Search Results (117)

Ternary metal chalcogenide quantum dots (QDs), such as CuInS₂, have attracted significant attention due to their lower toxicity compared to binary counterparts containing cadmium or lead, making them promising candidates for biomedical imaging and solar energy applications. The surfactant choice is critical for controlling nanocrystal nucleation, growth kinetics, and functionalization. This directly affects the toxicity and applications of QDs. In this work, we report a synthesis protocol for PVP-capped CuInS₂ QDs in an aqueous solution. Using density functional theory (DFT) calculations, we predicted the coordination patterns of PVP on the CuInS₂ QDs surface, providing insights into the stabilization mechanism. The synthesized QDs were characterized using TEM, XRD, XPS, and FTIR to assess their morphology, chemical composition, and surface chemistry. The QDs exhibited dual photoluminescence (PL) maxima at 550 nm and 680 nm, attributed to defect-related emissions, making them suitable for cell imaging applications. Cytotoxicity studies and cell imaging experiments demonstrate the excellent biocompatibility and effective staining capabilities of the PVP-capped CuInS₂ QDs, highlighting their potential as fluorescent probes for long-term, multicolor cell imaging including two-photon microscopy. Full article

The most commonly used optical oxygen sensing materials are phosphorescent molecules and functionalized nanocrystals. Many exploration studies on oxygen sensing have been carried out using the fluorescence or phosphorescence of semiconductor nanomaterials. Lead halide perovskite nanocrystals, a new type of ionic semiconductor, have excellent optical properties, making them suitable for use in optoelectronic devices. They also show promising applications in analytical sensing and biological imaging, especially manganese-doped perovskite nanocrystals for optical oxygen sensing. As a class of materials with diverse sources, copper iodide cluster semiconductors have rich structural and excellent luminescent properties, and have attracted attention in recent years. These materials have adjustable optical properties and sensitive stimulus response properties, showing great potential for optical sensing applications. This review paper provides a brief introduction to traditional oxygen sensing using organic molecules and introduces research on oxygen sensing using novel luminescent semiconductor materials, perovskite metal halides and copper iodide hybrid materials in recent years. It focuses on the mechanism and application of these materials for oxygen sensing and evaluates the future development direction of these materials for oxygen sensing. Full article

The need for eco-friendly, cost-effective, and scalable methods to synthesize carbon quantum dots (CQDs) remains a critical goal in nanotechnology. In this work, nitrogen-doped carbon quantum dots (N-CQDs) were successfully synthesized using cellulose nanocrystals (CNCs) derived from microcrystalline cellulose (MCC) and urea through a rapid one-step microwave-assisted method. The use of renewable cellulose as a precursor aligns with sustainable practices, offering a pathway to transform agricultural waste into valuable nanomaterials. Characterized by TEM, XRD, Raman, XPS, and PL spectroscopy, the N-CQDs demonstrated outstanding optical properties, including strong excitation-dependent fluorescence with an emission maximum at 420 nm. The N-CQDs exhibited exceptional selectivity and sensitivity toward Fe³⁺, achieving a detection limit of 75 nM. Additionally, the pH-dependent fluorescence and stability in diverse conditions highlight the N-CQDs’ versatility in environmental monitoring. This study establishes a foundation for using agricultural waste to produce high-performance nanostructures for sensing applications, advancing green nanotechnology and environmental solutions. Full article

We report super broad non-Hermitian line shape from out-of-phase and in-phase photon-phonon dressing (quantization) in Eu³⁺: NaYF₄ and Eu³⁺: BiPO₄ nanocrystals. The line shape is controlled by changing time gate position, time gate width, power, temperature, sample, photomultiplier tubes, and laser. We observed that the fluorescence (FL) line-shape contrasts are 69.23% for Eu³⁺: BiPO₄ and 43.75% for Eu³⁺: NaYF₄, owing to the stronger out-of-phase photon-phonon dressing (destructive quantization). Moreover, we observed that the spontaneous four-wave mixing (SFWM) line shape was approximately three times wider at 300 K than at 77 K for the [(12:1)-phase] Eu³⁺: NaYF₄ due to more high-frequency in-phase phonon dressing (strong constructive quantization). Furthermore, we showed that the noise line-shape width remains unchanged for Eu³⁺: BiPO₄ (16 nm) and Eu³⁺: NaYF₄ (12 nm) due to out-of-phase and in-phase photon-phonon dressing balance. Such results have potential applications in multi-channel band stop filter. Full article

A fluorescent probe based on ternary AgFeS₂ quantum dots has been prepared for the design of ternary chalcogenides. The nanoparticles are synthesized with oleylamine as a stabilizer at a low temperature (particle size in the range of 2 to 3 nm) and they exhibit an intense blue emission in aqueous media. As for their internal structure, each nanoparticle’s relative stoichiometric ratio (AgFe_1.01S_1.91) is very close to the theoretical value of 1:1:2. Their magnetic properties have been studied with a vibrating sample magnetometer and they have ferromagnetism between 4 K and 298 K (applied magnetic field ranging between −10,000 and 10,000 Oe). In the presence of iodide ions, the emission at 458 nm derived from AgFeS₂ QDs has been observed to give rise to fluorescence quenching. The detection system is based on a static quenching process and morphological change between iodide ions and AgFeS₂, which has a good linear range from 0 to 37.5 μmol/L, with a limit of detection of 0.99 μM. The nanoprobe responds within 30 s for the efficient detection of iodide. Such functional quantum dots will provide a powerful indicator in environmental and bio-sensing applications. Full article

Fluorescent materials for sensing have gained attention for the visual detection of different substances as metals and pesticides for environmental monitoring. This work presents fluorescent nanocomposites in solution, film, and paper obtained without capping and stabilizing agents, coming from quantum dots of cadmium sulfide (CdS QDs) and anionic–cationic polymer matrices. Fluorescent films were formed by casting and fluorescent paper by impregnation from the solutions. The optical properties of CdS QDs in solution showed absorption between 418 and 430 nm and a maximum emission at 460 nm. TEM analysis evidenced particle size between 3 and 6 nm and diffraction patterns characteristic of CdS nanocrystals. Infrared spectra evidenced changes in the wavenumber in the fluorescent films. The band gap values (2.95–2.82 eV) suggested an application for visible transmitting film. Fluorescent solutions by UV-vis and fluorescence evidenced a chemical interaction with glyphosate standard between 1 and 100 µg/mL concentrations. The analysis of red, green, and blue color codes (RGB) evidenced a color response of the fluorescent paper at 10 and 100 µg/mL, but the fluorescent films did not show change. Nanocomposites of chitosan and pectin, in solution and on paper, exhibited a behavior “turn-on” sensor, while carboxymethylcellulose had a “turn-off” sensor. This methodology presents three fluorescent materials with potential applications in visual sensing. Full article

Perovskite as an emerging semiconductor luminescent material has attracted widespread attention due to its simple preparation, high luminescence quantum yield, high color purity, tunable spectrum, and ability to cover the entire visible light band. However, due to the influence of water or other highly polar solvents, oxygen, temperature, and radiation, perovskite nanocrystals will aggregate or collapse in the lattice, eventually leading to luminescence quenching. This study starts from the postprocessing of perovskite, uses methyl methacrylate as the monomer and TPO as the photoinitiator, and encapsulates the perovskite powder prepared by the hot injection method through ultraviolet light initiation. A method is proposed to improve the luminescence and crystal structure stability of perovskite. By eliminating the influence of environmental factors on perovskite nanocrystals through the dense structure formed by organic polymers, the resistance of perovskite to strong polar solvents such as water will be greatly improved, and it has great potential in the protection of perovskite. Finally, by changing the proportion of halogen elements in the perovskite resin to change the color of the luminescent resin, a fluorescent coating emitting light in all visible light bands is prepared. Fluorescent coatings are widely used in life and industry fields such as plastics, sol, and paper. Full article

Perovskite is an advanced optoelectronic semiconductor material that has garnered significant attention in recent years. However, its drawback lies in its environmental instability, limiting its practical applications. To tackle this issue, this research delved into the idea of creating a space-confined structure and used electrospinning to produce a film of perovskite nanocomposite fibers. By effectively encapsulating perovskite nanocrystals into a polymer matrix, the perovskite could be shielded from water and oxygen in the environment, thereby reducing the likelihood of perovskite decomposition and enhancing the stability of its structure and properties. This study examined the influence of material composition and the spinning process on the nanofiber structure to create good spatial confinement. This strategy resulted in a high photoluminescence quantum yield of over 80% and a long-term environmental stability of as long as 1000 h over 90% of the original PLQY. By harnessing the flexibility of the composite fibers, this study demonstrated the potential applications and performance of this nanocomposite film in flexible quantum fluorescence conversion for LED applications. Full article

The vapochromic properties of [Pt(tpy)Cl](PF₆) crystals in the presence of acetonitrile and its effect on the crystal structure as well as the fluorescence spectrum of this complex have already been studied in the past. We synthesized nanocrystals of this compound for the first time, and discussed different parameters and methods that affect nanocrystal structure modulation. The study demonstrates the vapochromic properties of the nanocrystals toward acetonitrile vapor by investigating the morphology and fluorescence spectra of the nanocrystals. Vapochromic studies were conducted on [Pt(tpy)Cl](PF₆) nanocrystals for five cycles of absorption and desorption of acetonitrile, demonstrating shorter response times compared to regular bulk crystals. Full article

Utilizing glucose as a targeting agent represents a pioneering approach in selectively directing nanoparticles towards cancer cells, capitalizing on the pronounced glucose uptake observed in tumors attributable to the Warburg effect. In this study, we have successfully adopted this targeting strategy to facilitate the specific uptake of advanced nanotools, comprising carbon nanocrystals incorporating gold seeds (AuCDs). Leveraging the advantageous optical and size-related properties of carbon nanodots in conjunction with gold-mediated X-ray attenuation capabilities, these hybrid nanomaterials have been engineered as contrast agents for a bi-modal imaging modality, exploiting the synergistic benefits of fluorescence imaging and X-ray computed tomography. Notably, for the synthesis of AuCDs, we present, for the first time, the incorporation of gold seeds within the molecular precursors of carbon nanodots during their solvothermal synthesis process, showcasing the efficacy of this synthetic pathway in yielding nanoscale carbon structures incorporating bioeliminable gold ultrasmall nanoparticles (d < 5 nm). Subsequently, we employed an azido-alkyne click chemistry reaction to functionalize the nanoparticle surface with 2-deoxy-D-glucose as a targeting moiety. The demonstrated cancer-targeting proficiency, as assessed via fluorescence imaging, renders the proposed nanosystem highly promising for a spectrum of applications in precision anticancer theranostics, encompassing both diagnostic and therapeutic endeavors. Full article

In this research, upconversion nanocrystals incorporated with MOR zeolite composites were synthesized using the desilicated MOR zeolite as a host for the in situ growth of NaREF₄ (RE = Y, Gd) Yb/Er nanocrystals. The structure and morphology of the composites were studied with XRD, XPS, and TEM measurements, and the spectral studies indicated that the subsequent thermal treatment can effectively improve the upconversion emission intensity of Er³⁺. By using the NaYF₄:Yb/Er@DSi1.0MOR-HT composite that holds the strongest upconversion emission, a probe of UCNC@DSiMOR/BPEI was constructed with the modification of branched poly ethylenimine for the detection of Cu²⁺. It was indicated that the integrated emission intensity of Er³⁺ shows a linear dependence with the logarithm value of the Cu²⁺ concentration ranging from 0.1 to 10 μM. This study offered a feasible method for the construction of UCNC@zeolite composites with enhanced upconversion emission, which may have a potential application as fluorescent probes for the detection of various metal ions by adjusting the doping luminescent center. Full article

Even with significant developments in nanoscience, relatively little is known about the interactions of nanocrystal semiconducting materials with bio-macromolecules. To investigate the interfacial phenomena of cadmium selenide quantum dot (CdSe QD) nanocrystals with proteins extracted from Moringa oleifera seeds, different concentrations of cadmium selenide quantum dots–Moringa oleifera seed protein (CdSe–MSP) complexes were prepared. Respective CdSe QDs with hexagonal phase and crystalline size in the range of 4–7 nm were synthesized and labelled with the purified mesoporous MSP having a surface area of 8.4 m²/g. The interaction mechanism between CdSe QDs and MSP was studied using UV–Vis absorption, fluorescence emission and Fourier Transform Infrared spectroscopies. The UV–Vis absorption spectra showed absorption bands of CdSe–MSP complexes at 546.5 nm. The fluorescence intensity of CdSe QDs was found to decrease with increasing concentration of MSP. The thermodynamic potentials $∆H^{\theta }$ (−321.3 $\times {10}^3$ Jmol⁻¹);$∆S^{\theta }$ (156.0 JK⁻¹mol⁻¹) and $∆G^{\theta }$ (−46.6 $\times {10}^3$ Jmol⁻¹) were also calculated. The stability of the complex found is strongly influenced by electrostatics interaction and surface-bound complexation equilibrium attraction. This information can help to elucidate the surface characteristics of MSP and its potential interactions with other molecules or nanoparticles. Full article

Conventional single-component quantum dots (QDs) suffer from low recombination rates of photogenerated electrons and holes, which hinders their ability to meet the requirements for LED and laser applications. Therefore, it is urgent to design multicomponent heterojunction nanocrystals with these properties. Herein, we used CdSe quantum dot nanocrystals as a typical model, which were synthesized by means of a colloidal chemistry method at high temperatures. Then, CdS with a wide band gap was used to encapsulate the CdSe QDs, forming a CdSe@CdS core@shell heterojunction. Finally, the CdSe@CdS core@shell was modified through the growth of the ZnS shell to obtain CdSe@CdS@ZnS heterojunction nanocrystal hybrids. The morphologies, phases, structures and performance characteristics of CdSe@CdS@ZnS were evaluated using various analytical techniques, including transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy, fluorescence spectroscopy and time-resolved transient photoluminescence spectroscopy. The results show that the energy band structure is transformed from type II to type I after the ZnS growth. The photoluminescence lifetime increases from 41.4 ns to 88.8 ns and the photoluminescence quantum efficiency reaches 17.05% compared with that of pristine CdSe QDs. This paper provides a fundamental study and a new route for studying light-emitting devices and biological imaging based on multicomponent QDs. Full article

Quantum dots (QDs) are nanocrystal semiconductors that feature unique optical properties. However, they have a high density of dangling bonds on their surface, causing defects that can compromise their fluorescence. Their superficial passivation using another semiconductor is an alternative to reduce these defects. Herein, CdTe QDs stabilized with mercaptusuccinic acid (MSA) and cysteamine (CYA) were synthesized in water and coated with a ZnSe layer, forming a core–shell heterostructure. An improvement in photoluminescence greater than 300% was obtained for CdTe/ZnSe-MSA. However, for CdTe/ZnSe-CYA, the emission enhancement was around 55%. This study reinforces the importance of the experimental conditions to optimize QDs’ emission. Full article

In 1998, the diffracted X-ray tracking (DXT) method pioneered the attainment of molecular dynamics measurements within individual molecules. This breakthrough revolutionized the field by enabling unprecedented insights into the complex workings of molecular systems. Similar to the single-molecule fluorescence labeling technique used in the visible range, DXT uses a labeling method and a pink beam to closely track the diffraction pattern emitted from the labeled gold nanocrystals. Moreover, by utilizing X-rays with extremely short wavelengths, DXT has achieved unparalleled accuracy and sensitivity, exceeding initial expectations. As a result, this remarkable advance has facilitated the search for internal dynamics within many protein molecules. DXT has recently achieved remarkable success in elucidating the internal dynamics of membrane proteins in living cell membranes. This breakthrough has not only expanded our knowledge of these important biomolecules but also has immense potential to advance our understanding of cellular processes in their native environment. Full article