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RESEARCH PROFILE

Associate Professor Dr. Daniel Crespy

Materials Science and Engineering
Molecular Science and Engineering
Tel. 006633014153
Email daniel.crespy@vistec.ac.th
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Smart membranes and non-wovens

 

Research Overview

We combine synergistically the advantages of nanoparticles and nanofibers to create materials with superior properties. The materials can be used as support for catalysis and optical or biomedical applications.

Keywords: Controlled release; nanoarchitectonics; nanofibers; membranes; stimuli-responsive materials; water purification

Nanoparticles meet nanofibers

Fibers usually lack of functionality compared to nanoparticles but can be easily separated from a reactive medium when they are spun as non-woven. On the other hand, polymer nanoparticles and nanocapsules are difficult to separate in high yields while maintaining their structural integrity but they can be prepared with a large variety of functionalities. Therefore, we have created materials based on nanoparticles so as to benefit from the advantages of both nanoparticles and nanofibers, as described recently in one of our review [1]. Our group in is expert in the preparation of colloidal building blocks, nanoparticles and nanocapsules that can be further assembled in structures with higher hierarchical order. Several approaches have been developed such as the supraparticular assembly of magnetic nanoparticles in fibers [2-3] and the electrospinning of nanoparticles [4] (Figure 1). With the latter method, the obtained materials have been used for applications described below.


Figure 1. Scanning electron microscopy of electrospun nanoparticles. From reference [5].

Catalysis

Electrospun nanoparticles were used as support for olefin polymerizations [6]. After immobilization of the metallocene catalyst on the surface of the fibers, polymerization could take place and yielded well defined core-shell fibers with a hydrophilic core and a polyethylene shell. We used such support to fabricate metal oxide nanoparticles and the obtained non-wovens could be used efficiently to degrade photocatalytically organic molecules in water [7]. Such constructs are promising for water purification and we will further explore this concept for water desalination.

Double protection and double controlled release

Nanocapsules, i.e. core-shell nanoparticles with a liquid core, can be also electrospun. In this case, the encapsulated payload is protected by the organic or inorganic shell of the nanocapsules and by the fiber´s matrix. We have shown that this configuration is of high interest for materials for photon upconversion, i.e. the emission of light at shorter wavelength than the excitation wavelength. For nanocapsules containing upconverting dyes, the nanocapsules-in-nanofibers system was found to be more stable against oxygen than the sole nanocapsules thanks to the use of a fiber´s matrix with excellent oxygen barrier properties [8]. The fibers matrix can be additionally used to control the release of encapsulated payloads in nanocontainers [9]. This means that the release profile is then controlled by the stimuli-responsive properties of the nanocontainers and the ones of the fibers matrix [10] (Figure 2).


We are also interested in developing non-wovens for biomedical applications. We are currently applying the nanocontainers-in-nanofibers to produce unique wound dressing containing several antibacterial agents of opposite polarities. These antibacterial agents are showing a synergetic effect when encapsulated in the same construct. Such concept can be employed for combined therapy and to produce membranes for water purification.




Figure 2. Scheme showing redox-responsive silica nanocontainers embedded in pH-responsive crosslinked nanofibers (polyacrylic acid PAA). The hierarchical construct could be used to release selectively corrosion inhibitors. From reference 10.
 

Selected Publications

[1] Jiang, J.; Lv, L.P.; Landfester, K.; Crespy, D. Acc. Chem. Res. 2016, 49, 816
[2] Bannwarth, M.B.; Kazer, S.W.; Ulrich, S.; Glasser, G.; Crespy, D.; Landfester, K. Angew. Chem. Int. Ed. 2013, 52, 10107
[3] Bannwarth, M.B.; Utech, S.; Ebert, S.; Weitz, D.A.; Crespy, D.; Landfester, K. ACS Nano 2015, 9, 2720
[4] Crespy, D.; Friedemann, K.; Popa, A.M. Macromol. Rapid Commun. 2012, 33, 1978
[5] Friedemann, K.; Corrales, T.; Kappl, M.; Landfester, K; Crespy, D. Small 2012, 8, 144
[6] Joe, D.; Golling, F.E.; Friedemann, K.; Crespy, D.; Klapper, M.; Mullen, K. Macromol. Mater. Eng. 2014, 299, 1155
[7] Horzum, N.; Munoz-Espi, R.; Glasser, G.; Demir, M.M.; Landfester, K.; Crespy, D. ACS Appl. Mater. Interf. 2012, 4, 6338
[8] Wohnhaas, C.; Friedemann, K.; Busko, D.; Landfester, K.; Balouchev, S.; Crespy, D.; Turshatov, A. ACS Macro Lett. 2013, 2, 446 
[9] Jiang, S.; Lv, L.P.; Li, Q.; Wang, J.; Landfester, K.; Crespy, D. Nanoscale 2016, 8, 11511
[10] Jiang, S.; Lv, L.P.; Landfester, K.; Crespy, D. RSC Adv. 2016, 6, 43767