Name:

Dr. Robert Byrne 

 

Contact details

N205, Adaptive Sensors Group, National Centre of Sensor Research Dublin City University Dublin,Ireland

Tel: +353-1-7007926

e-mail: robert.byrne@dcu.ie

Qualifications

Ph.D (Chemistry) Preparation and Characterization of Photo-, Thermo-, and Solvatochromic Materials containing Benzospiropyran. 2008

BSc.(Hons) Chemical and Pharmaceutical Science. 2004

Project Summary

My research interests involve the design and development of photochromic materials for chemical sensing and actuation.My work is primarily focused on materials containing the photochrome benzospiropyran (BSP). Photochromism is the ability of a chemical species to reversibly change colour upon exposure to light. Photochromic compounds usually undergo a change in their molecular structure or conformation, which alters the absorption spectrum of the dye. The most highly studied family of photochromes is spiropyrans. Upon exposure to UV light, spiropyrans undergo a heterocyclic ring cleavage that results in the open merocyanine form. While the spiropyran or closed form is colourless, the open merocyanine structure has a strong absorption in the visible region. There are many potential applications for photochromic materials such as high-density optical storage and molecular switches. I am currently involved in three projects utilizing the properties of these fascinating molecules.

Project A: Optical Sensing

 

When the spiropyran absorbs UV light it switches to the merocyanine form, and this structure has an active binding site for cations. When transition metal cations bind to this site, the resulting colored complex has a new absorption band in the visible spectrum. By shining white light on the colored complex, the dye is reverted to the closed spiropyran form, and the cation is released. The reversible binding of the cation happens in solution, we recently developed a covalently immobilised spiropyran polymer film that can reversible bind cobalt(II)chloride in solution. Combining the spiropyran polymer film and novel LED-based sensor technology developed in our laboratory, we have developed a prototype chemical sensing system. This can be seen here; 

 http://www.dcu.ie/chemistry/asg/byrnero/files/spiro_project_v2_0001.wmv  

Project B: Molecular probe in Ionic Liquids

Ionic liquids (ILs) are a class of novel solvents with very interesting properties, which are attracting the attention of a growing number of scientists and engineers, as shown by the increasing number of publications in recent years. ILs are organic salts composed of anions and cations that are in the liquid state at ambient conditions and many show negligible volatility and non-flammability.  Hence, they are being actively investigated as alternative solvent media in synthesis, catalysis, polymerization, separation, electrochemistry and electrochemical devices.  However, the basic science involved with fully characterizing these ILs is still in its infancy, and this may be holding back the complete and most efficient utilization of these potentially, and only in some cases,  “green” solvents. Before the full potential of ILs as solvent systems can be explored, more information about their physicochemical properties needs to be gathered. ILs can replace molecular solvents only if the chemist is able to compare ILs with generally used reaction media in a rational way; however, much further information is needed to allow the categorization of new and existing ILs more precisely in terms of solvent properties.

 

Like other merocyanines, the MC, is a negative solvatochromic dye, i.e. with increasing solvent polarity the absorption band undergoes a hypsochromic (or blue) shift. The effect of the solvent on the electronic spectra has been investigated previously and it has been shown that, when the absorption maxima of MC (expressed in wavenumbers) or the transition energies are plotted against solvent polarity parameters such as E_T(30) values, Kosower’s Z values, Brooker’s Xb values and Brownstein’s values, reasonably linear plots are obtained. In addition to the solvatochromic effect, it has also been shown that changes in the absorption maxima, the intramolecular Lewis acid-base equilibrium between BSP-NO₂ and MC, and the thermal relaxation rates of MC back to BSP-NO₂ are intrinsically solvent dependent. Furthermore, the MC isomer has a phenolate anion site through which certain (d- and f-element) metal ions can bind, giving rise to a new absorption band in the visible spectrum. The type of metal ion only slightly influences the spectral properties of the complexes, in contrast to the relaxation time which can differ by one order of magnitude. Thus, metal ion coordination can influence the photochromic properties of BSP-NO₂.

 

 

 

 

 

Figure 1. Cations and anion used in this study: ethyl methyl imidazolium [emim]⁺, ethyl  dimethyl imidazolium [edmim]⁺,  N-propyl N-methyl-pyrrolidium [C₃mpyr]⁺, N-butyl N-methyl-pyrrolidium [C₄mpyr]⁺, trihexyltetradecylphosphonium [P_6,6,6,14]⁺, trioctyl, methyl ammonium [N_1,8,8,8]⁺ and bis(trifluoromethanesulfonyl) amide [NTf₂]^-.

 

In this work we have investigated the spectroscopic properties of BSP-NO₂ in a number of bis(trifluoromethanesulfonyl) amide, [NTf₂]^-, ionic liquids.  At the outset, the goal was to use this probe molecule to learn more about the modes of interaction and polarity of a number of the cations used in common ionic liquids.  In the process some unusual BSP-NO₂ spectroscopic effects have been observed that may be of interest in the various applications discussed above.

 

Figure 2. Molecular orbital of the [emim]+[MC] complex showing a through-space interaction between the phenolate oxygen and the carbon atom (the C2 position) on the [emim]+.

Publications

[1] R. Byrne, S. Coleman, S. Gallagher, and D. Diamond, "Designer molecular probes for phosphonium ionic liquids," Physical Chemistry Chemical Physics, vol. 12, pp. 1895-1904, 2010. [2] F. Benito-Lopez, R. Byrne, A. M. Raduta, N. E. Vrana, G. McGuinness, and D. Diamond, "Ionogel-based light-actuated valves for controlling liquid flow in micro-fluidic manifolds," Lab on a Chip, vol. 10, pp. 195-201, 2010. [3] A. Radu, R. Byrne, N. Alhashimy, M. Fusaro, S. Scarmagnani, and D. Diamond, "Spiropyran-based reversible, light-modulated sensing with reduced photofatigue," Journal of Photochemistry and Photobiology a-Chemistry, vol. 206, pp. 109-115, 2009. [4] S. Coleman, R. Byrne, S. Minkovska, and D. Diamond, "Investigating Nanostructuring within Imidazolium Ionic Liquids: A Thermodynamic Study Using Photochromic Molecular Probes," The Journal of Physical Chemistry B, vol. 113, pp. 15589-15596, 2009. [5] S. Coleman, R. Byrne, S. Minkovska, and D. Diamond, "Thermal reversion of spirooxazine in ionic liquids containing the [NTf2]- anion," Physical Chemistry Chemical Physics, vol. 11, pp. 5608-5614, 2009. [6] R. Byrne, S. Scaramagnani, A. Radu, F. Benito-Lopez, and D. Diamond, "Schizophrenic Molecules and Materials With Multiple Personalities - How Materials Science Could Revolutionise How we do Chemical Sensing," in Active Polymers, vol. 1190, Materials Research Society Symposium Proceedings, A. Lendlein, V. P. Shastri, and K. Gall, Eds., 2009, pp. 139-153. [7] R. Byrne, S. Coleman, K. J. Fraser, A. Raduta, D. R. MacFarlane, and D. Diamond, "Photochromism of nitrobenzospiropyran in phosphonium based ionic liquids," Physical Chemistry Chemical Physics, vol. 11, pp. 7286-7291, 2009. [8] F. Benito-Lopez, R. Byrne, Y. Wu, L. Nolan, J. Kim, K. T. Lau, G. G. Wallace, and D. Diamond, "Molecules with Multiple Personalities: How Switchable Materials Could Revolutionize Chemical Sensing," ECS Transactions, vol. 19, pp. 199-210, 2009. [9] N. Alhashimy, R. Byrne, S. Minkovska, and D. Diamond, "Novel synthesis and characterization of 3,3-dimethyl-5'-(2-benzothiazolyl)-spironaphth(indoline-2,3'-[3H]naphth[2,1-b] [1,4]oxazine) derivatives," Tetrahedron Letters, vol. 50, pp. 2573-2576, 2009. [10] R. Byrne, K. J. Fraser, E. Izgorodina, D. R. MacFarlane, M. Forsyth, and D. Diamond, "Photo- and solvatochromic properties of nitrobenzospiropyran in ionic liquids containing the [NTf2]- anion," Physical Chemistry Chemical Physics, vol. 10, pp. 5919-5924, 2008. [11] A. Radu, S. Scarmagnani, R. Byrne, C. Slater, K. T. Lau, and D. Diamond, "Photonic modulation of surface properties: a novel concept in chemical sensing," Journal of Physics D: Applied Physics, vol. 40, pp. 7238-7244, 2007. [12] S. Stitzel, R. Byrne, and D. Diamond, "LED switching of spiropyran-doped polymer films," Journal of Materials Science, vol. 41, pp. 5841-5844, 2006. [13] A. Radu, R. Byrne, N. Alhashimy, and D. Diamond, "Spiropyran-based smart surfaces: Development and characterization," Abstracts of Papers, 231st ACS National Meeting, Atlanta, GA, United States, March 26-30, 2006, pp. INOR-041, 2006. [14] R. J. Byrne, S. E. Stitzel, and D. Diamond, "Photoregenerable surface with potential for optical sensing," Journal of Materials Chemistry, vol. 16, pp. 1332-1337, 2006. [15] R. Byrne and D. Diamond, "Chemo/bio-sensor networks," Nature Materials, vol. 5, pp. 421-424, 2006.

Further Information

2006:6 month research visit to Prof. Doug MacFarlane's Ionic Liquids group at Monash University, Melbourne.

http://www.chem.monash.edu.au/ionicliquids/index.html

2003: 9 month internship in Prof. Paul Hanson's organic synthesis group at Kansas Univeristy.

http://www2.chem.ku.edu/PHansonGroup/