Journey of ZnO quantum dots from undoped to rare-earth and transition metal-doped and their applications

Use of Quantum Dots as Nanotheranostic Agents: Emerging Applications in Rare Genetic Diseases

Rare genetic diseases (RGDs) affect a small percentage of the global population but collectively have a substantial impact due to their diverse manifestations. Although the precise reasons behind these diseases remain unclear, roughly 80% of cases are genetically linked. Recent efforts focus on understanding pathology and developing new diagnostic and therapeutic approaches for RGDs. However, there persists a gap between fundamental research and clinical therapeutic approaches, where advancements in nanotechnology offer promising improvements. In this context, nanosized light-emitting quantum dots (QDs), ranging from 2-10 nm, are promising materials for diverse applications. Their size-tunable light emission, high quantum yield, and photostability allow for precise tracking of cargo. Additionally, QDs can be functionalized with therapeutic agents, antibodies, or peptides to target specific cellular pathways, enhancing treatment efficacy while minimizing side effects. By combining diagnostic and therapeutic capabilities in a single platform, QDs thus offer a versatile and powerful approach to tackle rare genetic disorders. Despite several reviews on various therapeutic applications of QDs, their utilization in the specific domain of RGDs is not well documented. This review highlight QDs' potential in diagnosing and treating certain RGDs and addresses the challenges limiting their application.

Cost-effective synthesis of zinc oxide/crab shell-derived chitosan nanocomposite: Insights into its biomedical applications

For biomedical applications, material scientists all over the world are working to develop cost-effective technologies and thereby synthesize new nanocomposite materials that are biocompatible, bioactive, scalable and naturally abundant. This study focuses on synthesizing and evaluating nanocomposites of zinc oxide (ZnO) and chitosan (CS) derived from crab shells, in three different weight proportions (1:0.5, 1:1, and 1:2). ZnO/CS nanocomposites were synthesized using a soft-chemical method. Characterization of the nanocomposites was done using XRD, FESEM, EDAX, FTIR, and PL techniques. Among the three formulations, the ZnO/CS nanocomposite with a 1:2 ratio (ZnO/CS)1:2 exhibited the most significant antioxidant, anti-diabetic, and antibacterial properties. The (ZnO/CS)1:2 demonstrated 89.46 and 90.85 % of inhibition in DPPH and superoxide free radical scavenging assays, respectively, and showed 91.86 % inhibition against the alpha-glucosidase enzyme. It also exhibited strong antibacterial activity against both gram-positive (Staphylococcus epidermidis, Bacillus subtilis) and gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Additionally, the cytotoxicity of the (ZnO/CS)1:2 nanocomposite was assessed against the MCF-7 breast cancer cell line, showing an IC50 value of 11.58 ± 0.05 μg/mL at 30 μg/mL. The (ZnO/CS)1:2 nanocomposite shows potential as a candidate for biomedical applications, particularly in antioxidant, anti-diabetic, and antibacterial activities.

Principles and Applications of ZnO Nanomaterials in Optical Biosensors and ZnO Nanomaterial-Enhanced Biodetection

Significant research accomplishments have been made so far for the development and application of ZnO nanomaterials in enhanced optical biodetection. The unparalleled optical properties of ZnO nanomaterials and their reduced dimensionality have been successfully exploited to push the limits of conventional optical biosensors and optical biodetection platforms for a wide range of bioanalytes. ZnO nanomaterial-enabled advancements in optical biosensors have been demonstrated to improve key sensor performance characteristics such as the limit of detection and dynamic range. In addition, all nanomaterial forms of ZnO, ranging from 0-dimensional (0D) and 1D to 2D nanostructures, have been proven to be useful, ensuring their versatile fabrication into functional biosensors. The employment of ZnO as an essential biosensing element has been assessed not only for ensembles but also for individual nanomaterials, which is advantageous for the realization of high miniaturization and minimal invasiveness in biosensors and biodevices. Moreover, the nanomaterials' incorporations into biosensors have been shown to be useful and functional for a variety of optical detection modes, such as absorption, colorimetry, fluorescence, near-band-edge emission, deep-level emission, chemiluminescence, surface evanescent wave, whispering gallery mode, lossy-mode resonance, surface plasmon resonance, and surface-enhanced Raman scattering. The detection capabilities of these ZnO nanomaterial-based optical biosensors demonstrated so far are highly encouraging and, in some cases, permit quantitative analyses of ultra-trace level bioanalytes that cannot be measured by other means. Hence, steady research endeavors are expected in this burgeoning field, whose scientific and technological impacts will grow immensely in the future. This review provides a timely and much needed review of the research efforts made in the field of ZnO nanomaterial-based optical biosensors in a comprehensive and systematic manner. The topical discussions in this review are organized by the different modes of optical detection listed above and further grouped by the dimensionality of the ZnO nanostructures used in biosensors. Following an overview of a given optical detection mode, the unique properties of ZnO nanomaterials critical to enhanced biodetection are presented in detail. Subsequently, specific biosensing applications of ZnO nanomaterials are discussed for ~40 different bioanalytes, and the important roles that the ZnO nanomaterials play in bioanalyte detection are also identified.

Effect of surface ligands on the photoinduced electron transfer rate and efficiency in ZnO quantum dots and graphene oxide assemblies

Apart from biocompatibility, ZnO quantum dots (QDs) are considered to be an efficient luminescence material due to their low cost and high redox potential. Here, we report the synthesis of ZnO QDs by using five different functionalizing ligands like mercaptoacetic acid (MAA), 3-mercaptopropionic acid (MPA), octadecene (ODE), ethylene glycol (EG), and oleyl amine (OLA) and fabricate their assemblies with graphene oxide (GO). We investigate the role of functionalizing ligands as a surface modifier of ZnO QDs for their attachment to GO. The steady-state photoluminescence (SSPL) and time-resolved photoluminescence (TRPL) analyses demonstrate the photoluminescence (PL) quenching of ZnO QDs in ZnO QDs-GO assembly. The highest reduction in PL intensity is observed with ZnO QDs-GO assembly with EG as a surface functionalizing ligand. Cyclic voltammetry (CV) analysis confirms the feasibility of charge transfer from ZnO QDs to the GO. The maximum (79.43%) charge transfer efficiency (ECT) is observed in the case of ZnO-MAA-GO as compared to other assemblies. This means the thiol group-containing ligands facilitate charge transfer as compared to hydroxyl and amine group ligands. This leads to the conclusion that charge transfer in ZnO QDs-GO assemblies depends strongly on the nature of surface ligands.

On the Fate of Lithium Ions in Sol-Gel Derived Zinc Oxide Nanocrystals

Among diverse chemical synthetic approaches to zinc oxide nanocrystals (ZnO NCs), ubiquitous inorganic sol-gel methodology proved crucial for advancements in ZnO-based nanoscience. Strikingly, unlike the exquisite level of control over morphology and size dispersity achieved in ZnO NC syntheses, the purity of the crystalline phase, as well as the understanding of the surface structure and the character of the inorganic-organic interface, have been limited to vague descriptors until very recently. Herein, ZnO NCs applying the standard sol-gel synthetic protocol are synthesized with zinc acetate and lithium hydroxide and tracked the integration of lithium (Li) cations into the interior and exterior of nanoparticles by combining various techniques, including advanced solid-state NMR methods. In contrast to common views, it is demonstrated that Li+ ions remain kinetically trapped in the inorganic core, enter into a shallow subsurface layer, and generate "swelling" of the surface and interface regions. Thus, this work enabled both the determination of the NCs' structural imperfections and an in-depth understanding of the unappreciated role of the Li+ ions in impacting the doping and the passivation of sol-gel-derived ZnO nanomaterials.

Inkjet printing of heavy-metal-free quantum dots-based devices: a review

Inkjet printing (IJP) has become a versatile, cost-effective technology for fabricating organic and hybrid electronic devices. Heavy-metal-based quantum dots (HM QDs) play a significant role in these inkjet-printed devices due to their excellent optoelectrical properties. Despite their utility, the intrinsic toxicity of HM QDs limits their applications in commercial products. To address this limitation, developing alternative HM-free quantum dots (HMF QDs) that have equivalent optoelectronic properties to HM QD is a promising approach to reduce toxicity and environmental impact. This article comprehensively reviews HMF QD-based devices fabricated using IJP methods. The discussion includes the basics of IJP technology, the formulation of printable HMF QD inks, and solutions to the coffee ring effect. Additionally, this review briefly explores the performance of typical state-of-the-art HMF QDs and cutting-edge characterization techniques for QD inks and printed QD films. The performance of printed devices based on HMF QDs is discussed and compared with those fabricated by other techniques. In the conclusion, the persisting challenges are identified, and perspectives on potential avenues for further progress in this rapidly developing research field are provided.

Recent advances on outstanding microwave absorption and electromagnetic interference shielding nanocomposites of ZnO semiconductor

The electromagnetic interference shielding and microwave attenuation capabilities of ZnO semiconductor nanocomposites have recently been improved using a variety of approaches by correctly modifying their permittivity. To improve microwave attenuation, ZnO semiconductor nanostructures have been combined with graphene, multi-wall carbon nanotubes, metal nanoparticles and their alloys, two-dimensional MXene, spinel ferrite magnetic nanoparticles, polymer systems, and textiles. This paper covers the opportunities and constraints that these cutting-edge nanocomposites in the field of electromagnetic wave absorption encounter as well as the research progress of ZnO semiconductor-based nanocomposite. The structure-function relationship of electromagnetic wave absorption nanocomposites, design strategies, synthesis techniques, and various types of advanced nanocomposites based on ZnO semiconductor are also covered. In order to design and prepare high efficiency ZnO semiconductor based electromagnetic wave absorbing materials for use in applications of next-generation electronics and aerospace, this article can offer some useful ideas.

Highly selective electroreduction of CO2 to CO with ZnO QDs/N-doped porous carbon catalysts

ZnO quantum dots (QDs) supported on porous nitrogen-doped carbon (ZnOQDs/P-NC) exhibited excellent electrochemical performance for the electroreduction of CO2 to CO with a faradaic efficiency of 95.3% and a current density of 21.6 mA cm-2 at -2.2 V vs. Ag/Ag+.

Green-route synthesis and ab-initio studies of a highly efficient nano photocatalyst:Ce/zinc-oxide nanopetals

In the present work, Zinc-oxide nanostructures and Ce/Zinc-oxide nanopetals were synthesized by a new environmentally friendly green synthesis method using the Withania coagulans plant. Cerium nitrate Ce(NO3)3 and zinc nitrate Zn(NO3)2 were used as precursors. The prepared nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet spectroscopy (UV-vis). Crystal planes (100), (002), (101), (102), (110), (103), (200), (112) and (201) at 2θ 31.75°, 34.35°, 36.2°, 47.55°, 56.6°, 62.75°, 66.3°, 67.9°, and 69.09° respectively confirmed the hexagonal wurtzite crystal structure of Zinc-oxide. Angular shifts for Ce1% doped Zinc-oxide and Ce3% doped Zinc-oxide nanopetal nanostructures were observed in the (100) and (101) planes of the crystal. More specifically, using Scherrer's equation, the crystallite sizes of Zinc-oxide, Ce1% doped Zinc-oxide nanopetals, Ce3% doped Zinc-oxide nanopetals, and Ce5% doped Zinc-oxide nanopetals were 16.48 ± 02 nm, 17.8 ± 2 nm, 18.8 ± 2 nm, and 18.87 ± 2 nm, respectively. The pure Zinc-oxide grain had the appearance of a nanoflower. On the other hand, the nanopetal structure of Ce5% doped Zinc-oxide nanopetals had oval-shaped nanopetal morphology. The absorption peaks were observed at 373, 376.4, 377, and 378 nm for Zinc-oxide, Ce1% doped Zinc-oxide nanopetals, Ce3% doped Zinc-oxide nanopetals, and Ce5% doped Zinc-oxide nanopetals, respectively, which results in a progressive redshift. The gap energies of Zinc-oxide, Ce1% doped Zinc-oxide nanopetals, Ce3% doped Zinc-oxide nanopetals, and Ce5% doped Zinc-oxide nanopetals were 2.796, 2.645, 2.534, and 2.448 eV, respectively. Photodegradation under visible light (>400 nm) indicates the high efficiency of the photocatalyst based on Ce5% doped Zinc-oxide nanopetals. DFT calculations, structural changes, charge analysis, and electronic band structures were carried out to confirm the experiment.

Exploring Functional Polymers in the Synthesis of Luminescent ZnO Quantum Dots for the Detection of Cr6+, Fe2+, and Cu2

The main aim of this work is to demonstrate that well-defined methacrylate-based copolymers with oligoethylene glycol side chains and functional groups such as thiol and glycidyl, obtained by photo-initiated reversible addition-fragmentation chain transfer (RAFT) in ethanol, are highly suitable as templates in the synthesis and protection of ZnO quantum dots (ZnO QDs) with remarkable photoluminescent properties. While the affinity of thiol groups to metallic surfaces is well established, their interaction with metal oxides has received less scrutiny. Furthermore, under basic conditions, glycidyl groups could react with hydroxyl groups on the surface of ZnO, representing another strategy for hybrid synthesis. The size and crystalline morphology of the resulting hybrids were assessed using DLS, TEM, and XRD, indicating that both polymers, even with a low proportion of functional groups (5% mol) are appropriate as templates and ligands for ZnO QDs synthesis. Notably, thiol-containing polymers yield hybrids with ZnO featuring excellent quantum yield (up to 52%), while polymers with glycidyl groups require combination with the organosilane aminopropyl triethoxysilane (APTES) to achieve optimal results. In both cases, these hybrids exhibited robust stability in both ethanol and aqueous environments. Beyond fundamental research, due to the remarkable photoluminescent properties and affordability, these hybrid ZnO QDs are expected to have potential applications in biotechnology and green science; in particular, in this study, we examined their use in the detection of environmental contaminants like Fe2+, Cr6+, and Cu2+. Specifically, the limit of detection achieved at 1.13 µM for the highly toxic Cr6+ underscores the significant sensing capabilities of the hybrids.

Optical and Antibacterial Properties of Chiral Arginine-Stabilized ZnO Nanoparticles

The surface ligands of nanoparticles (NPs) play essential roles in material synthesis, properties, and applications. Chiral molecules have been the new hot topic in tuning the properties of inorganic NPs. Herein, l-arginine- and d-arginine-stabilized ZnO NPs were prepared, and the TEM, UV-vis, and PL spectra were investigated, which demonstrated that the l-arginine and d-arginine have different effects on the self-assembly and photoluminescence properties of ZnO NPs, showing an evident chiral effect. Furthermore, the results of the cell viability assays, plate counting method, and bacterial SEM images showed that ZnO@LA possessed lower biocompatibility and higher antibacterial efficiency than those of ZnO@DA, implying that the chiral molecules on the surface of nanomaterials may affect their bioproperties.

Antibacterial Activity of Solvothermal Obtained ZnO Nanoparticles with Different Morphology and Photocatalytic Activity against a Dye Mixture: Methylene Blue, Rhodamine B and Methyl Orange

In this paper, we report the synthesis of ZnO nanoparticles (NPs) by forced solvolysis of Zn(CH3COO)2·2H2O in alcohols with a different number of –OH groups. We study the influence of alcohol type (n-butanol, ethylene glycol and glycerin) on the size, morphology, and properties of the obtained ZnO NPs. The smallest polyhedral ZnO NPs (<30 nm) were obtained in n-butanol, while in ethylene glycol the NPs measured on average 44 nm and were rounded. Polycrystalline particles of 120 nm were obtained in glycerin only after water refluxing. In addition, here, we report the photocatalytic activity, against a dye mixture, of three model pollutants: methyl orange (MO), methylene blue (MB), and rhodamine B (RhB), a model closer to real situations where water is polluted with many chemicals. All samples exhibited good photocatalytic activity against the dye mixture, with degradation efficiency reaching 99.99%. The sample with smallest nanoparticles maintained a high efficiency >90%, over five catalytic cycles. Antibacterial tests were conducted against Gram-negative strains Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa, and Escherichia coli, and Gram-positive strains Enterococcus faecalis, Bacillus subtilis, Staphylococcus aureus, and Bacillus cereus. The ZnO samples presented strong inhibition of planktonic growth for all tested strains, indicating that they can be used for antibacterial applications, such as water purification.

Concentration-dependent dielectric and electro-optical properties of composites based on nematic liquid crystals and CdS:Mn quantum dots

Composites in a wide concentration range of 0-0.6 wt% based on a nematic liquid crystal mixture and CdS quantum dots doped with manganese ions (Mn 6%) are presented. The effect of the CdS:Mn quantum dots on the phase diagram and electronic structure of composites was studied using differential scanning calorimetry and fluorescence analysis. Nonmonotonic concentration-dependent changes in the clearing point, which correlate with the fluorescence quenching behavior of the main CdS:Mn peak, were found. Dielectric spectroscopy and electro-optic studies revealed a corresponding increase in the dielectric permittivity anisotropy and birefringence in the 0.2-0.4 wt% range, where thermodynamic changes occur. The initiating factors behind this effect are supposed to be the self-assembly of quantum dots, and the distortion of the orientation order of liquid crystal molecules at a higher mass concentration of quantum dots.

Recent Progress in Solution Processed Aluminum and co-Doped ZnO for Transparent Conductive Oxide Applications

With the continuous growth in the optoelectronic industry, the demand for novel and highly efficient materials is also growing. Specifically, the demand for the key component of several optoelectronic devices, i.e., transparent conducting oxides (TCOs), is receiving significant attention. The major reason behind this is the dependence of the current technology on only one material-indium tin oxide (ITO). Even though ITO still remains a highly efficient material, its high cost and the worldwide scarcity of indium creates an urgency for finding an alternative. In this regard, doped zinc oxide (ZnO), in particular, solution-processed aluminum doped ZnO (AZO), is emerging as a leading candidate to replace ITO due to its high abundant and exceptional physical/chemical properties. In this mini review, recent progress in the development of solution-processed AZO is presented. Beside the systematic review of the literature, the solution processable approaches used to synthesize AZO and the effect of aluminum doping content on the functional properties of AZO are also discussed. Moreover, the co-doping strategy (doping of aluminum with other elements) used to further improve the properties of AZO is also discussed and reviewed in this article.

Influence of the Alcohols on the ZnO Synthesis and Its Properties: The Photocatalytic and Antimicrobial Activities

Zinc oxide (ZnO) nanomaterials are used in various health-related applications, from antimicrobial textiles to wound dressing composites and from sunscreens to antimicrobial packaging. Purity, surface defects, size, and morphology of the nanoparticles are the main factors that influence the antimicrobial properties. In this study, we are comparing the properties of the ZnO nanoparticles obtained by solvolysis using a series of alcohols: primary from methanol to 1-hexanol, secondary (2-propanol and 2-butanol), and tertiary (tert-butanol). While the synthesis of ZnO nanoparticles is successfully accomplished in all primary alcohols, the use of secondary or tertiary alcohols does not lead to ZnO as final product, underlining the importance of the used solvent. The shape of the obtained nanoparticles depends on the alcohol used, from quasi-spherical to rods, and consequently, different properties are reported, including photocatalytic and antimicrobial activities. In the photocatalytic study, the ZnO obtained in 1-butanol exhibited the best performance against methylene blue (MB) dye solution, attaining a degradation efficiency of 98.24%. The comparative study among a series of usual model dyes revealed that triarylmethane dyes are less susceptible to photo-degradation. The obtained ZnO nanoparticles present a strong antimicrobial activity on a broad range of microorganisms (bacterial and fungal strains), the size and shape being the important factors. This permits further tailoring for use in medical applications.

Effect of h-BN Support on Photoluminescence of ZnO Nanoparticles: Experimental and Theoretical Insight

Herein we report a simple and easily scalable method for fabricating ZnO/h-BN composites with tunable photoluminescence (PL) characteristics. The h-BN support significantly enhances the ultraviolet (UV) emission of ZnO nanoparticles (NPs), which is explained by the ZnO/h-BN interaction and the change in the electronic structure of the ZnO surface. When h-BN NPs are replaced with h-BN microparticles, the PL in the UV region increases, which is accompanied by a decrease in visible light emission. The dependence of the PL properties of ZnO NPs on the thickness of h-BN carriers, observed for the first time, is explained by a change in the dielectric constant of the support. A quantum chemical analysis of the influence of the h-BN thickness on the electron density redistribution at the wZnO/h-BN interface and on the optical properties of the wZnO/h-BN composites was carried out. Density functional theory (DFT) calculations show the appearance of hybridization at the h-BN/wZnO interface and an increase in the intensity of absorption peaks with an increase in the number of h-BN layers. The obtained results open new possibilities for controlling the properties of ZnO/h-BN heterostructures for various optical applications.

RAFT Hydroxylated Polymers as Templates and Ligands for the Synthesis of Fluorescent ZnO Quantum Dots

The remarkable photoluminescent properties, biocompatibility, biodegradability, and antibacterial properties of zinc oxide quantum dots (ZnO QDs) coupled with their low cost and nanoscale size guarantee bio-related and technological applications. However, the effect of the polymeric ligand during synthesis has hardly been investigated compared to other less environmentally friendly QDs. Thus, the objective of this work was to focus on the synthesis of fluorescent hybrid ZnO QDs by the sol-gel method using different polymers with hydroxyl groups as templates and ligands to obtain stable particles in different media. For this purpose, well-defined hydroxylated statistical polymers and block copolymers were synthesized using reversible-addition fragmentation chain transfer (RAFT) polymerization to establish the influence of molecular weight, hydrophobic/hydrophilic balance, and polymer architecture on the colloidal and photophysical properties of the synthesized hybrid ZnO QDs. Dynamic light scattering (DLS), TEM, and X-ray diffraction measurements indicated the formation of stable nanoparticles of a few nanometers. A remarkable enhancement in terms of fluorescence was observed when ZnO QDs were synthesized in the presence of the hydroxylated homopolymers and even more so with block copolymers architecture. Organosilanes combined with the hydroxylated polymers were used to improve the colloidal stability of ZnO QDs in aqueous media. These samples exhibited uniform and stable enhanced photoluminescence for nearly five months of being investigated. Among other applications, the hybrid ZnO QDs synthesized in this work exhibit high selectivity to detect Cr⁶⁺, Fe²⁺, or Cu²⁺ in water.

High-Efficiency Photodynamic Antibacterial Activity of NH2-MIL-101(Fe)@MoS2/ZnO Ternary Composites

Bacterial infections are a serious threat to human health, and the development of effective antibacterial agents represents a critical solution. In this study, NH₂-MIL-101(Fe)@MoS₂/ZnO ternary nanocomposites are successfully prepared by a facile wet-chemistry procedure, where MoS₂ nanosheets are grown onto the MIL-101 scaffold forming a flower-like morphology with ZnO nanoparticles deposited onto the surface. The ternary composites exhibit a remarkable sterilization performance under visible light irradiation toward both Gram-negative and Gram-positive bacteria, eliminating 98.6% of Escherichia coli and 90% of Staphylococcus aureus after exposure to visible light for 30 min, a performance markedly better than that with NH₂-MIL-101(Fe)@MoS₂ binary composites and even more so than MoS₂ nanosheets alone. This is ascribed to the unique electronic band structure of the composites, where the separation of the photogenerated carriers is likely facilitated by the S-scheme mechanism in the NH₂-MIL-101(Fe)@MoS₂ binary composites and further enhanced by the formation of a p-n heterojunction between MoS₂ and ZnO in the ternary composites. This interfacial charge transfer boosts the effective production of superoxide radicals by the reduction of oxygen, and the disproportionation reaction with water leads to the formation of hydroxy radicals, as attested in spectroscopic and microscopic measurements. Results from this study highlight the significance of structural engineering of nanocomposites in the manipulation of the electronic band structure and hence the photodynamic activity.

Hybrid ZnO nanostructures modified graphite electrode as an efficient urea sensor for environmental pollution monitoring

Herein, we propose a facile electrochemical sensing platform for urea detection using pencil graphite electrode modified nanocomposites of CuO/ZnO and Fe₂O₃/ZnO. The detection of urea is essential to monitor for identifying its pollution in the water, at the soil surface and in diagnosing urea cycle disorder related diseases. Therefore, an effective, accurate, cost-effective method of diagnosis is urgently needed. Nanostructured metal oxides have the potential ability to detect molecules even at trace level and to explore this, the present work is formulated with Cu and Fe based ZnO nanocomposites for enhancing the sensing performance towards electrochemical sensing of urea. The sensing responses were confirmed from the increase in oxidation current with respect to the concentration of urea. The results show that Fe₂O₃/ZnO coated graphite electrode has a higher response against urea compared to ZnO and CuO/ZnO. The cyclic voltammetry studies also validate urea sensing of Fe-ZnO in the linear range of 0.8 μg/mL to 4 μg/mL, with the detection limit of 2.5 μg/mL. This suggests that the cost-effective pencil graphite electrode modified Fe₂O₃/ZnO can be utilized as a promising analytical tool for urea sensing.

Exploring the photoexcited electron transfer dynamics in artificial sunscreen PBSA-coupled biocompatible ZnO quantum dots

Frequent exposure to ultraviolet (UV) radiation without any protection turns out to be a fatal threat leading to skin cancer, necessitating the use of sunscreen cosmetic product with enhanced efficiency to dissipate the UV absorbed energy.

Anodic near-infrared electrochemiluminescence from Cu-doped CdTe quantum dots for tetracycline detection

A sensitive anodic near-infrared electrochemiluminescence (ECL) immunosensor for the detection of tetracycline, based on Cu-doped CdTe quantum dots, was fabricated for the first time in this work. We have synthesized Cu-doped CdTe quantum dots by co-precipitation. The emission spectrum of the Cu-doped CdTe quantum dots could reach the near-infrared region at 730 nm in a short reflux time. More importantly, the ECL intensity of the CdTe quantum dots was enhanced by 2 fold after Cu element doping, which was attributed to the Cu d-orbital mixed with the conduction band and valence band of the host CdTe quantum dots. Inspired by the strong anodic ECL intensity of Cu-doped CdTe quantum dots, the anodic near infrared ECL sensor was constructed to detect tetracycline by competitive immunoassay. The detection range of the developed biosensor was 0.01-10 ng mL-1 and the detection limit was 0.0030 ng mL-1. In addition, the biosensor showed outstanding selectivity, long-term stability and high reproducibility, which has great potential in the field of analysis and detection.

Novel N,Cl-doped deep eutectic solvents-based carbon dots as a selective fluorescent probe for determination of morphine in food

In the present study, new N,Cl co-doped carbon dots (N,Cl-CDs) based on deep eutectic solvent (DES) were fabricated by a facile hydrothermal process. This fluorescent probe exhibited a good quantum yield of 14% and was applied for the sensitive and selective quantification of morphine in foods. In addition, the influence of solution pH, interaction time, system temperature, interfering substances and analogues on the determination was also investigated. Under the optimized conditions, the luminescence intensity of carbon dots increased linearly with the addition of morphine in the concentration range of (0.15–280.25) μg mL⁻¹ (R² > 0.9969) and the limit of detection (LOD) of 46.5 ng mL⁻¹. Based on these results, it is suggested that N,Cl-CDs is a promising fluorescent probe for sensitive and selective quantification of morphine in foods.

A schematic illustrating the synthesis and morphine detection of N,Cl-CDs.