Search Results (9)

The composition of the surface, optical response, and size of the carbon dots synthesized from Valencia orange peels (Citrus sinensis L. Osbeck) were studied. The peels used in the hydrothermal synthesis were at three ripeness stages, and the synthesis was carried out at 220 °C and 3 MPa. Infrared spectroscopy results showed that carbon dots synthesized from the peels of unripe oranges are functionalized with oxygenated groups, and the carbonization process was effective. Instead, carbon dots obtained from peels of ripe oranges exhibit a nitrogen-functionalized surface. These results were confirmed by the bond-breakdown analysis in photoelectron spectroscopy. Additionally, the self-doped surface modified the optical response of the carbon dots, exhibiting an enhancement of the absorption band located at 283 nm corresponding to the contribution from n-π* transitions in nitrogen. Also, the excitation and emission wavelengths present a red shift for the ripe peels. Based on the above and the transmission electron microscopy results, it is concluded that the emission mechanism is associated with surface states and not particle size. Statistical analysis yielded an average size of less than 10 nm, regardless of the orange peels’ ripeness stage. It was observed that the CDs-N3 sample has more crystalline nuclei, which is justified because ripe peels follow a shorter carbonization pathway. Full article

Graphitic carbon nitride (g-C₃N₄), an emerging metal-free semiconductor material, has attracted considerable attention in the field of photoelectrochemical (PEC) sensing due to its unique electronic structure, excellent chemical stability, and visible-light responsiveness. This article systematically reviews recent advances in research on g-C₃N₄-based PEC sensors applied to water environment monitoring. First, the fundamental physicochemical properties of g-C₃N₄ are introduced, along with its advantages and limitations in PEC sensing applications. Subsequently, four main performance enhancement strategies are outlined: heterojunction construction (including type II, Z-scheme, and S-scheme heterojunction), elemental doping and defect engineering, morphology control and nanostructure design, as well as various signal amplification approaches such as self-powered systems, dual-mode detection, and cyclic amplification. Furthermore, the current application status of these sensors in detecting typical water pollutants, including heavy metal ions (e.g., Pb²⁺, Cu²⁺, Cd²⁺, Hg²⁺), antibiotics (e.g., tobramycin, norfloxacin, kanamycin), pesticide residues (e.g., chlorpyrifos, atrazine, glyphosate), and pathogenic microorganisms (e.g., Salmonella, Candida albicans), is comprehensively reviewed, with particular emphasis on detection sensitivity, selectivity, and real-sample performance. Finally, the remaining challenges in terms of long-term stability, anti-interference capabilities in complex matrices, portability, and multifunctional integration are analyzed, and future development directions are proposed, including smartphone-based intelligent sensing, CRISPR/Cas12a-assisted signal amplification, and multi-target high-throughput detection. This review aims to provide a reference for the rational design and practical application of g-C₃N₄-based PEC sensors in the field of water environment monitoring. Full article

Cd-based perovskite materials have the advantages of high emission efficiency and tunable emission, as well as broad application prospects in the field of optoelectronics. However, achieving multimode dynamic luminescence under UV light excitation in a single system is a great challenge. Here, we successfully prepared Sb³⁺/Pb²⁺ co-doped Cs₇Cd₃Br₁₃ crystals by a simple hydrothermal method. Tunable emission from orange to white and then to blue, covering the wavelength range between 370 and 800 nm, was achieved by varying the doping concentration of Pb²⁺ ions in Cs₇Cd₃Br₁₃:0.5%Sb³⁺. Temperature-dependent photoluminescence (PL) spectra and density functional theory (DFT) calculations confirm that the wide-band white-light emission of Cs₇Cd₃Br₁₃: Sb³⁺/Pb²⁺ crystal comes from the first self-trapped exciton (STE1) of undoped Cs₇Cd₃Br₁₃ intrinsic capture state and the emission of free excitons (FEs) and STE2 induced by the confining effect and the Jahn–Teller effect by Pb²⁺ incorporation, as well as the Sb triplet self-trapped exciton (STE3). More specifically, the samples with the best co-doped ratio exhibit significant excitation-wavelength-dependent luminescence characteristics and can realize the conversion of the emission color from white and blue to orange. Based on the tunable emission characteristics of three emission colors, the material has good prospects in encryption and anti-counterfeiting applications. This work provides a new strategy for the application of Cd-based halides in the field of anti-counterfeiting. Full article

Cd_xNi_0.5−xCu_0.2Zn_0.3Fe₂O₄ (0 ≤ x ≤ 0.50) ferrite with a spinel structure was prepared using the sol–gel self-propagation method. The effects of Cd²⁺ doping on the structure, morphology, dielectric, and magnetic properties of Ni–Cu–Zn ferrite were examined using XRD, SEM, EDX, FTIR, MPMS, and dielectric tests. The cubic spinel structure was verified by XRD and FTIR analyses. The crystallite size and particle size information of the samples were obtained with XRD and SEM analysis. The sample particle size belonged to a class of nanoscale materials with a particle size range of 1–100 nm. The minor difference between the grain size and particle size indicated that the sample nanoparticles were composed of numerous microcrystals. The EDX spectra indicated that the samples contained all stoichiometric elements. MPMS was used to measure the hysteresis lines of the samples. According to the hysteresis line, the saturation magnetization intensity (M_s), coercivity (H_c), and magnetic moment (μ_B) of the sample increased and then decreased with the increase in cadmium concentration. The magnetization strength (M_s) is between 4–67 emu/g, and the coercivity (H_c) is between 9–46 Oe. The curves of the real part of the dielectric constant (ε′), the imaginary part of the dielectric constant (ε″), and the loss factor (tanδ) with frequency were measured in the frequency range 100 Hz–100 kHz by means of an impedance analyzer. The complex modulus spectrum was analyzed to understand the dynamics of the conduction process. Full article

The fibrillization and abnormal aggregation of β-amyloid (Aβ) peptides are commonly recognized risk factors for Alzheimer’s disease (AD) brain, and require an effective strategy to inhibit the Aβ deposition and treat AD. Herein, we designed and synthesized nitrogen-doped carbon dots (N-CDs) as an Aβ-targeted probe, which exhibits the capacity of inhibiting the 1–42 Aβ (Aβ_1–42) self-assembly in vitro. The N-CDs exhibited orange emission with an emission wavelength of 570 nm, which demonstrates their excellent optical properties with excitation-independent behavior. Meanwhile, the N-CDs have spherical morphologies with an average size of 2.2 nm, whose surface enriches the amino, carboxyl, and hydroxyl groups. These preparties are conducive to improving their biological water solubility and provide a large number of chemical bonds for further interaction with proteins. Contrary to this, the kinetic process, size evolutions, and morphologies changes of Aβ_1–42 were inhibited in the presence of N-CDs in the determination of a thioflavin T assay, dynamic light scattering, transmission electron microscope, etc. Finally, the safety application of N-CDs on Aβ_1–42-induced cytotoxicity was further demonstrated via in vitro cytotoxicity experiments. This work demonstrates the effective outcome of suppressing Aβ aggregation, which provides a new view into the high-efficiency and low-cytotoxicity strategy in AD theranostics. Full article

Dental caries, particularly secondary caries, which is the main contributor to dental repair failure, has been the subject of extensive research due to its biofilm-mediated, sugar-driven, multifactorial, and dynamic characteristics. The clinical utility of restorations is improved by cleaning bacteria nearby and remineralizing marginal crevices. In this study, a novel multifunctional dental resin composite (DRC) composed of Sr-N-co-doped titanium dioxide (Sr-N-TiO₂) nanoparticles and nano-hydroxyapatite (n-HA) reinforcing fillers with improved antibacterial and mineralization properties is proposed. The experimental results showed that the anatase-phase Sr-N-TiO₂ nanoparticles were synthesized successfully. After this, the curing depth (CD) of the DRC was measured from 4.36 ± 0.18 mm to 5.10 ± 0.19 mm, which met the clinical treatment needs. The maximum antibacterial rate against Streptococcus mutans (S. mutans) was 98.96%, showing significant inhibition effects (p < 0.0001), which was experimentally verified to be derived from reactive oxygen species (ROS). Meanwhile, the resin exhibited excellent self-remineralization behavior in an SBF solution, and the molar ratio of Ca/P was close to that of HA. Moreover, the relative growth rate (RGR) of mouse fibroblast L929 indicated a high biocompatibility, with the cytotoxicity level being 0 or I. Therefore, our research provides a suitable approach for improving the antibacterial and mineralization properties of DRCs. Full article

A multifunctional and biocompatible hybrid microgel (poly(VPBA-AAm)-CD) using N, S-doped carbon dots (CDs) and ethylene glycol dimethacrylate (EGDMA) as cross-linking agents, and 4-vinylbenzene boronic acid (VPBA) and acrylamide (AAm) as monomers, was designed in this work. This microgel can be easily prepared by a simple one-pot radical dispersion polymerization of the reactants using a rationally designed hydrogen-bonded complex method. The hybrid microgels were spherical particles with a smooth surface and an average particle size of 234 ± 8 nm. The poly(VPBA-AAm)-CD microgel displayed the glucose-responsive swelling within a clinically concerned range at a physiological pH and could realize the controllable release of insulin. In addition, the release rate of insulin in the hybrid microgel (poly(VPBA-AAm)-CD) could be triggered by glucose concentrations in the solution, and the increasing glucose concentrations can accelerate the insulin release. Further in vitro cytotoxicity studies showed that the microgel had good biocompatibility and no obvious toxicity to the cells. These indicate that the prepared microgel (poly(VPBA-AAm)-CD) may supply a new pattern for the self-regulating therapy of insulin deficiency in diabetes. Full article

In this work, we report on the effects of incorporating manganese (Mn) dopant into different sizes of cadmium selenide (CdSe) quantum dots (QDs), which improves the electronic and optical properties of the QDs for multiple applications such as light-emitting diodes, lasers, and biological labels. Furthermore, the greener inverse Micelle method was implemented using organic ligand, which is oleic acid. This binding of the surface enhanced the QDs’ surface trap passivation of Mn-doped CdSe, which then increased the quantity of the output. In addition, the inverse Micelle technique was used successfully to dope Mn into CdSe QDs without the risk of Mn dopants being self-purified as experienced by wurtzite CdSe QDs. Also, we report the X-ray photoelectron spectroscopy (XPS) results and analysis of zinc blended manganese-doped cadmium selenide quantum dots (Mn-doped CdSe QDs), which were synthesized with physical sizes that varied from 3 to 14 nm using the inverse Micelle method. The XPS scans traced the existence of the Se 3d and Cd 3d band of CdSe crystals with a 54.1 and 404.5 eV binding energy. The traced 640.7 eV XPS peak is proof that Mn was integrated into the lattice of CdSe QDs. The binding energy of the QDs was related to the increase in the size of the QDs. Full article

The fabrication and evaluation of a glassy carbon electrode (GCE) modified with self-doped polyaniline nanofibers (SPAN)/mesoporous carbon nitride (MCN) and bismuth for simultaneous determination of trace Cd²⁺ and Pb²⁺ by square wave anodic stripping voltammetry (SWASV) are presented here. The morphology properties of SPAN and MCN were characterized by transmission electron microscopy (TEM), and the electrochemical properties of the fabricated electrode were characterized by cyclic voltammetry (CV). Experimental parameters, such as deposition time, pulse potential, step potential, bismuth concentration and NaCl concentration, were optimized. Under the optimum conditions, the fabricated electrode exhibited linear calibration curves ranging from 5 to 80 nM for Cd²⁺ and Pb²⁺. The limits of detection (LOD) were 0.7 nM for Cd²⁺ and 0.2 nM for Pb²⁺ (S/N = 3). Additionally, the repeatability, reproducibility, anti-interference ability and application were also investigated, and the proposed electrode exhibited excellent performance. The proposed method could be extended for other heavy metal determination. Full article