Surface modification of CdS quantum dots using thiols—structural and photophysical studies

Thangadurai, P.; Balaji, S.; Manoharan, P. T.

doi:10.1088/0957-4484/19/43/435708

Cited by 93 publications

(60 citation statements)

References 42 publications

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“…The process of solidification improves the surface passsivation (δ 2 > δ 1 ), injecting electrons and pushing the defect levels further toward the CB. 67,25 When the surface states are almost energetically in line with V S + and/or V S 2+ states, the probability of recombination of electrons from lattice defects to the VB is more likely; hence, we can observe the emission lines corresponding to these energy states which match the literature in terms of offsets from the CB (Figure 6c), as was mentioned in the previous section. The upward band-bending caused by the O Ch is partially compensated by the electrons which were injected by PVP in the process of solidification, where δ 2 becomes a predominant interaction supported by W. Consequently, the bending would have been reduced, which aligns V S + and/or V S 2+ states with the surface defects, which are now relatively closer to the CB.…”

Section: Resultssupporting

confidence: 85%

Sensitive Surface States and their Passivation Mechanism in CdS Quantum Dots

2013

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We report on phase sensitive surface states of CdS quantum dots (QDs), where it is noticed that a simple phase change from dispersion to solid has shown significant influence on the emission spectrum. As the solvent evaporates from the dispersion, apparently yellow dispersion transforms into a white light emitter because of the conformal changes in the polymer that surrounds the QDs. In turn, these changes catalyze the emission from three specific wavelengths in the blue region of the spectrum, shifting the surface defects closer to the conduction band of CdS. In the phase change from dispersion to solid, flexible and dangling polymer chains are transformed into rigid moieties that can be treated as a modified chemical environment. Furthermore, to ascertain the origin of the new emission lines, we have studied a dipole interaction-based passivation mechanism between QDs and the polymer. The proposed mechanism may be valuable for designing future QD-based fluorophores and explains the sensitivity of the surface states in the case of CdS.

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Section: Resultssupporting

confidence: 85%

Sensitive Surface States and their Passivation Mechanism in CdS Quantum Dots

2013

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“…8, the direct band gap values were determined by extrapolating the linear portion of these plots to the energy axis. The estimated E g values are found to be 2.18 eV, which is close to the literature results (Table 5) (Thangadurai et al, 2008). As well as, the grain size also decreases with the influence of Complexing agent TEA.…”

Section: Uv-visible Spectra Analysissupporting

confidence: 88%

Deposition and Characterization of CdS Nano Thin Film with Complexing Agent Triethanolamine

Manikandan¹,

Dilip²,

Prabaharan³

et al. 2015

American Journal of Engineering and Applied Sciences

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Abstract:The equimolar concentration thin films of Cadmium Sulfide (Cd x S x ) with the complexing agent TEA were deposited on a glass substrate by the SILAR technique. The crystalline nature with face centered cubic crystal system of the CdS films is determined from Xray diffraction analysis. The broadened diffraction peaks indicated nano sized particles of the film materials. The surface morphology of the films was studied by SEM analysis. The Energy Dispersive Analysis of X-ray (EDAX) plot confirms the equimolar composition of Cd and S ions in the film materials. Surface topography of the film was studied by AFM. The optical characteristic of absorbance, transmittance and band gap was analyzed by UV-visible spectra. The band gap energy of the material was observed as 2.18 eV and chemical bonding was studied by FT-IR spectral analysis.

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“…Glutathione is a capping agent derived from L-cysteine and L-glutamine that has been shown previously to stabilize water-soluble CdS nanocrystals (22,49). However, unlike L-cysteine, glutathione is not a substrate for CSEs (50) and, therefore, acts solely as a capping agent.…”

Section: Cds Quantum Dot Growth Depends On Both H 2 S Production and mentioning

confidence: 99%

Single-enzyme biomineralization of cadmium sulfide nanocrystals with controlled optical properties

Dunleavy

Kiely

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

115

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Nature has evolved several unique biomineralization strategies to direct the synthesis and growth of inorganic materials. These natural systems are complex, involving the interaction of multiple biomolecules to catalyze biomineralization and template growth. Herein we describe the first report to our knowledge of a single enzyme capable of both catalyzing mineralization in otherwise unreactive solution and of templating nanocrystal growth. A recombinant putative cystathionine γ-lyase (smCSE) mineralizes CdS from an aqueous cadmium acetate solution via reactive H 2 S generation from L-cysteine and controls nanocrystal growth within the quantum confined size range. The role of enzymatic nanocrystal templating is demonstrated by substituting reactive Na 2 S as the sulfur source. Whereas bulk CdS is formed in the absence of the enzyme or other capping agents, nanocrystal formation is observed when smCSE is present to control the growth. This dualfunction, single-enzyme, aerobic, and aqueous route to functional material synthesis demonstrates the powerful potential of engineered functional material biomineralization.cadmium sulfide | quantum dot | biomineralization | enzyme | nanoparticle B iological systems have evolved a diverse array of mechanisms to synthesize inorganic materials from aqueous solutions under ambient conditions. This inherent control over material properties has created interest in using these biological routes to synthesize materials (1-3) such as biosilica from sponges and diatoms (4-8), biogenic CaCO 3 from mollusks (9-12), and magnetic particles from magnetotactic bacteria (13-15). Designing a biomineralization strategy requires control of both the material composition and structure; in nature, this control is typically achieved through the assembly of a multiprotein complex, including both structuredirecting proteins and proteins responsible for mineralization of a specific composition. In the current work, we demonstrate the reduction of this complexity to its simplest form: a single enzyme capable of both catalyzing CdS mineralization and controlling particle size within the quantum confined size range to form functional biomineralized CdS quantum dots.Two of the most studied biomineralization proteins are perlucin and silicatein. Perlucin (16) has been shown to mineralize crystalline forms of CaCO 3 , a common structural material that constitutes the shell of many marine organisms, in the form of organic-inorganic composites. The role of the nacre protein perlucin in crystallite templating has been elucidated through experiments demonstrating crystallite formation in the presence of purified perlucin, and perlucin selectively being removed from solution during crystallite formation in the presence of a mixture of water-soluble, nacre-associated proteins (17). Native silicatein harvested from sea sponge or engineered forms produced recombinantly are active for biomineralization of silica and titania into structures that are amorphous or crystalline (7,18,19). In particular, biomineralizatio...

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Surface modification of CdS quantum dots using thiols—structural and photophysical studies

Cited by 93 publications

References 42 publications

Sensitive Surface States and their Passivation Mechanism in CdS Quantum Dots

Sensitive Surface States and their Passivation Mechanism in CdS Quantum Dots

Deposition and Characterization of CdS Nano Thin Film with Complexing Agent Triethanolamine

Single-enzyme biomineralization of cadmium sulfide nanocrystals with controlled optical properties

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