Rare Earth Doping Research Articles

Enhanced stability of FA-based perovskite: Rare-earth metal compound EuBr2 doping

It is highly desirable to enhance the long-term stability of perovskite solar cells (PSCs) so that this class of photovoltaic cells can be effectively used for the commercialization purposes. In this contribution, attempts have been made to use the two-step sequential method to dope EuBr2 into FAMAPbI3 perovskite to promote the stability. It is shown that the device durability at 85 °C in air with RH of 20%–40% is improved substantially, and simultaneously the champion device efficiency of 23.04% is achieved. The enhancement in stability is attributed to two points: (i) EuBr2 doping effectively inhibits the decomposition and α–δ phase transition of perovskite under ambient environment, and (ii) EuBr2 aggregates in the oxidized format of Eu(BrO3)3 at perovskite grain boundaries and surface, hampering humidity erosion and mitigates degradation through coordination with H2O.

Lanthanide Doping into All-Inorganic Heterometallic Halide Layered Double Perovskite Nanocrystals for Multimodal Visible and Near-Infrared Emission.

The introduction of lanthanide ions (Ln3+) into all-inorganic lead-free halide perovskites has captured significant attention in optoelectronic applications. However, doping Ln3+ ions into heterometallic halide layered double perovskite (LDP) nanocrystals (NCs) and their associated doping mechanisms remain unexplored. Herein, we report the first colloidal synthesis of Ln3+ (Yb3+, Er3+)-doped LDP NCs utilizing a modified hot-injection method. The resulting NCs exhibit efficient near-infrared (NIR) photoluminescence in both NIR-I and NIR-II regions, achieved through energy transfer down-conversion mechanisms. Density functional theory calculations reveal that Ln3+ dopants preferentially occupy the Sb3+ cation positions, resulting in a disruption of local site symmetry of the LDP lattices. By leveraging sensitizations of intermediate energy levels, we delved into a series of Ln3+-doped Cs4M(II)Sb2Cl12 (M(II): Cd2+ or Mn2+) LDP NCs via co-doping strategies. Remarkably, we observe a brightening effect of the predark states of Er3+ dopant in the Er3+-doped Cs4M(II)Sb2Cl12 LDP NCs owing to the Mn component acting as an intermediate energy bridge. This study not only advances our understanding of energy transfer mechanisms in doped NCs but also propels all-inorganic LDP NCs for a wider range of optoelectronic applications.

From fundamental materials chemistry to sensing applications: Unravelling the water adsorption mechanism of a luminescent optical fibre sensor membrane

This work provides insight into the correlation between the luminescent response of a water-vapour optical fibre sensor and the textural properties of its lanthanide-doped silica coating. To this end, a library of 16 silica xerogels derived from combinations between 2 lanthanide dopants (EuIII, TbIII) and 8 antenna ligands was synthesised and characterised by photoluminescence spectroscopy and N2 and CO2 adsorption-desorption isotherms, among others. Based on the best luminescent response and most-suited porous texture, the material doped with TbIII and 2,2′-(4-(2-Ethoxyethoxy)pyridine-2,6-diyl)bis(4,5-dihydrooxazole) was selected to construct the probe. A film of this material was affixed to a commercial silica fibre by dip-coating and the resulting sensor was tested in a climatic chamber with relative humidity ranging from 20 to 90% to obtain normalised time-response and calibration curves at three temperatures. The response was linear up to certain water-vapour concentrations, beyond which abruptly changed to polynomial, acting against the sensor resolution. The adsorption mechanism was elucidated by comparing the isosteric enthalpies of adsorption calculated from the sensor calibration curves to those determined from the monolith water-vapour isotherms, revealing that capillary condensation in the membrane mesopores was the key phenomenon leading to the response deviating from linearity.

Planar triangular lattice of the LuMgGaO4: Clustered site-occupancy and the upconversion luminescence of the co-doped Er,Yb ions

The ordered and stable structure of inorganic lattice is the basis of constructing high-efficiency rare earth activated fluorescence, solid-state laser or other optical materials. The mixed sensitized and activated rare earth ions usually keeps a uniform space-occupying and the energy transfer depends much on the doping concentration, while the aggregation of rare earth dopants in order is rare. In this work, a series of LuMgGaO4 phosphors were synthesized and the detail lattice parameters are analyzed through Vietveld refinement and the new CIF file is provided. The site-occupancy of Er3+, Yb3+ shows clustered features and the Er–Yb sublattice structure with various Yb/Er ratios were constructed on the basis of planar triangular lattice. The long-distance excitation energy migration to lattice or defects can be effectively inhibited in case of the hexagonal circle Er-6Yb sublattice, in which the most intense green/red UCL was obtained. All the results demonstrate the novelty of regulating ordered site-occupancy of rare earth ions on a compact planar triangular lattice with higher efficiency of energy migration, which will pave a way for developing phosphor-converted materials or laser materials with better performance.

‘Out of the glovebox’ studies of a multifunctional [Gd3+‐Ho3+‐Dy3+]:CsPbI2.7Br0.3 perovskite semiconductor system for energy applications

AbstractBACKGROUNDThis work deciphers the first report on the treble lanthanide‐doped perovskite heterosystem [Gd3+‐Ho3+‐Dy3+]:CsPbI2.7Br0.3 (GHD:C‐PVSK) and subsequently explores its prospects for solar cells, energy generation, and charge storage.RESULTSGHD:C‐PVSK remained optically active for a period of 28 days with a band gap energy of 1.62–1.76 eV. The developed perovskite material possesses cubic phase with typical ABX3 geometry and the subsequently deposited thin films have compact morphology. As a light absorber layer, a GHD:C‐PVSK‐based solution‐processed perovskite solar cell executed an efficiency of 15.11% and an improved fill factor of 71.25%. In electrocatalytic assays, GHD:C‐PVSK emerged as a bifunctional catalyst for oxygen and hydrogen generation with greater tendency towards pure hydrogen production, exuding overpotential (ηHER) – that is, 143 mV and 123.4 mV dec−1 of the Tafel slope value. With a remarkable service life of 100 min inside the electrolyte, the GHD:C‐PVSK electrode was characterized by its excellent charge storage. It has a unit capacity of 383 mA h g−1 and is marked by reduced equivalent series resistance (Rs) of 0.66 Ω.CONCLUSIONThrough photoelectrical and electrical analysis, GHD:C‐PVSK has emerged as a sustainable and energy‐efficient material that can be stabilized by suitable thermal modulation and lanthanide doping. © 2024 Society of Chemical Industry (SCI).

Five near-infrared-emissive graphene quantum dots for multiplex bioimaging

Due to high tissue penetration depth and low autofluorescence backgrounds, near-infrared (NIR) fluorescence imaging has recently become an advantageous diagnostic technique used in a variety of fields. However, most of the NIR fluorophores do not have therapeutic delivery capabilities, exhibit low photostabilities, and raise toxicity concerns. To address these issues, we developed and tested five types of biocompatible graphene quantum dots (GQDs) exhibiting spectrally-separated fluorescence in the NIR range of 928–1053 nm with NIR excitation. Their optical properties in the NIR are attributed to either rare-earth metal dopants (Ho-NGQDs, Yb-NGQDs, Nd-NGQDs) or defect-states (nitrogen doped GQDS (NGQDs), reduced graphene oxides) as verified by Hartree-Fock calculations. Moderate up to 1.34% quantum yields of these GQDs are well-compensated by their remarkable >4 h photostability. At the biocompatible concentrations of up to 0.5–2 mg ml−1 GQDs successfully internalize into HEK-293 cells and enable in vitro imaging in the visible and NIR. Tested all together in HEK-293 cells five GQD types enable simultaneous multiplex imaging in the NIR-I and NIR-II shown for the first time in this work for GQD platforms. Substantial photostability, spectrally-separated NIR emission, and high biocompatibility of five GQD types developed here suggest their promising potential in multianalyte testing and multiwavelength bioimaging of combination therapies.

Dye-augmented bandgap engineering of a degradable cascade nanoreactor for tumor immune microenvironment-enhanced dynamic phototherapy of breast cancer

Non-invasive precision tumor dynamic phototherapy has broad application prospects. Traditional semiconductor materials have low photocatalytic activity and low reactive oxygen species (ROS) production rate due to their wide band gap, resulting in unsatisfactory phototherapy efficacy for tumor treatment. Employing the dye-sensitization mechanism can significantly enhance the catalytic activity of the materials. We develop a multifunctional nanoplatform (BZP) by leveraging the benefits of bismuth-based semiconductor nanomaterials. BZP possesses robust ROS generation and remarkable near-infrared photothermal conversion capabilities for improving tumor immune microenvironment and achieving superior phototherapy sensitization. BZP produces highly cytotoxic ROS species via the photocatalytic process and cascade reaction, amplifying the photocatalytic therapy effect. Moreover, the simultaneous photothermal effect during the photocatalytic process facilitates the improvement of therapeutic efficacy. Additionally, BZP-mediated phototherapy can trigger the programmed death of tumor cells, stimulate dendritic cell maturation and T cell activation, modulate the tumor immune microenvironment, and augment the therapeutic effect. Hence, this study demonstrates a promising research paradigm for tumor immune microenvironment-improved phototherapy. Statement of significanceThrough the utilization of dye sensitization and rare earth doping techniques, we have successfully developed a biodegradable bismuth-based semiconductor nanocatalyst (BZP). Upon optical excitation, the near-infrared dye incorporated within BZP promptly generates free electrons, which, under the influence of the Fermi energy level, undergo transfer to BiF3 within BZP, thereby facilitating the effective separation of electron–hole pairs and augmenting the catalytic capability for reactive oxygen species (ROS) generation. Furthermore, a cascade reaction mechanism generates highly cytotoxic ROS, which synergistically depletes intracellular glutathione, thereby intensifying oxidative stress. Ultimately, this dual activation strategy, combining oxidative and thermal damage, holds significant potential for tumor immunotherapy.

Energy storage mechanism and refinement engineering of SiO2-B2O3-Nb2O5 complex glass-ceramic doped with La2O3

Rare earth doping has demonstrated promising potential in improving material properties. This paper explored the influence mechanism of La2O3 on SiO2-B2O3-Nb2O5 (SBN) system energy storage glass-ceramic. The results reveal a significant impact of La2O3 doping on the physical properties, microstructure, and energy storage performance. Firstly, we observed the influences on the breakdown field strength through its effect on the grain size, density, and conductivity. The larger radius of La3+ triggers lattice vibrations, leading to a reduction in grain size and an increase in density. Moreover, the electronic shielding effect of the 4f layer reduces conductivity, which subsequently enhances the breakdown resistance. The dielectric constant exhibits improvements due to La2O3 doping. Increased crystallinity and polarization strength, along with the f-f transition of La3+ and reduced domain area, result in a peak dielectric constant at L4. Consequently, the energy storage performance is enhanced.

An investigation into RESZ (RE = Yb, Er, Gd, Sm) materials for CMAS resistance in thermal barrier coatings

The effects of rare earth dopants on the CMAS resistance of zirconia thermal barrier coating materials were systematically investigated using ceramic pellets and CMAS. Yb, Er, Gd and Sm elements were assessed as stabilising agents of zirconia at increasing concentrations for CMAS reactions at 1300 °C across timeframes of 1 to 60-minutes. Two distinct microstructures of the ceramic pellet –CMAS reaction layer were observed then characterised as a dense layer microstructure and a non-dense layer microstructure. The presence of each microstructure was dependent on the RE ionic radius and concentration. The thickness of the reaction layer and overall volume of precipitated reaction products increased with increasing RE ionic radius. Therefore, an optimal RE element would exhibit dense layer forming microstructure with the lowest overall infiltration depth. CMAS loading volume significantly impacted the rate of reaction product precipitation. The volume of apatite precipitate was inversely proportional to the CMAS loading quantity.

Effects of rare earth oxide additions on the corrosion resistance of TiC-based cermets

TiC-based cermets have inadequate corrosion resistance despite wide use in high-performance applications. Rare earth dopants like Nd2O3 and Yb2O3 aim to improve cermet properties, but their impacts on corrosion are unclear. This work prepared 0.7 wt% Nd2O3- and Yb2O3-doped TiC cermets via vacuum sintering. Experimental results revealed that Nd2O3 doping enhances corrosion resistance by promoting α-FeOOH in corrosion products, while Yb2O3 doping has little effect. First-principles calculations confirmed that Nd promotes α-FeOOH formation. By elucidating contrasting dopant impacts on corrosion, this study provides new insights to guide optimization of rare earth-containing cermet compositions for superior corrosion resistance.

X-ray excited optical luminescence from lanthanide ions in double phosphate and double silicate crystalline hosts

X-ray Excited Optical Luminescence (XEOL) from rare earth doped whitlockite phosphates and silicate garnets [Ca9La(PO4)7 and Ca9Lu(PO4)7, doped with 1 mol% Ce3+; Ca3Sc2Si3O12, doped with 0.5 mol% Pr3+, 1 mol% Eu3+ and 1 mol% Tb3+], was obtained upon X-ray excitation with a tunable synchrotron light source. Excitation at photon energies across the M5,4-edge of the dopants reveals additional information not normally obtainable with conventional UV/visible or an X-ray line source (Al Kα). It is found that despite the low concentration, photoluminescence yields excited with photon energy at the M5,4-edge of the rare-earth dopant can positively and negatively affect the overall energy transfer to the optical center. The implication of these observations is discussed. The application of XEOL in the investigation of X-ray scintillators is illustrated.

Cu- and Ce-doped MnCo2O4 spinel coatings on ferrite interconnects by electrophoretic deposition

MnCo2O4 spinel coating is considered as one of the most promising protective coatings on the surface of ferritic stainless steel interconnects in solid oxide fuel cells (SOFCs). And the doping of metallic elements and active rare earth elements may further improve the electrical conductivity and antioxidant properties of spinel coatings. In this work we firstly prepare the Cu-doped and Ce-doped MnCo2O4 spinel coatings (abbreviated as MCCu, MCCe) on the surface of SUS430 substrate by Sol-Gel and electrophoretic deposition methods. The optimal doped ratio of Cu and Ce based on the results of oxidized mass gain and area-specific resistance (ASR) tests are determined respectively. Then we deposit Cu-Ce co-doped MnCo2O4 spinel coatings (abbreviated as MCCuCe) accordingly. The successful deposition of the target modified spinel coating on the substrate surface is confirmed using SEM-EDS, XRD, XPS characterization. The performance test results of the MCCuCe coating on the SUS430 surface show that the mass gain after 500 h oxidation at 800 °C in air is 1.3564 × 10−3 mg cm−2, and the ASR at 800 °C after 500 h oxidation is 9.80mΩ cm2, which is much lower than those of the bare SUS430 substrate and the substrate with deposited MnCo2O4 spinel coating. And the MCCuCe protective coating plays a better role in preventing the diffusion of Cr from the substrate. Further analysis prove that the doping Cu mainly contributes to the electrical conductivity and adhesion to the substrate while the doping Ce mainly improve the anti-oxidation and Cr diffusion resistance. This work determines the optimal doped ratio of Cu and Ce and provides a simple way to prepare the Cu-Ce co-doped MnCo2O4 spinel coatings on the ferritic interconnects, which effectively improve comprehensive performances of MnCo2O4 spinel coatings and helps to accelerate the industrial application of SUS430 ferrite in the SOFCs.

Utilization of Aloe vera-infused Sm3+ doped La2MoO6 nanophosphors: Their role in anti-counterfeiting, white LEDs and transport properties

In the realm of anti-counterfeiting (AC) measures, the focus has increasingly turned towards fluorescent inks, appreciated for their practicality and environmentally friendly nature. However, their susceptibility to wear and vulnerability to moisture damage has hindered their widespread application. Additionally, most available fluorescent inks are single-colored, toxic, and skin-irritating, making them ill-suited for real-world use. In light of these challenges, this article delves into the impact of introducing Sm3+ ions into the La2MoO6 host lattice. The green solution combustion method is employed to synthesis 1–11 mol % Sm3+ doped La2MoO6:Sm3+ nanophosphors (LMO:Sm3+ (1–11 mol %) NPs. The effects of rare earth doping are examined through X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, and photoluminescence (PL) analysis. The PL spectra reveal four emission bands, with a prominent 603 nm wavelength band emitting an orange-red hue attributed to the electronic transition of Sm3+ ions. Notably, the impact of Sm3+ ion doping on the phosphor’s luminescence spectra is prominently featured. The optimal concentration is found to be 5 mol % (LMO:5Sm3+), with concentration quenching primarily attributed to exchange-type interactions. The luminescent properties are evidenced by Commission Internationale de l’éclairage (CIE) color coordinates (0.6063, 0.3901), color purity (CP = 99.10 %), and correlated color temperature (CCT = 1383 K). Furthermore, the study delves into optical parameters such as energy band gap and refractive index, revealing values of 2.313 and 2.252 eV, respectively, for the optimal molar concentration. These findings hold promise in the development of AC inks suitable for screen-printing and writing on a variety of surfaces. The resultant patterns exhibit vivid orange-red fluorescence under UV 365 nm irradiation, showcasing potential applications in encryption, security marking, and optical authentication.

High photoresponse detectors based on Yb-doped monolayer WS2 nanosheets

The study of rare-earth (RE) doping in two-dimensional (2D) transition metal dichalcogenides (TMDCs) has become an important research focus to modulate bandgaps and carriers for production of the exotic properties. Herein, approximately 7 at% of Yb substitutionally doped monolayer WS2 nanosheets are prepared by in-situ chemical vapor deposition (CVD) technique. Highly enhanced optical and electrical properties are obtained: Three times enhancement in photoluminescent intensities and 5.6 nm of red-shifts in wavelength are observed from their peaks after chemical doping. First-principles calculations based on density functional theory (DFT) demonstrate a shrinked bandgap of Yb-doped monolayer WS2 at K-point in Brillouin zone compared with that of the pristine WS2 monolayer, and a broadened absorption and reflectivity spectra from visible to near-infrared region, which is in good agreement with the experimental results. Photodetectors based on Yb-doped monolayer WS2 nanosheets show far higher of mobility (17 times), photocurrent, photoresponsivity, and external quantum efficiency than those of the pristine WS2. The results prove a high effectiveness of RE doping in 2D materials for high-performance optoelectronic devices.

Solid-state quantum nodes based on color centers and rare-earth ions coupled with fiber Fabry–Pérot microcavities

High-performance optical quantum memories serving as quantum nodes are crucial for the distribution of remote entanglement and the construction of large-scale quantum networks. Notably, quantum systems based on single emitters can achieve deterministic spin-photon entanglement, greatly simplifying the difficulty of constructing quantum network nodes. Among them, optically interfaced spins embedded in solid-state systems, as atomic-like emitters, are important candidate systems for implementing long-lived quantum memory due to their stable physical properties and robustness to decoherence in scalable and compact hardware. To enhance the light-matter-interaction strength, optical microcavities can be exploited as an important tool to generate high-quality spin-photon entanglement for scalable quantum networks. They can enhance the photon collection probability and photon generation rate of specific optical transitions and improve the coherence and spectral purity of emitted photons. For solid-state systems, open Fabry-Pérot cavities can couple single emitters that are not in proximity to the surface, avoiding significant spectral diffusion induced by the interfaces while maintaining the wide tunability, whichenables addressing of multiple single emitters in the frequency and spatial domain within a single device. This review describes the characteristics of single emitters as quantum memories with a comparison to atomic ensembles, the cavity-enhancement effect for single emitters and the advantages of different cavities, especially fiber Fabry-Pérot microcavities. Finally, recent experimental progress on solid-state single emitters coupled with fiber Fabry-Pérot microcavities is reviewed, with a focus on color centers in diamond and silicon carbide, as well as rare-earth dopants.

Role of 4f electrons and 3d-4f hybridization in metal-insulator transition in RE (La, Nd, Sm, Eu, Dy and Er)-doped vanadium dioxide for thermochromic applications

Vanadium dioxide is a promising thermochromic material for novel applications to smart optoelectronic devices due to its reversible insulator-to-metal transition which is accompanied by rapid variation in its optical properties. In this work, rare-earth (La, Nd, Sm, Eu, Dy and Er) dopants substituting vanadium site were investigated in detail to control the phase transition temperature (TMIT) and optical properties of VO2. It is found that TMIT is mainly related to the nature of 3d-4f hybridization in RE-doped VO2(M1): the direct overlapping of 3d-4f orbitals contributes to V–V dimerization, but it is less pronounced to lower TMIT; the indirect 3d-4f interaction via O-2p makes 4f electrons itinerant to egπ states to assist MIT from M1 to R phase at lower temperatures. The dominating nature of 3d-4f hybridization varies with changing RE dopant's ionic radius and electronegativity. Er offered the lowest TMIT with a decreasing rate of 12.8 °C/at. % due to effective 4f-O2p-3d hybridization. RE dopants were also found effective in changing optical properties by scaling Eg1 and Eg2 bandgaps of VO2. Hence, the fashion of 3d-4f interaction in RE-doped VO2 is found to play important role in modulating thermochromic properties of VO2 for smart window applications and smart optoelectronics devices.

Molten Salt Synthesized CaTa4O11:Er3+/Yb3+ with Superior Upconversion Luminescence.

Low phonon tantalate-based phosphors with a layer structure are considered to have excellent upconversion luminescence (UCL) intensity, which could be reduced due to the existence of impure phase defects and inappropriate doped rare earth ions. To improve their UCL performance, we have prepared single-phase CaTa4O11:Er3+/Yb3+ samples by a molten salt synthesis (MSS) using KCl as the reaction medium and compared its UCL properties with counterparts made by a conventional solid-state reaction (SSR) in this study. We have demonstrated that the MSS samples have a much higher UCL intensity under 980 nm laser excitation than the SSR ones due to accurate replacement of Ca2+ sites by Er3+/Yb3+ in high-purity single-phase MSS samples. We have further enhanced the green UCL intensity of the MSS samples by 1.57 times via acid picking (AP). Under 980 nm laser excitation at a high powder density of 61.3 W/cm2, the green UCL intensity of the MSS-AP samples can reach 3.72 times that of the SSR-AP samples. For potential luminescence thermometry applications, the maximum absolute sensitivity (SA) of the MSS-AP samples reaches 0.01316 K-1 at 501 K based on the luminescence intensity ratio. This study shows that CaTa4O11:Er3+/Yb3+ phosphors prepared by the MSS method are single-phase samples with excellent pure green UCL as a suitable temperature sensing material.

Enhanced photocatalytic activity of Er doped ZnO nanospindles and nanorods for degradation of organic pollutants

Rare earth doping in ZnO is an efficient way to improve the photocatalytic performance. In the present work, Er doped ZnO nanospindles and nanorods were prepared through a simple cost effective wet chemical approach and were thoroughly characterized by FESEM, XRD, Raman spectroscopy, UV–vis-DRS, UV–vis absorption and PL spectroscopy. Nanospindle and nanorod-like morphologies of the fabricated samples were revealed by FESEM. XRD analyses revealed hexagonal wurtzite structure of Er doped ZnO nanostructures and confirmed Er doping into ZnO. PL studies showed increased defect concentration in ZnO nanostructures doped with Er ions. The photodegradation ability of nanostructures was investigated using cationic and anionic dyes and photodecomposition rate of 0.042 min−1 was achieved for MB decolorization using 0.5 % Er doped ZnO sample upon 32 min of solar light illumination. The probable photodecomposition mechanism supported by in-situ radical trapping experiments and repeatability test have also been discussed and results suggest that Er doped ZnO photocatalyst exhibit potential for use as commercial solar-active photocatalysts.

Tripling magnetite's thermoelectric figure of merit with rare earth doping

Using density functional theory (DFT) and machine-learning force fields, we calculated the thermoelectric properties of magnetite doped with four rare-earth elements: lanthanum, cerium, praseodymium, and neodymium.

Inducing hollow and porous hematite nanorod photoanodes by rare earth and transition metal doping for enhanced solar water splitting

A hollow and porous Eu,Nb : Fe2O3 nanorod photoanode was fabricated by hybrid microwave annealing (HMA) induced conversion of shell Eu- and core Nb-doped FeOOH nanorods, simultaneously enhancing photocurrent density and reducing turn-on voltage.