Citation: Zhang, C.; Ren, H.; Jiang,
X.; Jia, G.; Pan, Z.; Liu, Y. The
Aggregation of Destabilized Ag
Triangular Nanoplates and Its
Application in Detection of Thiram
Residues. Nanomaterials 2022, 12,
2152. https://doi.org/10.3390/
nano12132152
Academic Editors: Deepak Kukkar
and Ki-Hyun Kim
Received: 11 May 2022
Accepted: 21 June 2022
Published: 23 June 2022
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Article
The Aggregation of Destabilized Ag Triangular Nanoplates
and Its Application in Detection of Thiram Residues
Chunhong Zhang
1
, Hao Ren
2
, Xiangkui Jiang
1
, Guangfeng Jia
3
, Zhigang Pan
1,
* and Yongchun Liu
2,
*
1
Xi’an Key Laboratory of Advanced Control and Intelligent Process, School of
Automation, Xi’an University of Posts & Telecommunications, Xi’an 710121, China;
finespring2007@126.com (C.Z.); jiangxiangkui@xupt.edu.cn (X.J.)
2
Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education,
School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710062, China;
renhao@snnu.edu.cn
3
School of Electronic Information Engineering, Xi’an Technological University, Xi’an 710021, China;
jgf97@126.com
* Correspondence: panzhigang0703@126.com (Z.P.); surfbioliu@snnu.edu.cn (Y.L.)
Abstract:
An aggregation or assembly of Ag triangular nanoplates (Ag TNPs) can cause dramatic
changes in their optical properties, which is widely used in applications in the field of sensing. The
assembly forms of nanoparticles are crucial for obtaining sensitive sensing signals, but it is unknown
what kind of assembly dominates the aggregated Ag TNPs in aqueous solutions. Herein, using
thiram-induced Ag TNP aggregation as a model, six different assembly models were established,
including three planar (side-by-side, side-to-tip, and tip-to-tip) assemblies and three tridimensional
(plane-to-plane, plane-to-tip, and plane-to-side) assemblies. The corresponding optical properties
were then investigated. Both theoretical and experimental findings indicate that three-dimensional
assemblies, especially plane-to-plane assembly, dominate the Ag TNPs aggregation solution, causing
a blue shift of the absorption spectrum. Analysis of charge distribution patterns in Ag TNPs indicates
that such a blue shift is caused by the electrostatic repulsive force in plane-to-plane assembly. Thus,
we propose a simple colorimetric method for thiram detection using Ag TNPs as an indicator. The
method exhibits a selective and sensitive response to thiram with a limit of detection of 0.13
µ
M in
the range of 0.2–0.5 µM, as well as excellent performance in real samples like wheat.
Keywords: aggregation; Ag triangular nanoplates; LSPR; colorimetric detection; thiram
1. Introduction
Thiram is a fungicide commonly used in the planting process. Due to its overuse,
thiram residues cause great health problems, such as strong irritation to the skin and
mucosa, and even liver damage [
1
,
2
]. Thus, it is very important to detect the presence of
thiram residues in the environment. The traditional detection methods of thiram residues,
including ion mobility spectrometry and high-pressure liquid chromatography, have to rely
on expensive and complicated equipment [
3
,
4
]. Currently, some noble metal nanoparticles-
based colorimetric detection methods of thiram residues have been developed. Chemi-
cally modified gold, silver, and copper nanoparticles have been applied to determine the
concentration of thiram using their unique localized surface plasmon resonance (LSPR)
effect [5–11]
. Nevertheless, most of the methods fail to achieve a satisfactory limit of
detection (LOD) or preparation procedures are too complex.
Nanoparticle aggregation-induced LSPR change is one of the most common nanoparticle-
based sensing methods. Since nanoparticles in solution have a high surface energy, once
the stabilizers that keep them dispersed are removed, they aggregate or assemble sponta-
neously. Different from other nanoparticles, Ag triangular nanoplates (TNPs) are notable
for their sharp tips and anisotropic plate structures that produce more abundant signal
Nanomaterials 2022, 12, 2152. https://doi.org/10.3390/nano12132152 https://www.mdpi.com/journal/nanomaterials
