This study introduces the synthesis, characterization, and utilization of carbon quantum dots (CQDs) from sunflower seed shells for the first time, specifically as a photoluminescence (PL) sensor for cadmium ion detection. CQDs were synthesized by a hydrothermal method. The CQDs were analyzed employing various physicochemical methods, including XRD, FTIR, TEM, UV–Vis spectroscopy, and fluorescence spectroscopy. The green-source CQDs demonstrated an average nanoscale dimension of 2.1 nm and displayed PL behavior, an emission peak at 497 nm, with a quantum yield (QY) of 33.5%. The synthesized CQDs exhibited significant selectivity for Cd2+ ion detection, with PL intensity diminishing as Cd2+ concentrations increased (1–10 μM). The detection limit was established at 0.12 μM, while the limit of quantification was set at 0.38 μM. Selectivity experiments demonstrated that the CQDs displayed a robust response to Cd2+ ions with negligible interference from other metal ions. The results indicate that the synthesized CQDs are a viable, economical, and eco-friendly material for the detection of cadmium contamination in water. Additionally, density functional theory (DFT) measurements were employed to investigate the quenching mechanism between CQDs and Cd2+ ions. The findings indicated that aldehyde groups on the CQD surface demonstrate the most robust interaction with Cd2+ ions, elucidating the fluorescence quenching mechanism.

Conductive polymer nanocomposites are attracting increasing interest for their potential in advanced optoelectronics, sensing, and energy applications, owing to their tunable electrical and optical properties. In this study, we present the fabrication and characterisation of novel PANI-CSA nanocomposite films doped with cobalt (Co), nickel (Ni), and a combination of Co–Ni nanoparticles. These materials were synthesised via chemical polymerisation in a camphor sulfonic acid (CSA) solution. Structural, optical, and electrical properties were systematically examined using four-point probe measurements, X-ray diffraction, scanning electron microscopy, and ultraviolet–visible (UV–Vis) spectroscopy. Our findings demonstrate that doping with Co and Ni nanoparticles reduces the optical bandgap, enhances electrical conductivity, and improves UV–visible light absorption. Theoretical modelling of surface plasmon resonance using the Kretschmann configuration further revealed that co-doping with Co and Ni significantly enhances sensitivity, positioning these films as promising candidates for plasmonic biosensing. The integration of dual-metal doping with CSA protonation in PANI offers an innovative approach for developing multifunctional nanocomposites tailored for advanced photonic and sensing applications.

Carbon quantum dots (CQDs) derived from biological sources have gained a great attention in healthcare and environmental applications, including biosensing bioimaging, electrocatalytic oxidation, and metal ion detection. In this study, for the first-time, the fabrication of water-soluble CQDs is reported using Prosopis farcta as a natural precursor via a one-pot hydrothermal synthesis. The green-synthesized CQDs were characterized in terms of their functional groups and morphology. Transmission electron microscopy (TEM) revealed an average particle size of 1.95 nm, while spectroscopic analysis confirmed a strong fluorescence emission with a quantum yield (QY) of 27.6%. The CQDs possess carbonaceous cores with surface functional groups and show a maximum green emission wavelength at 495 nm. Particularly, the characterized CQDs show excellent sensitivity toward Fe3⁺ ions, leading to fluorescence quenching, enabling the development of a facile and efficient fluorescent sensing method for Fe3⁺ detection. This sensor demonstrated a linear response in the range of 0.1–0.5 µM with a detection limit as low as 15 nM. Furthermore, the method was successfully adapted for the analysis of environmental water samples, achieving satisfactory recovery rates. This work introduces a novel, eco-friendly approach to CQD synthesis from Prosopis farcta and presents a promising strategy for highly sensitive and selective Fe3⁺ detection, with potential applications in optical nano-thermometry and environmental monitoring.

Cesium lead bromide (CsPbBr3) nanocrystals exhibit remarkable optoelectronic properties and exceptional stability. As a result, they have garnered signi5cant interest for their potential applications in various 5elds, including solar cells, light-emitting devices, photodetectors, and lasers. Despite its resistance to moisture, oxygen, and heat compared to other perovskite materials, CsPbBr3 still faces challenges maintaining its structural and optical stability over extended periods. ,is study proposes a robust solution to enhance and improve simultaneously the photoluminescence intensity and stability of CsPbBr3 nanocrystals. ,e solution involves doping the perovskite precursor with green-synthesized carbon quantum dots (CQDs) and tri-n-octyl phosphine (TOP). ,e results indicate that the photoluminescence intensity of the perovskite nanocrystals (NCs) is sensitive to varying CQD ratios. A high photoluminescence intensity enhancement of 45% was achieved at the optimal CQDs ratio. ,e synthesized perovskite NCs/CQDs also demonstrated improved stability by adding TOP into the mixture. After storage in the air for 45 days, the mixed perovskite NCs maintained their performance, which was almost unchanged. Solar cell devices based on the modi5ed perovskite NCs showed a power conversion of 7.74%. ,e devices also demonstrated a signi5cant open-circuit voltage (VOC), with the most successful device achieving a VOC of 1.193 V, an Isc of 10.5748 mA cm−2, and a 5ll factor (FF) of 61%. ,is study introduces a costeDective method for producing high-quality all-inorganic optoelectronic devices with enhanced performance and stability.

This study synthesized carbon quantum dots (CQDs) with green photoluminescence through a hydrothermal method that utilized mulberry juice as the carbon source. *e in1uence of fruit ripeness on the physical and chemical properties, focusing on the 1uorescence spectra, has been explored. Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray analysis (EDX) showed that there were oxygen-containing groups, and X-ray di9raction (XRD) showed that the carbon quantum dots (CQDs) were graphitic. *e results revealed that the CQDs had an average size of around 7.4 nm and 9.7 nm for unripe and ripe mulberry juice, respectively. *ese CQDs emitted green light at 500 nm and 510 nm in unripe and ripe mulberry juice, respectively, when excited at a wavelength of 400 nm. *e prepared CQDs exhibited excitation-dependent photoluminescence (PL) emission behavior, demonstrating their dependence on the excitation light. *e impact of fruit ripeness on optical properties was explored by examining 1uorescent spectra from di9erent fruits (including tomato and blackberry), demonstrating comparable behaviors observed in mulberry fruit. In addition, the prepared CQDs were utilized as a 1uorescent sensor with high speci>city to detect Cu2+ ions. *e detection limit (DL) for this sensor was determined to be 0.2687 µM, and the limit of quali>cation (LOQ) is 0.814 µM. *e linear range for detection lies between 0.1 and 1 µM. *e selectivity of the CQDs towards Cu2+ ions was con>rmed by recording the PL response for Cu2+ ions compared to the weak response of other metal ions. According to these results, the CQDs can be applied in various cellular imaging and biology applications, bio-sensing, optoelectronics, and sensors.