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Fluorescent carbon quantum dot hydrogels for direct determination of silver ions

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Nguồn:
Người gửi: Nguyễn Hòa
Ngày gửi: 12h:08' 11-07-2018
Dung lượng: 13.4 MB
Số lượt tải: 1
Số lượt thích: 0 người

Department of Chemistry, Faculty of Science and Technology, Thammasat University
A. Cayuela, M.L. Soriano, S.R. Kennedy, J.W. Steed, M. Valcárcel
Presented by Thuan Hoa Nguyen

for direct determination of silver ions
Talanta, Volume 151, 1 May 2016
Fluorescent carbon quantum dot hydrogels
V`
v
v
I ntroduction
Source of Ag+ pollutant
Carbon quantum dots (properties and applications)
Carbon quantum dot hydrogel
Method for determination of Ag+
Carbon quantum dot in applications
The erosion of soils
processing of ores
steel refining
cement manufacture
fossil fuel combustion
municipal waste incineration
3
Source of pollutant
Ag
Every year…
Over 2500 tons of silver are discharged as industrial wastes into the environment
it can cause damage to the liver, kidneys, nervous system and immune system,
Introduction
Source of Ag+ pollutant
4
Healthy body
The liver
The kidneys
The nervous system
The immune system
toxic to the cytologic and physiologic
Introduction
Quantum Dot
5
Very small semiconductor particles
Nanometres in size (2 – 10 nm diameter)
Unique optical
Transport properties
Size dependent emission wavelength
Narrow emission peak
Broad excitation range
Inorganic core
Inorganic shell
Aqueous organic coating
Conjugated functional group
The features of the different synthetic methods used for the preparation of CQDs
Incorporation
of dopants
Low toxicity
Photostability
Photo-response
Catalysis
Tunable PL
Bio-imaging
Drug delivery
Photovoltaic
Catalyst

CQDs
Sensor
Introduction
Carbon Quantum Dots
6
Carbon quantum dot in applications
Determination of Ag+ in water samples
Introduction
7
O


To develop a suitable fluorescent carbon quantum dot hydrogel as robust, rapid and simple fluorescent sensors.

To achieved preconcentration factor and the use of fluorescent carbon quantum dot hydrogels for direct determination of silver ions in sample water.
bjectives
8
Results and discussions
E xperimental
9
Experimental
Results and discussions
Synthesis
Characterization
Calibration
LOD/LOQ
Precision and accuracy
11
Experimental
Results and discussions
Preparation of passivation CQD
MWCNTs (0.2g)
H2SO4/HNO3 (3:1)
V = 20ml
140oC, 7.5h
Acetone
10 ml
13,000 rpm
10 min
NaNO3
10
the high temperature more number of bonds are broken during the carbonization process, which leads to the evolution of gas and, hence, a decrease in the size of the CQDs
heat
it provided non-fluorescent CDs (r-CDs) which were made highly fluorescent by surface passivation with acetone in an acid medium
Under these conditions, acetone was degraded to acetic acid and carbon dioxide , which allowed the incorporation of carboxylic groups onto CD surfaces
The role of acetone is to incorporate hydrogen-bonded carboxylic groups to the surface of CDs
p-CQDs in water
Experimental
Results and discussions
11
Gelator 5mg (1wt%)
& BMIM-BF4 10mL (2% )
500 ul of CQDs (1 mg mL-1) in aqueous solution
Sonication
1 min
Preparation of CQD gels
Sonication is the act of applying sound energy to agitate particles in a sample, for various purposes. Ultrasonic frequencies (>20 kHz) are usually used, leading to the process also being known as ultrasonication or ultra-sonication.
(A) passivate-Carbon Quantum Dots
(B) aliquots of D2O
Experimental
Results and discussions
Characterization of CQDs
1H NMR spectra of gelator (1) with increasing concentrations
12
0.7 ppm
Addition of p – CQDs

 A notable downfield shift in the urea NH resonances.
 Increasing as a function of CQD concentration.
Addition of D2O
 No shift in the NH chemical shift
the gelator hydrogen bonds directly with the CQDs, presumably via functionalities on the nanoparticle surface
 The gelator hydrogen bonds directly with the CQDs, presumably via functionalities on the nanoparticle surface.
Experimental
Results and discussions
13
Quenching study of the fluorescence of Carbon Quantum Dot
Hg2+ Pb2+ Ag+ Co2+ Mg2+ Fe3+ Au3+ Cu2+
in solution with and without bis (urea) gelator
in Gelator & Liquid
in liquid and solid like gels
CQD-based Gels
CQD-based Gels in liquid
CQD-based Gels in solid like gel
CQDs
CQDs
with gelator
Add...
spectrofluorometer
Fluorescence measurements
Experimental
Results and discussions
Quenching study of the fluorescence of Carbon Quantum Dot-based Gels in solution with and without bis (urea) gelator
Fluorescence measurements
14
(B) Thiol-Carbon Quantum Dot
(C) Amine-Carbon Quantum Dot
(A) Passivate-Carbon Quantum Dot
Strong binding with Ag+
In gelator
p-CQDs a-CQDs t-CQDs
Detectable for Ag+
Experimental
Results and discussions
15
Quenching study of the fluorescence of Carbon Quantum Dot-based Gels
Hg2+ Pb2+ Ag+ Co2+ Mg2+ Fe3+ Au3+ Cu2+
in solution with and without bis (urea) gelator
in Gelator & Liquid
in liquid and solid like gels
CQD-based Gels
CQD-based Gels in liquid
CQD-based Gels in solid like gel
CQDs
CQDs
with gelator
Add...
spectrofluorometer
Fluorescence measurements
Experimental
Results and discussions
Fluorescence measurements
16
Quenching study of the fluorescence of Carbon Quantum Dot-based Gels
in liquid and solid like gels
(B) Thiol-Carbon Quantum Dot
(C) Amine-Carbon Quantum Dot
(A) Passivate-Carbon Quantum Dot
Ag+
In gelator
p-CQDs a-CQDs t-CQDs
Co2+, Mg2+, Fe3+ were not detectable
Pb2+
Pb2+
Experimental
Results and discussions
(B) calibration plot of the quenching of the
p-CQD Gels versus Ag+ ions
(A) Photoluminescence response of p-CQD Gels
p-CQDG responses to different concentrations of Ag + ions.
 At high concentrations, the solid network is destroyed to form a liquid-phase solution
?
17
(Io/I) = 0.98403 + 0.055x[Ag+]
R2 = 0.998
Experimental
Results and discussions
Samples (Rabanales river)
Conditioning
Sample addition
Washing
Elution
: Ag+
: Interferents
CQDs
PL CQDGs
PL Quenching
Ag+
Application to samples
Solid-phase extraction (SPE)
Fluorescent Carbon quantum dots hydrogels
18
Experimental
Results and discussions
Recoveries of the enriched river water samples obtained at two different concentrations.
Application to water samples
 The method can be applied in environmental water samples.
19
Conclusions
20
Conclusions
MWCNTs
CQDs
CQD hydrogel
hydrogel
Surface passivation
Increasing both sensitivity and selectivity
 support accuracy
Changing the CQD peripheral groups
 Sensing capability of CQDs towards metal ions
Acknowledgements
Dr. Siriwit Buajarern
21
Thanks You

for Your Attention
23
Ag+
Fluorescence Intensity
wavelegth
wavelegth
Fluorescence Intensity
Introduction
Carbon Quantum Dots
24
Before added Ag+ ion
After added Ag+ ion
Surface Functionalization
Surface Passivation
CQDs
quenching fluorescence carbon quantum dot
Introduction
Solid-phase extraction (SPE)
25
Conditioning
Sample addition
Washing
Elution
: Ag+
: Interferents
SPE is based on the distribution of the analyte between the solid sorbent packed in a cartridge.
High selectivity
Reproducibility
Improvements in automation
Effective with variety of matrix
High-throughput capability

Low contact between the analytes and
the sorbent
Clogging the pores of the solid phase
Complexity and time consuming
Need for complex equipment
Images under visible light
Images under SEM
Experimental
Results and discussions
Characterization of CQDs
Images of passivate-Carbon Quantum Dot-based Gels.
Experimental
Results and discussions
Synthesis of CQDs and derivates
27
a-, c-, p- and t-CD gels 1 wt%
under 365 nm UV irradiation
Fluorescence emission spectra of aqueous CD solutions
1 mg mL-1
λex= 365 nm for c-CDs
λex= 370 nm for the others
and for 1wt%
CD-gels with 1a at the same CD concentration.
Experimental
Results and discussions
28
Ag+
wavelegth
Fluorescence Intensity
Introduction
Carbon Quantum Dots
29
After added Ag+ ion
Surface Functionalization
Surface Passivation
CQDs
CQDs
CQDs
CQDs
A thiol group is a fuctional group containing a sulfuratom bonded to a hydrogen atom. General formula: -SH
Thiol group
Passivation group
Amine group
Experimental
Results and discussions
Analytical performance
Comparison of the method
30
(B)
Thiol - Carbon Quantum Dot
-based Gels
(C)
Amine – Carbon Quantum Dot
-based Gels
(A)
Passivate - Carbon Quantum Dot
-based Gels
Experimental
Results and discussions
Fluorescence measurements
31
Quenching study of the fluorescence of Carbon Quantum Dot-based Gels
in liquid and solid like gels
The type of surface group CQDGs
Selective for certain ions involved in coordinating metal ions with CQDGs
Ionic bonding
Ethanol & p-CQDs
in water
mL of DIC (1 mmol)
85.73 mg of NHS (1.2 mmol)
10 mL of deoxygenated p-CDs (0.94 mg mL-1) at neutral pH.
Stired (inert atmosphere)
10 min
79.16 mL of Boc-EDA (0.5 mmol)
5 mL of TEA (3.58x10-3mmol)
stirred (at room temperature)
20 hours
functionalized CDs, Boc-CDs
100oC
10 minutes to remove all Boc-protected groups
several washing steps with chloroform to remove impurities were
carried out. The final a-CD
Amine-CQDs
The tert-butyloxycarbonyl protecting group is a protecting group used in organic synthesis. The BOC group can be added to the amine under aqueous conditions using di-tert-butyl dicarbonate in the presence of a base such as sodium bicarbonate
1
2
3
Experimental
Results and discussions
Preparation of CQD
32
Preparation of Amine-CQDs
4
 
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