Potential Of Quantum Dots Research Articles

Versatile Approaches of Quantum Dots in Biosensing and Imaging.

Cancer is considered a formidable global health threat, despite substantial strides in diagnosis, detection, and therapeutic strategies. Remarkable progress has been achieved in these realms, yet the survival rates for cancer patients have persisted at suboptimal levels over decades. Acknowledging the need to address the ongoing challenges in cancer survival rates, research efforts are being made to push the boundaries of innovation in diagnostic techniques, bioimaging, and drug delivery technologies. Over the past few years, nano(bio)technology-based approaches have been applied for biosensing and imaging applications to detect biochemical substances in various matrices. Among various nanoengineered particulates, quantum dots (QDs) have been recognized as versatile agents for these applications. QDs, often called artificial atoms, are characterized by the remarkable optical and electrical features which are essential for cytosensing, localized bioimaging and therapeutics. Here in this review, we have discussed various QDs as sensitive and selective agents for precise sensing and imaging of cancer cells. Both electrochemical and optical approaches have been used to describe the cytosensing detection methods. Furthermore, the bioimaging of malignant tumor cells and the drug delivery with therapeutic responses of QDs have also been highlighted. This review also lists the several kinds of QDs that are frequently used for such kinds of applications, such as carbon, graphene, zinc, and other types of hybrid-based QDs. Finally, to shed insight on prospective research, the advantages and potential of QDs are also highlighted. In this article, we also emphasize the limitations and address the difficulties associated with QDs in clinical applications in order to provide insights for potential solutions.

(Invited) Synthetic Strategies to Lower the Barrier for Making High Quality Quantum Dot Probes

Quantum dot (QD)-based bioimaging requires QDs with exceptional optical quality and well-controlled surface properties. Although extensive research has been carried out to produce high-quality nanocrystals and to design biocompatible ligands, significant expertise is required to synthesize the best quality QDs and ligands reported. Commercially available QDs often fail to meet the required quality and suffer from irreproducibility in their performance. These restrictions have limited the wide adoption of QDs for biomedical imaging in non-expert groups. My group strives to lower the barrier to preparing high-quality QD probes in a wide range of wavelengths. In this talk, I will discuss the synthetic strategies that we have developed to systematically grow high-quality nanocrystals of various sizes and materials with minimal human intervention and simplify the synthesis of polyimidazole ligands without compromising their quality. By lowering the synthetic barrier to high-quality QDs, we envision unleashing the full potential of QDs in various fields.

Exploring various Integration Methods of carbon quantum dots in CsPbCl3 perovskite solar cells for enhanced power conversion efficiency

In this study, we explore the integration of carbon quantum dots (QDs) in cesium lead halide perovskite solar cells (PSCs) across the electron transport layer (ETL), hole transport layer (HTL), and the perovskite absorber to enhance power conversion efficiency (PCE). We conduct a comprehensive investigation from thin film analysis to complete device characterization, encompassing eight different device topologies. Our results reveal that the integration of QDs in various layers significantly impacts the performance of the PSCs. Notably, adding QDs in the HTL and ETL improves charge transport and reduces recombination, enhancing device efficiency. Furthermore, introducing QDs in the perovskite layer leads to modifications in the energy landscape, reducing charge trapping and enhancing stability. We observe a trade-off between short-circuit current and overall PCE, with different QD integration strategies yielding distinct performance outcomes. Additionally, incorporating QDs in the ETL layer reduces hysteresis, attributed to mitigated ion migration and charge-trapping effects. Overall, the addition of QDs in these layers demonstrates improved charge transport, reduced recombination, and enhanced stability, ultimately contributing to the enhanced performance and efficiency of perovskite solar cells, reaching 22.5%. This study paves the way for future investigations into the potential of QDs in PSC technology and their impact on device forecasting and operational stability.

Gazing Beyond the Horizon: A Systematic Review Unveiling the Theranostic Potential of Quantum Dots in Alzheimer's Disease.

Alzheimer's disease (AD), a neurodegenerative disorder characterized by cognitive decline, poses a significant healthcare challenge worldwide. The accumulation of amyloid-beta (Aβ) plaques and hyperphosphorylated tau protein drives neuronal degeneration and neuroinflammation, perpetuating disease progression. Despite advancements in understanding the cellular and molecular mechanisms, treatment hurdles persist, emphasizing the need for innovative intervention strategies. Quantum dots (QDs) emerge as promising nanotechnological tools with unique photo-physical properties, offering advantages over conventional imaging modalities. This systematic review endeavors to elucidate the theranostic potential of QDs in AD by synthesizing preclinical and clinical evidence. A comprehensive search across electronic databases yielded 20 eligible studies investigating the diagnostic, therapeutic, or combined theranostic applications of various QDs in AD. The findings unveil the diverse roles of QDs, including inhibiting Aβ and tau aggregation, modulating amyloidogenesis pathways, restoring membrane fluidity, and enabling simultaneous detection of AD biomarkers. The review highlights the potential of QDs in targeting multiple pathological hallmarks, delivering therapeutic payloads across the blood-brain barrier, and facilitating real-time imaging and high-throughput screening. While promising, challenges such as biocompatibility, surface modifications, and clinical translation warrant further investigation. This systematic review provides a comprehensive synthesis of the theranostic potential of QDs in AD, paving the way for translational research and clinical implementation.

Double‐Layer Quantum Dots as Interfacial Layer to Enhance the Performance of CsPbI3 Solar Cells

AbstractCsPbI3 has drawn constant interest in the field of perovskite solar cells (PSCs), due to its remarkable photovoltaic performance and thermal stability. Nonetheless, further development of CsPbI3 PSCs requires solving larger energy loss problem, which is primarily caused by charge recombination and energy band mismatch at the interface. Here, a double‐layer interface engineering concept is introduced that uses CsPbBr3 and CsPbCl3 colloidal quantum dots (QDs) to reduce energy loss. Characterization results suggest that the QDs interfacial layer not only improves the quality of CsPbI3 film through passivating the defects on the film surface and grain boundaries (GBs), but also optimizes energy level structure and establishes additional charge transport paths to facilitate hole transportation. As a result, the power conversion efficiency (PCE) of the device with double‐layer QDs covering is boosted to 18.89% from 17.26%. Its moisture stability is enhanced as well. This work of designing double‐layer QDs provides a new idea for interface engineering, and further manifests the great potential of QDs as interfacial layer.

Permanent Electrochemical Doping of Quantum Dot Films through Photopolymerization of Electrolyte Ions.

Quantum dots (QDs) are considered for devices like light-emitting diodes (LEDs) and photodetectors as a result of their tunable optoelectronic properties. To utilize the full potential of QDs for optoelectronic applications, control over the charge carrier density is vital. However, controlled electronic doping of these materials has remained a long-standing challenge, thus slowing their integration into optoelectronic devices. Electrochemical doping offers a way to precisely and controllably tune the charge carrier concentration as a function of applied potential and thus the doping levels in QDs. However, the injected charges are typically not stable after disconnecting the external voltage source because of electrochemical side reactions with impurities or with the surfaces of the QDs. Here, we use photopolymerization to covalently bind polymerizable electrolyte ions to polymerizable solvent molecules after electrochemical charge injection. We discuss the importance of using polymerizable dopant ions as compared to nonpolymerizable conventional electrolyte ions such as LiClO4 when used in electrochemical doping. The results show that the stability of charge carriers in QD films can be enhanced by many orders of magnitude, from minutes to several weeks, after photochemical ion fixation. We anticipate that this novel way of stable doping of QDs will pave the way for new opportunities and potential uses in future QD electronic devices.

Quantum dots against SARS-CoV-2: diagnostic and therapeutic potentials.

The application of quantum dots (QDs) for detecting and treating various types of coronaviruses is very promising, as their low toxicity and high surface performance make them superior among other nanomaterials; in conjugation with fluorescent probes they are promising semiconductor nanomaterials for the detection of various cellular processes and viral infections. In view of the successful results for inhibiting SARS‐CoV‐2, functional QDs could serve eminent role in the growth of safe nanotherapy for the cure of viral infections in the near future; their large surface areas help bind numerous molecules post‐synthetically. Functionalized QDs with high functionality, targeted selectivity, stability and less cytotoxicity can be employed for highly sensitive co‐delivery and imaging/diagnosis. Besides, due to the importance of safety and toxicity issues, QDs prepared from plant sources (e.g. curcumin) are much more attractive, as they provide good biocompatibility and low toxicity. In this review, the recent developments pertaining to the diagnostic and inhibitory potentials of QDs against SARS‐CoV‐2 are deliberated including important challenges and future outlooks. © 2022 Society of Chemical Industry (SCI).

Apple juice and red wine induced mirror-image circular dichroism in quantum dots.

Juices, wines, and extracts from plants contain high concentrations of various chiral compounds such as carboxylic acids or sugars. Several prior studies reported the synthesis of metallic and semiconducting nanoparticles relying on components of complex biological solutions. Herein, we present preparation of chiral CdS and CdSe quantum dots (QDs) using apple juice and red wine via phase transfer ligand exchange. Although both apple juice and red wine contain a complex mixture of chiral and achiral compounds, we have successfully used them for selective induction of predicted chiroptical properties and confirmed L-malic acid from the apple juice and L-tartaric acid from the red wine as the chiral inducers. This work illustrates the capability of using complex mixtures to construct chiral QDs with desired chiroptical properties as well as potential of QDs to selectively report a chiral molecule in a complex chiral mixture without the need for elaborate chiral recognition system.

Adiabatic Switching Among Quantum Dot Eigenstates: Role of Anharmonicity and Gaussian White Noise

Current study inquires the time‐dependent quantum adiabatic switching (TDQAS) among the quantum dot (QD) eigenstates under the aegis of Gaussian white noise (GWN) with special emphasis on anharmonicity that may be present in the QD potential. The initial and the final eigenstates are distinguished by different values of magnetic field strength, confinement potential, anisotropy, and anharmonicity. The QAS has been conducted using four different switching functions (SFs), e.g., square, exponential, sinusoidal, and logarithmic. The time development of switching has been monitored with the help of overlap function and quantum information entropy (QIE). The SFs appear to recover the eigenstates of QD corresponding to the final Hamiltonian. The switching paths comprise features such as enhancement, depletion, maximization, minimization, and crossover of the overlap function and entropy. These characteristics of switching paths depend on presence/absence of noise, its pathway of application (additive/multiplicative), and symmetry (odd/even) of the anharmonic potential. The dependence on the type of SF used, however, has been found to be not much significant unless the exclusive role of noise strength on switching path is observed. The study merits importance in view of immense technological applications of QD‐based systems where the noise‐anharmonicity interplay may be exploited to a great extent.

Activity of CdTe Quantum-Dot-Tagged Superoxide Dismutase and Its Analysis in Capillary Electrophoresis.

Quantum dots (QDs) have a broad range of applications in cell biolabeling, cancer treatment, metastasis imaging, and therapeutic drug monitoring. Despite their wide use, relatively little is known about their influence on other molecules. Interactions between QDs and proteins can influence the properties of both nanoparticles and proteins. The effect of mercaptosuccinic acid-capped CdTe QDs on intercellular copper–zinc superoxide dismutase (SOD1)—one of the main enzymatic antioxidants—was investigated. Incubation of SOD1 with QDs caused an increase in SOD1 activity, unlike in the case of CdCl2, which inhibited SOD1. Moreover, this effect on SOD1 increased with the size and potential of QDs, although the effect became clearly visible in higher concentrations of QDs. The intensity of QD-SOD1 fluorescence, analyzed with the use of capillary electrophoresis with laser-induced fluorescence detection, was dependent on SOD1 concentration. In the case of green QDs, the fluorescence signal decreased with increasing SOD1 concentration. In contrast, the signal strength for Y-QD complexes was not dependent on SOD1 dilutions. The migration time of QDs and their complexes with SOD1 varied depending on the type of QD used. The migration time of G-QD complexes with SOD1 differed slightly. However, in the case of Y-QD complexes with SOD1, the differences in the migration time were not dependent on SOD concentration. This research shows that QDs interact with SOD1 and the influence of QDs on SOD activity is size-dependent. With this knowledge, one might be able to control the activation/inhibition of specific enzymes, such as SOD1.

Plasmon-Induced Trap State Emission from Single Quantum Dots.

Charge carriers trapped at localized surface defects play a crucial role in quantum dot (QD) photophysics. Surface traps offer longer lifetimes than band-edge emission, expanding the potential of QDs as nanoscale light-emitting excitons and qubits. Here, we demonstrate that a nonradiative plasmon mode drives the transfer from two-photon-excited excitons to trap states. In plasmonic cavities, trap emission dominates while the band-edge recombination is completely suppressed. The induced pathways for excitonic recombination not only shed light on the fundamental interactions of excitonic spins, but also open new avenues in manipulating QD emission, for optoelectronics and nanophotonics applications.

Colloidal stability and aggregation kinetics of nanocrystal CdSe/ZnS quantum dots in aqueous systems: effects of pH and organic ligands

Advancing the understanding of stability behavior and aggregation mechanisms of quantum dot (QD) nanoparticles in natural systems is fundamental to elucidate their fate and transport, bioavailability, environmental toxicity, and subsequent risks to environmental and public health. This study investigates the aggregation kinetics and colloidal stability of QDs as a function of pH and organic ligands—acetate, oxalate, and citrate. Results indicated an influence of solution chemistry upon both the aggregation kinetics and colloidal stability of QDs. The zeta potential of QDs, with a point of zero charge (pHPZC) between pH 1.5 and 3.5, decreased (from positive to negative) with increasing solution pH. The diameter of QD aggregates was ~500 nm in the region of pHPZC and decreased with pH when pH > pHPZC to 40–50 nm. Organic ligands enhanced the negative zeta potentials of QDs at pH = 1.5 and pH = 3.5. The impact of ligands on the levels and rates of aggregation was pH dependent; furthermore, the presence of ligands increased the diameters of all QD nanoaggregates at pH 3.5 (e.g., 817 nm for 0.001 M citrate). QDs and organic ligand-QD nanoparticle complexes remained stable across pH values 5–9. In terms of environmental and toxicological risk assessments, results revealed that QDs and organic ligand-QD nanoparticle complexes remain stable across a significant range of pH values (5–9), indicating that this stability behavior could enhance the mobility, transport, and residence time of QDs in terrestrial and aqueous environments, and facilitate the bioavailability of QDs, therefore augmenting the adverse effects of QDs in the environment.

Tempo-spectral multiplexing in flow cytometry with lifetime detection using QD-encoded polymer beads

Semiconductor quantum dots (QDs) embedded into polymer microbeads are known to be very attractive emitters for spectral multiplexing and colour encoding. Their luminescence lifetimes or decay kinetics have been, however, rarely exploited as encoding parameter, although they cover time ranges which are not easily accessible with other luminophores. We demonstrate here the potential of QDs made from II/VI semiconductors with luminescence lifetimes of several 10 ns to expand the lifetime range of organic encoding luminophores in multiplexing applications using time-resolved flow cytometry (LT-FCM). For this purpose, two different types of QD-loaded beads were prepared and characterized by photoluminescence measurements on the ensemble level and by single-particle confocal laser scanning microscopy. Subsequently, these lifetime-encoded microbeads were combined with dye-encoded microparticles in systematic studies to demonstrate the potential of these QDs to increase the number of lifetime codes for lifetime multiplexing and combined multiplexing in the time and colour domain (tempo-spectral multiplexing). These studies were done with a recently developed novel luminescence lifetime flow cytometer (LT-FCM setup) operating in the time-domain, that presents an alternative to reports on phase-sensitive lifetime detection in flow cytometry.

Wide-Spectrum-Responsive Paper-Supported Photoelectrochemical Sensing Platform Based on Black Phosphorus-Sensitized TiO2.

A wide-spectrum-responsive paper-based photoelectrochemical (PEC) sensor based on black phosphorus (BP) quantum dots (QDs)-sensitized titanium dioxide (TiO2-BP QDs) for prostate-specific antigen (PSA) detection was presented herein. Carbon nanotubes (CNTs) were first coated on paper to form a flexible conductive paper electrode. TiO2 nanoparticles were then in situ synthesized on the CNTs-modified paper working electrode with direct liquid-phase hydrolysis with normal temperature, shirtsleeve operation, and gentle solution. Meanwhile, BP QDs, derived from two-dimensional BP nanosheets, can harvest light from the ultraviolet to near-infrared region, broaden efficient utilization of light, add a new dimension to BP research, and impel the high expectation on the potentials of QDs. To implement an assay protocol, exciton-plasmon interactions between TiO2-BP QDs and gold nanoparticles were introduced into the PEC sensing platform for high sensitivity detection of the PSA antigen. Under the optimal conditions, this proposed method exhibited a linear response ranging from 0.005 to 50 ng/mL with a detection limit of 1 pg/mL. This sensing protocol offered a promising analytical method with favorable properties of high selectivity, stability, and reproducibility.

Physicochemical properties of chimie douce derived, digestively ripened, ultra-small (r

Ultra-small and uniform sized ZnO quantum dots (QDs) have been synthesized by using a chimie-douce, scalable and eco-friendly method. The physicochemical properties of digestively ripened ZnO QDs have been explored. Uniform sized colloidal QDs are achieved by employing a size control approach called digestive ripening (DR). In DR, monodispersed colloidal nanoparticles are obtained from polydispersed colloidal nanoparticles through the addition of substantial amount of a suitably chosen surfactant (having a suitable ligand). This is performed in the presence of a suitable solvent. Capping with the surfactant (triethanolamine) results in a change in the zeta potential of QDs (increased from 7 ± 3 mV to +22 ± 3 mV) which is responsible for the observed DR and a decrease in particle size from ˜3.5 ± 2 nm to ˜2.8 ± 0.5 nm also noticed. Hard-Soft-Acid-Base surface chemical interactions taking place between ZnO QDs and the surfactant (triethanolamine) are responsible for the formation of digestively ripened ZnO QDs. The as formed ZnO QDs are highly monodispersed in nature and the optical absorption studies indicate that band gap of ZnO QDs found to be Eg˜3.6 eV, indicating strong confinement. The photoluminescence (PL) studies clearly indicates that the major contribution to the photoluminescence is defects present of ZnO QDs-surface and the existence of oxygen vacancy defects on the ZnO QDs-surface are confirmed with PL studies. Time-resolved photoluminescence studies indicate that lifetimes of photo-generated carriers in digestively ripened (DRd) QDs is ˜12 ns and coating with digestive ripening agent reduces the surface-related emission and improves the radiative transitions in DRd ZnO QDs. Spectroscopic studies indicate that formation of highly pure ZnO QDs. These highly monodisperse, stable and ZnO QDs are prospectively useful in contemporary applications such as nanoscale electronic devices and photocatalysis.

Tyrosine kinase inhibitor conjugated quantum dots for non-small cell lung cancer (NSCLC) treatment

Non-small cell lung cancer is a major sub-type of lung cancer that is associated with a poor diagnosis resulting in poor therapy for the disorder. In order to achieve a better prognosis, innovative multi-functional systems need to be developed which will aide in diagnosis as well as therapy for the disorder. One such multi-functional delivery system fabricated is Quantum Dots (QDs). QDs are photo-luminescent inorganic nanoparticles utilized for tumor detection, preclinically. Erlotinib hydrochloride, a tyrosine kinase inhibitor, is a first-generation drug developed to treat NSCLC. Its active metabolite, Desmethyl Erlotinib (OSI-420), exhibits similar anticancer activity as erlotinib. OSI-420 was conjugated to QDs to fabricate a delivery system and was then characterized by FT-IR, H NMR, UV-VIS, particle size, zeta potential, fluorescence spectroscopy and TEM. Drug loading was estimated using UV-VIS spectroscopy (52.2 ± 7.5%). A concentration-dependent release of OSI-420 was achieved using esterase enzymes, which was further confirmed using LC-MS. A cellular uptake study revealed the internalization potential of QDs and QD-OSI 420. A cellular recovery study was performed to confirm the internalization potential. Cell viability studies revealed that QD-OSI 420 conjugates had significantly better efficacy than pure drugs in all tested cell lines. QD conjugated OSI-420 demonstrated an IC60 of 2.5 μM in erlotinib-resistant A549 cell lines, where erlotinib or OSI-420 alone could not exhibit 60% inhibition when evaluated up to 20 μM. Similar cytotoxic enhancement of erlotinib was seen with QD-OSI 420 in other NSCLC cell lines as well. These results were strengthened by 3D-SCC model of A549 which revealed that QD-OSI 420 was significantly better in reducing in-vitro 3D tumor volume, as compared to pure drugs. This study, being one of its kind, explores the feasibility of conjugating OSI-420 with QDs as an alternative to traditional anti-cancer therapy, by improving intracellular drug delivery.

Localization of Carriers in Quantum Dots with Uniaxial Anisotropy of Shape and Composition

The electronic and hole states in quantum dots (QD) of cubic II–VI semiconductors with a spheroidal shape and uniaxial anisotropy have been studied theoretically. The smooth potential energy profiles simulated by the Gauss function in all three spatial directions are considered. The energy level lowering and the energy splitting of the hole state from the valence band top Γ8 by momentum 3/2 into the states with projections ±3/2, ±1/2 on the anisotropy axis are analyzed. The QD anisotropies of three types are considered: the QD size anisotropy, the QD potential barrier anisotropy, and the combined anisotropy. In the first case, flattened quantum dots, in which the characteristic size in the structure plane is larger than the size along the anisotropy axis, are considered. In the second case, QDs, in which the potential barrier height in the plane is lower than that along the anisotropy axis, are considered. In the third case, flattened quantum dots with the anisotropy of the size and the potential barrier are considered. The conditions of the charge carrier localization inside QD have been found, and the influence of the form and composition anisotropies on the energies of exciton transitions in the structures with CdxZn1 – xSe quantum dots are discussed.

Локализация носителей в квантовых точках с одноосной анизотропией формы и состава

AbstractThe electronic and hole states in quantum dots (QD) of cubic II–VI semiconductors with a spheroidal shape and uniaxial anisotropy have been studied theoretically. The smooth potential energy profiles simulated by the Gauss function in all three spatial directions are considered. The energy level lowering and the energy splitting of the hole state from the valence band top Γ_8 by momentum 3/2 into the states with projections ±3/2, ±1/2 on the anisotropy axis are analyzed. The QD anisotropies of three types are considered: the QD size anisotropy, the QD potential barrier anisotropy, and the combined anisotropy. In the first case, flattened quantum dots, in which the characteristic size in the structure plane is larger than the size along the anisotropy axis, are considered. In the second case, QDs, in which the potential barrier height in the plane is lower than that along the anisotropy axis, are considered. In the third case, flattened quantum dots with the anisotropy of the size and the potential barrier are considered. The conditions of the charge carrier localization inside QD have been found, and the influence of the form and composition anisotropies on the energies of exciton transitions in the structures with Cd_ x Zn_1 – _ x Se quantum dots are discussed.

Room-temperature single dopant atom quantum dot transistors in silicon, formed by field-emission scanning probe lithography

Electrical operation of room-temperature (RT) single dopant atom quantum dot (QD) transistors, based on phosphorous atoms isolated within nanoscale SiO2 tunnel barriers, is presented. In contrast to single dopant transistors in silicon, where the QD potential well is shallow and device operation limited to cryogenic temperature, here, a deep (∼2 eV) potential well allows electron confinement at RT. Our transistors use ∼10 nm size scale Si/SiO2/Si point-contact tunnel junctions, defined by scanning probe lithography and geometric oxidation. “Coulomb diamond” charge stability plots are measured at 290 K, with QD addition energy ∼0.3 eV. Theoretical simulation gives a QD size of similar order to the phosphorous atom separation ∼2 nm. Extraction of energy states predicts an anharmonic QD potential, fitted using a Morse oscillator-like potential. The results extend single-atom transistor operation to RT, enable tunneling spectroscopy of impurity atoms in insulators, and allow the energy landscape for P atoms in SiO2 to be determined.

Nano interface potential influences in CdTe quantum dots and biolabeling

Nano interface influences in physiochemical properties of quantum dots (QDs) are the challenging approach to tailor its surface functionalities. In this study, a set of polar and non-polar solvents were selected to analyze the influences in solvent-based dynamic radius and surface potential of QDs. From the nano interface chemistry of polar and non-polar solvents, an appropriate mechanism of precipitation and hydrophobic ligand exchange strategy were elucidated by correlating Henry’s equation. Further, the in vitro cytotoxic potential and antimicrobial activity of QDs were assessed to perform biolabeling. From the observations, an appropriate dosage of QDs was fixed to label the animal ((RAW 264.7 cell lines) and bacterial cells (Escherichia coli) for effective cell attachment. Biolabeling was achieved by tailoring nano interface chemistry of QDs without additional support of biomolecules. Bacterial cell wall-based interaction of QDs was evaluated using SEM and EDAX analysis. Thus, provided clear insights into the nano interface chemistry in the development of highly photostable QDs will be helpful in biomedical applications.