Andries Meijerink

Utrecht University | UU · Department of Chemistry

Narrower band red and green emission in phosphor‐converted white light‐emitting diodes (wLEDs) can improve the efficacy and color gamut in lighting and display applications. A promising luminescent ion is Mn2+ that can have both narrowband green (tetrahedral coordination) and red (octahedral coordination) emission. Unlike in earlier lighting applic...

Lanthanide-doped (nano)crystals are an important class of materials in luminescence thermometry. The working mechanism of these thermometers is diverse but most often relies on variation of the ratio of emission intensities from two thermally coupled excited states with temperature. At low temperatures, nonradiative coupling between the states can...

Often the reactor or the reaction medium temperature is reported in the field of heterogeneous catalysis, even though it could vary significantly from the reactive catalyst temperature. The influence of the catalyst temperature on the catalytic performance and vice versa is therefore not always accurately known. We here apply EuOCl as both solid ca...

Temperature determines the reaction kinetics, thermodynamics and catalyst stability. However, very limited information is known about the local catalyst temperature. Here, operando thermometry over bifunctional Eu³⁺ is performed to study the interplay between reaction conditions and the catalyst temperature dynamics in the exothermic methane oxychl...

Blue absorbing near infrared (NIR) emitting phosphors are a promising class of materials for phosphor converted NIR LEDs, which can be used in compact NIR spectrometers. Preferably, these phosphors have a broad emission spectrum and show negligible luminescence quenching at LED operating temperatures (100 °C). Here, we investigated ASc(Si1-xGex)2O6...

The growth of two-dimensional platelets of the CdX family (X = S, Se, or Te) in an organic solvent requires the presence of both long- and short-chain ligands. This results in nanoplatelets of atomically precise thickness and long-chain ligand-stabilized Cd top and bottom surfaces. The platelets show a bright and spectrally pure luminescence. Despi...

Apart from the energy gap law, control parameters over nonradiative transitions are so far only scarcely regarded. In this work, the impact of both covalence of the lanthanoid–ligand bond and varying bond distance on the magnitude of the intrinsic nonradiative decay rate between the excited 6P5/2 and 6P7/2 spin–orbit levels of Gd3+ is investigated...

Materials with temperature-dependent luminescence can be used as local thermometers when incorporated in, for example, a biological environment or chemical reactor. Researchers have continuously developed new materials aiming for the highest sensitivity of luminescence to temperature. Although the comparison of luminescent materials based on their...

Cation exchange enables the preparation of nanocrystals (NCs), which are not reachable by direct synthesis methods. In this work, we applied Pb²⁺-for-Cd²⁺ cation exchange on CdSe nanoplatelets (NPLs) to prepare two-dimensional CdSe-PbSe heterostructures and PbSe NPLs. Lowering the reaction temperature slowed down the rate of cation exchange, making...

Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4fn energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution. Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzma...

Many phosphor materials rely on energy transfer (ET) between optically active dopant ions. Typically, a donor species absorbs light of one color and transfers the energy to an acceptor species that emits light of a different color. For many applications, it is beneficial, or even crucial, that the phosphor is of nanocrystalline nature. Much unlike...

Eu2+-activated phosphors of the UCr4C4 structure type have emerged as promising new (ultra-)narrow band phosphors. Especially the UCr4C4-type alkali lithosilicates have caused a sensation in the field of phosphor research in the recent years due to their consistent (ultra)narrow-band luminescence in the cyan and green range that can pave the way to...

The performance of scintillator materials and phosphors for x-ray imaging is adversely affected by afterglow, giving rise to ghost images and thus compromising image quality. Here, the afterglow of the well-known computed tomography (CT) phosphor Gd2O2S:Pr is investigated with time-delayed afterglow spectroscopy. It is shown that these afterglow sp...

The luminescence efficiency of Ce3+ in garnet phosphors is among the most stable for luminescent materials. Still, it has been observed to be reduced at high incident blue flux (known as droop) due to nonlinear processes caused by the high lumen density inside the materials. Herein, it is shown that in the case of Ce3+‐doped garnet concentrator rod...

Commercial lighting for ambient and display applications is mostly based on blue light-emitting diodes (LEDs) combined with phosphor materials that convert some of the blue light into green, yellow, orange, and red. Not many phosphor materials can offer stable output under high incident light intensities for thousands of operating hours. Even the m...

Scintillators based on Ce-doped garnets are regularly co-doped with Mg²⁺ or Ca²⁺ to form Ce ions in 4+ state and reduce undesired afterglow. However overly high Ce⁴⁺ concentration leads to poor light yield performance. In order to understand the reason for variation in luminescence efficiency of Ce³⁺- and Ce⁴⁺-doped garnets we investigate the diffe...

The temperature-sensitive luminescence of nanoparticles enables their application as remote thermometers. The size of these nanothermometers makes them ideal to map temperatures with a high spatial resolution. However, high spatial resolution mapping of temperatures >373 K has remained challenging. Here, we realize nanothermometry with high spatial...

The covalent character of (oxy)nitrides has enabled tuning of emission color for new Eu²⁺- and Ce³⁺-doped phosphors and widespread implementation in white light LEDs. Mn²⁺-doped (oxy)nitrides form a relatively unexplored class of luminescent materials with great potential as orange to near infrared (NIR) phosphor in white light and NIR LEDs. Here w...

Recent technological developments require knowledge of temperature down to the micro- or even nano-scale. Lanthanide-doped nanoparticles became a popular tool to achieve this. Their temperature sensitive luminescence enables their application as remote thermometer and for mapping temperature profiles with high spatial resolution. Applicability of l...

With increasing interest in mixed‐anionic hydrides, a number of interesting properties have been reported. Here, the structural and optical properties of (Eu²⁺‐doped) MCaH3–MCaF3 (M = Rb, Cs) are investigated. For M = Rb, a complete hydride–fluoride solid solution series is found and for M = Cs, the known solid solution series (0 ≤ x ≤ 1.70) can be...

Down conversion of solar UV and blue light is one of the few ways of surpassing the Shockley-Queisser limit of solar cells. One of the most efficient down conversion systems is the Pr³⁺ - Yb³⁺ lanthanide pair. However, these ions do not provide any strong absorption for solar UV and blue light, thus require sensitizing. In this work, we report self...

Lanthanide-doped NaYF 4 nanoparticles are most frequently studied host materials for numerous biomedical applications. Although efficient upconversion can be obtained in fluoride nanomaterials and good homogeneity of size and morphology is achieved, they are not very predestined for extensive material optimization toward enhanced features and funct...

In some materials, the absorption of a single photon can trigger a chain reaction that produces a large burst of light. The discovery of these photon avalanches in nanostructures opens the way to imaging and sensing applications. Highly nonlinear photon emission from lanthanide-doped nanoparticles.

Lanthanide-based photon-cutting phosphors absorb high-energy photons and ‘cut’ them into multiple smaller excitation quanta. These quanta are subsequently emitted, resulting in photon-conversion efficiencies exceeding unity. The photon-cutting process relies on energy transfer between optically active lanthanide ions doped in the phosphor. However,...

Luminescence thermometry is used in a variety of research fields for noninvasive temperature sensing. Lanthanide‐doped micro‐/nanocrystals are exceptionally suitable for this. The popular concept of luminescence‐intensity‐ratio thermometry is based on emission from thermally coupled levels in a single lanthanide ion, following Boltzmann's law. Thes...

Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials, are a new type of support for grafting lanthanide ions (Ln3+), which can be employed as ratiometric luminescent thermometers. In this work we have shown that COFs co‐grafted with lanthanide ions (Eu3+, Tb3+) and Cu2+ (or potentially other d‐metals) can synchronou...

Luminescent materials enable warm white LEDs, molecular tagging, enhanced optoelectronics and can improve energy harvesting. With the recent development of multi-step processes like down- and upconversion and the difficulty in sensitizing these, it is clear that optimizing all properties simultaneously is not possible within a single material class...

Covalent organic frameworks co‐grafted with lanthanide and Cu²⁺ ions can simultaneously be employed as a catalyst and luminescence nanothermometer during a chemical reaction. The catalyst and thermometer can be tuned by changing the grafted d‐metal and solvent environment. Abstract Covalent Organic Frameworks (COFs), an emerging class of crystalli...

Luminescence (nano)thermometry is an increasingly important field for remote temperature sensing with high spatial resolution. Most typically, ratiometric sensing of the luminescence emission intensities of two thermally coupled emissive states based on a Boltzmann equilibrium is used to detect the local temperature. Dependent on the temperature ra...

Lanthanide‐doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability, and minimal invasive thermal sensing properties. Here, four unique hybrid organic–inorganic materials prepared by combining β‐NaGdF4 and PMOs (periodic mesoporous organosilica) or mSiO2 (mesoporo...

New anion combination: Borate hydride Sr5(BO3)3H and deuteride Sr5(11BO3)3D were prepared and studied using a number of characterization methods, including 1H solid‐state MAS NMR and vibrational spectroscopy together with quantum chemical calculations as well as X‐ray and neutron powder diffraction. Doped with Eu2+, broad‐band orange‐red emission u...

This article outlines the main results of a research and development cooperation between Philips Research Eindhoven; Peter the Great St. Petersburg Polytechnic University; Ioffe Institute, St. Petersburg; Utrecht University; and Philips Healthcare. It reviews the properties of garnet ceramics in the (Lu,Gd) <sub xmlns:mml="http://www.w3.org/1998/Ma...

Recent research on white light LED (w-LED) phosphors has focused on narrow-band green and red luminescent materials to improve the efficacy of w-LEDs and to widen the color gamut of w-LED-based displays. Mn2+ is a promising emitter capable of narrow-band emission, either green or red, depending on the local coordination. However, the extremely low...

The unprecedented borate hydride Sr 5 (BO 3 ) 3 H and Sr 5 (BO 3 ) 3 D crystallizing in an apatite‐related structure iare reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu 2+ , it shows broad‐band orange‐red emission under UV excitation due to the 4f 6 5d‐4f 7 transition of Eu 2+ . A number...

The efficient 4f⁶5d→4f⁷ (d-f) luminescence from Eu²⁺ is well-known for host lattices where Eu²⁺ is substituted on a divalent (e.g. Ca²⁺, Sr²⁺) or monovalent (e.g. Na⁺, K⁺) cation site. Only recently some studies appeared concerning d-f emission from Eu²⁺ on a trivalent cation site. The stable Eu²⁺ emission was observed in X-ray irradiated LuPO4:Eu³...

Nanoplatelets (NPLs) of CdSe are an emerging class of luminescent materials, combining tunable and narrow emission bands with high quantum yields. This is promising for application in white light LEDs (w-LEDs) and displays. The origin of the narrow spectral width of exciton emission in core NPL compared to core-shell NPL and quantum dot (QD) emissi...

Ratiometric luminescence thermometry employing luminescence within the biological transparency windows provides high potential for biothermal imaging. Nd3+ is a promising candidate for that purpose due to its intense radiative transitions within biological windows (BWs) I and II and the simultaneous efficient excitability within BW I. This makes Nd...

The efficiency of single-junction solar cells is limited to about 30% (the Shockley-Queisser limit). Spectral mismatch losses (transparency to low-energy photons, thermalization of high-energy photons) strongly contribute to lowering the maximum efficiency. To reduce thermalization losses, photon splitting is proposed and observed for a variety of...

Phosphors have been used successfully for both research and commercial applications for decades. Eu³⁺-doped materials are especially promising, because of their extremely stable, efficient, and narrow red emission lines. Although these emission properties are ideal for lighting applications, weak absorption in the blue spectral range has until now...

The relaxation pathways of states in the energy region of the fundamental absorption of NaMgF3:Yb²⁺ and MgF2:Yb²⁺ are investigated using time-resolved vacuum ultraviolet spectroscopy. For NaMgF3:Yb²⁺, excitation into intrinsic free exciton states or above the band gap results in emission features associated with self-trapped excitons and impurity-t...

The Eu2+ - doped mixed alkaline metal strontium borohydride chlorides ASr(BH4)3-xClx (A = K, Rb, Cs) as well as Eu2+ - doped strontium borohydride chloride Sr(BH4)2-xClx have been prepared by mechanochemical synthesis. Intense blue photoluminescence for Sr(BH4)2-xClx (λem= 457 nm) and cyan photoluminescence for the perovskite-type mixed alkaline me...

Light yield, time response, afterglow and thermoluminescence of Ce-doped garnet scintillators and persistent luminescent materials are controlled by a complex interplay between recombination and trapping/detrapping processes. Extensive research has contributed to a good qualitative understanding of how traps, impurities and the presence of Ce⁴⁺ aff...

In situ and operando experiments play a crucial role in understanding the mechanisms behind catalytic processes. In these experiments it is important to have precise control over pressure and temperature. In this work, we use luminescence thermometry to map the temperature distribution in a 300 µm microelectromechanical system nano‐reactor with a r...

Photoluminescence is a powerful tool in temperature sensing. Recently, the application of upconversion (UC) nanocrystal (NC) has shown great potential for nanothermometry due to high spatial resolution, superior accuracy, and non-invasive nature. In addition to spectral changes upon heating, anomalous thermal enhancement of UC emission has been rep...

A magnetic-field-dependent spectroscopy study on single perovskite nanocrystals reveals the spectral signatures of an exciton dark state below the bright triplet states.

In our study of the optical properties of Eu²⁺-doped alkaline-earth metal hydride chlorides AE7H12Cl2 (AE = Ca and Sr) we observe yellow (AE = Sr) and orange-red (AE = Ca) emission. Compared to the emission energies of Eu²⁺ -doped fluorides, chlorides and mixed fluoride chlorides, this corresponds to a wide redshift of the Eu²⁺ 4f⁶5d¹–4f⁷ emission....

The shift of the conduction band (CB) edge for thirty different (Lu,Gd) 3 (Ga,Al) 5 O 12 :Ce compositions, with simultaneous variation in Lu/Gd and Ga/Al content was studied using thermally stimulated luminescence (TSL). Specific TSL peaks were related to impurities of Ta, Cr, Yb, Ti and Eu in Lu 1 Gd 2 Ga 3 Al 2 O 12 :Ce ceramics. The shift of Yb-...

Temperature control for Lab-on-Chip devices has resulted in broad applicability of microfluidics in e.g. polymerase chain reaction (PCR), temperature gradient focusing for electrophoresis, and colloidal particle synthesis. However, currently temperature sensors on microfluidic chips either probe temperatures outside the channel (resistance temperat...

Afterglow is an important phenomenon in luminescent materials and can be desired (e.g. persistent phosphors) or undesired (e.g. scintillators). Understanding and predicting afterglow is often based on analysis of thermally stimulated luminescence (TSL) glow curves assuming the presence of one or more discrete trap states. Here we present a new appr...

Fiducial markers are used in correlated light and electron microscopy (CLEM) to enable accurate overlaying of fluorescence and electron microscopy images. Currently used fiducial markers, e.g. dye‐labelled nanoparticles and quantum dots, suffer from irreversible quenching of the luminescence after electron beam exposure. This limits their use in CL...

The unusual temperature dependence of exciton emission decay in CsPbX3 perovskite nanocrystals (NCs) attracts considerable attention. Upon cooling extremely short (sub-ns) lifetimes were observed and explained by an inverted bright-dark state splitting. Here we report temperature dependent exciton lifetimes for CsPbCl3 NCs doped with 0 to 41% Mn2+....

Luminescence (nano)thermometry is an important technique for remote temperature sensing. The recent development of lanthanide-doped nanoparticles with temperature-dependent emission has expanded the field of applications, especially for ratiometric methods relying on the temperature variation of relative emission intensities from thermally coupled...

Red-emitting Mn⁴⁺-doped fluorides are a promising class of materials to improve the color rendering and luminous efficacy of white light-emitting diodes (w-LEDs). For w-LEDs, the luminescence quenching temperature is very important, but surprisingly no systematic research has been conducted to understand the mechanism for thermal quenching in Mn⁴⁺-...

Ag29 nanoclusters capped with lipoic acid (LA) can be doped with Au. The doped clusters show enhanced stability and increased luminescence efficiency. We attribute the higher quantum yield to an increase in the rate of radiative decay. With mass spectrometry, the Au-doped clusters were found to consist predominantly of Au1Ag28(LA)12³⁻. The clusters...

X-ray induced effects in LuPO4:Eu³⁺ sintered thermoluminescent material were investigated by absorption and photoluminescence measurements between 20 and 300 K. Evidence for Eu³⁺→Eu²⁺ conversion upon exposure to X-rays was obtained as narrow band blue Eu²⁺ photoluminescence was observed. The low temperature luminescence of Eu²⁺ ions in X-rayed LuPO...

Y2O3 codoped with Bi3+ and Yb3+ is considered as an efficient downconversion material combining strong broadband absorption of Bi3+ with photon splitting by cooperative energy transfer from Bi3+ to two Yb3+ neighbors. However, evidence for photon splitting is lacking. Here we investigate the Bi3+−to−Yb3+ energy-transfer mechanism. For cooperative e...

Luminescent nanoparticles have great potential for remote temperature sensing. Mapping of high temperature profiles under harsh conditions that are common in chemical reactors requires new thermally and chemically stable (nano)probes. Here, we report temperature dependent luminescence of Yb³⁺/Er³⁺-, Dy³⁺- and Eu³⁺-doped Y2O3 nanoparticles (NPs). We...

In this work, gold nanoparticles coated with a fluorescently labelled (rhodamine B) silica shell are presented as fiducial markers for correlative light and electron microscopy (CLEM). The synthesis of the particles is optimized to obtain homogeneous, spherical core-shell particles of arbitrary size. Next, particles labelled with different fluoroph...

Broad band near infrared (NIR) light sources are currently of great interest in many application areas, especially in near infrared spectroscopy (NIRS). Due to the declining availability of incandescent and halogen light sources, there is a strong demand for other efficient broad band NIR light sources. NIR phosphor converted (pc) LEDs are presentl...

Supramolecular systems have applications in areas as diverse as materials science, biochemistry, analytical chemistry, and nanomedicine. However, analyzing such systems can be challenging due to the wide range of time scales, binding strengths, distances, and concentrations at which non-covalent phenomena take place. Due to their versatility and se...

The main losses in solar cells result from the incomplete utilization of the solar spectrum. Via the addition of an upconverting layer to the rear side of a solar cell, the otherwise-unused sub-bandgap photons can be utilized. In this paper, we demonstrate an efficiency enhancement of a silicon solar cell under real sunlight due to upcon- version o...

Doping nanocrystals (NCs) with luminescent activators provides additional color tunability for these highly efficient luminescent materials. In CsPbCl3 perovskite NCs the exciton-to-activator energy transfer (ET) has been observed to be less efficient than in II-VI semiconductor NCs. Here we investigate the evolution of the exciton-to-Mn2+ ET effic...

Phosphate hosts doped with luminescent ions are widely applied for efficient spectral conversion in light emitting devices. However, in Xe discharge lamps a rapid degradation of light output is observed indicating a decrease in the efficiency of conversion of the VUV output of the Xe discharge. This work aims at providing a better understanding of...

Broad band near-infrared (NIR) light sources have great potential, e.g., in optical communication and non-invasive medical imaging. Here we report the optical properties of X3Sc2Ga3O12 (X = Lu, Y, Gd, La) garnets doped with Cr³⁺ showing efficient ⁴T2 → ⁴A2 broad band NIR emission between 600 and 1000 nm. The chromium-doped garnets were investigated...