Distance-Dependent Fluorescence Quenching and Binding of CdSe Quantum Dots by Functionalized Nitroxide Radicals

Tansakul, Chittreeya; Lilie, Erin; Walter, Éric; Rivera, Frank; Wolcott, Abraham; Zhang, Jin Z.; Millhauser, Glenn L.; Braslau, Rebecca

doi:10.1021/jp1005023

Cited by 84 publications

(82 citation statements)

References 87 publications

(163 reference statements)

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“…For the quenching of QD luminescence by organic radicals, a mechanism of the ligand exchange of TOPO with radicals was speculated by Heafey et al [32]. Recently a new mechanism was proposed requiring close proximity for electron transfer or spin exchange between the radical (electron acceptor) and the excited electron in the conduction band of QD (electron donor) [59].…”

Section: Comparison Of Oil-soluble Qds and Water-soluble Ctab-coated Qdsmentioning

confidence: 99%

Rapid detection of vegetable cooking oils adulterated with inedible used oil using fluorescence quenching method with aqueous CTAB-coated quantum dots

Xiong

et al. 2014

Sensors and Actuators B: Chemical

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a b s t r a c tVegetable cooking oils adulterated with inedible used oils or impure oils have posed a severe food safety problem. Current detection methods cannot meet the needs for rapid detection of adulterated oils on line or in field. Therefore, the objective of this research was to develop a rapid optical sensing method based on fluorescence quenching of CdSe/ZnS quantum dots (QDs) for identification of adulterated vegetable cooking oils. High quality hydrophilic photoluminescent nanoparticles were synthesized by encapsulating hydrophobic QDs into the micellar structure of an amphiphilic surfactant cetyltrimethyl ammonium bromide (CTAB) via phase transfer method. TEM, AFM, and fluorescence spectroscopy were used to characterize the prepared CTAB-coated QDs. Oil samples were first captured into the core of the twolayer-structural micelle and then the fluorescence of CTAB-coated QDs, working as fluorescence probes, was selectively quenched by components of the adulterated oils. Heavy metal ions and free radicals were presumed to be main quenchers. After quenching for 1 min, fluorescence intensity was measured and converted to quenching percentage to determine the adulteration concentration. The results showed that in comparison with oil-soluble QDs, water-soluble CTAB-coated QDs had a greater ability to identify oil adulteration. A good quantitative relationship between quenching percentage and adulteration concentration (y = 5.96x + 14.99; R 2 = 0.94) was obtained. The sensitive, simple and low-cost sensing method did not require sample pretreatment and could detect refined used oils at 0.4% or higher concentrations in soybean oil within 2 min, showing great potentials for rapid screening of used oils and quantitative analysis of used oil adulteration in field.

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Section: Comparison Of Oil-soluble Qds and Water-soluble Ctab-coated Qdsmentioning

confidence: 99%

Rapid detection of vegetable cooking oils adulterated with inedible used oil using fluorescence quenching method with aqueous CTAB-coated quantum dots

Xiong

et al. 2014

Sensors and Actuators B: Chemical

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“…[49][50][51][52][53][54] Alkoxyamines (with the exception of 1c and 1e) were prepared according to the method of Schoening et al, [55,56] whereby alkyl radicals are generated in situ from a ketone or aldehyde, copper (I) chloride, and hydrogen peroxide. In the presence of the nitroxide, nascent radicals are readily trapped, forming the desired alkoxyamines, listed in Scheme 2.…”

Section: Synthesismentioning

confidence: 99%

Experimental evidence for competitive N O and O C bond homolysis in gas-phase alkoxyamines

Marshall

Gryn’ova

Coote

et al. 2015

International Journal of Mass Spectrometry

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The extensive use of alkoxyamines in controlled radical polymerisation and polymer stabilisation is based on rapid cycling between the alkoxyamine (R1R2NO-R3) and a stable nitroxyl radical (R1R2NO•) via homolysis of the labile O-C bond. Competing homolysis of the alkoxyamine N-O bond has been predicted to occur for some substituents leading to production of aminyl and alkoxyl radicals. This intrinsic competition between the O-C and N-O bond homolysis processes has to this point been difficult to probe experimentally. Herein we examine the effect of local molecular structure on the competition between N-O and O-C bond cleavage in the gas phase by variable energy tandem mass spectrometry in a triple quadrupole mass spectrometer. A suite of cyclic alkoxyamines with remote carboxylic acid moieties (HOOC-R1R2NO-R3) were synthesised and subjected to negative ion electrospray ionisation to yield [M − H]− anions where the charge is remote from the alkoxyamine moiety. Collision-induced dissociation of these anions yield product ions resulting, almost exclusively, from homolysis of O-C and/or N-O bonds. The relative efficacy of N-O and O-C bond homolysis was examined for alkoxyamines incorporating different R3 substituents by varying the potential difference applied to the collision cell, and comparing dissociation thresholds of each product ion channel. For most R3 substituents, product ions from homolysis of the O-C bond are observed and product ions resulting from cleavage of the N-O bond are minor or absent. A limited number of examples were encountered however, where N-O homolysis is a competitive dissociation pathway because the O-C bond is stabilised by adjacent heteroatom(s) (e.g. R3 = CH2F). The dissociation threshold energies were compared for different alkoxyamine substituents (R3) and the relative ordering of these experimentally determined energies is shown to correlate with the bond dissociation free energies, calculated by ab initio methods. Understanding the structure-dependent relationship between these rival processes will assist in the design and selection of alkoxyamine motifs that selectively promote the desirable O-C homolysis pathway. homolysis is a competitive dissociation pathway because the O-C bond is stabilised by adjacent heteroatom(s) (e.g., R 3 = CH 2 F). The dissociation threshold energies were compared for different alkoxyamine substituents (R 3 ) and the relative ordering of these experimentally determined energies is shown to correlate with the bond dissociation free energies, calculated by ab initio methods.Understanding the structure-dependent relationship between these rival processes will assist in the design and selection of alkoxyamine motifs that selectively promote the desirable O-C homolysis pathway.

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“…One of the fundamental optical properties of these nanomaterials is their fluorescence emission. This property can be modified by controlling the particle size, i.e., the variation in bandgap width (Tansakul et al, 2010;Norris et al, 1993). In the last two decades, most research regarding quantum dots has been directed toward the synthesis of type III-V QDs (such as InP, GaAs and InAs) and type II-VI chalcogenides (such as CdSe, CdS and CdTe) (Medintz et al, 2006;Talapin et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Chemometric approach to study the influence of synthesis parameters on the size of CdTe quantum dots obtained from aqueous solutions

Navarrete

Román

Rojas

et al. 2019

Arabian Journal of Chemistry

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approach to study the influence of synthesis parameters on the size of cdte quantum dots obtained from aqueous solutions., Arabian Journal of Chemistry (2016), doi: http://dx. Abstract.This study reports CdTe quantum dots synthesis in an aqueous medium using cadmium chloride and sodium tellurite as precursors and sodium borohydride and mercaptosuccinic acid as reducing and capping agents, respectively. The synthesis process was optimized through experimental design, and particle characterization was carried out by UV-Vis spectroscopy and molecular fluorescence. In the first stage, a factorial design was used to establish the significance of each of the synthesis variables; i.e., the temperature, pH, reaction time and precursor molar ratios. In the second stage, a multivariate design was constructed to relate the synthesis variables with the maximum absorbance wavelengths, which allowed for predictions of the diameters of the CdTe quantum dots, which were compared with direct measurements of the particles analyzed by highresolution transmission electron microscopy, HR-TEM and X-ray diffraction, XRD. Finally, there is a brief discussion regarding the existing models predicting particle sizes.

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Distance-Dependent Fluorescence Quenching and Binding of CdSe Quantum Dots by Functionalized Nitroxide Radicals

Cited by 84 publications

References 87 publications

Rapid detection of vegetable cooking oils adulterated with inedible used oil using fluorescence quenching method with aqueous CTAB-coated quantum dots

Rapid detection of vegetable cooking oils adulterated with inedible used oil using fluorescence quenching method with aqueous CTAB-coated quantum dots

Experimental evidence for competitive N O and O C bond homolysis in gas-phase alkoxyamines

Chemometric approach to study the influence of synthesis parameters on the size of CdTe quantum dots obtained from aqueous solutions

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