Quantum dots (QDs) - Nanomaterials / Alfa Chemistry

Quantum Dots

Quantum dots (QDs) are semiconductor particles a few nanometers in size whose optical and electronic properties differ from those of larger particles through quantum mechanical effects. When a quantum dot is illuminated by UV light, the electrons in the quantum dot can be excited to a higher energy state. In the case of semiconductor quantum dots, this process corresponds to the transition of electrons from the valence band to the conduction band. The excited electrons can fall back to the valence band, releasing their energy in the form of light.

Inquiry Now

What is Quantum Dot?

A quantum dot is a semiconductor nanostructure that holds excitons in three spatial directions. This confinement can be due to electrostatic potentials, interfaces between two different semiconductor materials, surfaces of semiconductors, or a combination of all three. A quantum dot has a discrete, quantized energy spectrum. The corresponding wave functions are spatially localized in the quantum dot, but extend over several lattice periods. A quantum dot has a small number (1-100) of electrons, holes, or hole-electron pairs, i.e., the charge it carries is an integer multiple of the elementary charge.

What are the Features of Quantum Dots?

Controllable Emission Spectrum

The emission spectrum of quantum dots can be controlled by changing the size of quantum dots.

Good Photostability

The fluorescence intensity is 20 times higher than the most commonly used organic fluorescent materials, and the stability is more than 100 times higher.

Wide Excitation Spectrum and Narrow Emission Spectrum

The same excitation light source can be used to simultaneously detect quantum dots of different particle sizes.

Large Stokes Shift

It can avoid the overlap of emission spectrum and excitation spectrum, which is conducive to the detection of fluorescence spectrum signals.

Good Biocompatibility

After various chemical modifications, quantum dots can be specifically connected, with low cytotoxicity and little harm to organisms, and can be used for biological living body labeling and detection.

Long Fluorescence Lifetime

The fluorescence lifetime of quantum dots with direct band gap can last for tens of nanoseconds, while the fluorescence lifetime of quantum dots with quasi-direct band gap can last for more than 100μs.

Quantum Dot Products Products List

Oil-Soluble CdSe/ZnS QDs Oil-Soluble InP/ZnS QDs Oil-Soluble PbS QDs Oil-Soluble PbS/CdS QDs Oil-Soluble PbSe QDs Oil-Soluble CuInS/ZnS QDs Oil-Soluble CsPbX₃ (X = Cl, Br, I) Perovskite QDs Oil-Soluble ZnSe/ZnS QDs Oil-Soluble ZnCdS/ZnS QDs Oil-Soluble CdTe/CdSe/ZnS QDs Oil-Soluble CdS QDs Oil-Soluble CdSe QDs Oil-Soluble CdSeTe/ZnS QDs Oil-Soluble Cu-doped QDs Oil-Soluble Mn-doped QDs Oil-Soluble Cu and Mn Co-doped QDs Oil-Soluble CQDs Oil-Soluble Ag₂Se QDs Water-Soluble CdSe/ZnS QDs Water-Soluble InP/ZnS QDs Water-Soluble CQDs Water-Soluble ZnCdS/ZnS QDs Water-Soluble CdTe/CdS QDs Water-Soluble CdTe/CdSe/ZnS QDs Water-Soluble CdSeTe/ZnS QDs Water-Soluble ZnSe/ZnS QDs Water-Soluble Mn-doped QDs CdSe QD Microspheres InP QD Microspheres

What are the Applications of Quantum Dots?

Biology‌

In the biomedical field, quantum dots are used as fluorescent marker materials for biomonitoring and medical imaging due to their stable luminescence properties and tunable spectral properties.

‌Photovoltaic Devices

The tunable absorption spectrum and high extinction coefficient of quantum dots make them attractive for light-harvesting technologies such as photovoltaics.

‌Light-emitting Diodes

Methods of using quantum dots to improve existing light-emitting diode (LED) designs, including quantum dot light-emitting diode displays and quantum dot white light-emitting diode displays.

‌Basic Materials Science

Quantum dots can also be used to study fundamental effects in materials science. Artificial molecules can be created by coupling two or more such quantum dots.

Photodetector Devices

Quantum dot photodetectors have potential applications in visible and infrared cameras, machine vision, industrial inspection, spectroscopy, and fluorescent biomedical imaging.‌

Photocatalysts

Quantum dots are also used as photocatalysts for the light-driven chemical conversion of water into hydrogen as a route to solar fuels.

What are the Types of Quantum Dots We Provide?

Oil-Soluble Quantum Dots (QDs)

Water-Soluble Quantum Dots (QDs)

Quantum Dot (QD) Microspheres

Our Services for Nanomaterials

Alfa Chemistry is dedicated to advancing the field of nanomaterials through our comprehensive suite of services.

Custom Synthesis

Process R&D

Nanomaterials Synthesis

Nanomaterials Analysis and Research

Nanomaterial Application Services

Why Alfa Chemistry?

ISO 9001:2015

Alfa Chemistry is ISO 9001:2015 certified and focuses on collaboration and partnership.

Quality Assurance (QA)

Alfa Chemistry’s QA (Quality Assurance) department oversees all production and quality systems.

Quality Control (QC)

Alfa Chemistry’s QC (Quality Control) department ensures predetermined standards.

FAQs

How is safety of quantum dots?

Under certain conditions, some quantum dots pose risks to the environment. Notably, studies on quantum dot toxicity have focused on particles containing cadmium and have not been demonstrated in animal models after physiologically relevant administration. In vitro cell culture-based studies on the toxicity of quantum dots (QDs) suggest that their toxicity may arise from a variety of factors, including their physicochemical properties (size, shape, composition, surface functional groups, and surface charge) and their environment.

What are core/shell quantum dots?

Quantum dots are often coated with organic capping ligands to control growth, prevent aggregation, and facilitate dispersion in solution. However, these organic coatings can lead to non-radiative recombination after photogeneration, meaning that generated charge carriers can dissipate without photon emission, which can reduce the fluorescence quantum yield, or the efficiency with which absorbed photons are converted into emitted fluorescence. To address this problem, a semiconductor layer can be grown around the quantum dot core. Depending on the band gap of the core and shell materials, the fluorescence properties of the nanocrystal can be tuned. Additionally, tuning the thickness of each layer and the overall size of the quantum dot can affect the photoluminescence emission wavelength.

What are the methods for producing quantum dots?

There are several ways to make quantum dots. Possible methods include colloidal synthesis, self-assembly, and electrical gating.

What are metal-free quantum dots?

Many regions of the world now restrict or ban the use of toxic heavy metals in many household items, meaning that most cadmium-based quantum dots cannot be used in consumer product applications. To achieve commercial viability, a range of restricted, heavy-metal-free quantum dots have been developed that display bright emission in the visible and near-infrared regions of the spectrum and have similar optical properties to CdSe quantum dots. These materials include InP/ZnS, CuInS/ZnS, CuInZnSe/ZnS, Si, Ge, and C.