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- Analysis of Particle Size Distributions of Quantum Dots: From Theory to Application
- Microbial synthesis of chalcogenide semiconductor nanoparticles: a review
Biophys J — Anal Bioanal Chem — Hum Gene Ther — Langmuir — Cell Stem Cell — Histochem Cell Biol — J Nanobiotechnology Stem Cells — Dev Dyn — Sykova E, Jendelova P In vivo tracking of stem cells in brain and spinal cord injury [review]. Prog Brain Res — J Phys Chem B — Biophys J 97 2 — Exp Cell Res — J Biophotonics — Chem Rec — J Neurosci — Dahan M From analog to digital: exploring cell dynamics with single quantum dots.
New technology has potential to create a variety of multiplexed diagnostic tests
Curr Pharm Biotechnol — Guo P, Wei C Quantum dots for robust and simple assays using single particles in nanodevices [review]. Nanomedicine — Nucleic Acids Res Nanotechnology Neurosurgery — Angiogenesis — Texier I, Josser V In vivo imaging of quantum dots. Br J Cancer — Cai W, Chen X Preparation of peptide-conjugated quantum dots for tumor vasculature-targeted imaging.
Nat Protoc — Cancer Biomark — Adv Exp Med Biol — Chapter Unit Small — J Biomed Opt Lancet Oncol 7 8 — Nat Med — J Immunol Meth — Smith RA, Giorgio TD Quantitative measurement of multifunctional quantum dot binding to cellular targets using flow cytometry.
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Cytometry A — Abrams B, Dubrovsky T Quantum dots in flow cytometry. Nat Medicine — Lab Hematol — J Am Chem Soc — Ornberg RL, Harper TF, Liu H Western blot analysis with quantum dot fluorescence technology: a sensitive and quantitative method for multiplexed proteomics. Int J Mol Sci — Eur Biophys J — So, it is plausible to assume that different magic-sized clusters have local minima in chemical potentials. Previous investigations have noticed that magic-sized nanoclusters are frequently observed in the nucleation stage during the synthesis of elongated nanocrystals.
The formation of magic-sized nanoclusters originates from their local minimum chemical potential because of the closed-shell configurations. The formation of magic-sized nanoclusters happens under a relatively high chemical potential and they are only stable at relatively high monomer concentrations due to their extremely small sizes.
It is suggested that the magic-sized nanoclusters can undergo two pathways after the formation.
Analysis of Particle Size Distributions of Quantum Dots: From Theory to Application
This process is highly favored with a lower monomer concentration present in the solution. It has also been observed that magic-sized clusters are formed only at the high monomer chemical potentials needed to form the rod-shaped nanocrystals, thus their chemical potential corresponds to local minima in the progression from precursors to final nanorods.
Jiang and Kelly tried to propose a mechanism to explain the formation of magic-sized clusters MSCs and to fit the current available experimental data [ 20 ]. A number of species are discussed in the system including the nuclei, the magic-sized clusters, nanorods representing nanocrystals with highly anisotropic shapes , and nanospheres nanocrystals with low aspect ratio.
The central feature of the mechanism is the fast equilibrium between monomers and the magic-sized clusters. The monomer concentration has a saturation value of M 0. The magic-sized clusters can only form when the monomer concentration exceeds M 0 and will dissolve back when it is lower than the saturation value. The condensation and dissolution processes happen at a very fast rate so that magic-sized clusters serve as a reservoir for monomers.
In this proposed mechanism, the possibility of magic-sized clusters serving as intermediate between monomer and regular nanorods is excluded. Based on the chemical potential relation indicated above, several monomer concentration regimes can be identified. When the monomer concentration exceeds the saturation value M 0 , the additional monomer will form magic-sized clusters to keep monomer concentration within the saturation value M 0.
When the monomer concentration decreases below M 0 , no magic-sized clusters can be formed and the existing clusters will dissolve back to form monomers.
The biggest difference between the two proposed mechanisms lies in the possibilities of magic-sized nanoclusters directly towards regular nanocrystals with larger size. Further well-designed experiments are expected to help elucidating the puzzle. Theoretical calculations have been carried out to help understanding the MSQD forming mechanism.
First-principle calculations using ultrasoft pseudopotentials and the generalized gradient approximation show that CdSe n to be cage-like polyhedral [ 21 ]. The Cd and Se ions will connect alternatively to form zigzag networks composed of four- and six-membered rings.
Furthermore, the cage can be stabilized by filling with a core inside with connections to the cage. Thus, a selection of a highly symmetric cage with the right size of core will impose stringent restrictions for forming a stable nanostructure.