A5034596939- Organic Electronics and Photovoltaics
- Mass Spectrometry Techniques and Applications
- Photochemistry and Electron Transfer Studies
- Molecular Junctions and Nanostructures
- Terahertz technology and applications
- Porphyrin and Phthalocyanine Chemistry
- Organic Light-Emitting Diodes Research
- Photonic and Optical Devices
- Forensic Fingerprint Detection Methods
- Isotope Analysis in Ecology
- Analytical chemistry methods development
- Conducting polymers and applications
- Analytical Chemistry and Sensors
- Spectroscopy and Quantum Chemical Studies
- Photonic Crystals and Applications
- Mechanical and Optical Resonators
- Molecular Sensors and Ion Detection
- Electrochemical Analysis and Applications
- Luminescence and Fluorescent Materials
- Advanced Fluorescence Microscopy Techniques
- Energetic Materials and Combustion
- Semiconductor Quantum Structures and Devices
- Radioactive contamination and transfer
- Advanced Chemical Sensor Technologies
- Silicon Nanostructures and Photoluminescence
Netherlands Forensic Institute
2009-2020
Institute for Atomic and Molecular Physics
2005-2008
Leiden University
2004-2007
Imperial College London
2003-2005
University of Manchester
2004
National Academy of Sciences of Ukraine
2004
University of Amsterdam
1996-2003
Utrecht University
2001
Delft University of Technology
2001
UNSW Sydney
1996-2001
We study electron mobilities in nanoporous and single-crystal titanium dioxide with terahertz time domain spectroscopy. This ultrafast technique allows the determination of mobility after carrier thermalization lattice but before equilibration defect trapping states. The reported here for rutile (1 cm2/(V s)) porous TiO2 (10(-2) therefore represent upper limits transport at room temperature defect-free materials. large difference between bulk samples is explained using Maxwell-Garnett...
This paper describes the strategy toward novel monodisperse, well-defined, star-shaped oligofluorenes with a central truxene core and from monofluorene to quaterfluorene arms. Introduction of solubilizing n-hexyl groups at both fluorene moieties results in highly soluble, intrinsically two-dimensional nanosized macromolecules T1-T4. The radius for largest oligomer ca. 3.9 nm represents one known conjugated systems. Cyclic voltammetry experiments reveal reversible or quasi-reversible...
Abstract We present a careful study of the effects photo‐oxidation on emissive properties poly(9,9‐dioctylfluorene) (PFO) that addresses important issues raised by recent flurry publications concerning degradation blue light‐emitting, fluorene‐based homo‐ and copolymers. The photoluminescence (PL) spectra thin PFO films oxidized at room temperature comprise two major components, namely vibronically structured band green, structureless component, referred to hereafter as ‘g‐band’. These are...
We independently determine the subpicosecond cooling rates for holes and electrons in CdSe quantum dots. Time-resolved luminescence terahertz spectroscopy reveal that rate of hole cooling, following photoexcitation dots, depends critically on electron excess energy. This constitutes first direct, quantitative measurement electron-to-hole energy transfer, hypothesis behind Auger mechanism proposed which is found to occur a $1\ifmmode\pm\else\textpm\fi{}0.15\text{ }\text{ }\mathrm{ps}$ time scale.
We compare the generation and decay dynamics of charges excitons in a model polymer semiconductor (MEH-PPV) solution drop-cast thin films, by recording sub-ps transient complex conductivity using $\mathrm{THz}$ time-domain spectroscopy. The results show that quantum efficiency charge is two orders magnitude smaller $(\ensuremath{\sim}{10}^{\ensuremath{-}5})$ than solid film $(\ensuremath{\sim}{10}^{\ensuremath{-}3})$. proximity neighboring chains films apparently facilitates (hot) exciton...
Two new, rigid donor−bridge−C60(acceptor) dyads are presented. In one system (C60[3]TMPD) a 3-σ-bond bridge separates the fullerene from powerful tetraalkyl-p-phenylenediamine donor; in other (C60[11]DMA) comprises an extended array of 11 bonds, while donor unit is dimethylaniline group. Photoexcitation 3-bond induces fast (kcs ≥ 1.6 × 1010 s-1) and virtually complete intramolecular charge separation, irrespective solvent polarity. It concluded that this separation occurs under nearly...
We employ optical pump-THz probe measurements to study the formation of excitons and electron-hole plasmas following photogeneration a hot gas in direct gap semiconductor zinc oxide. Below Mott density, we directly observe evolution plasma into an insulating exciton $10\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}100\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ photoexcitation. The temperature dependence this process reveals that rate determining step for involves acoustic phonon...
We investigate the effect of charge-charge interactions on carrier mobility in titanium dioxide $(\mathrm{Ti}{\mathrm{O}}_{2})$ and silicon (Si) using terahertz spectroscopy. Charge scattering times plasma frequencies are directly determined as a function charge density. In Si, linear increase rate for densities exceeding ${10}^{21}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{\ensuremath{-}3}$ is attributed to electron-hole scattering. contrast, $\mathrm{Ti}{\mathrm{O}}_{2}$, suppressed due...
Liquid Extraction Surface Analysis (LESA) is a new, high throughput tool for ambient mass spectrometry.
Terahertz transient conductivity measurements are performed on pentacene single crystals, which directly demonstrate a strong coupling of charge carriers to low frequency molecular motions with energies centered around 1.1 THz. We present evidence that the is factor limiting in these organic semiconductors. Our observations explain apparent paradox “bandlike” temperature dependence beyond validity limit band model.
The results of isotope ratio mass spectrometry (IRMS) on hexamethylene triperoxide diamine (HMTD) and its precursor hexamethylenetetramine (hexamine) is presented. HMTD was prepared from hexamine using several different sources under both controlled laboratory conditions in field experiments that represent the less are likely to be observed forensic casework scenarios. Precursor product carbon δ values consistently fit a linear relationship regardless or conditions. magnitude fractionation...
We study the ultrafast charge generation in a semiconducting polymer (MEH-PPV) by measuring radiated $\mathrm{THz}$ field after photoexciting biased with femtosecond visible pulse. The subpicosecond temporal characteristics of emitted wave reflects photoconductivity dynamics and sets an upper limit for $200\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ following photoexcitation, reveals dispersive nature transport MEH-PPV. A comparison fields from MEH-PPV well-characterized model semiconductor...
Abstract Studying links between triacetone triperoxide ( TATP ) samples from crime scenes and suspects can assist in criminal investigations. Isotope ratio mass spectrometry IRMS gas chromatography GC )‐ were used to measure the isotopic compositions of its precursors acetone hydrogen peroxide. In total, 31 synthesized with different raw material combinations reaction conditions. For carbon, a good differentiation linear relationship observed for acetone– combinations. The extent negative (δ...
In this follow-up study the collaboration between two research groups from USA and Netherlands was continued to expand framework of chemical attribution for homemade explosive erythritol tetranitrate (ETN). Isotope ratio mass spectrometry (IRMS) analysis performed predict possible links ETN samples its precursors. Carbon, nitrogen, hydrogen oxygen isotope ratios were determined a wide variety precursor sources that prepared with selected The stability has been demonstrated melt-cast two-year...
The behavior is reported of three fluorescent D−bridge−A systems that display a fascinating temperature dependence in glass forming solvents over the range between 77 and 293 K. In two these systems, rigid, saturated alkane bridge maintains an extended conformation, as result, charge-transfer (CT) state giant dipolar nature. This causes position CT fluorescence to be extremely sensitive probe for reorientation polarization surrounding medium. As thermochromism continuous maximum...
The rate of photoinduced charge separation is measured as a function solvent for four donor (D)−bridge−acceptor (A) systems: DMN[10]DCV, DMN[10nb]DCV, DMN[10cy]DCV, and DMAN[10cy]DCV. In the first three members this series, D/A pair kept constant contains strong dimethoxynaphthalene (DMN) which enables detection electron transfer over wide range polarity. fourth member, DMN substituted by dimethoxyanthracene (DMAN) unit, decreases driving force about 0.58 eV thereby limits occurrence to...
Terahertz time-domain spectroscopy has been used to study the dielectric relaxation of pure 4'-n-pentyl-4-cyanobiphenyl (5CB) liquid crystal (LC) and its mixtures with 10 µm SiO 2 particles in frequency range 0.2-2 THz.For sample, we find that spatial inhomogeneities consisting oriented domains, comparable size our probe area (∼1 mm ), cause a large scatter measured function, due varying contributions from ordinary extraordinary components.In LC/particle mixtures, ordering LC at surface...