The primary purpose of this thesis is to pursue the complexation reaction on the surface of a quantum dot (Qdot). This thesis has been submitted by me to the Department of Chemistry, Indian Institute of Technology Guwahati for the award of the degree of Doctor of Philosophy.
- Synchronous Tricolor Emission-Based White Light from Quantum Dot
- Gold Nanocluster and Quantum Dot Complex in Protein for Biofriendly
- Zinc Quinolate Complex Decorated CuInS2/ZnS Core/Shell Quantum Dots
- A White Light Emitting Quantum Dot Complex for Single Particle Level Interaction with Dopamine Leading to Changes in Color and
A quantum dot complex that emits white light to interact at the individual particle level with dopamine leading to changes in color and at the level of interacting with dopamine leading to changes in color and.
- The Unique Optical Properties of Qdots and Controlling Parameters
- Quantum Confinement Effect
- Absorption and Photoluminescence
- Shell Passivation
- Surface Complexation Reaction
- Phase Transfer
- Targeted Cellular Imaging
- Chromaticity Tuning
The study of these three factors enables the understanding of the optical properties of Qdots and their influence on. 29-32 The dangling bonds present on the surface of presynthesized Qdots can be passivated by modifying their surface with chemical and/or biological moieties.
Light Emitting Diodes and White Light Emission
- Multicomponent System
- Disadvantages of Multicomponent System
- Single-component System
As for example, a white light emission was achieved by co-doping Mn and Cu in ZnSe Qdots. Silica-coated CdSe/ZnS Qdots were functionalized with blue-emitting oligofluorene to obtain white light emission.
Quantum Dot based Optical Sensors
- Sensing at Single Particle Level
- Blinking in Single Qdots
- Blinking Statistics of Single Qdots
- Applications of Single Qdots
However, the precise detection and quantification of biomolecules (which are usually responsible for causing human diseases) at the single particle level based on the variation of the scintillation statistics of a white light emitted by single Qdots is not yet to t was explored. In this thesis, a highly sensitive and selective method for the visual detection of a neurotransmitter (dopamine) at the single particle level using a single white light emitting QDC is demonstrated.
Overview of the Thesis
Therefore, the study of single WLE QDC will provide a newer paradigm for understanding their photophysical behavior at single particle resolution and developing powerful methodology for the development of ultrasensitive biosensors.
Color Temperature Control of Quantum Dot White Light Emitting Diodes by Grafting Organic Fluorescent Molecules. Wang, L.-j.; Ma, F.; Tang, B.; Zhang, C.-y., Base excision repair-induced construction of a single quantum dot-based sensor for sensitive detection of DNA glycosylase activity.
Synchronous Tricolor Emission-Based White Light from Quantum Dot Complex
After that, the resulting solution was centrifuged and the so-obtained pellet was redispersed in the same amount of solvent and further treated with 1.0 mM methanolic solution of ASA to form the complex on the dopant emission-quenched Qdots. Separately, 20.0 L of 5.0 mM Cu2+ solution was added to the 2.0 mL dispersion of the ASA treated Qdots, then centrifuged and redispersed in the same amount of solvent to check the effect of Cu2+ on the emission of ASA treated Qdots.
Results and Discussion
6 When the aqueous dispersion of the Qdots was treated with ASA, there was no significant change in the absorption spectrum (Figure 2.1A) of the Qdots. Previous observations in the laboratory indicated that the formation of ZnQ2 on the surface of the ZnS Qdot gives rise to green emission.
Redox-tuned three-color emission in double zinc sulfide (Mn and Cu) quantum dots. Reversible In-Situ Photoluminescence Tuning of Mn2+ Doped ZnS Quantum Dots by Redox Chemistry. Enhanced Photoluminescence and Thermal Stability of Zinc Quinolate After Complexation on the Surface of a Quantum Dot.
Gold Nanocluster and Quantum Dot Complex in Protein for Biofriendly White-Light-Emitting Material
The resulting solution was allowed to stir for 12 h and led to the formation of BSA-stabilized Au NCs. NC-QDC nanocomposite was synthesized after the reaction between BSA-stabilized Au NC-ZnS Qdot nanocomposite and 8-hydroxyquinoline (HQ). 200 µL of BSA-stabilized Au NCs (pH-6.8) was mixed with 2.8 mL of the synthesized BSA-stabilized ZnS Qdots in a cuvette.
Results and Discussion
The observed changes in the conformation of BSA may be due to the change in the pH of the medium. This may be the reason for the observed changes in the optical characteristics of the Au NCs embedded in BSA protein during the formation of WLE NC-QDC nanocomposite. 12, 23 This may be due to the environmental changes of the BSA protein of Au NCs during NC-Qdot and thus NC-QDC composite formation.
A fluorescent gold cluster containing a new three-component system for emitting white light through cascaded energy transfer. Synergistic effects in plasmon resonance coupling of metal nanoparticles with excited gold clusters.
Zinc Quinolate Complex Decorated CuInS 2 /ZnS Core/Shell Quantum Dots for White Light Emission
Initially, the absorbance of the thus obtained CuInS2/ZnS core/shell Qpoints was fixed at 0.12 (at a wavelength of 365 nm). L of 5.0 mM HQ (in ethanol) was sequentially added to 3.0 mL of a hexane dispersion of CuInS2/ZnS core/shell Qdots. 10.0 L of 5.0 mM HQ was found to be the optimal amount to generate near-white light chromaticity from 3.0 mL of a hexane dispersion of CuInS2/ZnS core/shell Qdots.
Results and Discussion
After a room temperature complexation reaction with HQ, no significant change in the UV-vis spectrum of CuInS2/ZnS core/shell Qdots (in hexane) was noticed (Figure 4.3 A). These results clearly indicated the formation of the ZnQ2 complex on the ZnS shell surface without degrading the optical properties of CuInS2/ZnS core/shell Qdots. Interestingly, under the same conditions, a bright white color was observed in the case of the dispersion of the HQ-treated CuInS2/ZnS core/shell Qdots.
Very bright yellow-green emitting CuInS2 colloidal quantum dots with core/shell/shell architecture for white light-emitting diodes. Integration of CuInS2-based nanocrystals for high efficiency and high color rendering of white light-emitting diodes. A white light emitting Quantum Dot complex to interact at a single particle level with dopamine, leading to.
A White Light Emitting Quantum Dot Complex for Single Particle Level Interaction with Dopamine Leading to
Changes in Color and Blinking Profile
Briefly, under vigorous stirring at 25oC, 2.0 ml of 0.5 M KOH (dissolved in ethanol) was added dropwise to a 50.0 ml ethanolic solution of 5.0 mM zinc acetate and the resulting mixture, colored milk white, it was kept for half. hour. A reported condensation reaction between salicylaldehyde and methylamine was followed to synthesize N-methylsalicylaldimine (MSA). 1-3 Briefly, 2 millimoles of methylamine were added dropwise to a solution of 2.0 millimoles of salicyaldehyde in 20.0 ml of methanol resulting in the mixture. , yellow in color, allowed to mix for 4 hours at 25 oC. Confocal imaging and single particle experiment of WLE QDC and dopamine added WLE QDC were performed by depositing the as-prepared dispersion (which was obtained by treating 9.9 M MSA on 3.0 mL ZnO Qdots by absorption of 0.10 at 350 nm at 225°C ) of the materials on a glass coverslip.
Results and Discussion
The y-axis represents the change in the photoluminescence intensity of the WLE QDC nanocomposite upon addition of the analyte. In addition, no significant change in the absorption spectrum of the WLE QDC nanocomposite was observed after dopamine addition (Figure A.5.8, Appendix). The results indicated that the yellow emission of the WLE QDC nanocomposite was sensitive to dopamine compared to the blue emission in the liquid medium.
Facile synthesis of molecularly imprinted graphene quantum dots for the determination of dopamine with tunable affinity. 3-Aminophenylboronic acid-functionalized CuInS2 Quantum Dots as a near-infrared fluorescent probe for the determination of dopamine. A general approach to study the thermodynamics of ligand adsorption to colloidal surfaces demonstrated using catechols binding to zinc oxide quantum dots.
Summary and Future Prospects
A2: Chapter 2
Zeta potential measurement of (A) Qdots, (B) ASA-treated Qdots, (C) HQ-treated Qdots, and (D) QDC in tabular form. Tabulated bands (or functional groups) versus vibrational frequencies obtained from QDC FTIR spectral data. CIE chromaticity coordinate value of (a) only ASA-added Qdots and (b) only HQ-added Qdots at different excitation wavelengths.
A3: Chapter 3
Emission spectra (ex - 320 nm) of (i) BSA-stabilized Au NCs and (ii) BSA-stabilized Au NC-ZnS Qdot composite. CIE coordinates of the HQ chromaticity value of the BSA-treated stabilized Au NC-ZnS composite (NC-QDC) at different time intervals. The CIE chromaticity coordinate value of the HQ treated BSA stabilized Au NC-ZnS composite (NC-QDC) in the solid state.
A4: Chapter 4
Fourier transform infrared (FTIR) spectra of the solid form of (i) CuInS2/ZnS core/shell Qdot and (ii) HQ treated CuInS2/ZnS core/shell Qdot. Effect of photoirradiation (using 365 nm light from a spectrofluorimeter) with time on the emission intensity at (i) 650 and (ii) 485 nm of the white light-emitting nanocomposite, respectively. Chromaticity color coordinates of white light emitting nanocomposite at different time intervals: (i) 0 h, (ii) 24 h and (iii) 48 h after HQ addition.
A5: Chapter 5
Excitation spectra recorded with respect to emission maxima at (A) 550 nm and (B) 440 nm of (i) ZnO Qdots, (ii) WLE QDC, and (iii) dopamine added WLE QDC. Time-resolved PL spectra (recorded using a 336 nm LED excitation source) monitored with respect to emission maxima at (A) 550 nm of (i) ZnO Qdots (in ethanol), (ii) WLE QDCs (in ethanol) and (B) 440 nm WLE QDC (in ethanol). A) Luminescence stability (up to 48 h) in colloidal form and (B) MTT-based cell viability assay of HEK 293 cells (after 24 h) after incubation with different concentrations of WLE QDC nanocomposite. Time-dependent scintillation profile (recorded using 64 x 64 . m2 frame size and 27 ms connection time with 63 mW excitation power for a 27 s time duration) of multiple WLE QDC particles.
Instruments and Softwares
UV-vis and photoluminescence measurements of the samples were carried out by using the Perkin Elmer LAMBDA 750 UV/Vis/NIR spectrophotometer and
CIE chromaticity analyzes were done using the CIE-1931 color space of the OSRAM color calculator. A Rigaku TTRAX III X-ray diffractometer and a transmission electron microscope (TEM, JEOL JEM 2100F, maximum accelerating voltage 200 kV) were used to analyze the morphology and size of the samples. The CIE-1931 color space of the OSRAM color calculator was used to calculate the chromaticity of the samples.
Cell Viability Assay
The photoluminescence decay of the samples was recorded using the Life-Spec-II spectrofluorimeter (Edinburgh Instrument, using the 375 nm Pico Quant LASER source) and the decay curves were analyzed with FAST software. Quinine sulfate solution in 0.1 M H2SO4 was used as a standard dye for calculating the quantum yield of the samples. Then, fresh media containing different concentrations of WLE QDC (1.6 g/mL – 33.3 g/mL), after removing the old medium, were added to the cells and incubated for 24 hours.
Quantum Yield Calculation
Then, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based cell viability assay was performed and the absorbance (at wavelength 550 nm) was recorded using Bio-Rad 680 microplate reader. Finally, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based cell viability assay was performed and the Bio-Rad 680 microplate reader was used to monitor the absorbance at wavelength 550 nm. Where single, bi- and tri-exponential functions were used to fit respective emission achieving close to.
List of Abbreviations
List of Publications
Presented an oral talk in MRSI YSC-2017 held at Indian Institute of Engineering Science and Technology, Shibpur, India
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