Co-reporter:Sarbjeet Kaur, Mandeep Kaur, Paramjit Kaur, Koen Clays, Kamaljit Singh
Coordination Chemistry Reviews 2017 Volume 343(Volume 343) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.ccr.2017.05.008
•Ferrocene chromophores constitute valuable nonlinear optical materials.•Structure dependence of the second-order nonlinear optical properties.•Fine tuning of NLO behaviour ensures futuristic growth potential.Fine tuning and switching the electronic properties of ferrocene chromophores has been an area of considerable significance and a plethora of new ferrocene-based chromophores with new properties are continually being reported in the current literature. Depending upon the oxidation state of the iron metal center and/or on the chemical constitution, the ferrocene unit in its chromophore behaves as an extremely strong donor or acceptor. This property has been extensively used in fine-tuning the electronic properties of organometallic chromophores. Suitably functionalized push-pull chromophores (D-π-A) in which an electron donor (D) ferrocene is connected by a π-conjugated spacer to a strong electron acceptor (A), have gathered significant interest for their synthesis, (spectro)electrochemical, and switchable optical and second-order nonlinear optical properties. These materials exhibit structure-based large second-order optical nonlinearities and are potentially useful for applications related to telecommunications, optical computing, optical storage, and optical information processing. In this review, these aspects of ferrocene chromophores have been presented and structure-property correlations have been drawn.Download high-res image (119KB)Download full-size image
Co-reporter:Anjul Khadria;Yovan de Coene;Przemyslaw Gawel;Cécile Roche;Harry L. Anderson
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 4) pp:947-956
Publication Date(Web):2017/01/25
DOI:10.1039/C6OB02319C
Pyropheophorbide-a methyl ester (PPa-OMe) has been modified by attaching electron-donor and -acceptor groups to alter its linear and nonlinear optical properties. Regioselective bromination of the terminal vinyl position and Suzuki coupling were used to attach a 4-(N,N-diethylaminophenyl) electron-donor group. The electron-acceptor dicyanomethylene was attached at the cyclic ketone position through a Knoevenagel condensation. Four different derivatives of PPa-OMe, containing either electron-donor or electron-acceptor groups, or both, were converted to hydrophilic bis-TEG amides to generate a series of amphiphilic dyes. The absorption and emission properties of all the dyes were compared to a previously reported push–pull type porphyrin-based dye and a commercial push–pull styryl dye, FM4-64. Electrochemical measurements reveal that the electron donor group causes a greater decrease in HOMO–LUMO gap than the electron-acceptor. TD-DFT calculations on optimized geometries (DFT) of all four dyes show that the HOMO is mostly localized on the donor, 4-(N,N-diethylaminophenyl), while the LUMO is distributed around the chlorin ring and the electron-acceptor. Hyper-Rayleigh scattering experiments show that the first-order hyperpolarizabilities of the dyes increase on attaching either electron-donor or -acceptor groups, having the highest value when both the donor and acceptor groups are attached. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) images of the bis-TEG amide attached dyes in lipid monolayer-coated droplets of water-in-oil reveal that the TPEF and SHG involve transition dipole moments in different orientations.
Co-reporter:Kuo Zhong, Mehran Khorshid, Jiaqi Li, Karen Markey, Patrick Hermann Wagner, Kai Song, Stijn Van Cleuvenbergen and Koen Clays
Journal of Materials Chemistry A 2016 vol. 4(Issue 33) pp:7853-7858
Publication Date(Web):26 Jul 2016
DOI:10.1039/C6TC02226J
An optomicrofluidic device was developed by introducing 3D wettability patterns into hollow SiO2 sphere colloidal photonic crystals. Aqueous liquids flow through the superhydrophilic channel due to the surface tension confinement effect. Based on the significant fluorescence enhancement from photonic band gap (PBG) effects in these channels, real-time specific bioassays with high sensitivity were realized. To demonstrate this strategy, with two complementary single stranded DNA molecules acting as a target (fluorophore labeled) and a probe respectively, a 150-fold enhancement of fluorescence was observed compared with a similar device on a standard glass plate. This enhancement results from the strong PBG effect in an aqueous environment for these structures. While the PBG effect diminishes from refractive index matching in conventional solid sphere colloidal photonic crystals with water infiltrated, it is effectively enhanced in hollow sphere colloidal photonic crystals. This is because the dense shell of the hollow spheres prevents water from infiltrating into the inner air cavity of the hollow spheres, while water fills the voids between spheres. This creates a larger refractive index contrast, resulting in a pronounced PBG effect and strong fluorescence enhancement.
Co-reporter:Kuo Zhong, Jiaqi Li, Liwang Liu, Ward Brullot, Maarten Bloemen, Alexander Volodin, Kai Song, Pol Van Dorpe, Niels Verellen, and Koen Clays
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 16) pp:10451
Publication Date(Web):March 31, 2016
DOI:10.1021/acsami.6b00733
We report a new type of nanosphere colloidal lithography to directly fabricate monodisperse silica (SiO2) nanorings by means of reactive ion etching of hollow SiO2 spheres. Detailed TEM, SEM, and AFM structural analysis is complemented by a model describing the geometrical transition from hollow sphere to ring during the etching process. The resulting silica nanorings can be readily redispersed in solution and subsequently serve as universal templates for the synthesis of ring-shaped core–shell nanostructures. As an example we used silica nanorings (with diameter of ∼200 nm) to create a novel plasmonic nanoparticle topology, a silica-Au core–shell nanoring, by self-assembly of Au nanoparticles (<20 nm) on the ring’s surface. Spectroscopic measurements and finite difference time domain simulations reveal high quality factor multipolar and antibonding surface plasmon resonances in the near-infrared. By loading different types of nanoparticles on the silica core, hybrid and multifunctional composite nanoring structures could be realized for applications such as MRI contrast enhancement, catalysis, drug delivery, plasmonic and magnetic hyperthermia, photoacoustic imaging, and biochemical sensing.Keywords: antibonding; colloidal lithography; hollow spheres; nanoring; reactive ion etching; self-assembled plasmonic nanoparticles; templates
Co-reporter:Ahmed Al-Yasari, Nick Van Steerteghem, Hani El Moll, Koen Clays and John Fielden
Dalton Transactions 2016 vol. 45(Issue 7) pp:2818-2822
Publication Date(Web):19 Jan 2016
DOI:10.1039/C6DT00115G
We show that polyoxometalates (POMs) are an excellent redox-active acceptor on which to base high performance 2nd order non-linear optical (NLO) chromophores. This is demonstrated through three new organoimido-Lindqvist derivatives with HRS β0-values exceeding those of any dipolar organic system with comparable donor, π-system and absorption profile. Thus, organoimido POMs may provide a new generation of high performance, high transparency, and potentially redox-switchable NLO materials.
Co-reporter:Kuo Zhong, Liwang Liu, Xiaodong Xu, Michael Hillen, Atsushi Yamada, Xingping Zhou, Niels Verellen, Kai Song, Stijn Van Cleuvenbergen, Renaud ValléeKoen Clays
ACS Photonics 2016 Volume 3(Issue 12) pp:
Publication Date(Web):November 22, 2016
DOI:10.1021/acsphotonics.6b00511
Up to now colloidal photonic crystal (CPC) lasers essentially relied on photonic band gap edge effects, as a consequence of the poor passband quality achieved by previously reported engineering methods. In this paper, we demonstrate lasing oscillation in CPCs based on the defect mode passband effect. As defect mode, we introduce a high-quality monolayer of silica spheres internally functionalized with laser dyes in a sandwiched CPC structure. This defect layer contains the gain medium for lasing action and at the same time breaks the translational symmetry of the crystal, resulting in a pronounced passband within the photonic band gap. The CPC acts as an optical resonator, effectively ensuring the feedback mechanism. The spectroscopic measurements and theoretical simulations match well and reveal that the relatively low-threshold lasing exhibited by the structure can uniquely be attributed to the efficient coupling of the spontaneous emission of the dye to the defect mode of the CPC. Our work provides a new promising strategy toward applications of functionalized self-assembled CPCs with a planar defect in all-optical switching, optoelectronics, and energy-harvesting, and even in the future generation of electro-optical devices, such as lab-on-a-chip with all-integrated optical spectroscopy techniques.Keywords: colloidal photonic crystals; laser; planar defect; self-assembly; spontaneous emission;
Co-reporter:Ismael López-Duarte, Phoom Chairatana, Yilei Wu, Javier Pérez-Moreno, Philip M. Bennett, James E. Reeve, Igor Boczarow, Wojciech Kaluza, Neveen A. Hosny, Samuel D. Stranks, Robin J. Nicholas, Koen Clays, Marina K. Kuimova and Harry L. Anderson
Organic & Biomolecular Chemistry 2015 vol. 13(Issue 12) pp:3792-3802
Publication Date(Web):16 Feb 2015
DOI:10.1039/C4OB02507E
We report the synthesis of four new cationic dipolar push–pull dyes, together with an evaluation of their photophysical and photobiological characteristics pertinent to imaging membranes by fluorescence and second harmonic generation (SHG). All four dyes consist of an N,N-diethylaniline electron-donor conjugated to a pyridinium electron-acceptor via a thiophene bridge, with either vinylene (–CHCH–) or ethynylene (–CC–) linking groups, and with either singly-charged or doubly-charged pyridinium terminals. The absorption and fluorescence behavior of these dyes were compared to a commercially available fluorescent membrane stain, the styryl dye FM4-64. The hyperpolarizabilities of all dyes were compared using hyper-Rayleigh scattering at 800 nm. Cellular uptake, localization, toxicity and phototoxicity were evaluated using tissue cell cultures (HeLa, SK-OV-3 and MDA-231). Replacing the central alkene bridge of FM4-64 with a thiophene does not substantially change the absorption, fluorescence or hyperpolarizability, whereas changing the vinylene-links to ethynylenes shifts the absorption and fluorescence to shorter wavelengths, and reduces the hyperpolarizability by about a factor of two. SHG and fluorescence imaging experiments in live cells showed that the doubly-charged thiophene dyes localize in plasma membranes, and exhibit lower internalization rates compared to FM4-64, resulting in less signal from the cell cytosol. At a typical imaging concentration of 1 μM, the doubly-charged dyes showed no significant light or dark toxicity, whereas the singly-charged dyes are phototoxic even at 0.5 μM. The doubly-charged dyes showed phototoxicity at concentrations greater than 10 μM, although they do not generate singlet oxygen, indicating that the phototoxicity is type I rather than type II. The doubly-charged thiophene dyes are more effective than FM4-64 as SHG dyes for live cells.
Co-reporter:Kuo Zhong, Pieter-Jan Demeyer, Xingping Zhou, Olga Kruglova, Niels Verellen, Victor V. Moshchalkov, Kai Song and Koen Clays
Journal of Materials Chemistry A 2014 vol. 2(Issue 41) pp:8829-8836
Publication Date(Web):04 Jul 2014
DOI:10.1039/C4TC00912F
We demonstrate a facile method for introducing planar defects into colloidal photonic crystals. Firstly, a 2D monolayer of SiO2 microspheres (guest spheres) was fabricated at the air/water interface by compressing the individual microspheres with a surfactant into long-range hexagonal arrays. The floating monolayer, which served as our defect layer, was then transferred onto a pre-deposited colloidal crystal slab consisting of PS@SiO2 microspheres (host spheres). Subsequently, a second colloidal crystal slab of host spheres was deposited on the surface of the defect layer. In comparison to previous methods to introduce planar defects into colloidal photonic crystals, this fabrication results in pronounced passbands in the band gaps of the colloidal photonic crystals. More importantly, the FWHM of the passband in our experiment is just 16 nm, which is narrower than the previously reported results to the best of our knowledge. Furthermore, the defect modes can be engineered by changing the diameter of the guest spheres and/or transforming the host spheres from PS@SiO2 spheres to hollow SiO2 spheres by calcination. The measured defect modes in the spectra match well with the simulated results.
Co-reporter:Pieter-Jan Demeyer, Stefaan Vandendriessche, Stijn Van Cleuvenbergen, Sophie Carron, Kevin Bogaerts, Tatjana N. Parac-Vogt, Thierry Verbiest, and Koen Clays
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 6) pp:3870
Publication Date(Web):February 21, 2014
DOI:10.1021/am4048464
Three-dimensionally ordered macroporous materials have unique structural and optical properties, making them useful for numerous applications in catalysis, membrane science, and optics. Accessible and economic fabrication of these materials is essential to fully explore the many possibilities that these materials present. A new templating method to fabricate three-dimensionally ordered macroporous materials without overlayers is presented. The resulting structures are freestanding inverse opals with large-area uniformity. The versatility and power of our fabrication method is demonstrated by synthesizing inverse opals displaying fluorescence, chirality, upconversion, second harmonic generation, and third harmonic generation. This economical and versatile fabrication method will facilitate research on inverse opals in general and on linear and nonlinear optical effects in 3D photonic crystals specifically. The relative ease of synthesis and wide variety of resulting materials will help the characterization and improvement of existing anomalous dispersion effects in these structures, while providing a platform for the discovery and demonstration of novel effects.Keywords: inverse opals; macroporous materials; nonlinear optics; photonic crystals; polymer doping; templating;
Co-reporter:Evelien De Meulenaere, Ngan Nguyen Bich, Marc de Wergifosse, Kristof Van Hecke, Luc Van Meervelt, Jozef Vanderleyden, Benoît Champagne, and Koen Clays
Journal of the American Chemical Society 2013 Volume 135(Issue 10) pp:4061-4069
Publication Date(Web):February 13, 2013
DOI:10.1021/ja400098b
We have successfully designed and expressed a new fluorescent protein with improved second-order nonlinear optical properties. It is the first time that a fluorescent protein has been rationally altered for this particular characteristic. On the basis of the specific noncentrosymmetry requirements for second-order nonlinear optical effects, we had hypothesized that the surprisingly low first hyperpolarizability (β) of the enhanced yellow fluorescent protein (eYFP) could be explained by centrosymmetric stacking of the chromophoric Tyr66 and the neighboring Tyr203 residue. The inversion center was removed by mutating Tyr203 into Phe203, with minor changes in the linear optical properties and even an improved fluorescence quantum yield. Structure determination by X-ray crystallography as well as linear optical characterization corroborate a correct folding and maturation. Measurement of β by means of hyper-Rayleigh scattering (HRS) as well as their analysis using quantum chemistry calculations validate our hypothesis. This observation can eventually lead to improved red fluorescent proteins for even better performance. On the basis of the specific function (second-harmonic generation), the color of its emission, and in analogy with the “fruit” names, we propose SHardonnay as the name for this Tyr203Phe mutant of eYFP.
Co-reporter:Luis González-Urbina, Kasper Baert, Branko Kolaric, Javier Pérez-Moreno, and Koen Clays
Chemical Reviews 2012 Volume 112(Issue 4) pp:2268
Publication Date(Web):December 23, 2011
DOI:10.1021/cr200063f
Co-reporter:Evelien De Meulenaere, Wei-Qiang Chen, Stijn Van Cleuvenbergen, Mei-Ling Zheng, Sotiris Psilodimitrakopoulos, Rik Paesen, Jean-Marc Taymans, Marcel Ameloot, Jos Vanderleyden, Pablo Loza-Alvarez, Xuan-Ming Duan and Koen Clays
Chemical Science 2012 vol. 3(Issue 4) pp:984-995
Publication Date(Web):25 Jan 2012
DOI:10.1039/C2SC00771A
A series of chromophores with enhanced second- and third-order nonlinear optical properties were engineered for use in combined second-harmonic and two-photon fluorescence microscopy. Electron-accepting moieties imparted nonlinear optical properties to the chromophores. The electron-rich carbazole core served as a template towards one- or two-dimensional chromophores. More efficient acceptor groups (pyridinium, benzazolium, benzothiazolium) on the carbazole donor core resulted in improved second- and third-order nonlinear optical properties. A selection of these chromophores was tested in a cellular environment with a multimodal multiphoton microscope. The structural differences of the chromophores resulted in high selectivity for mitochondria or the nucleus in two-photon fluorescence and ranging from no signal to high selectivity for mitochondria in the SHG channel.
Co-reporter:Laura de Vega, Stijn van Cleuvenbergen, Griet Depotter, Eva M. García-Frutos, Berta Gómez-Lor, Ana Omenat, Rosa M. Tejedor, José Luis Serrano, Gunther Hennrich, and Koen Clays
The Journal of Organic Chemistry 2012 Volume 77(Issue 23) pp:10891-10896
Publication Date(Web):November 5, 2012
DOI:10.1021/jo302297j
A set of chiral discotic phenylacetylenes have been synthesized by 3-fold Sonogashira coupling between different ethynylbenzenes and triiodobenzenes. The resultant bulk materials are fully characterized by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction. The octopolar nature of the target compounds is studied by UV–vis absorption spectroscopy and hyper-Raleigh scattering in solution. Optimization of the donor–acceptor substitution yields both high hyperpolarizability values and appreciable mesomorphic properties. A simple thin film device for second harmonic generation has been prepared from the nitro-substituted liquid crystalline derivative.
Co-reporter:Tomoya Ishizuka ; Louise E. Sinks ; Kai Song ; Sheng-Ting Hung ; Animesh Nayak ; Koen Clays ;Michael J. Therien
Journal of the American Chemical Society 2011 Volume 133(Issue 9) pp:2884-2896
Publication Date(Web):February 15, 2011
DOI:10.1021/ja105004k
Dynamic hyperpolarizability (βλ) values and depolarization ratios (ρ) were determined from hyper-Rayleigh light scattering (HRS) measurements carried out at an incident irradiation wavelength (λinc) of 1300 nm. The depolarization ratio data provide an experimental measure of chromophore optical symmetry; appropriate coupling of multiple charge-transfer oscillators produces structures having enormous averaged hyperpolarizabilities (βHRS values), while evolving the effective chromophore symmetry from purely dipolar (e.g., Ru(tpy)[4-(Zn-porphyrin)ethynyl-tpy](PF6)2, βHRS = 1280 × 10−30 esu, ρ = 3.8; Ru(tpy)[4′-(Zn-porphyrin)ethynyl-tpy](PF6)2, βHRS = 2100 × 10−30 esu, ρ = 3.8) to octopolar (e.g., Ru[4,4′′-bis(Zn-porphyrin)ethynyl-tpy]2(PF6)2, βHRS = 1040 × 10−30 esu, ρ = 1.46) via structural motifs that possess intermediate values of the depolarization ratio. The chromophore design roadmap provided herein gives rise to octopolar supermolecules that feature by far the largest off-diagonal octopolar first hyperpolarizability tensor components ever reported, with the effectively octopolar Ru[4,4′′-bis(Zn-porphyrin)ethynyl-tpy]2(PF6)2 possessing a βHRS value at 1300 nm more than a factor of 3 larger than that determined for any chromophore having octopolar symmetry examined to date. Because NLO octopoles possess omnidirectional NLO responses while circumventing the electrostatic interactions that drive bulk-phase centrosymmetry for NLO dipoles at high chromophore concentrations, the advent of octopolar NLO chromophores having vastly superior βHRS values at technologically important wavelengths will motivate new experimental approaches to achieve acentric order in both bulk-phase and thin film structures.
Co-reporter:Tao Ding, Liang Luo, Hong Wang, Li Chen, Kui Liang, Koen Clays, Kai Song, Guoqiang Yang and Chen-Ho Tung
Journal of Materials Chemistry A 2011 vol. 21(Issue 30) pp:11330-11334
Publication Date(Web):23 Jun 2011
DOI:10.1039/C1JM11194A
Patterning colloidal photonic crystals are a first step to the realization of integrated photonic circuits. In this paper, we introduce a new way to pattern colloidal photonic crystals by applying ultrasonication to selectively remove certain parts of the colloidal photonic crystal film from the substrate. These patterns with hydrophobicity can further function as templates to direct the growth of another layer of colloidal photonic crystal in order to reach dual-patterned photonic crystals with distinct hydrophilic and hydrophobic domains. The dual-patterns are responsive to water vapor, which can reversibly switch the reflection color of the hydrophilic regions on and off many times, while the hydrophobic parts are almost unaffected.
Co-reporter:Tao Ding, Ye Tian, Kui Liang, Koen Clays, Kai Song, Guoqiang Yang and Chen-Ho Tung
Chemical Communications 2011 vol. 47(Issue 8) pp:2429-2431
Publication Date(Web):20 Dec 2010
DOI:10.1039/C0CC04393A
Oxygen plasma etching of electrospun polymer fibers containing spherical colloids is presented as a new approach towards anisotropic colloidal nanoparticles. The detailed morphology of the resulting nanoparticles can be precisely controlled in a continuous way. The same approach is also amenable to prepare inorganic nanoparticles with double-sided patches.
Co-reporter:Ayele Teshome, M. Delower H. Bhuiyan, Graeme J. Gainsford, M. Ashraf, Inge Asselberghs, Grant V.M. Williams, Andrew J. Kay, Koen Clays
Optical Materials 2011 Volume 33(Issue 3) pp:336-345
Publication Date(Web):January 2011
DOI:10.1016/j.optmat.2010.09.002
The synthesis, linear and second-order nonlinear optical (NLO) properties of a series of ionic indoline and N,N-dimethylaniline based chromophores are described. In order to optimise the second-order NLO response of these compounds four basic variations to the molecules and/or their environments have been implemented and their effect studied. These consist of changes to the counter-anion (from iodide to p-toluenesulfonate to naphthalene-2-sulfonate), variation of the solvent polarity [dimethyl sulfoxide (DMSO) to methanol (MeOH) to chloroform (CHCl3)], annelation of the acceptor unit (pyridinium to quinolinium) and a change in the donor used (N,N-dimethylaniline to indoline). It is found that the strongest enhancements to the quadratic NLO response occur when the acceptor moiety is changed from pyridinium to quinolinium, while compounds with an indoline donor group are slightly superior to those containing dimethylaniline as donor. There is no real discernable change in the first hyperpolarizability on altering either the counter-anion or solvent used for the measurements. X-ray crystallographic data were obtained for two of the compounds, and they are found to pack in centrosymmetric fashion, and have a small degree of twisting between the donor and acceptor. From this data it is seen that there is a general agreement between the degree of bond-length alternation (BLA) and the NLO response of the chromophores, and that for charged chromophores such as these a BLA value of approximately 0.1 Å is optimal.
Co-reporter:James E. Reeve, Harry L. Anderson and Koen Clays
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 41) pp:13484-13498
Publication Date(Web):31 Aug 2010
DOI:10.1039/C003720F
Nonlinear optical imaging has revolutionized microscopy for the life sciences. Second harmonic generation (SHG), the younger sibling of two-photon excited fluorescence (2PF), is a technique that can produce high resolution images from deep inside biological tissues. Second harmonic light is generated by the coherent scattering of an ensemble of aligned chromophores in a focused, pulsed laser beam. SHG is only generated at the focal spot, reducing the background signal, and requires ordered chromophores, so is highly structure-specific. In contrast to two-photon fluorescence, the physical process that creates the signal does not require the formation of excited states, allowing elimination of harmful photochemistry. While the SHG of native proteins and biopolymers is well known, the use of exogenous dyes can provide SHG contrast from areas without a sufficiently high intrinsic quadratic hyperpolarizability, β. Dyes for SHG primarily target lipid bilayers; a trait that, combined with sensitivity to transmembrane potential, allows monitoring of action potentials in a variety of excitable cells, most importantly mammalian neurons. This article summarizes the principles of SHG imaging and explores approaches for maximizing the SHG signal from a biological specimen. We survey methods of optimizing the optical set-up, enhancing the β of the dye and achieving biological compatibility. In conclusion, we examine novel applications of SHG imaging and highlight promising directions for the development of the field.
Co-reporter:Tatiana Cañeque;Ana M. Cuadro;Julio Alvarez-Builla;Javier Pérez-Moreno;Gema Marcelo;Francisco Mendicuti;Obis Castaño;José L. Andrés;Juan J. Vaquero
European Journal of Organic Chemistry 2010 Volume 2010( Issue 33) pp:6323-6330
Publication Date(Web):
DOI:10.1002/ejoc.201000816
Abstract
A variety of alkynylazinium cationic (D-π-A+) chromophores were prepared in good yields by the reaction of bromoazinium (pyridinium, quinolinium, and isoquinolinium iodides) with alkynes under Sonogashira conditions. The analysis of the experimentally recorded spectra is supported by quantum chemical calculations using restricted configuration interaction and density functional methods. First-order hyperpolarizabilities of (D-π-A+) azinium-based cations as a new class of second-order nonlinear optical (NLO) chromophores were also studied by hyper-Rayleigh scattering experiments and computational procedures.
Co-reporter:Xiangqian Hu, Dequan Xiao, Shahar Keinan, Inge Asselberghs, Michael J. Therien, Koen Clays, Weitao Yang and David N. Beratan
The Journal of Physical Chemistry C 2010 Volume 114(Issue 5) pp:2349-2359
Publication Date(Web):January 15, 2010
DOI:10.1021/jp911556x
Successfully predicting the frequency dispersion of electronic hyperpolarizabilities is an unresolved challenge in materials science and electronic structure theory. We show that the generalized Thomas−Kuhn sum rules, combined with linear absorption data and measured hyperpolarizability at one or two frequencies, may be used to predict the entire frequency-dependent electronic hyperpolarizability spectrum. This treatment includes two- and three-level contributions that arise from the lowest two or three excited electronic state manifolds, enabling us to describe the unusual observed frequency dispersion of the dynamic hyperpolarizability in high oscillator strength M-PZn chromophores, where (porphinato)zinc(II) (PZn) and metal(II)polypyridyl (M) units are connected via an ethyne unit that aligns the high oscillator strength transition dipoles of these components in a head-to-tail arrangement. We show that some of these structures can possess very similar linear absorption spectra yet manifest dramatically different frequency-dependent hyperpolarizabilities, because of three-level contributions that result from excited state-to-excited state transition dipoles among charge polarized states. Importantly, this approach provides a quantitative scheme to use linear optical absorption spectra and very limited individual hyperpolarizability measurements to predict the entire frequency-dependent nonlinear optical response.
Co-reporter:Tao Ding, Kai Song, Koen Clays and Chen-Ho Tung
Langmuir 2010 Volume 26(Issue 13) pp:11544-11549
Publication Date(Web):June 9, 2010
DOI:10.1021/la101622d
We present a self-assembly approach for monolayer and multilayer deposition of ellipsoids with a controllable direction. The direction of the ellipsoids in the assembly can be conveniently tuned by external applied magnetic field. This level of control on positional and directional order suggests a way to build monolayer templates for lithography with two-dimensional patterns and three-dimensional anisotropic photonic crystals, which may open the way toward the complete photonic band gap in the visible.
Co-reporter:Maurizio Quintiliani, Javier Pérez-Moreno, Inge Asselberghs, Purificación Vázquez, Koen Clays and Tomás Torres
The Journal of Physical Chemistry B 2010 Volume 114(Issue 19) pp:6309-6315
Publication Date(Web):April 19, 2010
DOI:10.1021/jp100827k
Two series of tetrahedral phthalocyanine-based systems presenting a central carbon or silicon atom have been synthesized and fully characterized. Ethynyl spacers connect the peripheral Pc units to the central core. Some of the structures contain four identical Pc moieties, whereas other ones bear either an electron-withdrawing or an electron releasing group in the fourth subunit. The synthetic strategy consisted in metal mediated coupling reactions between tri-tert-butylethynylphthalocyanine and the corresponding methane or silane derivatives. A second-order nonlinear optical (NLO) study, through hyper-Rayleigh scattering measurements, reveals that, by combining centrosymmetrical moieties that are not second-order NLO active by themselves, in an octupolar fashion, a large second-order NLO response is achieved, in contrast to classical octupolar combinations of donor−acceptor NLO active dipolar moieties. In particular, the C-centered tetramer exhibits a large βHRS value, which is among the highest reported so far for octupolar Pc-based molecules. Interestingly, carbon-centered molecules show a better NLO response with respect to the silicon-centered ones, probably due to a different effective symmetry, largely Td for the C-centered compounds and D2d for the Si-centered systems. While other design strategies for second-order NLO effects have always fundamentally kept on relying on the old dipolar paradigm (even though the resulting molecular structure was octupolar - the most striking exponent of this is the octupolar 1,3,5-triamino-2,4,6-trinitrobenzene molecule, a simple octupolar expansion of the dipolar p-nitroaniline), we here present for the first time that the octupolar symmetry by itself, realized by four nondipolar moieties in a tetrahedral arrangement, results also in a large second-order nonlinear response.
Co-reporter:Tao Ding, Kai Song, Koen Clays and Chen-Ho Tung
Langmuir 2010 Volume 26(Issue 6) pp:4535-4539
Publication Date(Web):November 17, 2009
DOI:10.1021/la903371a
We combine the most efficient (chemical) approach toward three-dimensional photonic crystals with the most convenient (physical) technique for creating non-close-packed crystalline structures. Self-assembly of colloidal particles in artificial opals is followed by a carefully tuned plasma etching treatment. By covering the resulting top layer of more open structure with original dense opal, embedded defect layers and heterostructures can be conveniently designed for advanced photonic band gap and band edge engineering.
Co-reporter:Evelien De Meulenaere, Inge Asselberghs, Marc de Wergifosse, Edith Botek, Stijn Spaepen, Benoît Champagne, Jos Vanderleyden and Koen Clays
Journal of Materials Chemistry A 2009 vol. 19(Issue 40) pp:7514-7519
Publication Date(Web):07 Jul 2009
DOI:10.1039/B907789H
The second-order nonlinear optical properties of three fluorescent proteins (FPs) (green, EGFP; yellow, EYFP; and red, DsRed) have been experimentally determined by frequency-resolved femtosecond hyper-Rayleigh scattering. As expected, DsRed, with its lower-energy bandgap between ground and excited state, exhibits the largest intrinsic hyperpolarizability. The anomalously low first hyperpolarizability for the yellow variant has been rationalized in terms of the centrosymmetrical arrangement between the phenolic Tyr203 (Tyr = tyrosine) residue and the chromophoric Tyr66 moiety, leaving the small imidazolinone moiety as the only effective non-centrosymmetric chromophore for second-order nonlinear effects. The experimental findings are corroborated by high-level computational results and suggest molecular engineering strategies to produce a full rainbow of FPs with enhanced nonlinear optical properties.
Co-reporter:Florence Quist, Christophe M.L. Vande Velde, Delphine Didier, Ayele Teshome, Inge Asselberghs, Koen Clays, Sergey Sergeyev
Dyes and Pigments 2009 Volume 81(Issue 3) pp:203-210
Publication Date(Web):June 2009
DOI:10.1016/j.dyepig.2008.10.004
Novel, push–pull chromophores combining a cationic benzothiazolium acceptor moiety and either one or two thiophene rings as a part of the conjugated π-system between the donor and the acceptor moieties have been synthesized and characterized. The chromophores displayed pronounced quadratic NLO activity with their first molecular hyper polarizabilities in agreement with their linear spectral properties.
Co-reporter:Ayele Teshome, Andrew J. Kay, Anthony D. Woolhouse, Koen Clays, Inge Asselberghs, Gerald J. Smith
Optical Materials 2009 Volume 31(Issue 4) pp:575-582
Publication Date(Web):February 2009
DOI:10.1016/j.optmat.2008.06.016
The molecular linear and nonlinear optical (NLO) properties of a series of seven merocyanine dyes have been studied in solvents covering a broad range of polarity (dioxane to dimethylsulfoxide). The benchmark for the series was the “Right hand side” zwitterionic chromophore 1, with a short conjugation path and 4-pyridinylidene as the donor group. Optimization strategies to improve the nonlinear response involved an extension of the conjugation path (with one or two ethenyl groups), annelation (pyridine to quinoline), variation of the solvent polarity and partial ring locking of the π-conjugated system. All chromophores have as the acceptor moiety the cyanodicyanomethylidenedihydrofuran heterocycle. Optimising the NLO response of these zwitterionic dyes by decreasing the polarity of the solvent is only possible for the parent chromophore 1. This is because the three other successful strategies employed to further improve the second-order NLO response in polar media, result in detrimental aggregation in nonpolar media.
Co-reporter:Wim Libaers, Branko Kolaric, Renaud A.L. Vallée, John E. Wong, Jelle Wouters, Ventsislav K. Valev, Thierry Verbiest, Koen Clays
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 339(1–3) pp:13-19
Publication Date(Web):1 May 2009
DOI:10.1016/j.colsurfa.2009.01.012
An engineering approach towards combined photonic band gap properties and magnetic functionalities, based on independent nanoscale engineering of two different materials at different length scales, is conceptually presented, backed by simulations, and experimentally confirmed. Large (>200 nm) monodisperse nanospheres of transparent silica self-assemble into a photonic crystal with a visible band gap, which is retained upon infiltration of small (<20 nm) nanoparticles of magnetic iron oxide. Enhancing and tuning Faraday rotation in photonic crystals is demonstrated.
Co-reporter:Tao Ding, Zhan-Fang Liu, Kai Song, Koen Clays and Chen-Ho Tung
Langmuir 2009 Volume 25(Issue 17) pp:10218-10222
Publication Date(Web):May 14, 2009
DOI:10.1021/la901004m
Three-dimensional photonic crystals (or photonic band gap materials) have been fabricated with oblate spheroids as the photonic building block. The nonspherical shape was realized by the blown film extrusion process of a prefabricated colloidal photonic crystal of spherical polystyrene particles, with its voids infiltrated by polyvinyl alcohol. The extrusion was applied on the composite film at a temperature above the glass transition temperature of both polymers. The uniformly applied two-dimensional stretching retains the positional order in the prefabricated colloidal crystal; transforms the spheres into oblate spheroids; and results in orientational order between the spheroids. The morphology of the particles can be predictably changed from a sphere into an oblate spheroid with a specified aspect ratio by the extent of the blown film extrusion. Therefore, the concomitant photonic band gap properties can be tuned in a convenient way.
Co-reporter:Jérôme Fortage Dr.;Annabelle Scarpaci Dr.;Lydie Viau Dr.;Yann Pellegrin Dr.;Errol Blart Dr.;Magnus Falkenström Dr.;Leif Hammarström ;Inge Asselberghs;Ruben Kellens Dr.;Wim Libaers Dr. ;MattiasP. Eng Dr.;Fabrice Odobel Dr.
Chemistry - A European Journal 2009 Volume 15( Issue 36) pp:9058-9067
Publication Date(Web):
DOI:10.1002/chem.200900262
Abstract
We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at λ=739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP–ZnP and AuP–AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state (+ZnP–AuP.) that displays a particularly long lifetime (τ=4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at λ=739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper–Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (β=2100×10−30 esu at λ=1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push–pull porphyrin system.
Co-reporter:Zhan-Fang Liu, Tao Ding, Guo Zhang, Kai Song, Koen Clays and Chen-Ho Tung
Langmuir 2008 Volume 24(Issue 18) pp:10519-10523
Publication Date(Web):August 22, 2008
DOI:10.1021/la801137p
A ternary system, consisting of air, an air-core/dense-silica-shell core−shell particle, and liquids has been used to fabricate an inverse opal structure with low fill factor, high refractive index contrast, and reversible tuning capabilities of the bandgap spectral position. The original close-packed opal structure is a ternary self-assembled photonic crystal from monodisperse and spherical polystyrene-core/silica-shell colloidal particles with air as the void material. Calcination removed the polystyrene and converted the core−shell particles to hollow spheres with a dense shell. In a final step, liquid is infiltrated only in the voids between the hollow spheres, but does not penetrate in the shell. This allows facile and reversible tuning of the bandgap properties in an inverse opal structure.
Co-reporter:TimothyV. Duncan Dr.;Kai Song Dr.;Sheng-Ting Hung Dr.;Ivan Miloradovic;Animesh Nayak;André Persoons ;Thierry Verbiest ;MichaelJ. Therien
Angewandte Chemie International Edition 2008 Volume 47( Issue 16) pp:2978-2981
Publication Date(Web):
DOI:10.1002/anie.200703187
Co-reporter:Gunther Hennrich Dr.;Ma Teresa Murillo Dr.;Pilar Prados Dr.;Hassan Al-Saraierh;Abdelmeneim El-Dali;David W. Thompson Dr.;Julie Collins;Paris E. Georghiou Dr.;Ayele Teshome;Inge Asselberghs Dr. Dr.
Chemistry - A European Journal 2007 Volume 13(Issue 27) pp:
Publication Date(Web):3 JUL 2007
DOI:10.1002/chem.200700615
A number of wide- and narrow-rimmed functionalized alkynylcalix[4]arenes have been synthesized by Sonogashira coupling. With respect to their optical properties, these donor–acceptor systems are treated as ensembles of covalently linked, electronically independent tolane subchromophores. Linear UV/visible and fluorescence spectroscopic investigations revealed that the charge-transfer character of the electronic transitions in calixarenes, and also the second-order nonlinear optical (NLO) properties depend on the electron-withdrawing nature of the terminal ethynylphenyl substituent (NO2, CF3, H). The nitro derivatives display high values of the quadratic hyperpolarizability β. Not only do the (nonlinear) optical properties of the target compounds depend on the number and relative disposition of the subchromophores, but also on the geometry of the calixarenes. In particular, the opening angle of the calixarene cavity can be determined by the substitution pattern of the calixarene scaffold (wide- versus narrow-rim substitution) and the number of the acetylene functions introduced. Both the NLO properties and the conformational issues are conveniently assessed by using hyper-Rayleigh scattering (HRS) in solution, and supported by X-ray crystallography in the solid state.
Co-reporter:Anjul Khadria, Yovan de Coene, Przemyslaw Gawel, Cécile Roche, Koen Clays and Harry L. Anderson
Organic & Biomolecular Chemistry 2017 - vol. 15(Issue 4) pp:NaN956-956
Publication Date(Web):2016/12/20
DOI:10.1039/C6OB02319C
Pyropheophorbide-a methyl ester (PPa-OMe) has been modified by attaching electron-donor and -acceptor groups to alter its linear and nonlinear optical properties. Regioselective bromination of the terminal vinyl position and Suzuki coupling were used to attach a 4-(N,N-diethylaminophenyl) electron-donor group. The electron-acceptor dicyanomethylene was attached at the cyclic ketone position through a Knoevenagel condensation. Four different derivatives of PPa-OMe, containing either electron-donor or electron-acceptor groups, or both, were converted to hydrophilic bis-TEG amides to generate a series of amphiphilic dyes. The absorption and emission properties of all the dyes were compared to a previously reported push–pull type porphyrin-based dye and a commercial push–pull styryl dye, FM4-64. Electrochemical measurements reveal that the electron donor group causes a greater decrease in HOMO–LUMO gap than the electron-acceptor. TD-DFT calculations on optimized geometries (DFT) of all four dyes show that the HOMO is mostly localized on the donor, 4-(N,N-diethylaminophenyl), while the LUMO is distributed around the chlorin ring and the electron-acceptor. Hyper-Rayleigh scattering experiments show that the first-order hyperpolarizabilities of the dyes increase on attaching either electron-donor or -acceptor groups, having the highest value when both the donor and acceptor groups are attached. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) images of the bis-TEG amide attached dyes in lipid monolayer-coated droplets of water-in-oil reveal that the TPEF and SHG involve transition dipole moments in different orientations.
Co-reporter:Tao Ding, Ye Tian, Kui Liang, Koen Clays, Kai Song, Guoqiang Yang and Chen-Ho Tung
Chemical Communications 2011 - vol. 47(Issue 8) pp:NaN2431-2431
Publication Date(Web):2010/12/20
DOI:10.1039/C0CC04393A
Oxygen plasma etching of electrospun polymer fibers containing spherical colloids is presented as a new approach towards anisotropic colloidal nanoparticles. The detailed morphology of the resulting nanoparticles can be precisely controlled in a continuous way. The same approach is also amenable to prepare inorganic nanoparticles with double-sided patches.
Co-reporter:Ismael López-Duarte, Phoom Chairatana, Yilei Wu, Javier Pérez-Moreno, Philip M. Bennett, James E. Reeve, Igor Boczarow, Wojciech Kaluza, Neveen A. Hosny, Samuel D. Stranks, Robin J. Nicholas, Koen Clays, Marina K. Kuimova and Harry L. Anderson
Organic & Biomolecular Chemistry 2015 - vol. 13(Issue 12) pp:NaN3802-3802
Publication Date(Web):2015/02/16
DOI:10.1039/C4OB02507E
We report the synthesis of four new cationic dipolar push–pull dyes, together with an evaluation of their photophysical and photobiological characteristics pertinent to imaging membranes by fluorescence and second harmonic generation (SHG). All four dyes consist of an N,N-diethylaniline electron-donor conjugated to a pyridinium electron-acceptor via a thiophene bridge, with either vinylene (–CHCH–) or ethynylene (–CC–) linking groups, and with either singly-charged or doubly-charged pyridinium terminals. The absorption and fluorescence behavior of these dyes were compared to a commercially available fluorescent membrane stain, the styryl dye FM4-64. The hyperpolarizabilities of all dyes were compared using hyper-Rayleigh scattering at 800 nm. Cellular uptake, localization, toxicity and phototoxicity were evaluated using tissue cell cultures (HeLa, SK-OV-3 and MDA-231). Replacing the central alkene bridge of FM4-64 with a thiophene does not substantially change the absorption, fluorescence or hyperpolarizability, whereas changing the vinylene-links to ethynylenes shifts the absorption and fluorescence to shorter wavelengths, and reduces the hyperpolarizability by about a factor of two. SHG and fluorescence imaging experiments in live cells showed that the doubly-charged thiophene dyes localize in plasma membranes, and exhibit lower internalization rates compared to FM4-64, resulting in less signal from the cell cytosol. At a typical imaging concentration of 1 μM, the doubly-charged dyes showed no significant light or dark toxicity, whereas the singly-charged dyes are phototoxic even at 0.5 μM. The doubly-charged dyes showed phototoxicity at concentrations greater than 10 μM, although they do not generate singlet oxygen, indicating that the phototoxicity is type I rather than type II. The doubly-charged thiophene dyes are more effective than FM4-64 as SHG dyes for live cells.
Co-reporter:James E. Reeve, Harry L. Anderson and Koen Clays
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 41) pp:NaN13498-13498
Publication Date(Web):2010/08/31
DOI:10.1039/C003720F
Nonlinear optical imaging has revolutionized microscopy for the life sciences. Second harmonic generation (SHG), the younger sibling of two-photon excited fluorescence (2PF), is a technique that can produce high resolution images from deep inside biological tissues. Second harmonic light is generated by the coherent scattering of an ensemble of aligned chromophores in a focused, pulsed laser beam. SHG is only generated at the focal spot, reducing the background signal, and requires ordered chromophores, so is highly structure-specific. In contrast to two-photon fluorescence, the physical process that creates the signal does not require the formation of excited states, allowing elimination of harmful photochemistry. While the SHG of native proteins and biopolymers is well known, the use of exogenous dyes can provide SHG contrast from areas without a sufficiently high intrinsic quadratic hyperpolarizability, β. Dyes for SHG primarily target lipid bilayers; a trait that, combined with sensitivity to transmembrane potential, allows monitoring of action potentials in a variety of excitable cells, most importantly mammalian neurons. This article summarizes the principles of SHG imaging and explores approaches for maximizing the SHG signal from a biological specimen. We survey methods of optimizing the optical set-up, enhancing the β of the dye and achieving biological compatibility. In conclusion, we examine novel applications of SHG imaging and highlight promising directions for the development of the field.
Co-reporter:Tao Ding, Liang Luo, Hong Wang, Li Chen, Kui Liang, Koen Clays, Kai Song, Guoqiang Yang and Chen-Ho Tung
Journal of Materials Chemistry A 2011 - vol. 21(Issue 30) pp:NaN11334-11334
Publication Date(Web):2011/06/23
DOI:10.1039/C1JM11194A
Patterning colloidal photonic crystals are a first step to the realization of integrated photonic circuits. In this paper, we introduce a new way to pattern colloidal photonic crystals by applying ultrasonication to selectively remove certain parts of the colloidal photonic crystal film from the substrate. These patterns with hydrophobicity can further function as templates to direct the growth of another layer of colloidal photonic crystal in order to reach dual-patterned photonic crystals with distinct hydrophilic and hydrophobic domains. The dual-patterns are responsive to water vapor, which can reversibly switch the reflection color of the hydrophilic regions on and off many times, while the hydrophobic parts are almost unaffected.
Co-reporter:Ahmed Al-Yasari, Nick Van Steerteghem, Hani El Moll, Koen Clays and John Fielden
Dalton Transactions 2016 - vol. 45(Issue 7) pp:NaN2822-2822
Publication Date(Web):2016/01/19
DOI:10.1039/C6DT00115G
We show that polyoxometalates (POMs) are an excellent redox-active acceptor on which to base high performance 2nd order non-linear optical (NLO) chromophores. This is demonstrated through three new organoimido-Lindqvist derivatives with HRS β0-values exceeding those of any dipolar organic system with comparable donor, π-system and absorption profile. Thus, organoimido POMs may provide a new generation of high performance, high transparency, and potentially redox-switchable NLO materials.
Co-reporter:Evelien De Meulenaere, Inge Asselberghs, Marc de Wergifosse, Edith Botek, Stijn Spaepen, Benoît Champagne, Jos Vanderleyden and Koen Clays
Journal of Materials Chemistry A 2009 - vol. 19(Issue 40) pp:NaN7519-7519
Publication Date(Web):2009/07/07
DOI:10.1039/B907789H
The second-order nonlinear optical properties of three fluorescent proteins (FPs) (green, EGFP; yellow, EYFP; and red, DsRed) have been experimentally determined by frequency-resolved femtosecond hyper-Rayleigh scattering. As expected, DsRed, with its lower-energy bandgap between ground and excited state, exhibits the largest intrinsic hyperpolarizability. The anomalously low first hyperpolarizability for the yellow variant has been rationalized in terms of the centrosymmetrical arrangement between the phenolic Tyr203 (Tyr = tyrosine) residue and the chromophoric Tyr66 moiety, leaving the small imidazolinone moiety as the only effective non-centrosymmetric chromophore for second-order nonlinear effects. The experimental findings are corroborated by high-level computational results and suggest molecular engineering strategies to produce a full rainbow of FPs with enhanced nonlinear optical properties.
Co-reporter:Kuo Zhong, Pieter-Jan Demeyer, Xingping Zhou, Olga Kruglova, Niels Verellen, Victor V. Moshchalkov, Kai Song and Koen Clays
Journal of Materials Chemistry A 2014 - vol. 2(Issue 41) pp:NaN8836-8836
Publication Date(Web):2014/07/04
DOI:10.1039/C4TC00912F
We demonstrate a facile method for introducing planar defects into colloidal photonic crystals. Firstly, a 2D monolayer of SiO2 microspheres (guest spheres) was fabricated at the air/water interface by compressing the individual microspheres with a surfactant into long-range hexagonal arrays. The floating monolayer, which served as our defect layer, was then transferred onto a pre-deposited colloidal crystal slab consisting of PS@SiO2 microspheres (host spheres). Subsequently, a second colloidal crystal slab of host spheres was deposited on the surface of the defect layer. In comparison to previous methods to introduce planar defects into colloidal photonic crystals, this fabrication results in pronounced passbands in the band gaps of the colloidal photonic crystals. More importantly, the FWHM of the passband in our experiment is just 16 nm, which is narrower than the previously reported results to the best of our knowledge. Furthermore, the defect modes can be engineered by changing the diameter of the guest spheres and/or transforming the host spheres from PS@SiO2 spheres to hollow SiO2 spheres by calcination. The measured defect modes in the spectra match well with the simulated results.
Co-reporter:Kuo Zhong, Mehran Khorshid, Jiaqi Li, Karen Markey, Patrick Hermann Wagner, Kai Song, Stijn Van Cleuvenbergen and Koen Clays
Journal of Materials Chemistry A 2016 - vol. 4(Issue 33) pp:NaN7858-7858
Publication Date(Web):2016/07/26
DOI:10.1039/C6TC02226J
An optomicrofluidic device was developed by introducing 3D wettability patterns into hollow SiO2 sphere colloidal photonic crystals. Aqueous liquids flow through the superhydrophilic channel due to the surface tension confinement effect. Based on the significant fluorescence enhancement from photonic band gap (PBG) effects in these channels, real-time specific bioassays with high sensitivity were realized. To demonstrate this strategy, with two complementary single stranded DNA molecules acting as a target (fluorophore labeled) and a probe respectively, a 150-fold enhancement of fluorescence was observed compared with a similar device on a standard glass plate. This enhancement results from the strong PBG effect in an aqueous environment for these structures. While the PBG effect diminishes from refractive index matching in conventional solid sphere colloidal photonic crystals with water infiltrated, it is effectively enhanced in hollow sphere colloidal photonic crystals. This is because the dense shell of the hollow spheres prevents water from infiltrating into the inner air cavity of the hollow spheres, while water fills the voids between spheres. This creates a larger refractive index contrast, resulting in a pronounced PBG effect and strong fluorescence enhancement.
Co-reporter:Evelien De Meulenaere, Wei-Qiang Chen, Stijn Van Cleuvenbergen, Mei-Ling Zheng, Sotiris Psilodimitrakopoulos, Rik Paesen, Jean-Marc Taymans, Marcel Ameloot, Jos Vanderleyden, Pablo Loza-Alvarez, Xuan-Ming Duan and Koen Clays
Chemical Science (2010-Present) 2012 - vol. 3(Issue 4) pp:NaN995-995
Publication Date(Web):2012/01/25
DOI:10.1039/C2SC00771A
A series of chromophores with enhanced second- and third-order nonlinear optical properties were engineered for use in combined second-harmonic and two-photon fluorescence microscopy. Electron-accepting moieties imparted nonlinear optical properties to the chromophores. The electron-rich carbazole core served as a template towards one- or two-dimensional chromophores. More efficient acceptor groups (pyridinium, benzazolium, benzothiazolium) on the carbazole donor core resulted in improved second- and third-order nonlinear optical properties. A selection of these chromophores was tested in a cellular environment with a multimodal multiphoton microscope. The structural differences of the chromophores resulted in high selectivity for mitochondria or the nucleus in two-photon fluorescence and ranging from no signal to high selectivity for mitochondria in the SHG channel.
![Silane, trimethyl[(5''-nitro[2,2':5',2''-terthiophen]-5-yl)ethynyl]-](http://img.cochemist.com/ccimg/862100/862074-73-5.png)
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![Silane, trimethyl[(5'-nitro[2,2'-bithiophen]-5-yl)ethynyl]-](http://img.cochemist.com/ccimg/862100/862074-69-9.png)
![Silane, trimethyl[(5'-nitro[2,2'-bithiophen]-5-yl)ethynyl]-](http://img.cochemist.com/ccimg/862100/862074-69-9_b.png)
![Pyridinium, 4-[(1E)-2-(4-methoxyphenyl)ethenyl]-1-methyl-, iodide](http://img.cochemist.com/ccimg/95500/95495-29-7.png)
![Pyridinium, 4-[(1E)-2-(4-methoxyphenyl)ethenyl]-1-methyl-, iodide](http://img.cochemist.com/ccimg/95500/95495-29-7_b.png)
![Dithieno[3,2-e:3',2'-e']benzo[1,2-b:4,3-b']bis[1]benzothiophene, 2-nitro-](http://img.cochemist.com/ccimg/507500/507471-84-3.png)
![Dithieno[3,2-e:3',2'-e']benzo[1,2-b:4,3-b']bis[1]benzothiophene, 2-nitro-](http://img.cochemist.com/ccimg/507500/507471-84-3_b.png)
![Dithieno[3,2-e:3',2'-e']benzo[1,2-b:4,3-b']bis[1]benzothiophene-2-carbo
xaldehyde](http://img.cochemist.com/ccimg/507500/507471-90-1.png)
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xaldehyde](http://img.cochemist.com/ccimg/507500/507471-90-1_b.png)
![Methylium, tris[4-(dimethylamino)phenyl]-, chloride](http://img.cochemist.com/ccimg/40200/40123-00-0.png)
![Methylium, tris[4-(dimethylamino)phenyl]-, chloride](http://img.cochemist.com/ccimg/40200/40123-00-0_b.png)
![DITHIENO[3,2-E:3',2'-E']BENZO[1,2-B:4,3-B']BIS[1]BENZOTHIOPHENE-2-CARBOXYLIC ACID](http://img.cochemist.com/ccimg/507500/507471-87-6.png)
![DITHIENO[3,2-E:3',2'-E']BENZO[1,2-B:4,3-B']BIS[1]BENZOTHIOPHENE-2-CARBOXYLIC ACID](http://img.cochemist.com/ccimg/507500/507471-87-6_b.png)
![DITHIENO[3,2-E:3',2'-E']BENZO[1,2-B:4,3-B']BIS[1]BENZOTHIOPHEN-2-AMINE](http://img.cochemist.com/ccimg/507500/507471-83-2.png)
![DITHIENO[3,2-E:3',2'-E']BENZO[1,2-B:4,3-B']BIS[1]BENZOTHIOPHEN-2-AMINE](http://img.cochemist.com/ccimg/507500/507471-83-2_b.png)
![Dithieno[3,2-e:3',2'-e']benzo[1,2-b:4,3-b']bis[1]benzothiophene](http://img.cochemist.com/ccimg/30700/30689-66-8.png)
![Dithieno[3,2-e:3',2'-e']benzo[1,2-b:4,3-b']bis[1]benzothiophene](http://img.cochemist.com/ccimg/30700/30689-66-8_b.png)
![Dinaphtho[2,1-d:1',2'-f][1,3]dioxepin, 9,14-dinitro-](http://img.cochemist.com/ccimg/191800/191721-47-8.png)
![Dinaphtho[2,1-d:1',2'-f][1,3]dioxepin, 9,14-dinitro-](http://img.cochemist.com/ccimg/191800/191721-47-8_b.png)
![PROPANEDINITRILE, [5-(DIMETHYLAMINO)-2,4-PENTADIENYLIDENE]-](http://img.cochemist.com/ccimg/40300/40252-60-6.png)
![PROPANEDINITRILE, [5-(DIMETHYLAMINO)-2,4-PENTADIENYLIDENE]-](http://img.cochemist.com/ccimg/40300/40252-60-6_b.png)
![BENZO[1,2-B:4,3-B']DITHIOPHENE, 2,2'-(1,2-ETHENEDIYL)BIS-](http://img.cochemist.com/ccimg/78300/78270-95-8.png)
![BENZO[1,2-B:4,3-B']DITHIOPHENE, 2,2'-(1,2-ETHENEDIYL)BIS-](http://img.cochemist.com/ccimg/78300/78270-95-8_b.png)
![DITHIENO[3,2-E:3',2'-E']BENZO[1,2-B:4,3-B']BIS[1]BENZOTHIOPHENE-2-CARBOXALDEHYDE, 13-HYDROXY-](http://img.cochemist.com/ccimg/507500/507471-89-8.png)
![DITHIENO[3,2-E:3',2'-E']BENZO[1,2-B:4,3-B']BIS[1]BENZOTHIOPHENE-2-CARBOXALDEHYDE, 13-HYDROXY-](http://img.cochemist.com/ccimg/507500/507471-89-8_b.png)
![Gold, [[4-[(4-nitrophenyl)ethynyl]phenyl]ethynyl](triphenylphosphine)-](http://img.cochemist.com/ccimg/185200/185119-04-4.png)
![Gold, [[4-[(4-nitrophenyl)ethynyl]phenyl]ethynyl](triphenylphosphine)-](http://img.cochemist.com/ccimg/185200/185119-04-4_b.png)
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![Benzaldehyde, 4-[[4-[bis(2-hydroxyethyl)amino]phenyl]azo]-](http://img.cochemist.com/ccimg/93800/93730-55-3.png)
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-](http://img.cochemist.com/ccimg/185200/185119-00-0.png)
-](http://img.cochemist.com/ccimg/185200/185119-00-0_b.png)
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