Query: Semiconductor quantum dots: Technological progress and future challenges

Candidate papers:

abstract: Advances in colloidal quantum dots The confinement found in colloidal semiconductor quantum dots enables the design of materials with tunable properties. Garcia de Arquer et al. review the recent advances in methods for synthesis and surface functionalization of quantum dots that enable fine tuning of their optical, chemical, and electrical properties. These important developments have driven the commercialization of display and lighting applications and provide promising developments in the related fields of lasing and sensing. Science, aaz8541, this issue p. eaaz8541 A Review highlights advances in the synthesis of colloidal quantum dots that have enabled numerous applications. BACKGROUND Semiconductor materials feature optical and electronic properties that can be engineered through their composition and crystal structure. The use of semiconductors such as silicon gallium arsenide sparked technologies from computers and mobile phones to lasers and satellites. Semiconductor quantum dots (QDs) offer an additional lever: Because their size is reduced to the nanometer scale in all three dimensions, the restricted electron motion leads to a discrete atom like electronic structure and size dependent energy levels. This enables the design of nanomaterials with widely tunable light absorption, bright emission of pure colors, control over electronic transport, and a wide tuning of chemical and physical functions because of their large surface to volume ratio. ADVANCES The bright and narrowband light emission of semiconductor QDs, tunable across the visible and near infrared spectrum, is attractive to realize more efficient displays with purer colors. QDs are engineered compositionally and structurally to manipulate energy states and charge interactions, leading to optical gain and lasing, relevant to light emission across visible and infrared wavelengths and fiberoptic communication. Their tunable surface chemistry allows application as optical labels in bio imaging, made possible by tethering QDs with proteins and antibodies. The manipulation of QD surfaces with capping molecules that have different chemical and physical functions can be tailored to program their assembly into semiconducting solids, increasing conductivity and enabling the transduction of photonic and chemical stimuli into electrical signals. Optoelectronic devices such as transistors and photodetectors lead to cameras sensitive to visible and infrared light. Highly crystalline QDs can be grown epitaxially on judiciously chosen substrates by using high temperature and vacuum conditions, and their use has led to commercially viable high performance lasers. The advent of colloidal QDs, which can be fabricated and processed in solution at mild conditions, enabled large area manufacturing and widened the scope of QD application to markets such as consumer electronics and photovoltaics. OUTLOOK From a chemistry perspective, further advances in QD fabrication are needed to sustain and improve desired chemical and optoelectronic properties and to do so with high reproducibility. This entails the use of inexpensive synthesis methods and precursors that are able to retain laboratory scale QD properties to market relevant volumes. A better understanding of the yet incomplete picture of QD surfaces, atomic arrangement, and metastable character is needed to drive further progress. From a regulatory perspective, added attention is needed to achieve high quality materials that do not rely on heavy metals such as Cd, Pb, and Hg. The role of nanostructuring in toxicity and life cycle analysis for each application is increasingly important. From a materials and photophysics perspective, exciting opportunities remain in the understanding and harnessing of electrons in highly confined materials, bridging the gap between mature epitaxial QDs and still up and coming colloidal QDs. The yet imperfect quality of the latter a price paid today in exchange for their ease of manufacture remains a central challenge and must be addressed to achieve further increased performance in devices. From a device perspective, colloidal QD manufacturing must advance to translate from laboratory scale to large area applications such as roll to roll and inkjet printing. Photocatalysis, in which light is used to drive chemical transformations, is an emerging field in which QDs are of interest. Quantum information technologies, which rely on the transduction of coherent light and electrons, bring new challenges and opportunities to exploit quantum confinement effects. Moving forward, opportunities remain in the design of QD enabled new device architectures. Semiconductor quantum dot technologies. Quantum dots feature widely tunable and distinctive optical, electrical, chemical, and physical properties. They span energy harvesting, illumination, displays, cameras, sensors, communication and information technology, biology, and medicine, among others. These have been exploited to realize efficient lasers, displays, biotags, and solar harvesting devices available in the market and are emerging in photovoltaics, sensing, and quantum information. In quantum confined semiconductor nanostructures, electrons exhibit distinctive behavior compared with that in bulk solids. This enables the design of materials with tunable chemical, physical, electrical, and optical properties. Zero dimensional semiconductor quantum dots (QDs) offer strong light absorption and bright narrowband emission across the visible and infrared wavelengths and have been engineered to exhibit optical gain and lasing. These properties are of interest for imaging, solar energy harvesting, displays, and communications. Here, we offer an overview of advances in the synthesis and understanding of QD nanomaterials, with a focus on colloidal QDs, and discuss their prospects in technologies such as displays and lighting, lasers, sensing, electronics, solar energy conversion, photocatalysis, and quantum information.
author_names: F Pelayo Garcia de Arquer

Dmitri V Talapin

Victor I Klimov

Yasuhiko Arakawa

Manfred Bayer

Edward H Sargent
title: Semiconductor quantum dots: Technological progress and future challenges
venue: Science
year: 2021

abstract: Abstract Semiconductor based photocatalysis is one of the renewable and sustainable technologies for direct solar to chemical energy conversion to tackle the energy crisis and environmental pollution. Since being rediscovered in 2014, black phosphorus (BP) a two dimensional (2D) layered material, has aroused extensive interests in the scientific community. In particular, 0D BP quantum dots (BPQDs) derived from 2D BP nanosheets have emerged as a promising candidate for full spectrum solar energy conversion due to their favorable structural, electronic and optical characteristics. Herein, the most recent advances in the preparation of BPQDs and their unique advantages as well as applications in full spectrum solar to chemical energy conversion like water splitting for hydrogen evolution, CO2 photoreduction and organic pollutant removal are highlighted. Further, the challenges and perspectives of BPQDs based nanostructures on the possible future research directions in solar driven heterogeneous photocatalysis are discussed, aiming to timely update one of the most active forefronts for the photo(electro) catalytic community and beyond.
author_names: Wanying Lei

Xin Pang

Guanglu Ge
title: Recent progress on black phosphorus quantum dots for full spectrum solar to chemical energy conversion
year: 2021

abstract: Carbon dots (CDs) have recently emerged as a promising cost effective alternative to replace high cost semiconductor quantum dots (QDs) There are three kinds of fluorescent CDs which are carbonized polymer dots (CPDs) carbon nanodots (CNDs) and graphene quantum dots (GQDs) Wide attention has been focused on CDs because of their characteristics such as water solubility, high biocompatibility, excellent photostability, low toxicity, and excitation wavelength dependent photoluminescence (PL) behavior. Moreover, the recent discovery of a multigram one step synthesis of GQDs from coal or carbon sources opens the possibility of their large scale industrial production. Although CPDs, CNDs and GQDs have similar quantum fluorescent carbon materials, they have different chemical and physical properties because of the differences in spatial arrangements of carbon atoms. This chapter aims to demonstrate the recent progress in the synthesis, properties and applications of CD based composites in disease detection, optoelectronics, photovoltaics, hydrogen (H2) evolution, photocatalysis, etc. We also highlight the challenges and future direction of CD based composites in this booming research field, with a perspective toward the ultimate achievement of highly efficient and long term stable CD based composites.
author_names: L C Sim

S S Terng

J J Ng

Woon Chan Chong

Kah Hon Leong

Panchamoorthy Saravanan
title: Chapter 6. Carbon Dot based Composites: Recent Progress, Challenges and Future Outlook
year: 2021

abstract: ABSTRACT Colloidal semiconductor nanocrystals, referred to as quantum dots (QDs) have unique and superb photophysical properties, promising a variety of applications ranging from optoelectronics and energy harvesting to agriculture. The last decade witnessed a tremendous advance in QDs and their successful debut in displays, and now, QDs are equipped with environmental benignity to expand their territory to everyday life. From this perspective, the current research status and future perspective of environmentally benign QDs as building blocks for light generating and light harvesting applications are provided. Also provided is an overview of the progress made in the chemistry (colloidal synthesis, surface chemistry, and heterostructuring) and in their photophysical and electrical properties from the viewpoint of their use in light emitting or light harvesting applications. Grounded on the current status of heavy metal free QDs compared with cutting edge technologies, the perspective of environmentally benign QDs for practical use and future research directions is discussed.
author_names: Donghyo Hahm

Donghyun Ko

Byeong Guk Jeong

Sohee Jeong

Jaehoon Lim

Wan Ki Bae

Changhee Lee

Kookheon Char
title: Environmentally benign nanocrystals: challenges and future directions
venue: Journal of Information Display
year: 2019

abstract: Abstract Having been inspired by the tremendous progress in material nanoscience and device nanoengineering, hybrid phototransistors combine solution processed colloidal semiconductor quantum dots (QDs) with graphene or two dimensional (2D) semiconductor materials. Novel detectors demonstrate ultrahigh photoconductive gain, high and selective photoresponse, low noise, and very high responsivity in visible and near infrared ranges. The outstanding performance of phototransistors is primarily due to the strong, selective, and size tunable absorption of QDs and fast charge transfer in 2D high mobility conductors. However, the relatively small mobility of QD nanomaterials was a technological barrier, which limited the operating rate of devices. Very recent innovations in detector design and significant progress in QD ligand engineering provide effective tools for further qualitative improvements. This article reviews the recent progress in material science, nanophysics, and device engineering related to hybrid phototransistors. Detectors based on various QD nanomaterials and several 2D conductors are compared, and advantages and disadvantages of various nanomaterials for applications in hybrid phototransistors are identified. We also benchmark the experimental characteristics with model results that establish interrelations and tradeoffs between detector characteristics, such as responsivity, dark and noise currents, the photocarrier lifetime, response, and noise bandwidths. We have shown that the most recent phototransistors demonstrate performance limited by the fundamental generation recombination noise in high gain devices. Interrelation between the dynamic range of the detector and the detector sensitivity is discussed. The review is concluded with a brief discussion of the remaining challenges and possible significant improvements in the performance of hybrid phototransistors.
author_names: Kimberly A Sablon

Andrei Sergeev

Sina Najmaei

Madan Dubey
title: High response hybrid quantum dots 2D conductor phototransistors: recent progress and perspectives
year: 2017

abstract: Abstract Semiconductor quantum dots (QDs) and organic inorganic halide perovskites have emerged as two important families of excellent photovoltaic materials and contributed to the rapid progress in photovoltaic field during the past decade. This review seeks to provide an insight into an advanced concept on the synergistic combination of QDs and perovskites, which affords a number of exciting synergies for the further advancements in hybrid solar cells, including growth promotion of perovskite crystals, complementary light harvesting, rapid extraction of charge carriers, efficient carrier transport, surface and interface engineering, and improved stability. The emphasis is placed on the most widely studied system of PbS and CH3NH3PbI3, which enables the heteroepitaxial growth of perovskites on QDs. Issues related to fundamental physical and chemical features, lattice coherence, materials and films processing, and energy transfer between QDs and perovskites, as well as advances in device architecture and photovoltaic performance are discussed. In addition, prospects overriding current challenges are also proposed for future work toward practical realization of highly efficient and stable hybrid solar cells.
author_names: Ru Zhou

Zhou Yang

Jinzhang Xu

Guozhong Cao
title: Synergistic combination of semiconductor quantum dots and organic inorganic halide perovskites for hybrid solar cells
year: 2018

abstract: Abstract Forster resonance energy transfer (FRET) configurations incorporating colloidal semiconductor quantum dots (QDs) have proven to be a valuable tool for bioanalysis and bioimaging. Mirroring well established techniques with only fluorescent dyes, "traditional" FRET configurations with QDs have involved single step energy transfer to organic dye acceptors mediated by biomolecular interactions. Here, we review recent progress in characterizing non traditional FRET configurations incorporating QDs and their application to challenges in biosensing, energy conversion, and fabrication of optoelectronic devices. Such non traditional FRET configurations with QDs include substitution of organic dyes with lanthanide complexes, polypyridyl transition metal complexes, azamacrocyclic metal complexes, graphene (oxide) carbon nanotubes, gold nanoparticles, and dyes exhibiting photochromism. Other non traditional configurations of interest include FRET relays (with or without organic dyes) that feature multiple sequential energy transfer steps, and thin films of QDs where discrete FRET pairs cannot be defined, including those where QDs are layered in a size sequential or "rainbow" structure. The calculation of FRET efficiencies and donor acceptor distances in the above configurations are reviewed, as are distance scaling relationships for non zero dimensional acceptors, and the related dipolar energy transfer mechanism, nanosurface energy transfer (NSET) To illustrate the utility of non traditional QD FRET configurations, we highlight examples of optically switchable probes, photonic wires, time gated and multiplexed probes for biosensing, enhanced light harvesting in QD and dye sensitized solar cells (DSSC) and colour conversion in light emitting diodes (LEDs) We close by providing a perspective on how the combined utility of these non traditional QD FRET configurations may be useful for engineering complex nanoscale devices in the future.
author_names: W Russ Algar

Hyungki Kim

Igor L Medintz

Niko Hildebrandt
title: Emerging non traditional Forster resonance energy transfer configurations with semiconductor quantum dots: Investigations and applications
year: 2014

abstract: Carbon based luminescent nanomaterials have attracted much attention in the biomedical field. Compared to traditional photoluminescent materials (such as rare earth based semiconductors and organic dyes) they have excellent biocompatibility, low toxicity, excellent optical stability and site targeting properties in addition to their low cost and environmentally friendly features. Carbon dots, a typical carbon based luminescent material, have great application potential in biomedicine, biological imaging and optoelectronics. Actual biological imaging, however, uses low level photon scattering and light absorption to avoid self fluorescence by the target tissues, requiring the light waves to have strong tissue penetration ability. Long wavelength (red and near infrared) is known to have strong tissue penetration. However, carbon dots in the long wavelength region give a low quantum yield. Thus, obtaining long wavelength emitting carbon dots with high quantum yield is a big challenge in practical bioimaging and phototherapy. In this paper, recent progress in the development of long wavelength, strongly luminescence emitting carbon dots, the mechanisms and methods to regulate their optical properties and improve their quantum yield are reviewed. Recent applications of carbon dots in biosensing, bioimaging and therapy are described. Finally, the future challenges and prospects of long wavelength carbon based luminescent materials are discussed.
author_names: Feng Huo

Wenqiong Li

Yuhang Liu

Xiaohong Liu

Chong Yew Lee

Wei Zhang
title: Review of long wavelength luminescent carbon based nanomaterials: preparation, biomedical application and future challenges
venue: Journal of Materials Science
year: 2020

abstract: Asymmetric catalysis is one of the most attractive strategies to obtain important enantiomerically pure chemicals with high quality and production. In addition, thanks to the abundant and sustainable advantages of solar energy, photocatalysis possesses great potential in environmentally benign reactions. Undoubtedly, asymmetric photocatalysis meets the strict demand of modern chemistry: environmentally friendly and energy sustainable alternatives. Compared with homogeneous asymmetric photocatalysis, heterogeneous catalysis has features of easy separation, recovery, and reuse merits, thus being cost and time effective. Herein, the state of the art progress in asymmetric photocatalysis by heterogeneous nanomaterials is addressed. The discussion comprises two sections based on the type of nanomaterials: typical inorganic semiconductors like TiO2 and quantum dots and emerging porous materials including metal organic frameworks, porous organic polymers, and organic cages. Finally, the challenges and future developments of heterogeneous asymmetric photocatalysis are proposed.
author_names: Xueying Qiu

Yin Zhang

Yanfei Zhu

Chang Long

Lina Su

Shaoqin Liu

Zhiyong Tang
title: Applications of Nanomaterials in Asymmetric Photocatalysis: Recent Progress, Challenges, and Opportunities.
venue: Advanced materials
year: 2020

abstract: Carbon quantum dots (CQDs) have emerged as a potential material in the diverse fields of biomedical applications due to their numerous advantageous properties including fluorescence, water solubility, biocompatibility, low toxicity, small size and ease of modification, inexpensive scale up production, and versatile conjugation with other nanoparticles. Thus, CQDs became a preferable choice in various biomedical applications such as nanocarriers for drugs, therapeutic genes, photosensitizers, and antibacterial molecules. Further, their potentials have also been verified in multifunctional diagnostic platforms, cellular and bacterial bio imaging, development of theranostics nanomedicine, etc. This review provides a concise insight into the progress and evolution in the field of CQD research with respect to methods/materials available in bio imaging, theranostics, cancer/gene therapy, diagnostics, etc. Further, our discussion is extended to explore the role of CQDs in nanomedicine which is considered to be the future of biomedicine. This study will thus help biomedical researchers in tapping the potential of CQDs to overcome various existing technological challenges.
author_names: Pooja Devi

Shefali Saini

Ki-Hyun Kim
title: The advanced role of carbon quantum dots in nanomedical applications.
venue: Biosensors bioelectronics
year: 2019