Center for Molecular Modeling - L. Van der Schueren

Polycaprolactone and polycaprolactone/chitosan nanofibres functionalised with the pH-sensitive dye Nitrazine Yellow

hemel — Thu, 31 May 2012 12:04:11 +0000

L. Van der Schueren, T. De Meyer, I. Steyaert, O. Ceylan, K. Hemelsoet, V. Van Speybroeck, K. De Clerck

Carbohydrate Polymers

91 (1), 284-293

2013

Abstract

Nanofibres functionalised with pH-sensitive dyes could greatly contribute to the development of stimuli-responsive materials. However, the application of biocompatible polymers is vital to allow for their use in (bio)medical applications. Therefore, this paper focuses on the development and characterisation of pH-sensitive polycaprolactone (PCL) nanofibrous structures and PCL/chitosan nanofibrous blends with 20% chitosan. Electrospinning with added Nitrazine Yellow molecules proved to be an excellent method resulting in pH-responsive non-wovens. Unlike the slow and broad response of PCL nanofibres (time lag of more than 3 h), the use of blends with chitosan led to an increased sensitivity and significantly reduced response time (time lag of 5 min). These important effects are attributed to the increased hydrophilic nature of the nanofibres containing chitosan. Computational calculations indicated stronger interactions, mainly based on electrostatic interactions, of the dye with chitosan (ΔG of -132.3 kJ/mol) compared to the long-range interactions with PCL (ΔG of -35.6 kJ/mol), thus underpinning our experimental observations. In conclusion, because of the unique characteristics of chitosan, the use of PCL/chitosan blends in pH-sensitive biocompatible nanofibrous sensors is crucial.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1016/j.carbpol.2012.08.003

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13 carbo. polymers 91(1)284 Van.derScheuren.pdf

The influence of a polyamide matrix on the halochromic behaviour of the pH-sensitive azo dye Nitrazine Yellow

hemel — Thu, 19 Jan 2012 10:39:52 +0000

L. Van der Schueren, K. Hemelsoet, V. Van Speybroeck, K. De Clerck

Dyes and Pigments

94 (3), 443-451

2012

Abstract

It is of great interest to introduce pH-sensitive dyes into fibrous materials since this may result in flexible sensor systems. However, to date, the effect of a textile matrix on the halochromic properties of dyes is still unknown which severely limits their further development. Therefore, this paper focuses on an in-depth study of the halochromism of the azo pH-indicator dye Nitrazine Yellow in solution and incorporated in polyamide textile matrices with different structures. Based on both experimental spectroscopic data and computational calculations, an azo hydrazone tautomerism was found to be responsible for the halochromism of Nitrazine Yellow in solution. The hydrazone tautomer was most stable in neutral pH while the deprotonated dye molecule was believed to be an azo tautomer, resulting in a bathochromic shift with increasing pH. This tautomerism was, moreover, also present in the polyamide matrices. However, the equilibrium was clearly affected by the polymeric environment resulting in a shift and broadening of the dynamic pH-range. The polyamide type and textile structure influenced the halochromic response due to different interactions and accessibility of the dye. In conclusion, the halochromism of Nitrazine Yellow is present in all studied systems and is always based on an azo hydrazone tautomerism but the polyamide matrix causes distinct alterations in the tautomeric equilibrium.

DOI

http://dx.doi.org/10.1016/j.dyepig.2012.02.013

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12 dyes and pigments 94 (3) 443 Van der Schueren.pdf

Investigating the Halochromic Properties of Azo Dyes in an Aqueous Environment by Using a Combined Experimental and Theoretical Approach

michel — Wed, 23 Nov 2011 13:27:56 +0000

T. De Meyer, K. Hemelsoet, L. Van der Schueren, E. Pauwels, K. De Clerck, V. Van Speybroeck

Chemistry - A European Journal

18 (26), 8120-8129

2012

Abstract

The halochromism in solution of a prototypical example of an azo dye, ethyl orange, was investigated by using a combined theoretical and experimental approach. Experimental UV/Vis and Raman spectroscopy pointed towards a structural change of the azo dye with changing pH value (in the range pH 5–3). The pH-sensitive behavior was modeled through a series of ab initio computations on the neutral and various singly and doubly protonated structures. For this purpose, contemporary DFT functionals (B3LYP, CAM-B3LYP, and M06) were used in combination with implicit modeling of the water solvent environment. Static calculations were successful in assigning the most-probable protonation site. However, to fully understand the origin of the main absorption peaks, a molecular dynamics simulation study in a water molecular environment was used in combination with time-dependent DFT (TD-DFT) calculations to deduce average UV/Vis spectra that take into account the flexibility of the dye and the explicit interactions with the surrounding water molecules. This procedure allowed us to achieve a remarkable agreement between the theoretical and experimental UV/Vis spectrum and enabled us to fully unravel the pH-sensitive behavior of ethyl orange in aqueous environment.

DOI

http://dx.doi.org/10.1002/chem.201103633

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12_chem_eur_j_18(26)8120_DeMeyer.pdf

pH-sensitivity of azo dyes

thierry — Thu, 28 Jun 2012 08:18:18 +0000

T. De Meyer, L. Van der Schueren, K. Hemelsoet, V. Van Speybroeck, K. De Clerck

p. 103-104

Talk

Conference / event / venue

Fiber Society Spring Conference 2012

EMPA, Lausanne, Switzerland

Wednesday, 23 May, 2012 to Friday, 25 May, 2012

Abstract (private)

Fiber Society finaal.pdf

Conference reference

Fiber Society Spring 2012 Conference

UV-VIS spectra of azo dyes in aqueous environment: a combined TD-DFT and molecular dynamics study

thierry — Tue, 17 Apr 2012 09:07:07 +0000

T. De Meyer, K. Hemelsoet, L. Van der Schueren, E. Pauwels, K. De Clerck, V. Van Speybroeck

Poster

Conference / event / venue

DFTM2012

Gent, Belgium

Sunday, 1 April, 2012 to Friday, 6 April, 2012

Abstract (private)

DFTM2012abstract.pdf

Conference reference

DFTM2012

The pH-sensitive properties of azo dyes in aqueous environment

thierry — Wed, 18 Jan 2012 22:14:16 +0000

T. De Meyer, K. Hemelsoet, L. Van der Schueren, E. Pauwels, K. De Clerck, V. Van Speybroeck

Poster

Conference / event / venue

QCB10

Brussel

Friday, 10 February, 2012

Abstract (private)

Thierry De Meyer poster abstract.pdf

Conference reference

QCB10

The pH-sensitive properties of azo dyes in aqueous environment

thierry — Wed, 18 Jan 2012 22:10:02 +0000

T. De Meyer, K. Hemelsoet, L. Van der Schueren, E. Pauwels, K. De Clerck, V. Van Speybroeck

http://www.cecam.org/workshop-3-699.html?poster_id=7740

Poster

Conference / event / venue

Molsim2012

Amsterdam

Monday, 9 January, 2012 to Friday, 20 January, 2012

Abstract (private)

2012 Molsim TDeMeyer.pdf

Conference reference

Molsim-2012