优化水溶性ZnS：Mn2+/Fe3O4量子点/ SiO2结构的光学与超顺磁性能：表面改性与SiO2厚度调控
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本文研究了表面改性和SiO2厚度对水溶性ZnS：Mn2+纳米线（ZnS:Mn2+ NWs）/ Fe3O4量子点（Fe3O4 QDs）/ SiO2异质结构的光学和超顺磁性能的影响。这项工作发表在2013年的《结晶工程通讯》(CrystEngComm)上，第15卷，第6971篇，接收日期为2013年5月28日，接受日期为同年7月3日，DOI为10.1039/c3ce40939b。作者团队由Jian Cao等人组成，他们通过Stöber方法成功合成了一维的ZnS:Mn2+ NWs/ Fe3O4 QDs/ SiO2异质结构，制备出了一种水溶性的荧光/超顺磁纳米复合材料。
ZnS:Mn2+ NWs的平均直径约为6-8纳米，而Fe3O4 QDs的尺寸则在4-5纳米之间。这两个部分通过ZnS:Mn2+ NWs表面的羧基和Fe3O4 QD表面的羟基之间的共轭作用实现共价连接。这种连接方式有助于有效抑制ZnS:Mn2+ NWs间的能量转移，从而影响整个异质结构的光学特性。
研究发现，表面改性不仅影响了纳米线与量子点之间的相互作用，而且通过调控SiO2层的厚度，能够进一步调控纳米复合材料的光学性能，如荧光效率和吸收光谱。超顺磁性能，即材料在没有外磁场时表现出接近于绝对零磁化强度的磁性，也可能受到SiO2层厚度的影响，因为这可能影响到Fe3O4 QDs的磁性屏蔽或相互作用。
此外，文章还可能探讨了不同表面改性方法（如氧化、还原、烷基化等）对纳米线和量子点性能的具体影响，以及如何通过精确控制SiO2厚度来优化超顺磁响应。通过这些实验结果，研究人员可以为设计新型水溶性纳米材料，特别是在生物医学、光电子学和磁性存储等领域找到潜在的应用可能性。
这篇研究提供了关于纳米材料界面工程的重要见解，展示了表面改性和SiO2厚度作为调控纳米复合材料性能的关键参数，对于理解和优化异质结构在光学和磁性方面的性能具有重要意义。
Cite this: CrystEngComm, 2013, 15,
6971
Effects of surface modification and SiO
2
thickness on
the optical and superparamagnetic properties of the
water-soluble ZnS:Mn
2+
nanowires/Fe
3
O
4
quantum
dots/SiO
2
heterostructures
Received 28th May 2013,
Accepted 3rd July 2013
DOI: 10.1039/c3ce40939b
www.rsc.org/crystengcomm
Jian Cao,*
ab
Bingji Wang,
ab
Donglai Han,
cd
Shuo Yang,
cd
Jinghai Yang,*
ab
Maobin Wei,
ab
Lin Fan,
ab
Qianyu Liu
ab
and Tingting Wang
ab
In this paper, one-dimensional ZnS:Mn
2+
nanowires (NWs)/Fe
3
O
4
quantum dots (QDs)/SiO
2
hetero-
structures were successfully synthesized by the Sto
¨
ber method to form the water-soluble fluorescent/
superparamagnetic nanocomposites. The average diameter of the ZnS:Mn
2+
NWs, Fe
3
O
4
QDs and
ZnS:Mn
2+
NWs/Fe
3
O
4
QDs/SiO
2
heterostructures was about 6–8 nm, 4–5 nm and 18 nm, respectively. The
Fe
3
O
4
QDs were covalently linked to the ZnS:Mn
2+
NWs by the conjugation of the hydroxyl groups on the
surface of the QDs and the carboxyl groups modified on the surface of the NWs. It was found that the
covalent bonds between the NWs and QDs could effectively suppress the energy transfer from the
ZnS:Mn
2+
NWs to the Fe
3
O
4
QDs. As the SiO
2
shell thickness increased, the fluorescence intensity reached
the highest value when the hydrolysis time of tetraethyl orthosilicate was 5 hours, which was comparable
to that of the ZnS:Mn
2+
NWs. The superparamagnetic properties of the heterostructures were observed at
room temperature, which decreased as the SiO
2
thickness increased.
Introduction
Next generation molecular probes combining magnetic and
fluorescent properties in one entity open up broader avenues
for their applications as dual-modality imaging probes in the
fields of biological imaging, cell tracing, magnetic bio-
separation, targeted drug delivery, etc.
1–5
Among the widely
studied fluorescent labeling nanomaterials, ZnS has great
advantages as follows: (1) low toxicity, (2) high photostability,
(3) relative lower price, (4) simple synthesis procedure.
6
It is
well known that doping Mn
2+
ions into the ZnS lattice can give
rise to the strong yellow-orange light emission located at about
583 nm (through the
4
T
1
to
6
A
1
internal transition) with a high
quantum yield, the luminescence lifetime of which is about 1
ms.
7
Such a strong luminescence and long lifetime allows the
light penetrate into and out of the tissues and distinguish the
luminescence from the background autofluorescence. These
excellent optical properties make ZnS:Mn
2+
nanocrystals
potential candidates for fluorescent labeling agents.
Magnetic Fe
3
O
4
nanoparticles are the most prominent class
of magnetic nanoparticles (MNPs) for their biocompatibility
and stability.
8–10
At diameters less than 10 nm, Fe
3
O
4
MNPs
have unique properties such as high surface area, super-
paramagnetism and low Curie temperature etc., and smaller
particles may undergo rapid biodegradation when they are
directly exposed to biological environments.
11,12
Therefore, bi-
functional optical-magnetic ZnS:Mn
2+
/Fe
3
O
4
nanocomposites
are highly desired in the biological field due to their appealing
applications. However, fluorescence quenching always occurs
due to the energy-transfer process between the ZnS:Mn
2+
and
Fe
3
O
4
.
13
To solve the problem, some transition layers, e.g.
silica, polymer etc. have been used in the synthesis of the core–
shell nanomaterials.
14–16
However, so far, the resultant
nanocomposites are usually larger, and the synthetic proce-
dure is rather complex and time-consuming. So, covalent
linking between the ZnS:Mn
2+
and Fe
3
O
4
is highly desired to
attenuate the energy-transfer process and increase the stability
of the nanocomposites.
17
For further bioimaging applications,
it is required to transfer the hydrophobic nanocomposites to
water by surface modification, such as polymer, silica, or
carbon coating techniques.
18–20
Among them, silica coating
has attracted a great deal of attention because of its excellent
chemical stability, biocompatibility and facile further conjuga-
tion with various functional groups.
21
To date, only a few
a
Institute of Condensed State Physics, Jilin Normal University, Siping 136000, P. R.
China. E-mail: caojian_928@163.com; jhyang1@jlnu.edu.cn; Fax: +86 434 3294566;
Tel: +86 434 3290009
b
Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of
Education, Jilin Normal University, Siping 136000, P. R. China
c
Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of
Sciences, Changchun 130033, P. R. China
d
University of Chinese Academy of Sciences, Beijing 100049, P. R. China
CrystEngComm
PAPER
This journal is
ß
The Royal Society of Chemistry 2013 CrystEngComm, 2013, 15, 6971–6978 | 6971
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