Combined Theoretical–Experimental Approach to the Growth Kinetics of Colloidal Semiconductor Nanocrystals

Ferreira, Diego Lourençoni; Ferreira, Sebastião Rodrigo; Silva, A. Germana; Schiavon, Marco A.

doi:10.1021/acs.jpcc.9b05615

Cited by 6 publications

(11 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both processes are dependent on the concentration gradient/difference at the surface of nanocrystals and the diffusion of monomers (solute atoms). The mass transport for the growth of nanocrystals in a solution can be described by Fick’s law, − and most studies have been based on the growth in an infinite space and the negligible effect of surface curvature. According to the Gibbs–Thomson equation, the concentration of monomers (solute atoms) on a curved surface is different from that on a flat surface.…”

Section: Introductionmentioning

confidence: 99%

Diffusion-Limited Growth of a Spherical Nanocrystal in a Finite Space

Yang

2021

Langmuir

View full text Add to dashboard Cite

Reason for the work: The potential applications of nanoscale materials in nanophotonics, nanoelectronics, bioimaging, and biosensing have stimulated the research in the synthesis of nanocrystals, nanowires, and so forth. There is a great need to understand the spatiotemporal evolution of nanocrystals in the solution-route synthesis in order to better design advanced synthesis techniques for the manufacturing of monodisperse nanocrystals of high quality. Most significant results: We analyze the size effect on the diffusion-limited growth of a spherical nanoparticle in a finite space (spherical cavity) on the basis of the Gibbs−Thomson relation and obtain an analytical formulation of the monomer concentration in the finite space in an implicit form and an integro-differential equation for the growth rate of the spherical nanoparticle. The monomer concentration in the finite space decreases slower than that with a stationary nanoparticle. The growth of the spherical nanoparticle consists of two stages−an initially linear growth stage and a later power-law stage. The result from the infinite space with a stationary nanoparticle is inapplicable to the analysis of the growth of spherical nanoparticles in a finite space. Conclusions: There exists a size effect on the growth of nanocrystals in a finite space. The dependence of the growth behavior of nanocrystals on the growth time and temperature needs to be investigated in order to experimentally determine the fundamental mechanisms controlling the growth of nanocrystals in the solution-route synthesis.

show abstract

Section: Introductionmentioning

confidence: 99%

Diffusion-Limited Growth of a Spherical Nanocrystal in a Finite Space

Yang

2021

Langmuir

View full text Add to dashboard Cite

show abstract

“…At D = D c , there is an equilibrium between QDs and monomers in the bulk solution, yielding a null growth rate. Therefore, D c establishes a threshold for both particle dissolution or shrinkage ( D < D c , negative growth rate) and growth ( D > D c , positive growth rate). ,− Then, returning to our original problem, when an ensemble of QDs in a particular colloidal medium is subjected to laser irradiation, some of the dispersed particles may be partially or completely decomposed into smaller fragments and/or individual atoms and molecules if the energy absorbed by the particles from the laser pulse is enough for that . Consequently, the interaction of the laser beam with the colloidal particles generates additional monomer units that are transported back to the reaction medium, instantaneously increasing the supersaturation degree S of the bulk solution.…”

Section: Results and Discussionmentioning

confidence: 98%

“…In addition, Δ E Coulomb is the energy shift due to the Coulomb interaction between the electron and the hole, and Δ E Pol is the energy shift resulting from the QD surface polarization associated with the dielectric mismatch between the QD material and the surrounding medium. The extensive algebraic form of the DLF equation and the numerical parameters required for its implementation are presented in detail in refs , along with the resulting bandgap vs particle size curve for CdTe colloidal QDs in an aqueous solution.…”

Section: Theoretical Sectionmentioning

confidence: 99%

Size-Dependent Photobleaching Mechanism and Kinetics Induced by Nanosecond Laser Pulses in Colloidal Semiconductor Quantum Dots

et al. 2022

Self Cite

View full text Add to dashboard Cite

An experimental-theoretical approach is proposed to investigate the size-dependent photobleaching of colloidal semiconductor quantum dots (QDs) excited by a nanosecond pulsed laser. In the experimental background, the ground-state absorption and photoluminescence (PL) spectra of chemically prepared QDs are monitored over an excitation time at distinct laser irradiances. The magnitude of photobleaching in the QD solution is quantified by the decay rate of the PL signal as a function of the excitation time and the laser power. A theoretical spectroscopy model is then used to estimate the particle size distribution (PSD) in colloidal solution from the absorption data generated at different laser powers. The resulting evolution of the PSD of the QD ensemble under irradiation is analyzed in terms of classical crystallization theories dealing with the formation, growth, and dissolution of colloidal particles in a supersaturated medium. The QD response to laser irradiation is also interpreted by a simple mechanical model that correlates the photoinduced hydrostatic strain at the solid/liquid interface and the predicted variation of the mean particle size. The reported experimental and theoretical methods are used to completely elucidate the basic physico-chemical processes responsible for the laser-induced photobleaching kinetics of glutathione-capped CdTe aqueous QDs with very small mean sizes. For this purpose, we synthesized a series of colloidal QD samples with mean particle diameters ranging from 1.95 to 2.68 nm. Our results indicate that a faster photobleaching rate occurs in QD samples with smaller sizes in which particle dissolution under laser irradiation is predominant. On the other hand, the photobleaching rate becomes slower in samples with larger dot sizes, possibly due to the formation of core/shell structures in solution via thermal degradation of thiol ligands either during the chemical synthesis or as a consequence of the subsequent interaction with the excitation laser.

show abstract

“…37 To determine the average size of our QD samples, we have used a recently developed theoretical methodology that allows converting the measured PL spectrum into realistic estimates for the particle size distribution (PSD) of semiconductor QDs synthesized in a colloidal medium. 38,39 Such a spectroscopic model turned out to be particularly accurate for describing ensembles of nearly spherical colloidal QDs with extremely small sizes (average diameter as small as 1-3 nm), that have not been fully incorporated into the currently available empirical sizing equations. 32 The predicted PSDs exhibited an excellent agreement with those obtained from atomic force microscopy (AFM) and transmission electron microscopy (TEM), especially for aqueous CdTe QDs passivated with L-glutathione, which strictly corresponds to the same QD system investigated in the present work.…”

Section: Resultsmentioning

confidence: 99%