We have determined the Schottky barrier height (0.23 eV) and efficient photoelectron generation in novel multisegmented Au/TiO₂ nanorod arrays.

Simple, low-cost methods for sensing volatile organic compounds that leave no trace and do not have a detrimental effect on the environment are able to protect communities from the impacts of contaminants in water supplies. This paper reports the development of a portable, autonomous, Internet of Things (IoT) electrochemical sensor for detecting formaldehyde in tap water. The sensor is assembled from electronics, i.e., a custom-designed sensor platform and developed HCHO detection system based on Ni(OH)₂–Ni nanowires (NWs) and synthetic-paper-based, screen-printed electrodes (pSPEs). The sensor platform, consisting of the IoT technology, a Wi-Fi communication system, and a miniaturized potentiostat can be easily connected to the Ni(OH)₂–Ni NWs and pSPEs via a three-terminal electrode. The custom-made sensor, which has a detection capability of 0.8 µM/24 ppb, was tested for an amperometric determination of the HCHO in deionized (DI) and tap-water-based alkaline electrolytes. This promising concept of an electrochemical IoT sensor that is easy to operate, rapid, and affordable (it is considerably cheaper than any lab-grade potentiostat) could lead to the straightforward detection of HCHO in tap water.

Due to the non-electroactivity of carcinogenic organic compound acrylamide, an indirect electrochemical detection by using molecularly imprinted polymer is proposed as a detection method. Polyaniline was chosen due to the conductivity, interesting properties and wide usage in the field of sensors. Polyaniline was prepared by the different electropolymerisation process to achieve different morphologies, properties. Cyclic voltammetry was further chosen for electropolymeristion of polyaniline, in which propanamide was imprinted as a template molecule. Due to the same size, shape and functional groups, so imprinted polyaniline presents a proof of concept molecule for further acrylamide bonding. Successful imprinting was confirmed by surface analysis technique (FTIR) and simple electrochemical measurements of polyaniline response.

A Ni nanowires-based electrodes for formaldehyde (HCHO) detection were fabricated via a template-assisted electrodeposition. The as-deposited Ni nanowires (NWs) were characterized by scanning electron microscope (SEM). In order to form an active redox couple of Ni(OH)₂/NiOOH on the surface of nanowires, the Ni NWs were electrochemically modified in 0.5 mol L⁻¹ KOH using cyclic voltammetry. The presence of Ni(OH)₂/NiOOH on the surface of Ni NWs was confirmed by transmission electron microscopy (TEM). Furthermore, the ability of modified Ni NWs-based electrode (i.e., receptor element) was investigated for HCHO electro-oxidation in alkaline media via cyclic voltammetry and amperometry. The fabricated Ni NWs-based electrode exhibited fast response (3s), good selectivity, a high sensitivity and low limit of detection 0.8 μmol L⁻¹.

Acrylamide (AA), C₃H₅NO, is used worldwide in the synthesis of polymers and gels for wastewater treatments and in the paper industry. Naturally, it is formed in heat-treated food, mostly during the frying and baking of potatoes, cereals, and coffee beans. Its presence in food is dangerous as it is a neurotoxic and genotoxic compound. Triggered by new EU regulations, there is a high demand for reliable and cost-effective sensors in food and home appliances. In view of this, electrochemical sensors show high potential for the detection of toxic compounds. In the present work, we show the development of electrochemical biosensor elements, since AA is a non-active molecule and direct electrochemical detection is not possible. The sensors’ receptor element is based on modified commercial screen-printed electrodes (SPEs) that offer on-site and cost-efficient sensing. As an electrochemical transducer, conductive polyaniline (PANI) decorated with Au NPs was applied, enabling high sensitivity and limit of detection below the 10⁻⁶ M range. As a biological component, enzyme amidase was selected, since it is known that it catalyzes the hydrolysis of acrylamide into carboxyl acid and ammonia. The ammonia was finally detected using chronoamperometry. The chemical interaction between PANI and ammonia is well-known and thus was used as a base for the fabrication of an amperometric sensory platform for its aqueous detection at neutral pH. To understand AA and amidase interaction and decomposition into ammonia, PANI electrochemical synthesis and redox behavior in acidic and neutral media were used to study the mechanism of AA indirect detection.

We have developed a new type of testing strategy based on the electrochemical biosensing aspect for rapid and portable detection of SARS-CoV-2. The detection platform is based on a highly conductive matrix (fabricated polystyrene/polyaniline-Au nanocomposite) enabling immobilization of representative receptor elements (antibodies) that are specific to the target, i.e., SARS-CoV-2 spike (S)-protein. The concept of a detection system is to translate specific covalent interaction between antibodies and its corresponding binding viral S-protein, into a measurable, concentration-dependent electrochemical signal. The biosensor is able to monitor the electrochemical response in PBS, without using hazardous [Fe(CN)]63-/4- redox couple. By creating an electrochemical readout (CV, EIS, and DPV), data enables qualitative and quantitative analysis. Additionally, it exploits outstanding conductivity and biocompatibility, thus resulting in high analytical sensitivity and a low detection limit of $15.6\ \mu g/mL$ , which is within the physiologically relevant concentration range. Thus, the proposed feasible design of the biosensor platform represents an excellent starting point for practical and low-cost testing of asymptomatic patients or people before symptom onset.