Advances in Science and Technology Vol. 175

Abstract: Carbon Quantum Dots (CQDs) are a remarkable class of nanocarbon materials with average particle size below 10 nm. They have good photoluminescence properties, and they can be easily synthesized from natural biomass through simple synthesis routes like hydrothermal and thermal decomposition of organic matter. The biocompatibility and the simplicity of the synthesis process make this class of materials a high candidate to replace the highly toxic semiconductor quantum dots. This study details the preparation of CQDs using pomegranate husk via a simple pyrolysis synthesis route. The optical, morphological, and structural characteristics of the synthesized CQDs were investigated using UV-vis absorption spectrophotometry, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD), respectively. Also, FTIR spectroscopy was measured to study the function groups attached to the CQDs. TEM analysis confirmed the presence of nearly spherical dot particles with a narrow size distribution, yielding an average diameter of 6.2 nm. The optical characterization revealed that the obtained CQDs exhibit fluorescence with maximum emission at 450 nm, and notably, the fluorescence emission maxima was observed to shift towards higher wavelengths (red shift) with excitation wavelength.

Abstract: This study assesses the photovoltaic potential of pure Bismuth Ferrite (BiFeO₃) and its doped variants, specifically Samarium (Sm)-doped and Cobalt–Samarium (Co–Sm) co-doped BiFeO₃ nanoparticles. The materials were synthesized using sol-gel methods, followed by post-annealing to promote high crystallinity. A comprehensive characterization was performed to evaluate the structural, morphological, and optical properties utilizing X-ray diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), and UV-Vis spectroscopy. The findings indicate that doping and co-doping have a substantial influence on the optical bandgap, particle morphology, and crystallite dimensions. Sm and Co–Sm doping reduced the bandgap, enhancing visible-light absorption and solar energy-harvesting efficiency, whereas pure BiFeO₃ exhibited a bandgap of 2.03 eV. Electrical investigations further revealed greater charge separation, underscoring the superior charge-transport properties of the modified materials. The results indicate that doped BiFeO₃ systems hold potential as tunable multiferroic materials for advanced, high-efficiency solar applications.

Abstract: Red-emitting carbon dots (r-CDs) are among the most challenging categories of carbon-based luminescent materials to synthesize with high emission color purity, photoluminescent quantum yield, and photostability. While r-CDs are used as red phosphors in white LEDs to compensate for spectral deficiencies caused by strong blue and green emissions, their emission mechanisms warrant further investigation. Herein, we synthesized r-CDs via a facile, one-step, environmentally benign solvothermal method. We analyzed the structure of our r-CDs using Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier infrared spectrometry (FTIR). Subsequently, the optical properties were investigated using a UV-Vis spectrophotometer and spectrofluorometer. The TEM image showed well-dispersed quasi-spherical dots with an average diameter of 3.47 nm. The photophysical investigation revealed that the r-CDs exhibit excitation-dependent emissions from 400 to 750 nm in water, whereas in DMSO, the emission spectra are excitation-independent, with a peak centered at 680 nm. The excitation-independent spectra observed were attributed to DMSO-induced deprotonation of surface functional groups on r-CDs, resulting in solvent-induced red emission and a high photoluminescent quantum yield (PLQY) of 31.3%.

Abstract: Harnessing ambient kinetic energy from water droplets is a promising route for sustainable power. However, efficient wireless delivery of this energy remains challenging. This study demonstrates a droplet-based electricity generator (DEG) using a composite interfacial structure of ferroelectric polyvinylidene fluoride (PVDF) and triboelectric fluorinated ethylene propylene (FEP). The device achieves an open-circuit voltage up to 254 V and an energy output of 17.17 μJ per droplet. An impedance-matched electronic switch (E-Switch) enables efficient excitation of a magnetically coupled LC resonator, facilitating wireless energy transfer over 50 cm using compact 2-cm coils. System evaluations confirm stable transmission under varying distances and misalignments. This work provides a self-powered, cable-free energy platform well-suited for environmental monitoring and distributed electronics.

Abstract: Achieving high-performance polymer-based piezoelectric-triboelectric nanogenerators (PTNGs) remains challenging due to the limited electroactive phase content and inefficient dipole alignment in polymer matrices. Here, we propose a liquid-metal doping strategy, supported by molecular dynamics (MD) simulations, to construct β-PVDF-LM composites with enhanced pie-zoelectric and triboelectric properties. Simulations indicate that liquid-metal atoms preferentially interact with fluorine in PVDF chains, stabilizing the all-trans conformation and promoting dipole ordering under an external electric field. In addition, the liquid metal and its native oxide layers act as electron-trapping centers during triboelectric contact, leading to higher interfacial charge storage and retention. As a result, the β-PVDF-LM composites exhibit a high β-phase fraction of 91% and deliver outstanding electrical outputs. The optimized β-PVDF-LM/PA6 PTNG achieves a peak-to-peak voltage of 1831 V, a current density of 214.3 mA/m², a charge density of 254.4 μC/m², and a maximum power density of 83.8 W/m². This work provides new in-sights into the design of liquid-metal-assisted PTNGs and highlights their potential for efficient energy harvesting.

Abstract: This work introduces a novel PVP/SbSI nanocomposite that exhibits a significant piezoelectric response to variations in air pressure. Demonstrated functionalities include its use as a pressure sensor and nanogenerator under dynamic conditions. For a sandwich-type configuration with nanofibers oriented perpendicularly to the electrodes, the sample generated a peak voltage of about 2.1 V, a charge generation rate of 97.1 pC/N, a sensitivity of about 0.23 mV/bar, a surface power density of over 12 µW/cm², and an energy output of 3.5 nJ under a differential pressure of 17 bar. The study also examines the agreement among various methods of efficiency evaluation.

Abstract: Ethylene carbonate (EC) is essential for establishing a passivating surface film on graphite; in practice, however, EC is commonly blended with dimethyl carbonate (DMC), which alters Li⁺ solvation and interfacial chemistry. Here, we compare 1 mol dm⁻³ (M) LiClO₄/EC+DMC with 1 M LiClO₄/DMC using in situ electrochemical atomic force microscopy (AFM) during cyclic voltammetry on the basal plane of highly oriented pyrolytic graphite (HOPG). Both media follow a two-stage pathway—solvent cointercalation (subsurface pre-insertion) followed by surface precipitate formation—yet their electrochemical responses and morphologies diverge. In EC+DMC, pronounced second-cycle suppression of the cathodic current accompanies the development of a laterally continuous, fine particulate precipitate layer after the first cycle. In the DMC‑only electrolyte, large cathodic currents persist and AFM reveals edge-dominated blistering, step disruption, and patchy deposits, indicative of sustained cointercalation and incomplete passivation. Taken together, these results indicate that the principal passivating film is EC-derived, whereas DMC chiefly modulates cointercalation and coalescence kinetics, thereby amplifying lateral heterogeneity. The measurements provide potential-resolved benchmarks for formation-protocol design and a reference for interpreting mixed-carbonate electrolytes.

Abstract: Solid polymer electrolyte (SPE) with PVdF polymer and LiBOB salt has been prepared with the doctor blade method. To improve the membrane ionic conductivity, TiO₂ was added in different variations: 0%, 5%, 10%, and 15%. Surface morphology analysis was performed using SEM and energy-dispersive X-ray (EDX) spectroscopy. The conductivity behavior was studied using AC impedance spectroscopy (EIS). SEM and EDXS analyses revealed that TiO₂ addition played a role in pore formation in the solid polymer electrolyte membrane. The highest room-temperature ionic conductivity of the PVdF–LiBOB solid polymer electrolyte system in this study was 4.65 mS cm⁻¹ at 10% TiO₂. It was also found that the agglomeration of TiO₂ particles on the surface of the membrane resulted in a decrease in ionic conductivity.

Abstract: PLA is a common, eco-friendly polymer for FDM printing. The infill patterns and densities play a significant role in determining the mechanical properties of three-dimensional (3D) printed PLA. In this work, two different infill patterns (Concentric and Rectilinear) and infill densities (30% and 100%) were printed. PLA filaments were characterized using Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and Scanning Electron Microscopy analysis (SEM) techniques. The tensile test results revealed that the 100% concentric pattern has the highest ultimate tensile strength of 67.5 MPa, while the 100% rectilinear pattern shows 63.6 MPa. On the other hand, the 30% infill density samples show low strength, 32.4 MPa for concentric and 20.8 MPa for rectilinear infill patterns. Similar results can be derived from elastic modulus, yield strength, and stress at break results, while 30% concentric shows the maximum elongation rate of 0.016.