Organic–Inorganic Hybrid Functional Carbon Dot Gel Glasses

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Organic–Inorganic Hybrid Functional Carbon Dot Gel Glasses

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Organic–Inorganic Hybrid Functional Carbon Dot Gel Glasses

Zheng Xie ,Fu Wang ,and Chun-yan Liu * anomaterials (NMs) are currently of great fundamental and N

technical interest due to their unique size-dependent properties and exible chemical processability. However, with the excep-tion of biological applications, most of the envisioned applica-tions or devices are not based on single-particle NMs or their

[1solutions. ] Hence, developing methods for stably embedding

NMs in an appropriate matrix or assembling to solid-state

[1three-dimensional (3D) macrostructures , 2 ] and retaining the

inherent properties of individual NMs are extremely chal-lenging. Organic-inorganic hybrid materials (OIHMs) have received considerable attention as the NM-embedded compos-ites because they combine the advantages of organic and inor-[3,4]ganic materials. Among OIHMs, sol-gel derived organically

modi ed silicate (Ormosil) glasses embedded with functional dopants have attracted particularly attention, and can be applied

[5–11]in various optical materials and devices. Ormosil glasses

are expected a better choice as host materials for mechanical stability, facile preparation technique, and molecular level uni-formity of dopants. They are also better than polymer matrices, especially for application in the elds of photonics and opto-[9]electronics, because of their long-term, thermal stability and

[8]designable microstructures.

A popular method for preparing NM-silica gel composites

is to simply-physically disperse NMs in silica sol precursor medium. The disadvantages of this method are low solubility and inevitable agglomeration of NMs. These drawbacks are detrimental to the desired properties of the composite. For example, quantum dot (QD)-silica composites can be typically prepared by melting precursors in a glass or compatibilizing QDs with silica sol precursors, including ligand-exchange, arrested precipitation, silane post-functionalization assembly, which is generally followed by gelation, annealing, and/or

[1]required multistep processes. , 12–14 These steps and inevitable

agglomeration can risk losing the high photoluminescence (PL)

[13]quantum yield (QY) and loading fractions of QDs, which are

Dr. Z. Xie ,F. Wang ,Prof. C.-y. Liu Key Laboratory of Photochemical Conversion and Optoelectronic Materials

Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100190, P. R. China Fax: ( +86)-010-82543573 E-mail: cyliu@http://www.mianfeiwendang.com Dr. F. Wang Graduate School of the Chinese Academy of Sciences Beijing 100806, P. R. China

Organic–Inorganic Hybrid Functional Carbon Dot Gel Glasses

DOI: 10.1002/adma.201104962

[15

] The loading fractions critical factors in many applications.

and QYs of QD-silica composites are often less than 1% and 3–10%. The highest values are only 13% and 35% for in-situ pre-[13pared CdSe QD-silica lms, ] respectively. The large (mm-cm)

[13D macrostructure monoliths of chalcogenide QDs , 16 ] and

[15bmiscible nanocomposites ] have been realized by sol-gel, self-assembly, and polymer-brush coating method, but they are lim-ited for most optical applications because of their low transpar-ency, even opacity. Hence, chemical bonding of dopants to the

silicate matrix would be preferable. To avoid low loading frac-tions, agglomeration, and phase separation in the preparation of composites, as well as provide with desired properties, many dopants have to be generally modi ed with silane after their for-mation to realize silane covalent functionalization. The defects

[8,14,17–20]of the silane post-functionalization for inorganic NMs,

[4,9–11]which differ from organopolymer dopants, are obviously

compared with silane pre-functionalization. The preparation of

[2][2a,8,17–19]macrostructures and silica gel hybrid materials for

carbon NMs (CNMs) though the above-mentioned methods is especially dif cult, and CNMs can but be modi ed by silane

[8,17–20]post-functionalization.

As the latest form of CNMs and novel green QDs, uo-rescent carbon dots (CDs) hold not only favorable properties, such as good biocompatibility and easy surface functionaliz-ability, but also excellent photostability and up-converting prop-[21–23]erty. Hence, CDs could be used in a wide range of tech-[24,25]nologies, such as bioimaging, LED, [26 ] energy conversion/

[27][28]storage, drug delivery, sensors, photocatalyst, [29 ] etc. To our

best knowledge, there were no reports on CDs stably embedded in an appropriate matrix or prepared to solid macrostructures,

[30]only uniform CD thin lms have been reported very recently.

In this paper, we report the design and versatile preparation of various silane pre-functionalized CDs (SiCDs), their Ormosil nanohybrid gel glass composites (SiCD-Gel glasses) and macro-structure monoliths (100% SiCD-Gel glasses), as shown sche-matically in Figure 1 . The method involves a one-pot prepara-tion of SiCDs using organic polybasic acid and silanes, subse-quent hydrolysis, and self-condensation or hybrid polyconden-sation with silanes to form SiCD-Gels. These materials exhibit excellent PL emissions (QY = 47% for SiCD and 88% for SiCD-Gel glasses) and broadband optical limiting (OL). The loading fraction of SiCDs can be easily controlled from 0% to 100%, and the properties of the as-obtained SiCD-Gel glasses could be modulated accordingly. Agglomeration and phase separation are completely prevented and resultant SiCD-Gel glasses offer sustained PL and OL performance.

Recently, we developed a simple technique, one-pot organic

pyrolysis method, for synthesizing organic pre-functionalized

[25,31]highly luminescent CDs. For example, multiaminosilane

AEAPMS is used as a coordinating solvent by pyrolyzing citric

1716

http://www.mianfeiwendang.com© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Organic–Inorganic Hybrid Functional Carbon Dot Gel Glasses

Adv. Mater. 2012, 24, 1716–1721

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