Angewandte
Chemie
DOI: 10.1002/anie.201301930
Click Chemistry
Plasmon Resonance Scattering Spectroscopy at the Single-
Nanoparticle Level: Real-Time Monitoring of a Click Reaction**
Lei Shi, Chao Jing, Wei Ma, Da-Wei Li, Jonathan E. Halls, Frank Marken, and Yi-Tao Long*
Understanding and monitoring chemical reactions is crucial
for the characterization of reaction mechanisms in organic
chemistry. Various analytical methods including nuclear
nanoparticles at the single-particle level. When multiple
plasmonic nanoparticles are in close proximity, it is worthy to
note that their plasmonic oscillations can couple together,
resulting in a large increase in light-scattering intensity as well
as a spectral red-shift and the obvious color changes observed
[1]
[2]
magnetic resonance spectroscopy, mass spectrometry,
[
3]
and Raman spectroscopy have been employed to study
chemical reactions. For example, the oxidation of carbon
monoxide on gold catalyst surfaces was studied using time-
[
11]
in DFM.
This phenomenon has been used to construct
[
12]
plasmon rulers. For example, when two gold nanoparticles
were linked by DNA, the intensity would increase by 44 times
and the wavelength would red-shift by 75 nm compared with
an individual nanoparticle.
Click chemistry is a powerful, highly reliable and selective
method in synthesis chemistry. Cu -catalyzed azide–alkyne
1,3-dipolar cycloaddition (CuAAC) is considered as a typical
click reaction with very high yields and good regioselectivity,
and has attracted widespread interest. To date, it has been
[
4]
resolved IR spectroscopy. However, the averaged signals
obtained from multiple nanoparticles cannot provide as
accurate information on the nanoscale level compared to
[13]
[
5]
the signals obtained from a single nanoparticle. Differences
in size and shape are unavoidable in nanoparticle production,
and such differences cannot be distinguished by averaged
measurements. Moreover, nanoparticles with different size
and shape exhibit different physical and chemical properties,
including spectral bands, reaction activity, and efficiency.
Measurements from single nanoparticles could reveal the
unique function of individual particles, and thus be superior to
the averaged measurements taken from bulk solutions.
Notably, every single nanoparticle could serve as an inde-
pendent sensor and provide significant signals with high
[
14]
+
[
15]
widely applied in polymer and material science,
discovery, biochemistry, pharmaceutical science, and
also used to functionalize the surface of nanoparticles (Au,
drug
[
16]
[17]
[18]
[
19]
Ag) to construct sensors.
+
Herein, we describe a novel method to monitor a Cu -
catalyzed click reaction at the single-nanoparticle level by
using PRRS spectroscopy and DFM. Click reactions result in
interparticle cross-linking, which induces a color change of
GNPs in DFM and a scattering spectral red-shift. To the best
of our knowledge, this is the first time that a click reaction has
been monitored at the single-nanoparticle level, thus making
this method a valuable technique for the real-time monitoring
of chemical reactions in organic chemistry.
Our strategy is shown in Scheme 1. We synthesized
terminal azide- and alkyne-functionalized thiols and prepared
the system shown through the following steps (see the
Supporting Information for more details): 1) immobilization
of 60 nm GNPs on a cleaned ITO (indium tin oxide) glass
slide; 2) self-assembly of the azide-functionalized thiol on the
[
6]
signal-to-noise ratio, which dramatically lowers the detec-
tion limit and enables higher spatial and temporal resolution.
For example, single gold nanoparticles (GNPs) could be used
[7]
to detect single unlabled proteins.
The advent of plasmon resonance Rayleigh scattering
PRRS) spectroscopy and dark-field microscopy (DFM) has
(
helped the study of the size, shape, composition, and the local
[
8]
environment of single plasmonic nanoparticles. DFM is
[
8a,9]
a highly sensitive direct means to probe chemical analytes.
However, the application of DFM to monitor chemical
[10]
reactions is rare. To observe the behavior of nanoparticles
during reactions, it is essential to monitor the spectra of
[
+]
[+]
[
*] L. Shi, C. Jing, Dr. W. Ma, Dr. D.-W. Li, Prof. Y.-T. Long
State Key Laboratory of Bioreactor Engineering
Shanghai Key Laboratory of Functional Materials Chemistry &
Department of Chemistry
East China University of Science and Technology
Shanghai, 200237 (P. R. China)
E-mail: ytlong@ecust.edu.cn
J. E. Halls, Prof. F. Marken
Department of Chemistry, University of Bath
Claverton Down, Bath BA2 7AY (UK)
+
[
] These authors contributed equally to this work.
[
**] This research was supported by the 973 Program (2013CB733700),
the National Science Fund for Distinguished Young Scholars
+
Scheme 1. a) Cu -catalyzed click reaction at the single-particle level.
(
(
21125522), and the National Natural Science Foundation of China
91027035).
b) A typical dark-field image of a modified GNP on a microscopy slide
before (I) and after (II) the addition of Cu and sodium ascorbate.
2+
c) Corresponding scattering spectra of a single GNP before (I) and
after (II) the click reaction.
Angew. Chem. Int. Ed. 2013, 52, 1 – 5
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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