Nobel Prize in Chemistry 2023

Moungi Bawendi, Louis Brus and Alexei Ekimov receive the prize for their work on glowing nanoparticles that are used in fields from electronics to surgery.

Inorganic semiconductors, organic emitters and colloidal quantum dots are pushing the LED revolution in lighting and displays.

This issue features a theme on colloidal quantum dots, bringing together primary research findings and overviews, along with articles on the commercialization of this technology.

Quantum dots — semiconductor nanocrystals that have custom designable optical properties — are opening up opportunities in the bio-imaging, display and lighting sectors, reports Duncan Graham-Rowe.

A small industry could be on the verge of a boom, reports Katharine Sanderson.

From fundamental physics and chemistry to digital cameras, improved displays and more natural lighting, nanoscale semiconductor structures called quantum dots are having an impact on many areas of science and technology.

The properties of semiconductor quantum dots can now be controlled down to the level of single electrons and spins. These solid-state 'artificial atoms' have inspired scientists to look at them as possible building blocks for realizations of quantum computers, with unexpected consequences.

Three decades after the first fundamental studies on semiconductor nanocrystals, the materials can be found in a range of commercial devices.

Nanoscale systems are ideally suited to study quantum mechanical effects and explore these as resources for emerging quantum technology such as quantum sensing, communication or computing.

The authors show that metal oxide and colloidal quantum dots can be combined to fabricate monochrome LEDs with a brightness that matches that of the best organic-based quantum-dot LEDs, but with the advantage of improved shelf-life robustness. The reported maximum external electroluminescence efficiency is nearly 0.1%, which represents a 100-fold improvement over previously reported structures

Nanoparticles functionalized with ligands that target tumours can be cleared from the body through the kidneys if they have a hydrodynamic diameter of less than 5.5 nm.

This Review article summarizes the key advantages of using quantum dots (QDs) as luminophores in light-emitting devices (LEDs) and outlines the operating mechanisms of four types of QD-LED. The key scientific and technological challenges facing QD-LED commercialization are identified, together with on-going strategies to overcome these challenges.

Repairing the blood vessels in cancerous tumours can improve the delivery of small nanoparticles.

The average single-nanocrystal spectral linewidth within an ensemble of nanocrystal emitters in solution can be directly and quantitatively measured using photon-correlation Fourier spectroscopy (S-PCFS). Variations in single-nanocrystal linewidths between batches are found to be significant and synthetically tunable, introducing new avenues for the optimization of nanocrystals for optical applications.

Red quantum-dot light-emitting diodes with an external quantum efficiency of 18%, close to the theoretical maximum of 20%, are reported. Using a layer of zinc oxide nanocrystals provides highly effective electron transport, resulting in devices with a low operating voltage and a high luminous power efficiency of 25 lm W⁻¹.

The use of colloidal quantum dots in optical applications is hampered by difficulties in optimizing their physical properties. The synthesis of high-quality quantum dots that simultaneously exhibit narrow emission linewidths and minimal blinking potentially overcomes this problem.

Fabricating low-temperature solution-processed solar cells with good power-conversion efficiency and stability in ambient conditions has proved challenging. The use of ligands that protect colloidal quantum dots from degradation in air and tune their energy levels is now shown to be a viable approach for the realization of spin-coated solar cells with very high efficiency.

Lead sulphide colloidal nanocrystals offer a solid-state answer for infrared-to-visible upconversion.

An efficient, cost effective microspectrometer that consists of a two-dimensional absorptive filter array of 195 different colloidal quantum dots is presented, and its performance demonstrated by measuring shifts in spectral peak positions as small as one nanometre.

Electronic bandgap tuning in semiconductors enables key functionalities in solid-state devices. Here, the authors present a strategy to control the bandgap of atomically thin WS₂ and WSe₂semiconductors via manipulation of the surrounding dielectric environment rather than by modifications of the materials themselves.

Functionalized InAs quantum dots emitting in the short-wavelength infrared spectral region enable functional biomedical imaging at unprecedentedly high spatial resolution, deep penetration and fast acquisition speeds.

Lead halide perovskites have unique electronic properties that depend on the crystal’s anharmonicity. Dielectric solvation theories, developed for molecules dissolved in polar liquids, are shown here to reproduce the temperature behavior of carrier solvation in the electronic spectra, implying strongly anharmonic lattice dynamics.

A luminescent photonic substrate with a controlled angular emission profile is introduced and its ability to generate high-contrast dark-field images of micrometre-sized living organisms is demonstrated using standard optical microscopy equipment.

Photoluminescence blinking is a ubiquitous phenomenon that detrimentally reduces emission stability and quantum yield. Now, an all-optical method, which employs ultrafast mid-infrared pulses, can effectively suppress the blinking of single CdSe/CdS core–shell quantum dots.

A terahertz camera based on an upconversion mechanism to the visible range can image both THz polarization state and field strength.

Large perovskite nanocrystals are synthesized to increase the cryogenic exciton radiative rate. At liquid helium temperatures, single photons from perovskite nanocrystals coalesce at a beam splitter, signalling the existence of indistinguishable photon emission.

Exciton-polaritons present opportunities for quantum photonics, next generation qubits, and tuning material photophysics. Here Laitz et al. study the temperature dependence of 2D perovskite microcavity polaritons, revealing material-specific relaxation mechanisms towards the control of polariton momentum.

Colloidal quantum dots are a potential source of scalable single-photon emitters, but they typically exhibit broad emission linewidths. Proppe et al. show narrow-linewidth emission from heavy-metal-free InP/ZnSe/ZnS dots with coherence times of up to 250 ps.

Intracellular biothiols can degrade nanoparticle monolayers, compromising the function of these potentially promising tools. Here, we describe a label-free method for quantifying the intracellular stability of quantum dot monolayers, using laser desorption/ionization mass spectrometry coupled with inductively coupled plasma mass spectrometry.

Tuning the selectivity for [2+2] photocycloadditions remains challenging. Now, triplet–triplet energy transfer from CdSe quantum dots enables the homo- and heterocouplings of 4-vinylbenzoic acid derivatives via [2+2] photocycloaddition. Preorganization of substrates on the quantum dots reverses intrinsic stereoelectronic preferences to yield cyclobutane products with unprecedented diastereo- and regioselectivity.

Transition-metal single-atom catalysts display excellent activity per metal atom site, but suffer from low metal atom densities (typically less than 5 wt% or 1 at.%), which limits their overall catalytic performance. Now, the use of a graphene-quantum-dot primary support, later interweaved into a carbon matrix, has enabled the synthesis of single-atom catalysts with high transition-metal atom loadings of up to 40 wt% or 3.84 at.%.

Hybrid structures made up of quantum dots functionalized with molecules are highly tunable platforms for light-driven applications; however, the interaction between their components is often weak. Now it has been shown that by connecting molecules to silicon quantum dots via p-conjugated tethers, strongly coupled exciton states can be generated that prove advantageous for photon upconversion.

The demonstration of high-resolution quantum-dot light-emitting diodes by transfer printing could prove useful for next-generation displays.

Channeling between enzymes is a uniquely nanoscale phenomenon that can improve multienzymatic reaction rates. Here, the authors demonstrate that multistep enzyme cascades can self-assemble with nanoparticles into nanoclusters that access channeling and improve the underlying catalytic flux by several fold.

The conversion of methane to target one-carbon oxygenates relies on a two-step process that is carbon and energy intensive. Direct oxidation offers a sustainable alternative pathway. Here, the authors report on the selective photocatalytic oxidation of methane at room temperature using bismuth vanadate catalyst, realizing high methanol and formaldehyde selectivity.

In analogy to the coupling of atoms into molecules, the authors fuse colloidal semiconductor nanocrystals into quantum dot dimers. These nanocrystal ‘molecules’ exhibit significant quantum coupling effects, making them promising for applications in devices and potential quantum technologies.

All-inorganic nanocrystals are of great importance for a variety of electronic applications. Here, the authors use metal salts to remove organic ligands to obtain passivated nanocrystals with improved fluorescence yield for direct optical patterning.

Narrow emission is desired for light-emitting devices. Here, Kovalenko et al. demonstrate that the emission line-broadening in perovskite quantum dots is dominated by the coupling between excitons and surface phonon modes which can be controlled by minimal surface modifications.

Lignin-first approaches, which prioritize lignin upgrade over cellulose, can open the way to full biomass valorization, but are still hampered by the need of harsh reaction conditions and difficulties in catalyst recovery. Now, a photocatalytic strategy based on the use of cadmium sulfide quantum dots is reported that overcomes these limitations.

Material–microbe hybrids represent a promising strategy for harnessing biochemical reactivity using sunlight, yet little is known about the effect of the interaction on the organism. Here the interface of a CO₂- and N₂-fixing bacterium to CdTe alters its biochemical pathways, resulting in quantum efficiency close to the theoretical limit.

Exciton/recombination events in semiconductor quantum dots are highly dependent on surface coordination environments and these processes are well studied. Here, conversely, the authors use sum-frequency generation spectroscopy to probe the effect of the quantum dot on the vibrational structure of the ligands.

Nitride based photoelectrodes are promising candidates for photoelectrochemical water splitting and hydrogen generation but suffer from quick degradation. Here the authors show indium gallium nitride activated by InN quantum dots on silicon which can be used as stable photoanode for efficient water splitting.

Colloidal quantum dot devices demonstrating electrically pumped amplified spontaneous emission are described, showing strong, broadband optical gain and bright edge emission, opening the path to solution-processable laser diodes.

The authors develop a method for the production of ultra-bright, efficient and stable perovskite light-emitting diodes, achieved with a simple in situ reaction process.

A method of engineering efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes (QD-LEDs) has improved their performance to the level of state-of-the-art cadmium-containing QD-LEDs, removing the problem of the toxicity of cadmium in large-panel displays.

Ultrasmall monodisperse perovskite quantum dots are synthesized in situ on a substrate via ligand structure regulation, yielding the highest external quantum efficiency blue perovskite LEDs reported so far.

The chemistry of the magic ingredient in this ancient glass is no longer a mystery.

NeCLAS is a machine learning pipeline that can accurately and efficiently predict nanoscale interactions, which has broad applications in biological processes and material properties.

The application of quantum dots for quantum communication is limited by the wetting layer, which is inherent to the Stranski–Krastanov growth method. Here, the authors advance this method by decoupling the quantum dot and wetting layer states, which modifies their excitonic properties.

Droplet GaAs quantum dots are interconnectable sources of single photons. Near-identical photons from remote GaAs quantum dots now show an interference visibility of 93% with quantum entanglement between the separate photon streams from the two sources.

An efficient control strategy is designed for quantum dot arrays, drawing inspiration from classical semiconductor technology. A two-dimensional array of 16 semiconductor quantum dots is operated using only a few shared control lines.

This Review examines the use of colloidal quantum dots in the development of next-generation electronics, including luminescent, optoelectronic, memory and thermoelectric devices.

Colloidal quantum dots are promising materials for realizing versatile, wavelength-tunable, solution-processed lasers. This Review surveys recent advances in colloidal quantum dot lasing, provides an in-depth analysis of outstanding challenges and discusses a path forward to implementing technologically viable lasing devices.

Machine learning can be applied for the controlled synthesis of nanoparticles with precise properties. This Review discusses different machine learning approaches for the synthesis of semiconductor, metal, carbon-based and polymeric nanoparticles, and highlights key approaches for the collection of large datasets.

Inorganic nanocrystals coated with surfactant-like organic molecules have a vast range of properties arising from the combination of their components. In this Review, the role of the organic ligands on the synthesis of colloidal nanocrystals is discussed with a focus on the tails of the ligands and their collective effects on the surface.

Quantum-dot-based solar cells promise to deliver efficiencies approaching those of crystalline solar cells but with the manufacturing simplicity of organics.

Semiconductor qubits are expected to have diverse future quantum applications. This Review discusses semiconductor qubit implementations from the perspective of an ecosystem of applications, such as quantum simulation, sensing, computation and communication.

The role of surface ligands in tuning the optoelectronic properties, controlling the stability and determining the performance in applications of colloidal nanocrystals is discussed in this Review.

Quantum dots couple to form artificial molecules that allow for variable colour emission in response to an electric field.

Single-particle spectroscopic techniques that provide insights into the fundamental photophysical properties of functional nanomaterials are reviewed.

Scientists have engineered semiconducting nanocrystals called quantum dots that lack toxic heavy metals and are highly efficient light emitters. These nanostructures might be used in displays, solar cells and light-emitting diodes.

On the evidence of Nature's recent conference in Tokyo, technologies at the nanometre scale are now within reach. But how are they to be realized, and what form will they take?

A new variation on an old theme in atomic physics, a spectral distortion known as the Fano effect, has been revealed — not in an atom, but in an artificial nanostructure known as a quantum dot.

Liquid suspensions of semiconductor nanocrystals that can be printed or coated onto a substrate promise a new era of low-cost optoelectronics. The demonstration of infrared image sensors and displays based on this approach and fully integrated with silicon electronics suggests that the technology is maturing rapidly.

The rapidly improved performance of LEDs based on multilayers of highly luminescent quantum dots could lead to promising applications in next-generation displays and lighting.

Semiconducting quantum dots have been extensively investigated with the idea of using single spins for quantum computing. Whereas access to single electrons and their spins has become routine, the challenges posed by nuclear spins remain ever present.

Semiconducting quantum dots (QDs) can serve as light-absorbing components in efficient artificial photosynthetic systems for H₂ evolution. This Review describes how we can optimize QDs for H₂ evolution using sacrificial reductants, before moving on to sustainable strategies for the photolysis of biomass or H₂O.

The biosynthesis of inorganic nanomaterials in microorganisms is an environmentally friendly alternative to chemical synthesis. This Review describes the engineering of microorganisms to rationally prepare nanomaterials for diverse applications.

Solar cells based on solution-processed colloidal quantum dots are promising alternatives to conventional devices. This Review discusses recent advances and outstanding challenges for the field of quantum dot solar cells towards their commercialization.

This Perspective highlights recent advances in the use of nanoparticles in super-resolution microscopy and single-molecule tracking. It offers guidance for users interested in these tools and discusses potential future directions.