Implementation Of Quantum Dots Research Articles

Перспективы использования наночастиц (квантовых точек) в офтальмологии

Review Prospects for the use of nanoparticles (quantum dots) in ophthalmology V.O. Ponomarev, K.A. Tkachenko Eye Microsurger y Ekaterinburg Center, Ekaterinburg, Russian Federation Purpose. A systematic analysis of domestic and foreign literature devoted to the potential use of quantum dots (QD) in ophthalmology, as well as the identification of the main problems regarding the implementation of QD in ophthalmic practice. Material and methods. To carry out the review, a systematic analysis of scientific publications of domestic and foreign authors was carried out on the resources of PubMed, Medline, eLibrary from 2008 to 2021, devoted to the determination of physicochemical parameters, as well as the practical use of QD. Results. QD-based semiconductor nanoparticles are increasingly entrenched in modern science and medicine, in particular ophthalmology. This review defines the main physical parameters and physical and chemical properties of QD. Their potential applications are wide enough and focused on imaging, drug delivery, electrical stimulation and broad spectrum of anti-infective activity. Conclusion. To date, the existing limitations in the sphere of active QD application in ophthalmic practice are related to fundamental research in the field of acute and chronic cytotoxicity, selection of safe doses and concentrations of QD, working out mechanisms of their delivery, as well as in the study of mechanisms of chemical and biological interaction with the structures of the visual analyzer at dynamically changing physical parameters of QD (shape, size, features of functionalization and silanization). Interdisciplinary interactions between the pillars of fundamental medicine, physics, biology, chemistry, and ophthalmology, in particular, will probably allow us to realize in the nearest five years in clinical practice all the fundamental principles laid down in the previous studies. Key words: nanoparticles, quantum dots, anti-infective activity, imaging method, fluorescence

An Overview of Paclitaxel and Molecular Imprinted Polymers Capped with Quantum Dots as an Alternative Approach for Paclitaxel Extraction and Detection

Abstract:Paclitaxel (Taxol) is a drug that belongs to the class of compounds called Taxane. It is a strong and potent chemotherapeutic drug that inhibits the growth of certain types of cancer cells; however, its abundance is very low, and various types of methodologies have been implemented to extract paclitaxel from the bark of different plants and herbs. The molecularly imprinted polymers (MIPs) could be the best alternative to purify the paclitaxel molecule. MIPs have become an attractive solution for the selective and fine-tuned determination of target templates in complex forms where other comparable and relevant structural compounds could coexist. Implementation of quantum dots in MIPs improves their extraction features due to the presence of distinct functional sites. Quantum dots can be employed to modulate the size, detectability, and state of the imprinted materials, depending on the selected application. This review aims to summarize and illustrate the modern and innovative strategies based on the aggregation of MIPs with quantum dots. Quantum dot embedded MIPs can be exploited for simultaneous extraction, preconcentration, and detection of paclitaxel obtained from various sources.

Influence of Geometrical Shape on the Characteristics of the Multiple InN/InxGa1-xN Quantum Dot Solar Cells.

Solar cells that are based on the implementation of quantum dots in the intrinsic region, so-called intermediate band solar cells (IBSCs), are among the most widely used concepts nowadays for achieving high solar conversion efficiency. The principal characteristics of such solar cells relate to their ability to absorb low energy photons to excite electrons through the intermediate band, allowing for conversion efficiency exceeding the limit of Shockley–Queisser. IBSCs are generating considerable interest in terms of performance and environmental friendliness. However, there is still a need for optimizing many parameters that are related to the solar cells, such as the size of quantum dots, their shape, the inter-dot distance, and choosing the right material. To date, most studies have only focused on studying IBSC composed of cubic shape of quantum dots. The main objective of this study is to extend the current knowledge of IBSC. Thus, we analyze the effect of the shape of the quantum dot on the electronic and photonic characteristics of indium nitride and indium gallium nitride multiple quantum dot solar cells structure considering cubic, spherical, and cylindrical quantum dot shapes. The ground state of electrons and holes energy levels in quantum dot are theoretically determined by considering the Schrödinger equation within the effective mass approximation. Thus, the inter and intra band transitions are determined for different dot sizes and different inter dot spacing. Consequently, current–voltage (J-V) characteristic and efficiencies of these devices are evaluated and compared for different shapes. Our calculations show that, under fully concentrated light, for the same volume of different quantum dots (QD) shapes and a well determined In-concentration, the maximum of the photovoltaic conversion efficiencies reaches 63.04%, 62.88%, and 62.43% for cubic, cylindrical, and spherical quantum dot shapes, respectively.

Numerical modeling of the size effect in CdSe/ZnS and InP/ZnS-based Intermediate Band Solar Cells

New generation of solar cells based on the implementation of quantum dots in the intrinsic region has attracted much attention due to the fact to that it takes advantage of photons with energies lower than the band gap for achieving high solar conversion efficiency. However, there is still a need for optimizing many parameters related to the solar cells, such as the size of quantum dots and nature of semiconductor materials. The main objective of this study is to extend the current knowledge of the intermediate band solar cells. In particular, we analyze the effect of dot size on the photonic properties of CdSe/ZnS and InP/ZnS quantum dot solar cells by considering the Schrodinger equation within the effective mass approximation. It is demonstrated that quantum dot size is a critical parameter to be controlled for high efficiency CdSe/ZnS and InP/ZnS quantum dot solar cells. Our results show that open-circuit voltage weakly depends on dot size for both systems while short-circuit current density is increased with dot size increasing. As a result, maximum efficiency values of 31.73% and 32.90% are obtained for CdSe/ZnS and InP/ZnS, respectively under full concentrated light for a dot size of 2.3 nm, thereby demonstrating the potentiality of these proposed heterostructures.

Preparation and Analysis of Quantum Dots: Applications of Capillary Electrophoresis.

The implementation of quantum dots in analytical chemistry has already advanced from basic research activities to routine applications of commercially available fluorescent agents present in sophisticated assays kits. Nevertheless, a further development of new preparation and characterization methods of nanoparticles is still required to increase the sensitivity of analytical methods substantially. Thus, in many bioanalytical applications, important molecules such as DNA, proteins, and antibodies are routinely conjugated with fluorescent tags to reach even the absolute sensitivity, that is, the capability to detect a single molecule in complex matrices. Semiconductor quantum dots have already proved to be suitable components of highly luminescent tags, probes, and sensors with broad applicability in analytical chemistry. Quantum dots provide high extinction coefficients together with wide ranges of excitation wavelengths, size- and composition-tunable emissions, narrow and symmetric emission spectra, good quantum yields, relatively long size-dependent luminescence lifetime, and low photobleaching. Most of these properties are superior when compared with conventional organic fluorescent dyes. In this chapter, optimized procedures for the preparation of water-dispersed CdTe quantum dots; their coatings and conjugation reactions with antibodies, DNA, and macrocycles; and their analyses by capillary electrophoresis are described. The potential of capillary electrophoresis for fast analyses of nanoparticles, their conjugates with antibodies and immunocomplexes with targeted antigens, is demonstrated as an example.

Nanoscale Wet Chemical Engineering of III-V Quantum Dots for Emerging Solar Applications

Multi-junction solar cells architectures have gained interest among the photovoltaic community, as they are very promising architectures for high efficiency devices. Among the different configuration envisaged, the use of III-V materials has yet proved to be relevant. More especially, recent studies have shown that the implementation of quantum dots on the surface of a III-V layer leads to the generation of an intermediate band with the benefit to reach efficiencies around 48%. Two issues are considered: the elimination of the wetting layer detrimental for optoelectronic properties and then the control of the quantum dots shape and chemistry to adjust the band-gap. Wet chemistry is a conventional strategy used for III-V material surface engineering. In the present case, specific formulations and protocols are developed to fulfill the nanometric dimension considerations and take account for specificities of this 1 or 0-Dimension like structuration, on the base of surface analyses expertise.

Nanobodies and Antibodies for Duplexed EGFR/HER2 Immunoassays Using Terbium-to-Quantum Dot FRET

Biosensors based on the combination of semiconductor quantum dots (QDs) and Forster resonance energy transfer (FRET) have demonstrated many advantages for simple, fast, sensitive, and multiplexed diagnostics. However, the implementation of QDs as functional standard materials into homogeneous (single-step) FRET immunoassays has not yet been accomplished, because profound investigations of antibody-conjugation strategies concerning their influence on diagnostic performance for quantifying clinical biomarkers are lacking. Here, we report about a systematic study of size, type, orientation, specificity, nonspecific binding, and cross-reactivity of antibodies conjugated to QDs for single and duplexed EGFR and HER2 immunoassays. Time-gated terbium-to-quantum dot FRET detection on a clinical immunoassay fluorescence plate reader (KRYPTOR) enabled a direct comparison of matuzumab, cetuximab, trastuzumab, and pertuzumab monoclonal antibodies and EgA1, EgB4, 11A4, and 18A12 VHH nanobodies conjugated to 605 and 650...

Towards quantum dot and device implementation with InP–GaAs–InP nanostructure

Nanomaterial-based ultra-low-energy device design is one of the prime research areas in nanoscale computation. In ‘more-than-Moore’ technological trends, new device designs with quantum dot nanostructure have become an emerging domain of research. Various quantum dot-based devices, especially quantum dot cellular automata, have been designed both experimentally and by simulation. These quantum devices operate solely on the principle of charge localisation, which accounts for their high speed and ultra-low energy consumption. Quantum dots have an innate ability to confine electrons. As a result, quantum dot formation in a device is highly desirable in order to design quantum devices. Quantum dot implementation with interfacing indium phosphide (InP)–gallium arsenide (GaAs)–indium phosphide nanostructure and quantum dot formation within the redox centres of an allyl molecule are reported in this paper. The formation of the quantum dot is confirmed by the density-of-state studies conducted by the density functional theory calculation on the proposed nanostructures. The possibility of a new device design with two polarised states, namely ‘state x’ and ‘state x −1’, is also explored. Further, outlined in this paper is the design of quantum devices using Python coding, which makes it easier for a programmer to design any kind of complex nanostructure for nanoscale computation.

A Fluoroimmunoassay Method Using Quantum Dot Labels for Detection of Melamine

An indirect competitive immunoassay using quantum dots (QDs) as the fluorescent label has been developed for detection of melamine in milk products. The method exhibited a response for melamine with IC50 value of 11.3 ng mL-1 and a detection limit of 0.27 ng mL-1. Milk and milk powder samples spiked with melamine have been analyzed, and the method provided recoveries ranging from 84.2% to 108.0%, and a CV of 12.8%. The implementation of QDs provides for at least 30 fold improvement of detection limit when compared with optically-based ELISA screening methods that have been reported. The analytical performance in combination with simplicity of sample and antibody preparation provides the basis for a practical method for melamine detection.

MBE growth of Ge quantum dot structures in oxide windows

The implementation of Quantum Dots (QDs) in devices allows novel electronic and opto-electronic functions. Strain driven Stranski-Krastanov growth mode enables the formation of nanometric islands (on wetting layer) whose density and geometry depend on growth conditions (temperature, rate) and surface structure (cleaning). The island positions are random. However, they can be influenced by surface patterning. In this work, the MBE growth of self-organized Ge QD structures in oxide windows is investigated. The studied Ge QD structures are composed by either a single Ge layer directly grown on a Si substrate, or double layer formed by a Ge QD layer on top of a Si buffer layer. Different surface preparation (dry etching with and without anisotropic wet etching) and cleaning (HF dip or RCA cleaning) schemes have been used. It is found that the cleaning and the Si buffer layer growth have strong influence on island nucleation. Preferred nucleation at the window edge and/or nucleation at the window center is observed under certain conditions. Interestingly, negligible influence (this is needed for most device works) is found only if Ge is grown directly on the RCA cleaned window.