Ongoing projects

Experimental set-up for micro Raman and photoluminescence studies of individual one-dimensional Moiré crystals. 01/04/2021 - 31/03/2022

Abstract

Moiré crystals are the superstructures formed by the superposition of two periodic incommensurate lattices. In two dimensions, they exhibit peculiar quantum features ranging from Van Hove singularities and mini Dirac points to Hofstadter butterflies. The Moiré interactions may have even more fascinating properties in one-dimensional materials due to the quantum confinement and strong many-body interactions, but they are currently underexplored. In this project, we probe incommensurate double-walled carbon nanotubes as an ideal system for investigating Moiré physics in one-dimension. We will couple the widely wavelength-tunable laser set-up and microscope with the available spectroscopic instruments in the NANOrOPT research group to create a worldwide unique facility for wavelength-dependent high-resolution Raman and photoluminescence (PL) spectroscopy and microscopy on the same individual nanotubes. The micro Raman and PL studies will allow accessing fundamental physical properties of Moiré crystals, free of ensemble averaging effects in the highly polydisperse samples.

Researcher(s)

Research team(s)

TunabLe pulsed And continuouS-wavE laseR facility (T-LASER). 01/01/2020 - 31/12/2021

Abstract

T-LASER comprises the extension of a laser facility to a versatile wavelength-tunable pulsed and continuous-wave (CW) laser platform operating from the ultraviolet to the infrared range of the optical spectrum, for enabling a wide range of advanced spectroscopic techniques and laser-based applications – the key research capabilities of the ECM group. Thanks to a large fraction (78%) of co-funding, a laser platform will be built that is not only essential to all of ECM's ongoing research projects and its many collaborations, but actually establishes a world-wide unique laser facility. Moreover, this central laser platform will be complemented with a range of optical satellite setups that are already available (and already unique) and will be further developed. The versatility of the laser facility, both in pulse duration and wavelength tunability, will enable unprecedented optical experiments, such as widely continuously tunable resonance Raman scattering, and nonlinear optical scattering such as widely wavelength-tunable (second- and third-order) hyper-Rayleigh and hyper-Raman scattering. This will form a highly complementary set of unique techniques, making UAntwerp an extremely desirable partner for research groups active in the involved technologies, worldwide.

Researcher(s)

Research team(s)

Structure-specific competitive surfactant interactions with carbon nanotubes: a hyperspectral route to their separation by diameter and chiral structure. 01/10/2019 - 30/09/2023

Abstract

This is a fundamental research project financed by the research council of the University of Antwerp through a DOCPRO4 BOF research grant. The project was funded after selection by the research council. The objective of this Research project is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Chirality-defined sorting and optical characterization of double-wall carbon nanotubes. 01/10/2019 - 30/09/2022

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Hyperspectral imaging of the endo- and exohedral interactions of molecules with single-wall carbon nanotubes. 01/10/2019 - 30/09/2021

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Electrical and physical characterization of trap states at the SiC/gate dielectric interface in SiC metal-oxide-semiconductor field-effect transistors. 01/04/2019 - 31/03/2023

Abstract

This is a research project financed by the Vlaio agency for innovation and entrepreneurship (VLAIO - Vlaanderen). The project was subsidized after selection by the expert panel. The project is conducting in collaboration with Flemish Industry.

Researcher(s)

Research team(s)

Nonlinear Optics of Bistable Molecules and One-Dimensional Arrays. 01/01/2018 - 31/12/2021

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Functional Carbon Nanotube Nanohybrids: from Synthesis to Advanced Spectroscopic Characterization 01/01/2018 - 31/12/2021

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Carbon nanomaterial enhanced optical fibres for biomedical imaging and sensing (CHARMING). 01/01/2018 - 31/12/2021

Abstract

Optical fibres are very well-known for their application in telecommunications. In the last decades, they have also become increasingly popular in biomedical applications, where they are used as very sensitive sensors to detect minute amounts of biological cells or as flexible light sources enabling in-vivo microscopy of biological tissue, and as such allow for early diagnosis of medical conditions. At the same time, new so-called 'nanocarbon' materials with very particular characteristics have emerged, i.e. graphene and carbon nanotubes. The former is made of a sheet-like single layer of carbon atoms, whilst the latter consists of nanoscale hollow tubes rolled-up from the same carbon sheet. They both feature unique mechanical, electrical and optical properties. CHARMING's objective is to exploit these exceptional properties and to supplement them with the proven cutting-edge potential of optical fibrebased sensors and imaging systems to produce a novel class of devices for detecting and visualizing cancer cells with unprecedented sensitivity. More specifically, CHARMING will research into nanocarbon equipped optical fibres enabling the detection of down to 10 cancer cells as well as imaging of proteins in a tumorous environment with a 10-fold better sensitivity compared to current systems. By delivering this technology, CHARMING aims to contribute to the advent of advanced fibre-based tools empowering early in-vivo cancer diagnosis.

Researcher(s)

Research team(s)

Functional Hybrids of Carbon Nanotubes 01/10/2017 - 30/09/2022

Abstract

New functional hybrids of diverse molecules encapsulated within single-walled carbon nanotubes will be designed, synthesized and investigated by a combination of high-resolution optical spectroscopy and microscopy.

Researcher(s)

Research team(s)

Diameter-dependent phase transitions in one-dimensional arrays of molecules confined inside single-wall carbon nanotubes. 01/10/2017 - 30/09/2021

Abstract

This is a fundamental research project financed by the research council of the University of Antwerp through a DOCPRO4 BOF research grant. The project was funded after selection by the research council. The objective of this Research project is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Order in one dimension: Functional hybrids of chiralitysorted carbon nanotubes (ORDERin1D). 01/05/2016 - 31/10/2021

Abstract

The hollow structure of carbon nanotubes (CNTs) with a wide range of diameters forms an ideal host system to study restricted diameter-dependent molecular transport and to achieve unique molecular order in one dimension. This project finances fundamental research in the framework of an ERC starting grant, under horizon 2020.

Researcher(s)

Research team(s)

Past projects

Spectroscopic identification of defects in materials for perovskite-based hybrid solar cells. 01/10/2018 - 30/09/2020

Abstract

Organometal trihalide perovskite solar cells have in the few years since their first introduction (in 2009) demonstrated very high power conversion efficiencies, up to 21% with potential for further increase. It is announced to become a game changer in the field of thin film photovoltaics, but this will critically depend on avoiding defect formation in the perovskite layer as well as at the interfaces with adjacent layers. The defects act as trapping centers for negative and positive charge carriers and as such impede the carriers to contribute to the photocurrent. The defects may result from the material synthesis and device fabrication methods, but they can also appear due to degradation, thereby reducing the useful lifetime of the solar cells. The main goal of my project is the identification and characterization of the defects that set a limitation to the solar cell performance. To learn about the geometric and electronic structure of these defects I will apply multi-frequency electron paramagnetic resonance (EPR) techniques which are able to reveal the nature of the defects and of their surroundings. Knowledge of the electronic structure and creation processes of the defects will allow to design better perovskite materials for these solar cells and to optimize the device fabrication process.

Researcher(s)

Research team(s)

Hyperspectral imaging of the endo- and exohedral interactions of molecules with single-wall carbon nanotubes. 01/10/2017 - 30/09/2019

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Spectroscopic identification of defects in materials for perovskitebased hybrid solar cells. 01/10/2016 - 30/09/2018

Abstract

Organometal trihalide perovskite solar cells have in the few years since their first introduction (in 2009) demonstrated very high power conversion efficiencies, up to 21% with potential for further increase. It is announced to become a game changer in the field of thin film photovoltaics, but this will critically depend on avoiding defect formation in the perovskite layer as well as at the interfaces with adjacent layers. The defects act as trapping centers for negative and positive charge carriers and as such impede the carriers to contribute to the photocurrent. The defects may result from the material synthesis and device fabrication methods, but they can also appear due to degradation, thereby reducing the useful lifetime of the solar cells. The main goal of my project is the identification and characterization of the defects that set a limitation to the solar cell performance. To learn about the geometric and electronic structure of these defects I will apply multi-frequency electron paramagnetic resonance (EPR) techniques which are able to reveal the nature of the defects and of their surroundings. Knowledge of the electronic structure and creation processes of the defects will allow to design better perovskite materials for these solar cells and to optimize the device fabrication process.

Researcher(s)

Research team(s)

Advanced in situ optical spectroscopy to unravel the separation of carbon nanotubes by diameter and chiral structure. 01/01/2016 - 31/12/2018

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Spectroscopic identification of charge carriers and defects in materials for perovskite-based hybrid solar cells. 01/10/2015 - 30/09/2016

Abstract

Organometal trihalide perovskite solar cells have in the few years since their first introduction (in 2009) demonstrated very high power conversion efficiencies, up to 18% with potential for further increase. It is announced to become a game changer in the field of thin film photovoltaics, but this will critically depend on avoiding defect formation in the perovskite layer as well as at the interfaces with adjacent layers. The defects act as trapping centers for negative and positive charge carriers and as such impede the carriers to contribute to the photocurrent. The defects may result from the material synthesis and device fabrication methods, but they can also increasingly appear due to degradation, thus reducing the useful lifetime of the solar cells. The main goal of my project is the identification of the defects that either set an initial limitation to the solar cell performance or else cause degradation of the solar cell during operation. To learn about the geometric and electronic structure of these defects I will apply multi-frequency electron paramagnetic resonance (EPR) techniques which are able to reveal the nature of the defects. Knowledge of the electronic structure and creation processes of the defects will allow designing better perovskite materials for these solar cells and to optimize the device fabrication.

Researcher(s)

Research team(s)

Fullerene-free solution-processed bulk heterojunction organic photovoltaics. 01/01/2015 - 31/12/2018

Abstract

The general objective of this project is to improve organic solar cell performance on the basis of a more detailed fundamental understanding of the underlying properties and processes - such as electronic structure, charge transfer and transport, loss processes and bulk heterojunction blend morphology development - taking advantage of chemical engineering of non-fullerene electron acceptor materials (with all their possible advantages and hurdles to overcome).

Researcher(s)

Research team(s)

Synthesis, chirality sorting and advanced spectroscopy of functional nanohybrids of organic molecules inside carbon nanotubes. 01/10/2014 - 30/09/2017

Abstract

This is a fundamental research project financed by the Research Foundation – Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. The objective of the FWO's Research projects is to advance fundamental scientific research.

Researcher(s)

Research team(s)

Correlation between structural and magnetic properties in chemically disordered FePt thin films 15/07/2014 - 30/04/2015

Abstract

The main objective of this project is to understand the correlation between the magnetic configuration of chemically disordered FePt thin films and the structural properties. The domain structure of FePt films depends strongly on the out of plane anisotropy (Kperp), film thickness, exchange constant and the saturation magnetization (Ms). Below a critical thickness (depending on the growing conditions) planar magnetic domains are found, while for larger thickness a stripe‐like magnetic structure forms. In order to obtain a phase diagram in critical thickness vs. the quality factor Q= Kperp/2Ms**2, we have grown a series of fifteen samples varying the film thickness and the Ar pressure in the sputtering chamber from 5 to 9 mTorr. By this procedure it is possible to maintain an almost constant crystalline texture, but relaxing the in‐plane stress. Previous measurements showed that stress is the predominant contribution in the perpendicular anisotropy. With an AFM‐MFM microscope, we have observed the transition from a striped pattern to in‐plane magnetic domains and we have also combined the image information with dc magnetization and ferromagnetic resonance (FMR) measurements at different microwave frequencies. We have already characterized the dynamical properties of FePt films in a limited set of samples obtaining the damping parameter from FMR linewidths as a function of excitation frequency. Extending these measurements to the new set of samples will allow us to examine a dependence of damping with the fabrication conditions. FMR measurements at high frequencies (W‐band, f=95GHz) are extremely useful for the precise determination of the damping parameter.

Researcher(s)

Research team(s)

Pioneering work in the field of processing, purification, separation, and spectroscopic characterization of carbon nanotubes and nanofunctional hybrids. 13/11/2013 - 31/12/2014

Abstract

This project represents a research contract awarded by the University of Antwerp. The supervisor provides the Antwerp University research mentioned in the title of the project under the conditions stipulated by the university.

Researcher(s)

Research team(s)

Nanochemistry of molecular materials for 2-photon functional applications (Nano2Fun). 01/09/2013 - 31/08/2017

Abstract

Technological development through research and knowledge transfer are the flag-words of Nano2Fun, a multidisciplinary project that will bring the techniques of two-photon microscopy (2PM) and two-photon polymerization (2PP) to their full maturity, allowing their exploitation in commercially and industrially relevant applications.

Researcher(s)

Research team(s)

Fully Automated Frequency Agile Characterisation of Organic Nonlinear Optical Materials 01/01/2013 - 31/12/2016

Abstract

Organic molecular materials can exhibit remarkably strong nonlinear optical (NLO) responses which are promising for photonic applications such as ultrafast electro-optic modulators and frequency converters. Most experimental work on their haracterisation and subsequent optimisation is generally limited to one or a few laser wavelengths. Yet, recent measurements on prototypical systems using our unique setup for precise and widely wavelength-tuneable incoherent second-harmonic light scattering (hyper-Rayleigh scattering, HRS) have revealed a far more complex NLO dispersion than generally assumed, implying that the almost universally applied extrapolations to the static limit (for comparison among different compounds or with theory) and to technologically relevant frequency components of the NLO response, are often off by an order of magnitude and more. Based on much more extensive wavelength dependent measurements practical yet accurate models for the NLO dispersion will be developed. To this end, we propose to lift these techniques to a new level and drastically improve the throughput of the setup, by upgrading the laser source to a fully automatically tuneable optical parametric amplifier (OPA), and integrating it with software for automatic calibration and data processing. This will allow for detailed and reliable laser-wavelength dependent NLO characterisation by hyper-Rayleigh as well as hyper-Raman scattering to be performed routinely for a wide range of systems, providing us with a solid basis for the rational design of optimised NLO materials.

Researcher(s)

Research team(s)

Static and Dynamic Investigation of Large Second-Order Optical Nonlinearity Induced by Spontaneous Symmetry Breaking. 01/01/2013 - 31/12/2015

Abstract

This is a groundbreaking fundamental research project financed by the Fund for Scientific Research of Flanders, Belgium (FWO). The project was subsidized after selection by the competent FWO-expert panel.

Researcher(s)

Research team(s)

Imaging and advanced spectroscopy of individual carbon nanotubes by IR fluorescence microscopy. 01/01/2013 - 31/12/2015

Abstract

This is a fundamental research project financed by the Research Foundation - Flanders (FWO). The project was subsidized after selection by the FWO-expert panel. It involves the advanced spectroscopy of individual carbon nanotubes with IR fluorescence microscopy.

Researcher(s)

Research team(s)

Separation, sorting and enhanced optical properties of intact carbon nanotubes and their composites. 01/01/2012 - 31/12/2015

Abstract

Carbon nanotubes (CNTs) exhibit unique and remarkably diverse electronic, optical and mechanical properties, implying potential applications ranging from ultrastrong composite materials to organic solar cells, organic light emitting diodes (O-LEDs), thin-film transistors, biomolecular sensors, nano-electro-mechanical devices (NEMS) and nanofluidic systems. This diversity in properties is at the same time a major challenge in the study and applications of CNTs, as synthesis methods produce a mixture of structures, and their virtual insolubility has long hindered their processing and purification. However, important breakthroughs have been made in our lab in the processing (by solubilization using natural bile salt surfactants), spectroscopic characterization (thanks to the high resolution achieved on the individualized, surfactant coated CNTs), and purification of CNTs (by density gradient ultracentrifugation [DGU] of the solubilized tubes). E.g., we recently demonstrated that empty (intact, end-capped) and water-filled (opened) CNTs coexist in aqueous solution, that these can be separated by DGU, and that the former posses far more ideal, unperturbed properties than the commonly used (unwittingly) water-filled tubes. All this opens a wide range of high-impact research opportunities. The empty (and full-length) CNTs allow for an enhanced further sorting according to diameter, electronic type (metallic and semiconducting), chirality, and even handedness, through density gradient ultracentrifugation. Further development of these separation/preparation methods will be combined with advanced optical spectroscopic techniques, for which our lab is particularly well equipped, to study the enhanced properties of these newly isolated intact CNTs, and their composites with organic functional molecules and polymers.

Researcher(s)

Research team(s)

High throughput, high performance second order light scattering spectroscopy. 01/01/2012 - 31/12/2015

Abstract

This project concerns the study of nonlineair optical response of molecules in the liquid phase, through incoherent second order light scattering using a widely wavelength tuneable picosecond amplified laser source.

Researcher(s)

Research team(s)

Development of a set-up for single-molecule spectroscopy and imaging of individual carbon nanotubes 01/01/2012 - 31/12/2012

Abstract

Our state-of-the-art wavelength-dependent fluorescence excitation setup (previously used for bulk spectroscopy) will be adapted to study single-walled carbon nanotubes at the single molecule level, through the purchase of a high numerical aperture oil-immersion objective and an xyz-translation stage. Using a SiCCD camera, the nanotube dynamics and the filling-dynamics can be imaged and studied by optical spectroscopy.

Researcher(s)

Research team(s)

Nonlinear optical properties of single-wall carbon nanotubes and organic nanohybrids: enhancement through double resonance, coherent addition and symmetry breaking. 01/10/2011 - 30/09/2014

Abstract

Organic nonlinear optics (NLO) deals with the nonlinear response of organic molecular materials exposed to intense light beams, with prospective applications in optical telecommunication based on ultrafast switches and modulators, and highly efficient frequency convertors. In this research project, novel approaches will be examined to significantly amplify the molecular NLO response, in particular: (i) doubly (one- and twophoton) resonant enhancement, (ii) coherent addition of contributions from multiple molecular units and (iii) symmetry-breaking in formally centrosymmetric yet bistable molecules. To this aim, the NLO response of different molecular systems will be directly determined through ultrasensitive wavelength-dependent hyper-Rayleigh scattering (HRS) experiments in the appropriate wavelength ranges, using the setup I developed recently and which is unique in terms of both sensitivity and spectral tuneability. Measurements will be performed on well-designed organic molecules, as well as on single-wall carbon nanotubes (SWNTs), both empty and filled with efficient NLO chromophores. For the empty SWNTs, not only the second-order NLO response, but also the third-order response will be characterised by HRS at the tripled frequency. Finally, low-symmetry radial vibrational modes, never observed before but theoretically expected to be highly dependent on tube diameter and environmental interactions (e.g. filling), will be accessible by ultrasensitive (second- and third-order) hyper-Raman experiments.

Researcher(s)

Research team(s)

Advanced spectroscopy of empty and water-filled carbon nanotubes: Improved diameter sorting, exciton photophysics and one-dimensional molecular transport. 01/10/2011 - 30/09/2014

Abstract

Solubilization of single-walled carbon nanotubes (SWNTs) with bile salt surfactants allows for the sorting of the SWNTs by diameter using density gradient ultracentrifugation (DGU). Recent breakthroughs in the observation of water-filling and the sorting of empty and water-filled SWNTs will lift this sorting to a higher level, as the resolution in DGU is expected to increase drastically when using only empty and full-length SWNTs. These intact tubes possess superior optical properties, which is interesting for studying the very specific exciton photophysics of the nanotubes. The water-filling occurs even for very thin diameters, enabling the study of one-dimensional molecular transport inside the tubes and the different ordering and phase behavior of water (and other molecules) after confinement.

Researcher(s)

Research team(s)

Ultra-wide range wavelength dependent characterisation and modeling of organic nonlinear optical molecules. 01/01/2011 - 31/12/2013

Abstract

Recent measurements in our laboratory have shown that current models for the dispersion of the molecular nonlinear optical (NLO) response (hyperpolarisability ß), widely used in the interpretation of experimental data on organic/organometallic NLO molecules, fail at predicting the correct evolution with wavelength. This is very important to the fundamental understanding of the underlying physical mechanisms determining the NLO response, and hence also to be able to optimise the NLO molecules, and to derive the NLO response at technologically relevant frequencies ¿ and in the static limit, which is needed to compare with different molecules (showing different resonances) and with theoretical calculations. By implementing an improved detection scheme using a deep-depletion liquid nitrogen cooled CCD, and thereby significantly extending the wavelength range and sensitivity of our high performance setup for wavelength dependent hyper-Rayleigh scattering measurements (already unique in the world), we will be able to accurately measure the hyperpolarisability dispersion of representative model systems over an extremely wide wavelength range (fundamental wavelength ~400-2200nm), making optimal use of the available state-of-the-art picosecond amplified laser system. This will allow us to propose and accurately test refined models for the hyperpolarisability dispersion, properly accounting for vibronic coupling, and both homogeneous and inhomogeneous broadening effects, which play a quite different role in the NLO dispersion (unlike in linear optical properties).

Researcher(s)

Research team(s)

Separation and high-resolution spectroscopic characterisation of carbon nanotubes and nanocomposites. 01/01/2011 - 31/12/2011

Abstract

In order to fully exploit the exciting fundamental research opportunities created by the solubilisation/preparation techniques developed in the group, and making use of the available expertise in advanced spectroscopic research we aim at (1) Optimising the density gradient ultracentrifugation separation of different types of SWNTs by using pristine, full-length and empty SWNTs. This will involve the study of the subtle interactions of water and various surfactant molecules with the different types of SWNTs by high resolution Raman spectroscopy, in order to understand the separation mechanism and find the optimal conditions. It will of course also involve the spectroscopic characterization of the composition of the separated fractions. (2) Studying the obtained purified SWNTs using advanced optical techniques, which are not possible, or at least far less informative, for samples containing a mixture of SWNT types. This includes, for instance, ultrafast laser spectroscopy where individual types of SWNTs cannot be selectively excited in mixed samples. (3) Studying the interaction of SWNTs with other molecules in composites prepared from these separated SWNT types, which will again yield far more detailed information than current work involving mixtures of dozens of different SWNT types.

Researcher(s)

Research team(s)

Charge transfer in semiconducting polymer / CVD diamond heterostructures. 01/01/2010 - 31/12/2013

Abstract

The general objective of this project is the study of the formation and the characterisation of organic materials/diamond heterostructures. Besides the fundamental interest in investigating different aspects of this new class of material systems, such structures can play an important role in future photovoltaic applications, photoelectrochemistry, etc. The key issues of the project are the deposition of new conjugated polymers and short change organic molecules, tailored for attachment to differently terminated diamond surfaces, the physical and chemical bonding between these two materials, and the examination of the possible charge-transfer mechanisms that will occur.

Researcher(s)

Research team(s)

Optimisation and automation of hyper-Rayleigh scattering measurements. 01/01/2010 - 31/12/2011

Abstract

The current state-of-the-art setup for hyper-Rayleigh scattering measurements is optimised and automised, through the purchase of a computer-controlled spectrograph which can be combined with the available ultrasensitive camera. In this way, the wavelength-dependent nonlinear optical measurements planned within the framework of my personal FWO postdoctoral project, can be performed efficiently and precisely over a broader wavelength range.

Researcher(s)

Research team(s)

Inter-university Research Center for Multi-frequency pulsed Electron paramagnetic resonance spectroscopy. 19/12/2008 - 18/12/2013

Abstract

This project represents a research contract awarded by the University of Antwerp. The supervisor provides the Antwerp University research mentioned in the title of the project under the conditions stipulated by the university.

Researcher(s)

Research team(s)

Optical and laserspectroscopical research of organic and nanostructured materials for opto-electronic applications. 01/10/2008 - 30/09/2018

Abstract

Using advanced optical and laserspectroscopic techniques, the electronic and optical properties of carbon nanotubes (CNTs) and metal nanoparticles, as well as their organic nanohybrids, are investigated. This research aims both at the development of novel functional nanomaterials for opto-electronic applications, as well as at the development of reliable characterisation methods for these materials. In addition, organic and organometallic molecules are developed for nonlinear optics, and characterised in particular with our unique setup for wavelength dependent nonlinear optical measurements.

Researcher(s)

Research team(s)

One-photon light sources based on doped diamond nanocrystals. 01/10/2008 - 30/06/2013

Abstract

Nitrogen and silicon associated vacancy defects in diamond are incorporated inside diamond nanocrystals for the production of single-photon light sources with promising perspectives for use in quantum cryptography and quantum computing. The dependence on production method and size of the nanocrystals will be studied, as well as the influence of irradiation and thermal posttreatments, in order to determine the optimal preparation routes.

Researcher(s)

Research team(s)

Determination and modeling of the dispersion of the molecular first hyperpolarisability: octupolar etallodendrimers and carbon nanotubes. 01/10/2008 - 30/09/2011

Abstract

The aim of this research project is to examine the dispersion of the molecular first hyperpolarisability ß, in order to develop a proper ß dispersion model. By performing wavelength-dependent HRS measurements onto a number of well-chosen model systems, the current models can be tested and improved, and if necessary a new approach can be developed.

Researcher(s)

Research team(s)

Mass Transport through Carbon Nanotubes. 01/07/2008 - 31/12/2012

Abstract

Based on our recent breakthroughs in the opening/closing and water-filling of carbon nanotubes, the selective mass transport through individual types of carbon nanotubes will be characterised in view of possible applications in nanofluidics and nanofiltration.

Researcher(s)

Research team(s)

PolySpec - Nanostructured POLYmer phototvoltaic devices for efficient solar SPECtrum harvesting. 01/01/2008 - 31/12/2011

Abstract

The project aims at increasing the energy conversion efficiency of organic nanostructured bulk heterojunction photovoltaic devices as well as improving the stability of their nanomorphology. Progress on both fronts would allow envisaging outdoor large-scale application of these nanostructured PV-devices.

Researcher(s)

Research team(s)

Microscopic structure and transformation processes of impurity defects in bismuth oxides: relation with photorefractive and scintillator properties of these materials. (FWO Vis.Fel., Vera GOSPODINOVA, Bulgaria) 01/04/2007 - 31/03/2008

Abstract

In doped bismuth-oxide crystals we will investigate the structure of impurity defects, as well as their transformations under optical and thermal treatments. This will be achieved by a combination of optical and EPR methods. The project will lead to a better understanding of the origin of the technologically important properties of these materials, and to new opportunities for their optimization.

Researcher(s)

Research team(s)

Boron-related centers in diamond in the cross-over region from p- to n-type conductivity: an investigation by electron paramagnetic resonance spectroscopy 01/02/2007 - 30/11/2007

Abstract

In boron doped diamond, the microscopic structure of B-related defects with acceptor or donor character will be investigated. EPR and ENDOR techniques will be applied to determine the defect symmetry and the interactions with neighboring nuclei. Measurements in the X-, Q- and W-band (9.4 GHz, 35 GHz and 94 GHz, resp.), including pulse EPR, will be performed for higher spectral resolution and selectivity.

Researcher(s)

Research team(s)

Selective linear and nonlinear optical spectroscopy of carbon nanotubes and their interactions with organic molecules. 01/01/2007 - 31/12/2010

Abstract

Researcher(s)

Research team(s)

Interaction between conjugated molecules and single-walled carbon nanotubes. 01/01/2007 - 31/12/2008

Abstract

Carbon nanotubes (CNTs) are very interesting as one-dimensional systems with metallic or semiconducting properties. The conduction and mobility of holes and electrons can be described in the same way. It is also possible to dope these nanotubes by inserting small molecules in the CNTs. These doped CNTs are very stable by exposure to air and the choice of the inserted molecule controls the degree of doping. This project will deal with two different subjects. First we will study the charge transfer from the conjugated molecules to the SW CNTs. This charge transfer is of great importance for the use of such composites in plastic solar cells. Second, we will consider doping of the CNTs by inserting different conjugated molecules inside the CNTs. Both systems wil be studied by optical spectroscopy, pulsed laserspectroscopy and electron paramagnetic resonance (EPR).

Researcher(s)

Research team(s)

Solubilisation and purification of carbon nanotubes. 01/03/2006 - 31/12/2007

Abstract

Based on the recent discovery that bile salt surfactants are unusually efficient at solubilising individual single wall carbon nanotubes in water, and that the bile salt micelles form an unusually regular, unperturbing environment for the SWNTs, solubilisation and purification methods are developed. The goal is to produce individually isolated SWNTs in sufficient quantity and purity for spectroscopic research on liquid solutions and composites.

Researcher(s)

Research team(s)

Complex Spectroscopy of Defects Related to n-type Conductivity in Diamond: Microstructure and Kinetics. 01/01/2006 - 31/12/2007

Abstract

The goal of this project is to study the electronic properties, microstructure and migration of defects supplying efficient n-type conductivity in thin diamond layers, to investigate their migration and interaction with other defects under thermal and thermobaric treatments. We also include the study of n-type defects that are compensating the acceptors in electron irradiated boron-doped bulk diamond. Methods of optical (Raman scattering, photoluminescence, absorption), EPR (continuous-wave and pulse methods), and deep level transient spectroscopies will be used in conjunction with electrical measurements to characterize n-type defects in the samples synthesized in the NSC GPI team. The joint research of the teams from GPI and UA in the last few years concerning defects in diamond, offers a good basis for the successful realization of this project.

Researcher(s)

Research team(s)

Investigation of structure and dynamics of surfactant layers around carbon nanotubes by means of spin-probe and spin-label EPR methods. (FWO Vis. Fel., Jelena CULIN) 01/11/2005 - 31/10/2006

Abstract

The spin-probe and spin-label methods in EPR will be applied to investigate the structure and dynamics of the contact regions between carbon nanotubes (CNTs) and conjugated polymers. For this purpose, advantage will be taken from the very efficient solubilization by bile salt surfactants. The micelles formed around the CNTs will also be studied by the spin-probe method.

Researcher(s)

Research team(s)

Optical properties of nanostructured organic materials based on carbon nanotubes. 01/10/2005 - 30/09/2008

Abstract

The objectives of the study are: 1) To apply advanced optical techniques to the isolated CTN's in liquid and solid solution to get a better understanding of the electronic and optical properties of CNT's. 2) To develop a reliable characterization method using these optical techniques, for analyzing the composition of CNT materials. 3) To prepare composites of the individually dissolved CNT's with other molecules and polymers, and study the interactions occurring in these.

Researcher(s)

Research team(s)

Interaction between conjugated molecules and single-walled carbon nanotubes. 01/01/2005 - 31/12/2006

Abstract

Carbon nanotubes (CNTs) are very interesting as one-dimensional systems with metallic or semiconducting properties. The conduction and mobility of holes and electrons can be described in the same way. It is also possible to dope these nanotubes by inserting small molecules in the CNTs. These doped CNTs are very stable by exposure to air and the choice of the inserted molecule controls the degree of doping. This project will deal with two different subjects. First we will study the charge transfer from the conjugated molecules to the SW CNTs. This charge transfer is of great importance for the use of such composites in plastic solar cells. Second, we will consider doping of the CNTs by inserting different conjugated molecules inside the CNTs. Both systems wil be studied by optical spectroscopy, pulsed laserspectroscopy and electron paramagnetic resonance (EPR).

Researcher(s)

Research team(s)

Electronic structure, morphology and charge transfer in low-band gap polymers and polymer/carbon nanotubes hyrid films. 01/01/2004 - 31/12/2007

Abstract

De goal of this project is a fundamental investigation of a new class of conjugated polymers, called `low-bandgap polymers'. The essential targets can be summarized as follows: (1) Study of the electronic structure in low-bandgap polymers, in particular de band structure, the localized and excited states. To this end, further development of ultra-sensitive electro-optic characterization techniques, with the emphasis on photo-induced conductivity. (2) Investigation of transportmechanisms in these materials, such as the mobilities of the charge carriers and the factors by which they are determined. (3) Analysis of the mechanisms of charge carrier generation in these polymers and charge transfer in polymer mixtures and hybrid materials (polymer/fullerene or polymer/carbon nanotubes). (4) Study of the correlations between morfological and functional characteristics, which are partly determined by the forementioned properties.

Researcher(s)

Research team(s)

Characterization of high-spin transition metal compounds by means of sophisticated EPR-techniques at high microwave frequency. 01/01/2004 - 31/12/2005

Abstract

By means of high frequency (95GHz) EPR-techniques specific families of organo metallic compounds can be studied. These systems have a high groundstate spin and can behave as single molecule magnets. The key to such behaviour is the zero-field splitting of the energy levels (=splitting of the energy levels in the abscence of a magnetic field). These zero-field splittings can be precisely analyzed using high frequent EPR techniques.

Researcher(s)

Research team(s)

Nanosolar : Novel Nanostructured Hybrid Material Systems and Integration in Innovative Photovoltaic Concepts. 01/10/2003 - 30/11/2007

Abstract

The Nanosolar project aims to achieve a major step forward in the control of the morphology and functionality of organic based nanostructured hybrid material systems and their implementation in innovative photovoltaic devices. It is expected that resolving the issues encountered for photovoltaic devices will lead to a broad knowledge base, which encompasses fundamental insights in the relations between structure, morphology, and ultimate performance of nanostructured hybrid materials in electrical and electro-optical applications. To this end activities are planned to (1) develop new organic and polymeric materials enabling performant nanostructured hybrid materials, (2) study morphology, electronic structure, optical and electronic properties, electrical transport mechanisms and charge or energy transfer mechanisms of the hybrid materials obtained and (3) incorporate these materials in innovating photovoltaic concepts and explore additional generic valorisation possibilities. It is also within the objectives of the project to develop materials which are compatible with environmentally friendly solvents for processing and thin film technology, suitable for large-scale production.

Researcher(s)

Research team(s)

Systematic investigation of the mechanisms for efficient 3-photon absorption and fluorescence in organic molecules. 01/10/2003 - 30/09/2004

Abstract

Hyper-Rayleigh scattering measurements are being performed, using a picosecond amplified lasersystem with a new efficient setup with gated parallel detection. With this system it is possible to perform hyper-Rayleigh scattering measurements at a whole range of wavelengths, to determine the dispersion of the first hyperpolarisability of organic molecules. Thanks to the high sensitivity of the setup it is also possible to measure third-order hyper-Rayleigh scattering for the determination of the second hyperpolarisability of organic molecules. In addition, the non-linear optical processes 3-photon absorption and fluorescence (3PF) will be examined. Therefore instrumental developments are necessary, in order to determine the 3PF-efficiencies and their dependence on the excitation wavelength.

Researcher(s)

Research team(s)

Excitons and polarons in low bandgap polymers : optical generation and charge carrier separation. 01/10/2003 - 30/09/2004

Abstract

In this Ph.D-project research will be done on the characterisation of the properties of polymers with applications in plastic electronics, photovoltaic cells, organic light-emitting diodes and organic semi-conductors. In particular the characterisation of the photo-excited states (singlet and triplet states), the study of polarons and the study of the charge separation process, of vital importance in photovoltaics. The following techniques will be used; optical absorption and fluorescence spectroscopy, (L)EPR-spectroscopy ((Light induced) Electron Paramagnetic Resonance) and ODMR-spectroscopy (Optical Detected Magnetic Resonance) in X-band (~9.5GHz) as well as in W-band (~95GHz).

Researcher(s)

Research team(s)

Supramolecular Functional Systems: Interaction of Molecular Components with Microcrystalline Semiconductors. 01/01/2003 - 31/12/2004

Abstract

Recent imaging systems based on silver halide or AgX technology use combinations of spectral sensitisers (organic molecules) to increase the sensitivity. When two different sensitisers are brought together on one surface new processes occur. In order to further optimise the sensitivity more information about the interaction between the different molecules on the surface is needed. In this study the influence of the interaction on the electron hole processes will be studied by a number of optical and magnetic resonance techniques. The EPR-spectrum is a characteristic for the paramagnetic radicals that are formed during illumination of the sample. Differences in the energy levels caused by the interaction between the molecules will give rise to different optical absorption spectra and growth and decay kinetics of the radicals.

Researcher(s)

Research team(s)

Multi-wavelength nonlinear optical spectroscopy of organic materials. 01/10/2002 - 30/09/2005

Abstract

Organic and organometallic materials for non-linear optical (NLO) applications are investigated by non-linear and time-resolved laser spectroscopy. Molecular hyperpolarisabilities are determined, e.g. by hyper-Rayleigh scattering at variable laser wavelength with fluorescence correction through spectral analysis. Based on the experimental results, and in close collaboration with several synthesis groups, new NLO materials are developed. Also materials for two-photon absorption and two-photon induced fluorescence applications are developed.

Researcher(s)

Research team(s)

Structure determination of paramagnetic centers in solids and in molecular compounds by means of high frequency (95GHz) and pulsed EPR and ENDOR spectroscopy. 01/01/2002 - 31/12/2005

Abstract

In this project we wish to study by means of pulsed W?band EPR- and ENDOR-spectroscopy, the electronic structure of paramagnetic centers in a series of solids and molecular compounds which could not be previously investigated. W-band EPR is needed because of different reasons: insufficient resolution of the EPR-spectrum at lower frequencies, high zero-field splittings for which a minimal energy quantum is needed, or very small dimensions of the available single crystals for which a higher absolute sensitivity is a important. Pulsed or FT EPR yield information about the spin relaxation times, which is a first step to obtain selective measurements of EPR spectra via Elektronen-Spin-Echo-(ESE)-detection. An important part however is the precise determination of hyperfine interactions between the electrons and nuclei in the the center which can be obtained either by Electron Spin Echo Envelope Modulation (ESEEM) or by means of Pulsed ENDOR. (Implementation of pulsed W-band ENDOR has been submitted but not yet been accepted in this project).

Researcher(s)

Research team(s)

Modern EPR spectroscopy-methodology and applications in physics, chemistry and biology. (Conference project) 01/01/2002 - 31/12/2004

Abstract

Electron Paramagnetic Resonance (EPR) spectroscopy has witnessed during the last 15 years tremendous methodological and instrumental developments primarily in the directions of high field EPR and pulsed EPR. These include multi-frequency, multi- resonance and multi-dimensional experiments, analogous to the earlier developments in NMR spectroscopy. These advances increase considerably the information content extracted from EPR measurements and has therefore impacted various areas of chemistry, materials, physics and biology. The objectives of the school is to disseminate modern EPR methodology to the scientific community through its young researchers. It will effectively expose young scientists to the newest developments in EPR spectroscopy along with novel research applications, and it will give them the theoretical tools essential for the comprehension of the various techniques.

Researcher(s)

Research team(s)

Characterization of high-spin transition metal compounds by means of sophisticated EPR-techniques at high microwave frequency. 01/01/2002 - 31/12/2003

Abstract

By means of high frequency (95GHz) EPR-techniques specific families of organo metallic compounds can be studied. These systems have a high groundstate spin and can behave as single molecule magnets. The key to such behaviour is the zero-field splitting of the energy levels (=splitting of the energy levels in the abscence of a magnetic field). These zero-field splittings can be precisely analyzed using high frequent EPR techniques.

Researcher(s)

Research team(s)

Nonlinear light scattering and multiphoton absorption in molecular optical materials. 01/01/2001 - 31/12/2006

Abstract

The 2nd and 3rd order nonlinear optical (NLO) properties of organic and organometallic compounds will be investigated by means of advanced spectroscopic techniques, in particular elastic and inelastic nonlinear light scattering 'hyper-Rayleigh (at the 2nd and 3rd harmonic) en hyper-Raman scattering' and also multiphoton absorption spectroscopy. To this end, a high-performance apparatus will be constructed based on a novel laser system with kilohertz repetition rate and a multi-channel detector for parallel measurement of the spectra.

Researcher(s)

Research team(s)

Defects in diamond-like materials of the B/C/N system. 11/12/2000 - 11/12/2003

Abstract

Diamond and cubic boron nitride (cBN), as materials with very similar structure, exhibit, remarkable structural and electronic properties. Due to their extreme hardness both materials are the choice superabrasives in machine tooling operations. As wide gap semiconductors, diamond and especially cBN are very promising materials, in the form of thin films, for a future generation of high- temperature, high-pressure and radiation-resistant fast microelectronic devices, optoelectronic applications and field effect devices. Despite the crucial influence of the lattice defects (intrinsic or impurity type) on the physical and materials related properties, the defect characterization of these materials, especially as crystalline films, has begun only recently to receive a more systematic attention. In addition, nowadays diamond and cBN can be both p- and n-type doped, but the current results are still very far from the expectation as concerns the carrier mobility, doping reproducibility and understanding how dopants are incorporated. This concerns specially the n-type diamond and p- type cBN. In addition the preparation of cBN in the form of thin films is still a technological endeavor. For electronic applications, even the hexagonal BN is a very wide gap interesting material of which the main properties are unknown.

Researcher(s)

Research team(s)

Laser spectroscopy of ultrafast relaxation and transport phenomena in complex material systems. 01/10/2000 - 30/09/2008

Abstract

Ultrafast and nonlinear laser spectroscopies are applied to the investigation of the properties of epitaxially grown semiconductor structures and of organic compounds for photonic applications. Also hybrid systems, consisting of organic films on semiconductor substrates, will be studied.

Researcher(s)

Research team(s)