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The development of the IoT demands small, durable, remote sensing systems that have energy harvesters and storage. Various energy harvesters are developed, including piezoelectric, triboelectric, electromagnetic, and reverse-electrowetting-on-dielectric. However, integrating energy storage and sensing functionality receives little attention. This paper presents an electrochemical vibration sensor with a galvanic cell (Zn-Cu cell) as energy storage and a vibration transducer. The frequency response, scale factor, long-term response, impedance study, and discharge characteristics are given. This study proved the possibility of integrating energy storage and vibration sensing functionality with promising performance. The performance of the sensor halved within 74 min. The longevity of the sensor is short due to the spontaneous reactions and ions drained. The sensitivity can be restored after refilling the electrolyte. The sensor could be rechargeable by changing to a reversible electrochemical system such as a lead–acid cell in the future.

Aiming at the development needs of low-frequency and high-sensitivity vector hydrophones, this paper has developed a micro-electro-mechanical system (MEMS) based co-oscillating electrochemical vector hydrophone. We obtained the optimized geometric parameters through simulation analysis of the diameter of the rubber membrane, the length of the flow channel and the diameter of the flow holes. Based on the simulation results, electrodes were fabricated using MEMS technology, and were then assembled and tested. Device characterization was conducted, where the sensitivity and bandwidth were quantified as 0.5–150 Hz, −187 dB ref. 1 V/μPa, respectively. Compared with a previously reported co-oscillating vector hydrophone, the co-oscillating vector hydrophone developed in this article featured a lower working frequency band.

A vibration sensor based on electrochemical principle can be widely used in the field of seismology. For its instinctive bandwidth is limited, compensation by circuit is essential to expand the bandwidth. This article presents a method of frequency compensation by circuit based on the original amplitude-frequency characteristic of the electrochemical vibration sensor. The bandwidth is broadened obviously from 2s-10Hz to 25s-20Hz. The noise performance of the final output compared to the CME6011 is also presented.

In this study, gold nanoparticles (AuNPs) were electrodeposited on samples of a carbon-paste electrode (CPE) with different thicknesses. The prepared AuNPs were characterized using different analysis techniques, such as FTIR, UV–Vis, SEM, EDX, TEM images, and XRD analysis. The fabricated modified electrode AuNPs/CPE was used for the sensitive detection of Congo red (CR) dye. Electrochemical sensing was conducted using square-wave voltammetry (SWV) in a 0.1 M acetate buffer solution at pH 6.5. The proposed sensor exhibited high efficiency for the electrochemical determination of CR dye with high selectivity and sensitivity and a low detection limit of 0.07 μM in the concentration range of 1–30 μM and 0.7 μM in the concentration range of 50–200 μM. The practical application of the AuNPs/CPE was verified by detecting CR dye in various real samples involving jelly, candy, wastewater, and tap water. The calculated recoveries (88–106%) were within the acceptable range.

Energy harvesting from piezoelectric materials is quite common and has been studied for the past few decades, but, recently, there have been a lot of new advancements in harnessing electrical energy via piezoelectric materials. In this regard, several studies were carried out in electrochemistry and fluid flow. Furthermore, consideration of productive and valuable resources is important to meet the needs of power generation. For this purpose, energy harvesting from fluids such as wind and water is significant and must be implemented on a large scale. So, developing self-powering devices can resolve the problem like that, and piezoelectric materials are gaining interest day by day because these materials help in energy generation. This review paper discusses different techniques for harnessing energy from fluid flows using piezoelectric materials. In addition, various vibration-based energy-harvesting mechanisms for improving the efficiency of piezoelectric energy harvesters have also been investigated and their opportunities and challenges identified.

Today, due to industrialization and urbanization, the world is facing serious water shortage and environmental alarms. The reusability of polluted water could be a promising approach for the sustainable wastewater management strategy. In the view, the present work compiles the synthesis of zinc ferrite (ZnFe 2 O 4 ) nanoparticles by a simple, economic, and eco-friendly route. The investigation of structural properties, thermal properties, and optical properties was carried out successfully by standard characterization techniques. The X-ray diffraction patterns confirmed the spinel-cubic lattice with Fd-3m space group for all the samples. The presence of vibrational frequency modes of Zn–O and Fe–O was ensured by FTIR spectra. The nano-size, morphology, atomic percentage, and some agglomeration of the nanoparticles were revealed by SEM–EDX and TEM images. The bandgap values were calculated from UV–Visible analysis data, and found to be 2.36 eV. The distribution of pore size by BJH method and BET surface area was evaluated by Nitrogen adsorption–desorption isotherms, and is found to be 19.74 m 2 /g. The thermogravimetric and differential thermal analysis affirmed percentage of weight loss and phase formation. The photocatalytic activity of methylene blue was evaluated under visible light and the removal efficiency of 96% and nano-catalyst shows active reusability. The cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for the study of electrochemical properties of nanoparticles. Further, the antimicrobial activity of the nanoparticles was investigated using Gram-positive, Gram-negative bacteria and some selected fungi strains. The obtained results revealed that the newly synthesized ZnFe 2 O 4 can act as potential photocatalyst, electrochemical sensor, and antimicrobial agent.

Captopril (CAP) is one of the most broadly consumed anti-hypertension drug that caused various harmful effects such as zinc deficiency, cough, agranulocytosis, and angioedema. Thus, monitoring the low-level concentration of CAP through reliable and sensitive method is of great significance. The electrocatalytic properties of newly fabricated sensor based on SnO 2 /rGO/PtE was evaluated through Tafel plot and electrochemical impedance spectroscopy. The engineered sensor exhibited excellent response for CAP under optimal conditions e.g., PBS electrolyte (pH 5), scan sweep 90 mV/s and potential window (0.6 to 1.9 V). For effectiveness of developed sensor, two low and high concentration ranges of CAP were optimized as 1 to 700 nM and 10 100 µM, respectively. The LOD’s of SnO 2 /rGO/PtE for CAP for low and high concentrations were calculated as 0.061 nM and 0.0018 µM. Moreover, the exceptional long-term stability and anti-interference profile of SnO 2 /rGO/PtE suggested the reliability of chemically modified sensor. Graphical Abstract

This paper describes an inexpensive, handheld device that couples the most common forms of electrochemical analysis directly to “the cloud” using any mobile phone, for use in resource-limited settings. The device is designed to operate with a wide range of electrode formats, performs on-board mixing of samples by vibration, and transmits data over voice using audio—an approach that guarantees broad compatibility with any available mobile phone (from low-end phones to smartphones) or cellular network (second, third, and fourth generation). The electrochemical methods that we demonstrate enable quantitative, broadly applicable, and inexpensive sensing with flexibility based on a wide variety of important electroanalytical techniques (chronoamperometry, cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, and potentiometry), each with different uses. Four applications demonstrate the analytical performance of the device: these involve the detection of (i) glucose in the blood for personal health, (ii) trace heavy metals (lead, cadmium, and zinc) in water for in-field environmental monitoring, (iii) sodium in urine for clinical analysis, and (iv) a malarial antigen (Plasmodium falciparum histidine-rich protein 2) for clinical research. The combination of these electrochemical capabilities in an affordable, handheld format that is compatible with any mobile phone or network worldwide guarantees that sophisticated diagnostic testing can be performed by users with a broad spectrum of needs, resources, and levels of technical expertise.

This article reviews the recent advances in the field of batteryless near-field communication (NFC) sensors for chemical sensing and biosensing. The commercial availability of low-cost commercial NFC integrated circuits (ICs) and their massive integration in smartphones, used as readers and cloud interfaces, have aroused great interest in new batteryless NFC sensors. The fact that coil antennas are not importantly affected by the body compared with other wireless sensors based on far-field communications makes this technology suitable for future wearable point-of-care testing (PoCT) devices. This review first compares energy harvesting based on NFC to other energy-harvesting technologies. Next, some practical recommendations for designing and tuning NFC-based tags are described. Power transfer is key because in most cases, the energy harvested has to be stable for several seconds and not contaminated by undesired signals. For this reason, the effect of the dimensions of the coils and the conductivity on the wireless power transfer is thoroughly discussed. In the last part of the review, the state of the art in NFC-based chemical and biosensors is presented. NFC-based tags (or sensor tags) are mainly based on commercial or custom NFC ICs, which are used to harvest the energy from the RF field generated by the smartphone to power the electronics. Low-consumption colorimeters and potentiostats can be integrated into these NFC tags, opening the door to the integration of chemical sensors and biosensors, which can be harvested and read from a smartphone. The smartphone is also used to upload the acquired information to the cloud to facilitate the internet of medical things (IoMT) paradigm. Finally, several chipless sensors recently proposed in the literature as a low-cost alternative for chemical applications are discussed.

In this work, the novel hybrid nanomaterial SWCNT/SiPc made of single walled carbon nanotubes (SWCNT) cross-linked via axially substituted silicon (IV) phthalocyanine (SiPc) was studied as the active layer of chemiresistive layers for the detection of ammonia and hydrogen. SWCNT/SiPc is the first example of a carbon-based nanomaterial in which an axially substituted phthalocyanine derivative is used as a linker. The prepared hybrid material was characterized by spectroscopic methods, thermogravimetry, scanning and transmission electron microscopies. The layers of the prepared hybrid were tested as sensors toward ammonia and hydrogen by a chemiresistive method at different temperatures and relative humidity as well as in the presence of interfering gases like carbon dioxide, hydrogen sulfide and volatile organic vapors. The hybrid layers exhibited the completely reversible sensor response to both gases at room temperature; the recovery time was 100–200 s for NH3 and 50–120 s in the case of H2 depending on the gas concentrations. At the relative humidity (RH) of 20%, the sensor response was almost the same as that measured at RH 5%, whereas the further increase of RH led to its 2–3 fold decrease. It was demonstrated that the SWCNT/SiPc layers can be successfully used for the detection of both NH3 and H2 in the presence of CO2. On the contrary, H2S was found to be an interfering gas for the NH3 detection.