NaGdF4:Dy3+ nanocrystals: new insights into optical properties and energy transfer processes

NaGdF4:Dy3+ nanocrystals (NCs) have been synthesized using a precipitation technique. The structural characteristics and morphology of the materials were analyzed using X-ray diffraction patterns and scanning electron microscopy images, respectively. The photoluminescence excitation spectra, emission spectra and decay curves of all samples were recorded at room temperature. The color feature of Dy3+ luminescence was estimated using CIE chromaticity coordinates and the correlated color temperature. The radiative properties of the Dy3+:4F9/2 level in the material were analyzed within the framework of JO theory. In NaGdF4:Dy3+ NCs, the energy transfer from Gd3+ to Dy3+ causes an enhancement in the luminescence of the Dy3+ ions. The rate of the processes taking part in the depopulation of Gd3+ ions was estimated. The energy transfer between Dy3+ ions leads to the luminescence quenching of NaGdF4:Dy3+. In this process, the dipole-dipole interaction, which is found by using the Inokuti-Hirayama model, is the dominant mechanism. The characteristic parameters of the energy transfer processes between Dy3+ ions have also been calculated in detail.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

A novel green emitting NaGdF4:Dy3+,Ho3+ phosphor with tunable photoluminescence

Dy³⁺,Ho³⁺ co-doped β-NaGdF₄ nanomaterials emitted different shades of green light, which varies from the light blue area towards the blue-green area and ultimately to the green area with the increase of Ho³⁺ ions.

A novel color-tunable phosphor, Na5Gd9F32:Ln3+ (Ln = Eu, Tb, Dy, Sm, Ho) sub-microcrystals: structure, luminescence and energy transfer properties

Ln3+-Doped fluorides are economical and highly efficient luminescent materials, which play a crucial role in LEDs, biolabeling, and sensors. Therefore, Na5Gd9F32:Ln3+ sub-microspheres with tunable multicolor emissions were successfully synthesized via a simple water bath method employing colloidal Gd(OH)CO3 spheres as precursors. Samples were characterized by XRD, SEM, TEM, EDS and PL. It was found that the hydrolysis of BF4- ions had a dynamic effect on the retention of the morphology of the product owing to the mild reaction environment caused by the low hydrolysis rate of BF4- ions. Upon excitation by ultraviolet light, the Na5Gd9F32:Ln3+ (Ln = Eu, Tb, Dy, Sm, Ho) phosphors underwent characteristic f-f transitions and gave rise to red, green, green, yellow, and pale green emissions, respectively. Moreover, various emission colors could be obtained by using different excitation wavelengths and adjusting the Eu3+/Tb3+ molar ratio owing to energy transfer between Tb3+ and Eu3+ ions in the Na5Gd9F32 host. The energy transfer mechanism was demonstrated to be a dipole-dipole interaction. The multicolor luminescent phosphors with a certain dopant concentration based on a single host and excitation wavelength may have potential applications in the field of lighting displays.

Peculiarly Structured Janus Nanofibers Display Synchronous and Tuned Trifunctionality of Enhanced Luminescence, Electrical Conduction, and Superparamagnetism

Flexible peculiarly structured [(Fe₃ O₄ /PVP)@(Tb(BA)₃ phen/PVP)]//[PANI/PVP] (PVP=polyvinylpyrrolidone, BA=benzoic acid, phen=1,10-phenanthroline, and PANI=polyaniline) Janus nanofibers synchronously endowed with tuned and enhanced luminescent-magnetic-electrical trifunctionality have been prepared by electrospinning technology by using a homemade coaxis//monoaxis spinneret. It is satisfactorily found that the luminescent intensity of the peculiarly structured Janus nanofibers is higher than those of the counterpart conventional [nanofiber]//[nanofiber] Janus nanofibers and composite nanofibers owing to its peculiar nanostructure. Compared with the counterpart conventional Janus nanofibers of two independent partitions, the coaxial nanocable is used as one side of the peculiarly structured Janus nanofiber instead of nanofiber, and three independent partitions are successfully realized in the peculiarly structured Janus nanofiber, thus the interferences among various functions are further reduced, leading to the fact that excellent multifunctionalities can be obtained. The Janus nanofibers possess excellent green luminescence, superparamagnetism, and electric conductivity, and further, these performances can be, respectively, tunable by modulating the Tb(BA)₃ phen, Fe₃ O₄ , and PANI contents. The design philosophy and construction technique for the peculiarly structured Janus nanofibers provide guidance for fabricating other multifunctional Janus nanofibers with various performances.

White light emitting MgAl2O4:Dy3+,Eu3+ nanophosphor for multifunctional applications

An efficient energy transfer from Dy³⁺ to Eu³⁺ in MgAl₂O₄ offers white light emission and self-referencing thermal behaviour.

A novel and facile approach to obtain NiO nanowire-in-nanotube structured nanofibers with enhanced photocatalysis

NiO nanowire-in-nanotube structured nanofibers were easily and directly fabricated via one-pot uniaxial electrospinning followed by calcination process for the first time. Firstly, Ni(CH₃COO)₂/PVP composite nanofibers were prepared by a conventional electrospinning method, and then NiO nanowire-in-nanotube structured nanofibers were successfully synthesized by two-stage calcination procedure of Ni(CH₃COO)₂/PVP composite nanofibers which was determined to be the key process for preparing NiO nanowire-in-nanotube structured nanofibers. The NiO nanowire-in-nanotube structured nanofibers have pure cubic phase structure with space group of Fm3̄m, and the outer diameter and wall thickness of nanotubes and nanowire diameter are 130 ± 0.99 nm, 30 nm and 40 nm, respectively. Preliminarily, it is satisfactorily found that NiO nanowire-in-nanotube structured nanofibers used as photocatalyst for water splitting exhibit higher H₂ evolution rate of 622 μmol h⁻¹ than counterpart NiO hollow nanofibers of 472 μmol h⁻¹ owing to its novel nanostructure. The possible formation mechanism of NiO nanowire-in-nanotube structured nanofibers is proposed. To evaluate the universality of this novel preparative technique, taking Co₃O₄ as an example, it is found that Co₃O₄ nanowire-in-nanotube structured nanofibers are also successfully fabricated via this novel method. The special nanowire-in-nanotube structure of the one-dimensional nanomaterials makes them have promising applications in catalysis, lithium-ion battery, drug delivery, etc. This manufacturing strategy has some advantages over other methods to form nanowire-in-nanotube structured nanofibers, such as easy, highly efficient and cost effective. The design idea and synthetic technique provide a novel perspective to create other nanowire-in-nanotube structured nanomaterials.

NiO nanowire-in-nanotube structured nanofibers were easily and directly fabricated via one-pot uniaxial electrospinning followed by designed calcination procedures.

Understanding the remarkable luminescence enhancement via SiO2 coating on TiO2:Eu3+ nanofibers

Red luminescence is enhanced by coating an SiO₂ layer on TiO₂:Eu³⁺ nanofibers, and the luminescence enhancement mechanism is discussed.

Tunable photoluminescence and room temperature ferromagnetism of In2S3:Dy3+,Tb3+ nanoparticles

In₂S₃:6%Dy³⁺,yTb³⁺ nanoparticles exhibit tunable optical properties and room temperature ferromagnetism, which have been further investigated using VASP calculations.

Tunable multicolor luminescence and white light emission realized in Eu3+ mono-activated GdF3 nanofibers with paramagnetic performance

GdF₃:Eu³⁺ nanofibers with luminescent–magnetic bi-functionality have been successfully fabricated by combination of electrospinning followed by subsequent calcination with fluorination technology.