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Selective detection of dopamine in the presence of ascorbic acid via fluorescence quenching of InP/ZnS quantum dots.

Ankireddy SR, Kim J - Int J Nanomedicine (2015)

Bottom Line: The surface of the QDs was modified with l-cysteine by coupling reaction to increase the selectivity of dopamine.The fluorescence of cysteine-capped indium phosphide/zinc sulfide QDs was quenched by dopamine with various concentrations in the presence of ascorbic acid.This method shows good selectivity for dopamine detection, and the detection limit was 5 nM.

View Article: PubMed Central - PubMed

Affiliation: Department of chemical and Biological Engineering, Gachon University, Seongnam, South Korea.

ABSTRACT
Dopamine is a neurotransmitter of the catecholamine family and has many important roles, especially in human brain. Several diseases of the nervous system, such as Parkinson's disease, attention deficit hyperactivity disorder, restless legs syndrome, are believed to be related to deficiency of dopamine. Several studies have been performed to detect dopamine by using electrochemical analysis. In this study, quantum dots (QDs) were used as sensing media for the detection of dopamine. The surface of the QDs was modified with l-cysteine by coupling reaction to increase the selectivity of dopamine. The fluorescence of cysteine-capped indium phosphide/zinc sulfide QDs was quenched by dopamine with various concentrations in the presence of ascorbic acid. This method shows good selectivity for dopamine detection, and the detection limit was 5 nM.

No MeSH data available.


Related in: MedlinePlus

The optical absorption (A) and normalized PL spectra (B) of InP/ZnS QDs and l-cysteine-capped InP/ZnS QDs.Note: Original InP/ZnS QDs were insoluble in water but these QDs were soluble in DI water after surface modification with l-Cys amino acid. That is why QDs were dispersed in two-layered mixture of toluene and DI water under UV illumination.Abbreviations: QDs, quantum dots; UV, ultraviolet; Cys, cysteine; InP/ZnS QDs, indium phosphide/zinc sulfide quantum dots; PL, Photoluminescence; DI, deionized.
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f3-ijn-10-113: The optical absorption (A) and normalized PL spectra (B) of InP/ZnS QDs and l-cysteine-capped InP/ZnS QDs.Note: Original InP/ZnS QDs were insoluble in water but these QDs were soluble in DI water after surface modification with l-Cys amino acid. That is why QDs were dispersed in two-layered mixture of toluene and DI water under UV illumination.Abbreviations: QDs, quantum dots; UV, ultraviolet; Cys, cysteine; InP/ZnS QDs, indium phosphide/zinc sulfide quantum dots; PL, Photoluminescence; DI, deionized.

Mentions: The optical absorption and normalized PL spectra of InP/ZnS QDs before and after surface modification with l-Cys are shown in Figure 3A and B. InP/ZnS QDs were dispersed in toluene, while l-Cys-modified QDs were dispersed in DI water. Inset is the photograph of the QDs, before and after surface modification, dispersed in two-layered mixture of toluene and DI water under UV illumination. The figure shows that absorption and PL peaks of the QDs were red-shifted by the surface modification, which may be due to the interaction between solute and solvent molecules to form n–π* transitions apart from π–π* transitions. In the excited state, the solvent dipoles can reorient or relax around, which lowers the energy of the excited electrons. As the solvent polarity is increased, this effect becomes larger, resulting in redshift. The variation of PL spectra of cysteine-capped InP/ZnS QDs by the addition of 500 µM of AA (A) and plot of normalized fluorescence intensity versus time (B) are shown in Figure 4. When AA solution was added into the reaction mixture, the AA molecules were absorbed on QDs surface due to moderate electrostatic interaction, and excited electrons were transferred from QDs to dehydro-AA, resulting in fluorescence quenching up to 22%. Figure 4B shows the fluorescence intensity of cysteine-capped InP/ZnS QDs versus time. Figure 4 shows the nonlinear emission peak intensity of QDs with time.


Selective detection of dopamine in the presence of ascorbic acid via fluorescence quenching of InP/ZnS quantum dots.

Ankireddy SR, Kim J - Int J Nanomedicine (2015)

The optical absorption (A) and normalized PL spectra (B) of InP/ZnS QDs and l-cysteine-capped InP/ZnS QDs.Note: Original InP/ZnS QDs were insoluble in water but these QDs were soluble in DI water after surface modification with l-Cys amino acid. That is why QDs were dispersed in two-layered mixture of toluene and DI water under UV illumination.Abbreviations: QDs, quantum dots; UV, ultraviolet; Cys, cysteine; InP/ZnS QDs, indium phosphide/zinc sulfide quantum dots; PL, Photoluminescence; DI, deionized.
© Copyright Policy
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4554434&req=5

f3-ijn-10-113: The optical absorption (A) and normalized PL spectra (B) of InP/ZnS QDs and l-cysteine-capped InP/ZnS QDs.Note: Original InP/ZnS QDs were insoluble in water but these QDs were soluble in DI water after surface modification with l-Cys amino acid. That is why QDs were dispersed in two-layered mixture of toluene and DI water under UV illumination.Abbreviations: QDs, quantum dots; UV, ultraviolet; Cys, cysteine; InP/ZnS QDs, indium phosphide/zinc sulfide quantum dots; PL, Photoluminescence; DI, deionized.
Mentions: The optical absorption and normalized PL spectra of InP/ZnS QDs before and after surface modification with l-Cys are shown in Figure 3A and B. InP/ZnS QDs were dispersed in toluene, while l-Cys-modified QDs were dispersed in DI water. Inset is the photograph of the QDs, before and after surface modification, dispersed in two-layered mixture of toluene and DI water under UV illumination. The figure shows that absorption and PL peaks of the QDs were red-shifted by the surface modification, which may be due to the interaction between solute and solvent molecules to form n–π* transitions apart from π–π* transitions. In the excited state, the solvent dipoles can reorient or relax around, which lowers the energy of the excited electrons. As the solvent polarity is increased, this effect becomes larger, resulting in redshift. The variation of PL spectra of cysteine-capped InP/ZnS QDs by the addition of 500 µM of AA (A) and plot of normalized fluorescence intensity versus time (B) are shown in Figure 4. When AA solution was added into the reaction mixture, the AA molecules were absorbed on QDs surface due to moderate electrostatic interaction, and excited electrons were transferred from QDs to dehydro-AA, resulting in fluorescence quenching up to 22%. Figure 4B shows the fluorescence intensity of cysteine-capped InP/ZnS QDs versus time. Figure 4 shows the nonlinear emission peak intensity of QDs with time.

Bottom Line: The surface of the QDs was modified with l-cysteine by coupling reaction to increase the selectivity of dopamine.The fluorescence of cysteine-capped indium phosphide/zinc sulfide QDs was quenched by dopamine with various concentrations in the presence of ascorbic acid.This method shows good selectivity for dopamine detection, and the detection limit was 5 nM.

View Article: PubMed Central - PubMed

Affiliation: Department of chemical and Biological Engineering, Gachon University, Seongnam, South Korea.

ABSTRACT
Dopamine is a neurotransmitter of the catecholamine family and has many important roles, especially in human brain. Several diseases of the nervous system, such as Parkinson's disease, attention deficit hyperactivity disorder, restless legs syndrome, are believed to be related to deficiency of dopamine. Several studies have been performed to detect dopamine by using electrochemical analysis. In this study, quantum dots (QDs) were used as sensing media for the detection of dopamine. The surface of the QDs was modified with l-cysteine by coupling reaction to increase the selectivity of dopamine. The fluorescence of cysteine-capped indium phosphide/zinc sulfide QDs was quenched by dopamine with various concentrations in the presence of ascorbic acid. This method shows good selectivity for dopamine detection, and the detection limit was 5 nM.

No MeSH data available.


Related in: MedlinePlus