled eumelanin

Eumelanin is the most common form of the pigment melanin in the human body, with functions including antioxidant behavior, metal chelation, and free radical scavenging. This biopigment is of interest for biologically derived batteries and supercapacitors. In this work, we characterized the voltammetric properties of chemically controlled eumelanins produced from 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) building blocks, namely, DHI-melanin, DHICA-melanin, and natural eumelanin, extracted from the ink sac of cuttlefish, Sepia melanin. Eumelanin electrodes were studied for their cyclic voltammetric properties in acidic buffers including Na+, K+, NH4+, and Cu2+ ions

Recovery of palladium from waste fashion items through food waste by-products

ABSTRACT: Palladium is a non-toxic platinum group metal indispensable for several industrial applications. It is among the 44 endangered elements; hence, its recycling from secondary sources is crucial. Waste plated metal wires from the fashion industry are an important waste stream for this precious metal. We propose a sustainable route for Pd recovery where palladium peels off in its metallic state in a single-step, room-temperature process. At the same time, readily oxidizable base metals are leached under very mild conditions using a green oxidant, hydrogen peroxide, and lactic acid, a food chain byproduct. This strategy is chemically rational, cost-effective, and environmentally friendly. The recovered Pd was successfully recycled to fabricate source and drain electrodes in organic field-effect transistors. Waste wires, recovered palladium flakes, and e-beam evaporated Pd electrodes were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy to examine their morphology and (surface) chemical composition

Ion-gated transistors based on porous and compact TiO2 films: Effect of Li ions in the gating medium

Ion-gated transistors (IGTs) are attractive for chemo- and bio-sensing, wearable electronics, and bioelectronics, because of their ability to act as ion/electron converters and their low operating voltages (e.g., below 1 V). Metal oxides are of special interest as transistor channel materials in IGTs due to their high mobility, chemical stability, and the ease of processing in air at relatively low temperatures (<350 °C). Titanium dioxide is an abundant material that can be used as a channel material in n-type IGTs. In this work, we investigate the role of the morphology of the TiO2 channel (porous vs compact films) and the size of the cations in the gating media ([EMIM][TFSI] and [Li][TFSI] dissolved in [EMIM][TFSI]) to study their role on the electrical characteristics of IGTs. We found that both the film morphology and the type of gating medium highly affect the electrical response of the devices

Solution-Processed Titanium Dioxide Ion-Gated Transistors and Their Application for pH Sensing

ABSTRACT: Titanium dioxide (TiO₂) is an abundant metal oxide, widely used in food industry, cosmetics, medicine, water treatment and electronic devices. TiO₂ is of interest for next-generation indium-free thin-film transistors and ion-gated transistors due to its tunable optoelectronic properties, ambient stability, and solution processability. In this work, we fabricated TiO₂ films using a wet chemical approach and demonstrated their transistor behavior with room temperature ionic liquids and aqueous electrolytes. In addition, we demonstrated the pH sensing behavior of the TiO2 IGTs with a sensitivity of ~48 mV/pH. Furthermore, we demonstrated a low temperature (120°C), solution processed TiO2-based IGTs on flexible polyethylene terephthalate (PET) substrates, which were stable under moderate tensile bending

An electrochemical study of natural and chemically controlled eumelanin

ABSTRACT: Eumelanin is the most common form of the pigment melanin in the human body, with functions including antioxidant behavior, metal chelation, and free radical scavenging. This biopigment is of interest for biologically derived batteries and supercapacitors. In this work, we characterized the voltammetric properties of chemically controlled eumelanins produced from 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) building blocks, namely, DHI-melanin, DHICA-melanin, and natural eumelanin, extracted from the ink sac of cuttlefish, Sepia melanin. Eumelanin electrodes were studied for their cyclic voltammetric properties in acidic buffers including Na⁺, K⁺, NH₄⁺, and Cu²⁺ ions. (C) 2017 Author(s)

Electrical response and biodegradation of Sepia melanin-shellac films printed on paper

ABSTRACT: Sepia melanin, a biopigment extracted from the ink sac of cuttlefish, is relevant to sustainable organic electronics. In this work, we flexographically print films from an ink of Sepia melanin including shellac as a bio-sourced binder on silver electrode-patterned paper. We examine the electrical response in high humidity and ambient conditions (here the electronic conductivity is as high as 10−4 S/cm). Additionally, we study the biodegradation of the printed films and their individual constituents based on their mineralization into CO2 under composting conditions. The printed films exhibit biodegradation levels of about 97 ± 25% in 85 d. We observe microorganism colonization on the printed film’s surface. The analysis of the microbial community on the compost reveals that bacterial species within the Acidimicrobiia class, specifically Actinomarinales order, are potentially responsible for the biodegradation of the printed film. Meanwhile, ecotoxicity tests conducted by germinating Lolium multiflorum and Tagetes erecta suggest that printed films have negligible phytotoxicity