What Are InP/ZnS Quantum Dots?
Indium phosphide/zinc sulfide (InP/ZnS) quantum dots (QDs) are a class of semiconductor nanocrystals that exhibit exceptional optical properties due to their quantum confinement effects. The core of these nanocrystals consists of indium phosphide (InP), a III–V semiconductor known for its direct bandgap and tunable emission in the visible to near-infrared (NIR) range. A zinc sulfide (ZnS) shell coating improves both stability and fluorescence quantum yield for InP cores by passivating surface defects and reducing non-radiative recombination pathways. The core-shell structure enhances photostability and quantum efficiency while reducing toxicity through encapsulation of hazardous core components.
Fig.1 Surface functionalized InP/ZnS QDs[1].
How Are InP/ZnS Quantum Dots Constructed?
Researchers produce InP/ZnS QDs through thermal decomposition of indium halides and tris(trimethylsilyl)phosphine precursors in coordinating solvents while maintaining an inert atmosphere throughout the process. The growth of the shell structure progresses by injecting zinc and sulfur precursors either stepwise or continuously. The optical properties of the ZnS shell are critically influenced by its thickness and crystallinity because thicker shells provide better photostability and emission efficiency.
Fig.2 Synthesis of InP/ZnS QDs[2].
InP/ZnS QDs from Alfa Chemistry provide precise size control, narrow emission bandwidths and customizable surface chemistries for diverse applications.
| Catalog | Product Name | |
| ACMA00000281 | InP/ZnS Quantum Dots | Inquiry |
How Do InP/ZnS Quantum Dots Compare to Traditional Cd-Based Quantum Dots?
InP/ZnS QDs were developed as safer alternatives to cadmium-containing quantum dots (e.g., CdSe/ZnS), which raise significant environmental and biological toxicity concerns. The absence of heavy metals such as cadmium makes InP-based quantum dots an attractive choice for bioimaging, in vivo tracking, and clinical research settings, where biocompatibility is paramount. While early InP QDs exhibited inferior optical properties compared to their Cd-based counterparts, recent advances in synthetic protocols and surface passivation techniques have enabled quantum yields exceeding 80%, as well as excellent photostability and narrow full-width at half maximum (FWHM) values.
Moreover, the emission wavelengths of InP/ZnS QDs can be precisely tuned by adjusting the size of the InP core, offering spectral control from 500 nm (green) to over 700 nm (red and NIR). The ZnS shell further stabilizes the QDs against oxidation and photobleaching, making them suitable for long-term imaging and device integration.
What Are the Key Applications of InP/ZnS Quantum Dots?
- Biomedical Imaging and Diagnostics
Researchers prefer to use InP/ZnS QDs for bioimaging applications because they exhibit low cytotoxicity and high fluorescence brightness. The NIR window emission of InP/ZnS QDs between 650 and 900 nm enables deep tissue penetration while minimizing autofluorescence background to improve imaging contrast. Site-specific labeling of cellular or molecular targets becomes possible through functionalization with targeting ligands like antibodies, peptides or aptamers. In immunofluorescence assays InP/ZnS QDs deliver bright and stable signals that surpass the performance of traditional organic dyes.
Fig.3 Biocompatibility and bioimaging studies with pure-blue-emitting [−] InP/ZnS QDs[3].
- Display and Optoelectronic Devices
Quantum dot light-emitting diodes (QLEDs) benefit from InP/ZnS QDs, which play a crucial role in green consumer electronics. Because of their tunable emission properties, high color purity and solution processing compatibility these nanoparticles act as ideal components for RGB pixelation in display technologies. The ZnS shell improves thermal and photo-stability, which helps prolong device life while minimizing color degradation when devices operate continuously. These quantum dots have been studied as components in down-conversion layers for backlit LCD displays as well as quantum dot-enhanced films, which are referred to as QDEFs.
- Photovoltaics and Photocatalysis
InP/ZnS QDs are also being explored as photosensitizers in solar cells and photochemical reactors. Their ability to absorb and convert solar energy into electricity or drive redox reactions is attributed to their high absorption coefficients and multiple exciton generation (MEG) potential. In dye-sensitized solar cells (DSSCs) and hybrid quantum dot solar cells, InP QDs serve as non-toxic sensitizers, enabling greener photovoltaic solutions.
Fig.4 InP/ZnS quantum dots are used in solar cells[4].
How Are InP/ZnS QDs Surface-Engineered for Targeted Use?
The surface chemistry of InP/ZnS QDs plays a pivotal role in defining their dispersion characteristics as well as their stability and functional capabilities across various settings. Ligands that originally possess hydrophobic properties can be swapped out through post-synthetic ligand exchange to introduce either hydrophilic or functionalized ligands, which enable aqueous dispersion and bioconjugation capabilities. Mercaptocarboxylic acids (such as MPA and DHLA), polyethylene glycol (PEG), and zwitterionic ligands serve as common ligands that deliver varying benefits regarding solubility, biocompatibility, and colloidal stability.
Fig.5 InP/ZnS quantum dots are used in solar cells[3].
What Are the Optical and Physical Characteristics of InP/ZnS QDs?
| Parameter | Typical Value/Range |
| Core diameter (InP) | 2–6 nm |
| Emission range | 500–750+ nm (size-tunable) |
| Quantum yield | Up to 80–90% (depending on synthesis) |
| Photostability | High (improved by ZnS shell) |
| FWHM of emission peak | 30–50 nm |
| Crystal structure | Zinc blende or wurtzite |
| Surface functionalization | Carboxyl, amine, PEG, zwitterionic, etc. |
| Solubility | Organic solvents or water (after ligand exchange) |
The parameters can be adjusted extensively through various synthesis techniques and the core-shell composition along with the type of surface ligands used. Alfa Chemistry offers detailed technical datasheets and assistance to help researchers choose the best InP/ZnS QDs for their research needs.
How Is Toxicity Mitigated in InP/ZnS Quantum Dots?
The reduced toxicity of InP/ZnS QDs arises from both material choice and structural engineering. InP quantum dots eliminate toxic heavy metals such as cadmium and lead, and their ZnS protective shell functions as a diffusion barrier, which reduces ion leakage and oxidative damage. Biological applications benefit from surface coatings like PEGylation, which enhance biocompatibility by reducing protein adsorption and immune system detection.
The reduced cytotoxicity of InP/ZnS nanoparticles compared to cadmium-based nanoparticles has been demonstrated in multiple laboratory and animal studies, which positions them as more appropriate for biomedical research applications.
FAQs About InP/ZnS Quantum Dots
Q1: Are InP/ZnS QDs completely non-toxic?
A1: While InP/ZnS QDs are significantly less toxic than Cd-based QDs, they are not entirely inert. Their biocompatibility improves with proper surface passivation and functionalization.
Q2: What emission colors can InP/ZnS QDs produce?
A2: The emission can be tuned from green (~500 nm) to near-infrared (~750 nm) by adjusting the core size.
Q3: Can I use InP/ZnS QDs in live-cell imaging?
A3: Yes, provided the QDs are surface-modified for aqueous solubility and biocompatibility.
Q4: How stable are InP/ZnS QDs under UV exposure?
A4: The ZnS shell enhances resistance to photobleaching. Proper storage and formulation further extend shelf life and stability.
Q5: Are custom surface modifications available?
A5: Yes. Alfa Chemistry offers custom surface chemistries, including carboxyl, amine, PEG, and other functional groups tailored for bioconjugation or industrial use.
Q6: Do InP/ZnS QDs support QLED applications?
A6: Absolutely. Their high color purity and tunable emission make them ideal for QLED and display technologies.
For more information or to request custom formulations of InP/ZnS quantum dots, contact Alfa Chemistry and explore their extensive portfolio of nanomaterials.
References
- Martyanov T., et al. Adsorption of Meso-Tetra(3-Pyridyl)Porphyrin on InP/ZnS Colloidal Quantum Dots. Journal of Nanoparticle Research (2022).
- Zhang W., et al. High Quantum Yield Blue InP/ZnS/ZnS Quantum Dots Based on Bromine Passivation for Efficient Blue Light‐Emitting Diodes. Advanced Optical Materials (2022).
- Roy P., et al. Blue-Emitting InP Quantum Dots Participate in An Efficient Resonance Energy Transfer Process in Water. Chem. Sci (2023).
- Pidluzhna A., et al. InP/ZnS Quantum Dots Synthesis and Photovoltaic Application. Applied Nanoscience (2023).
