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Bismuth sulfide (Bi2S3) is a chalcogenide semiconductor with a relatively narrow energy band gap that is promising for use in solar cells and photodetectors. This paper presents a highly efficient microwave synthesis of Bi2S3 submicrometric structures using poly(vinyl alcohol) (PVA) as a viscosity modification agent. The chemical composition, morphology, crystal structure, and optical properties of the prepared materials were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance spectroscopy (DRS). The use of PVA in Bi2S3 synthesis resulted in a change in material morphology from microrods to nanosheets and a slight increase in the energy band gap from 1.34 eV to 1.43 eV. The Bi2S3 nanosheets were examined as photosensitive materials for the detection of visible light. High ON/OFF ratios of 66, 44, and 15 and large specific detectivities of 1.12 × 1011, 7.68 × 1010, and 6.43 × 1010 Jones were achieved under blue (468 nm, 0.52 μW cm−2), green (517 nm, 0.95 μW cm−2), and red (628 nm, 0.13 μW cm−2) light illuminations, respectively. The photosensitive properties of Bi2S3 nanosheets were remarkable compared to that of many other photodetectors based on Bi2S3 micro- and nanostructures. [ABSTRACT FROM AUTHOR]

Battery-free and biodegradable sensors can detect biological elements in remote areas. The triboelectric nanogenerator (TENG) can potentially eliminate the need for a battery by simply converting the abundant vibrations from nature or human motion into electricity. A biodegradable sensor system integrated with TENG to detect commonly found disease-causing bacteria (E. coli) in the environment is showcased herein. In this system, D -mannose functionalized 3D printed polylactic acid (PLA) with the brush-painted silver electrode was used to detect E. coli by a simple carbohydrate–protein interaction mechanism. The adsorption capacity of D -mannose is generally altered by varying the concentration of E. coli resulting in changes in resistance. Thus, the presented biosensor can detect bacterial concentrations by monitoring the output current. The PLA TENG generates an output of 70 V, 800 nA, and 22 nC, respectively. In addition, tap water and unpasteurized milk samples are tested for detecting bacteria, and the output is measured at 6 μA and 5 μA, respectively. Further, the biosensor was tested for biodegradability in soil compost by maintaining constant temperature and humidity. This study not only proposes an efficient and fast method for screening E. coli but also gives important insights into the ability to degrade and long-term reliability of TENG-based sensor platforms. [ABSTRACT FROM AUTHOR]

The energy crisis and depletion of non-renewable energy resources have been aggravated due to the drastic rise in world pollution and the energy demand. Facile hydrogen production through water splitting has become a popular alternative source of energy owing to the numerous environmentally friendly and economic benefits it provides. Additionally, it is preferred due to the depletion of non-renewable energy resources, pollution caused by the burning of non-renewable energy resources, and climate change. Hydrogen is generated from water and acts as a clean energy without contributing to carbon emissions. Various water-splitting methods such as electrolysis, thermochemical, mechanocatalysis, plasmolysis, photocatalysis, and photoelectrocatalysis can be applied to obtain hydrogen and oxygen. This review highlights the multifunctional materials used in photo-electrochemical water splitting and their superior properties for producing carbon-free energy from water. Multifunctional materials help reduce aqueous protons to hydrogen and oxidize water to oxygen during the splitting of water. This paper discusses a wide class of materials such as carbon materials, metal–organic frameworks, perovskites, and semiconducting oxides for efficient hydrogen production. Different types of water-splitting methods and multifunctional materials with varying properties can lead to improved results. The review sheds light upon the hydrogen economy and future prospects, elucidating the selection of multifunctional materials for efficient hydrogen production. [ABSTRACT FROM AUTHOR]

Harvesting mechanical energy from the surroundings can be a promising power source for micro/nanodevices. The triboelectric nanogenerator (TENG) works on the principle of triboelectrification and electrostatic induction. So far, metals and polymers have mostly dominated the conventional triboelectric series, but there is a need to find novel materials to extend the triboelectric series and further improve the performance of a TENG. Herein, a zeolitic imidazole framework (ZIF-67) was synthesized using a room temperature solvent-assisted route. Extensive material analysis was performed to understand its structural and chemical properties. Further, a simple vertical contact mode S-shaped TENG device (abbreviated further as S-TENG) was fabricated using an additive manufacturing approach. ZIF-67 acted as a positive triboelectric layer while Teflon/PDMS acted as a negative triboelectric layer. The multi-unit S-TENG device was further utilized for self-powered recognition of the various gaits using a digital signal processing approach. The S-TENG device based on ZIF-67 and Teflon produced a voltage of 118 V, a current of 1.7 mA, and a power density of 15 mW cm2 at a load resistance of 50 MO. The gait analysis of different volunteers was recorded by employing the S-TENG device and the digital signal processing route to effectively distinguish the gait patterns for the prevention of falls and injury. The S-TENG device was utilized to charge a commercial capacitor for powering a wristwatch and further it was attached to a robotic gripper for object identification. [ABSTRACT FROM AUTHOR]

The switchable dipole moments and high piezoelectric coefficients in ferroelectric materials are the state-of-the-art used in piezoelectric energy harvesting. Hybridizing the triboelectric (TENG) and piezoelectric (PNG) shows great potential in harvesting the biomechanical energy by utilizing the ferroelectric dipoles embedded within the polymer. Unlike most of the previous approach to increase hybrid output by the external configuration of piezoelectric and triboelectric between two contact surfaces, in this paper, the output performance is significantly enhanced by improving the output performance of TENG by introducing a ferroelectric (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3−x BiHoO3 (x = 0.02, 0.04, 0.06, 0.08, 0.1) (BCZTBH termed further) particles in PDMS which acts as a negative triboelectric layer. The structural and piezoelectric properties of BCZTBH particles are correlated in this report with the necessary characterization techniques. The systematic study of integrating single unit hybrid generator (S-HG) in a stacked manner paves the way to develop cost-effective, highly efficient ferroelectric films for utilization in the next-generation energy harvesting. The performance of the device is boosted by adopting a multi-stack configuration by designing a multi-stack hybrid generator (MS-HG) that could generate an electrical output of 300 V and a power density of 157 mW m−2 upon mechanical excitations. Further, enhanced and reliable performance of the MS-HG is demonstrated as a proof of application by effectively integrating a capacitor, infrared transmitter and receiver into a self-powered wireless infrared communication module and body activity counter/monitoring. [ABSTRACT FROM AUTHOR]