Co-doped Nanocrystals Research Articles

Bivalent metal ion co-doped methylammonium lead tribromide perovskite nanocrystal scintillator for X-ray imaging

Perovskite scintillators with low cost, easy preparation, environmental stability, and high-resolution have become candidates for X-ray imaging applications. Here, based on the calculation results of surface formation energy (Ef) and vacancy defect energy (Evac), a series of co-doped perovskite nanocrystals (NCs) with photoluminescence high quantum yield (PLQY) and fast luminescence decay time had been prepared by doping several bivalent metal ions into the B-site of methylammonium lead tribromide (MAPbBr3). In addition, the scintillator with flexibility was prepared using poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) as the carrier, showing excellent stability and scintillation performance, with a light yield of 21,200 photons/MeV, imaging resolution reached 11.7 lp/mm, and low detection limits of 462 nGyair s−1. Finally, we demonstrated the scintillator characteristic with high-quality imaging results and excellent tolerance under high dose rate X-ray (25 mGy s−1). Therefore, the combination of co-doped nanocrystals with excellent optical properties and PVDF-HFP further paves the way for the development of a scintillator.

Temperature sensing of novel Tb3+/Ho3+/Bi3+ co-doped lead-free double perovskite Cs2AgInCl6 nanocrystals

Up to now, the research field of application of lanthanide ions doped lead-free double perovskite Cs2AgInCl6 nanocrystals (NCs) was relatively limited, even less in temperature sensing. Here, Tb3+/Ho3+/Bi3+ ions were successfully doped into Cs2AgInCl6 NCs by hot-injection. The temperature sensing performance of co-doped NCs by using the fluorescence intensity ratio (FIR) was studied through the temperature-dependent emission spectra. By analyzing the influence of ions' doping concentration on temperature sensing performance, the optimal doping concentration of co-doped Cs2AgInCl6 NCs was determined to be 7 % Tb3+, 20 % Ho3+ and 1 % Bi3+. The highest absolute and relative sensitivities reach 1.48 K−1 and 2.48 %/K, respectively. We provide a new doping scheme of lead-free double perovskite NCs which have good temperature sensing performance. This co-doped NCs have great potential application value in non-contact temperature sensing in nanoscale.

In-situ formed decrystallized interphase enabled high performance all-in-one all-solid-state batteries

All-inorganic solid-state batteries (AISSBs) hold great promise as the next-generation energy storage technology, offering exceptional safety and high energy density. However, achieving satisfactory solid-to-solid interfacial contact between battery components presents a significant challenge. An ideal approach is the integration of electrodes with electrolyte to form an all-in-one battery. While feasible using a molten lithium as anode, the cathodic side poses more challenges due to detrimental elemental diffusion during high-temperature treatment. Here, we demonstrate a simple and cost-effective liquid-phase sintering assisted in-situ interfacial growth strategy. This strategy enables the formation of an integrated LiCoO2cathode on Li6.5La3Zr1.5Ta0.5O12 (LLZTO) electrolyte, connected by a unique decrystallizing interlayer. Notably, this interlayer consists of Co-doped LLZTO nanocrystals dispersed in its amorphous matrix (referred to as the NAM area), where the amorphous matrix effectively blocks detrimental elemental diffusion, while the nanocrystals facilitate Li+ transport. Benefitting from this unique NAM structure, the fabricated all-in-one all-solid-state battery exhibits an impressive long cycle life (over 500 cycles at 0.2C). This remarkable cycling performance demonstrates the robustness and reliability of the interlayer. This finding would pave the way for the development of practical AISSBs, offering new prospects in the field of advanced energy storage.

Photoinduced electron transfer in Eu2+ and Sm3+ co-doped CaF2 nanocrystals prepared by co-precipitation

We report on the photoinduced electron transfer in Eu2+ and Sm3+ co-doped CaF2 nanocrystals prepared by a facile co-precipitation method using CaCl2, EuCl2, SmCl3 and NH4F. The doping of divalent Eu2+ was realized by employing granular zinc in the CaCl2/EuCl2 solution under nitrogen to reduce Eu3+→ Eu2+. The CaF2:xEu,0.2%Sm nanocrystals were prepared with different Eu concentrations of x = 0, 0.2, 0.5, 1.5, and 2.5%, resulting in an average crystallite size between 54 and 36 ± 1 nm. The maximum luminescence intensities of Eu2+ and Sm2+ were obtained for the x = 0.5% sample. Photoinduced electron transfer and back transfer in the CaF2:0.5%Eu,0.2%Sm nanocrystals were measured by detecting the Eu2+ and Sm2+ luminescence, upon exposure to 340 and 310 nm UV LED light. Interestingly, the photoionization of Eu2+ occurred 6 times faster for the sample co-doped with 0.2% Sm. Upon exposure to 340 nm light, a reduction and increase of the Eu2+ and the Sm2+ luminescence were observed, respectively. Subsequent exposure to 310 nm light decreased the Sm2+ luminescence, but the luminescence of Eu2+ kept on being bleached, albeit at a lower rate. Whilst the Sm valence state could be reversibly changed between the trivalent and divalent state by 340 and 310 nm light, the observation that the Eu2+ luminescence did not recover may indicate that a third centre is involved in the photoinduced electron transfer mechanisms.

Investigating the Electrical and Optical Properties of Nickle and Strontium Co-Doped CsPbBr3 Nanocrystals: Potential Absorber Material for Perovskite Solar Cells

Investigating the Electrical and Optical Properties of Nickle and Strontium Co-Doped CsPbBr3 Nanocrystals: Potential Absorber Material for Perovskite Solar Cells

Dual second harmonic generation and up-conversion photoluminescence emission in highly-optimized LiNbO3 nanocrystals doped and co-doped with Er3+ and Yb3.

Preparation from the aqueous alkoxide route of doped and co-doped lithium niobate nanocrystals with Er3+ and Yb3+ ions, and detailed investigations of their optical properties are presented in this comprehensive work. Simultaneous emission under femtosecond laser excitation of second harmonic generation (SHG) and up-conversion photoluminescence (UC-PL) is studied from colloidal suspensions according to the lanthanide ion contents. Special attention has been paid to produce phase pure nanocrystals of constant size (∼20 nm) thus allowing a straightforward comparison and optimization of the Er content for increasing the green UC-PL signals under 800 nm excitation. An optimal molar concentration at about 4 molar% in erbium ions is demonstrated, that is well above the concentration usually achieved in bulk crystals. Similarly, for co-doped LiNbO3 nanocrystals, different lanthanide concentrations and Yb/Er content ratios are tested allowing optimization of the green and red up-conversion excited at 980 nm, and analysis of the underlying mechanisms from excitation spectra. All together, these findings provide valuable insights into the wet-chemical synthesis and potential of doped and co-doped LiNbO3 nanocrystals for advanced applications, combining both SHG and UC-PL emissions from the particle core.

Thermal sensitivity of Ho3+ fluorescence in oxyfluoride nanocrystals and derivative embedded fibers

(Y1-x-yHoxYby)OF/polyacrylonitrile (YOF-HuYv/PAN) composite fibers prepared by electrostatic spinning have been demonstrated to possess effective upconversion (UC) luminescence and sensitive temperature feedback properties for laser display and real-time temperature monitoring in complex environments. When the excitation power density is increased to 73 mW/mm2, the total luminous flux reaches 3.35 mlm, demonstrating that the Ho3+/Yb3+ co-doped YOF nanocrystals embedded in the composite fibers are efficient luminous materials. The quantum yields (QYs) of green and red emissions from Ho3+ are derived to be 2.97 × 10−5 and 1.40 × 10−5 respectively when the pump power density arrives at 73 mW/mm2 under 977 nm laser, and the high photon generation efficiency ensures sufficient fluorescence intensity for tracing temperature feedback. The maximum relative sensitivities appear at 303 K, while the absolute sensitivity (SA) and relative sensitivity (SR) of the nanofibers retain 13.77% K−1 and 0.34% K−1 at 433 K respectively, demonstrating that the nanofibers have superior optical temperature sensing properties. The composite fibers with effective luminescence and high temperature sensitivity as luminescent materials provide a potential option for the field of laser display and temperature sensing.

Multicolor emission from lanthanide ions doped lead-free Cs3Sb2Cl9 perovskite nanocrystals

The toxicity of lead ions has become the severe challenge for the all-inorganic lead halide perovskite materials, although some works have reported the lead-free perovskite nanocrystals (NCs), the photoluminescence quantum yield (PLQY) of these materials is still unsatisfactory. Meanwhile, because the halogen ions can be easily exchanged, the controllable multicolor emission in perovskite NCs is difficult to realize in current reports. In this work, we introduced lanthanide ions into lead-free Cs3Sb2Cl9 perovskite NCs. Benefitting from the energy transfer between Cs3Sb2Cl9 perovskite NC host and lanthanide ions, the multicolor emission was realized. Based on controlling the doping concentration of Tb3+ and Eu3+ ions, the white light emission under UV excitation would be turned easily in the Tb3+/Eu3+ codoped NCs. In addition, efficient energy transfer from perovskite NCs to Tb3+ or Eu3+ ions is beneficial to improving the optical properties of lead-free perovskite NCs, resulting in maximum PLQYs of red, green and white light emission of 22.6%, 19.7% and 28.5%, respectively. Finally, a white light emitting device (WLED) was fabricated with a power efficiency of 18.5 lm/W, which presents the Commission Internationale de l’Eclairage (CIE) of (0.33, 0.35).

Pressure-Induced Structural Phase Transition of Co-Doped SnO2 Nanocrystals

Co-doped SnO2 nanocrystals (with a particle size of 10 nm) with a tetragonal rutile-type (space group P42/mnm) structure have been investigated for their use in in situ high-pressure synchrotron angle dispersive powder X-ray diffraction up to 20.9 GPa and at an ambient temperature. An analysis of experimental results based on Rietveld refinements suggests that rutile-type Co-doped SnO2 undergoes a structural phase transition at 14.2 GPa to an orthorhombic CaCl2-type phase (space group Pnnm), with no phase coexistence during the phase transition. No further phase transition is observed until 20.9 GPa, which is the highest pressure covered by the experiments. The low-pressure and high-pressure phases are related via a group/subgroup relationship. However, a discontinuous change in the unit-cell volume is detected at the phase transition; thus, the phase transition can be classified as a first-order type. Upon decompression, the transition has been found to be reversible. The results are compared with previous high-pressure studies on doped and un-doped SnO2. The compressibility of different phases will be discussed.

Direct observation of the distribution of impurity in phosphorous/boron co-doped Si nanocrystals

Doping in Si nanocrystals is an interesting topic and directly studying the distribution of dopants in phosphorous/boron co-doping is an important issue facing the scientific community. In this study, atom probe tomography is performed to study the structures and distribution of impurity in phosphorous/boron co-doped Si nanocrystals/SiO2 multilayers. Compared with phosphorous singly doped Si nanocrystals, it is interesting to find that the concentration of phosphorous in co-doped samples can be significantly improved. Theoretical simulation suggests that phosphorous–boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy, which also reduces the formation energy of phosphorous in Si nanocrystals. The results indicate that co-doping can promote the entry of phosphorous impurities into the near-surface and inner sites of Si nanocrystals, which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals such as the observed enhancement of conductivity and sub-band light emission.

Understanding Yb3+-sensitized photon avalanche in Pr3+ co-doped nanocrystals: modelling and optimization.

Among different upconversion processes where the emitted photon has higher energy than the one absorbed, photon avalanche (PA) is unique, because the luminescence intensity increases by 2-3 orders of magnitude in response to a tiny increase in excitation intensity. Since its discovery in 1979, PA has been observed in bulk materials but until recently, obtaining it at the nanoscale has been a significant challenge. In the present work, the PA phenomenon in β-NaYF4 colloidal nanocrystals co-doped with Pr3+ and Yb3+ ions was successfully observed at 482 nm (3P0 → 3H4) and 607 nm (3P0 → 3H6) under excitation at 852 nm. The impact of Pr3+ ion concentration and pump power dependence on PA behavior was investigated, i.e. PA non-linearity slopes of luminescence intensity curves as a function of pump power density as well as PA thresholds. The highest slopes, namely 8.6 and 9.0, and the smallest thresholds equal to 286 kW cm-2 and 281 kW cm-2, observed for emission bands at 607 nm and 482 nm, respectively, were obtained for NaYF4:0.5%Pr3+,15%Yb3+@NaYF4 colloidal nanocrystals. Besides experimental research, simulations of PA behavior in Pr3+, Yb3+ co-doped materials were performed based on differential rate equations describing the phenomena that contribute to the existence of PA. The influence of different processes leading to PA, e.g. the rates of nonradiative and radiative transitions as well as energy transfers, on PA performance was simulated aiming to understand their roles in this complex sensitized system.

Self-Trapped Excitons Mediated Energy Transfer to Sm3+ in Cs2AgIn(1–x)SmxCl6:Bi Double Perovskite Nanocrystals

Lanthanide ions (Ln3+) are well-known dopants for controlling the optoelectronic properties of double perovskites (DPs). However, the excitation energy of Ln3+-doped Cs2AgInCl6 being too high (∼250–290 nm) limits its direct excitation by commercial UV light-emitting diodes (≥365 nm). To overcome this challenge, we employed Bi3+ as a sensitizer to induce the emission of Sm3+ at much lower excitation energy in Sm3+–Bi3+ codoped Cs2AgInCl6 DP nanocrystals (NCs). Spectral analysis shows that a trace amount of Bi3+ (∼1%) doping provides dual emission of self-trapped excitons (STEs) and characteristic emissions of Sm3+ assigned to 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions with 368 nm excitation energy. Transient absorption spectroscopic results revealed the existence of nonradiative energy transfer from STE states. Subsequently, we propose a mechanism to explain the formation of energy-transfer channels from STEs to excited states of Sm3+. Our study demonstrates that Bi3+ can efficiently sensitize Sm3+ to modify the optical properties of lead-free DP NCs to expand their luminescence application.

A simple and fast strategy for rare earth doped phosphors prepared by 980 nm laser thermal effect

The phosphors synthesize by the sol-gel method show low cost and good homogeneity, but it also requires furnace annealing at high-temperatures. This report uses a 980 nm laser annealing strategy to replace the furnace annealing in the sol-gel combustion synthesis. The fast laser annealing can improve the preparation efficiency of rare earth doped phosphor. Er3+/Li+ co-doped Y2O3 nanocrystals are synthesized by laser annealing strategy. The structures and spectral properties of the phosphors prepared by laser annealing are studied. The phosphors prepared by laser annealing have the same crystal structure and spectral properties as those organized by furnace annealing. In addition, phosphors can be heated into crystals using a high-power 980 nm laser. Under 980 nm excitation, the crystal prepared by laser annealing shows a much stronger fluorescence intensity than phosphors.

Photon upconversion-based non-invasive temperature sensing using Gd1−x-yYbxEr yScO3 perovskite nanocrystals

High thermal stability, high bandgap, and low phonon energy (452 cm−1) of GdScO3 perovskite make it ideal for optical applications, particularly for infrared (IR)-to-visible photon upconversion (UC) emission. This phase has been typically synthesized either in single crystal or in thin film forms which require high temperatures and a longer time. Thin films/single crystals of GdScO3 have limited optical application mostly as lasing material. Unexpectedly, the photon UC-based emission and correlated applications are completely ignored in this host so far. Herein, we have successfully synthesized pristine and Yb3+, Er3+ co-doped GdScO3 nanocrystals (powder) at low temperatures and further analyzed their crystal structure, phase, and optical absorption and emission properties at length. The photon-UC property in GdScO3 nanocrystal has been studied for the first time. Further, the material has been used for the non-contact luminescence-based temperature sensor application also. Our study shows that the maximum relative sensitivity (Sr) and absolute sensitivity (Sa) obtained for Yb3+, Er3+: GdScO3 nanocrystal is better than most of the reported oxide-based perovskite materials.

Effect of cobalt incorporation on the photocatalytic degradation of brilliant green using SnO2 nanoparticles under visible light irradiation

• Bare and Co-doped nanocrystals of SnO 2 were synthesized by a simple chemical precipitation method. • The result of UV-DRS proposed a band gap narrowing effect on SnO 2 with cobalt doping. • The defects and vacancies induced band gap reduction and increased BET surface area on cobalt doping, have played a vital role in the photochemistry of SnO 2 . Suggested here are a simple chemical precipitation method in order to synthesize bare and various levels of Co doping samples. The harvested samples were tested for their structural, optical, morphological and photocatalytic properties. The optical study shows a decline in the band gap of SnO 2 on 0.075 M of cobalt doping. The tuned band gap of SnO 2 on doping utilizes the visible light for the photodegradation of brilliant green (BG) and recommends the usage of the optimum level of Co-doped SnO 2 in environmental remediation applications.

Studies on Rare-Earth Co-Doped: Calcium Tungstate Nano-Crystals

Abstract: We report the synthesis of co-doped Calcium tungstate (CaWO4) nano-crystals with Gadolinium (Gd) and Neodymium (Nd) rare earth ions by hydrothermal synthesis method for the first time. The synthesized nano-crystals were characterized by Xray diffraction (XRD) with energy dispersive analysis of the X-rays (EDAX) and Field-emission scanning electron microscopy (FESEM), and photo-luminescence excitation studies. The phase of the nano-crystals under study was identified by X-ray diffraction (XRD). The Field-Emission Scanning Electron Microscope (FESEM) image shows that the synthesized nano-crystals are in the size range of 51nm – 80nm. The presence of Gd and Nd rare earth ions in the GD-Nd co-doped CaWO4 nano-crystals was confirmed by the energy dispersive analysis of the X-rays (EDAX). The photoluminescence properties of the Gd-Nd co-doped CaWO4 nano-crystals were compared with the undoped CaWO4 nano-crystals and are reported. The synthesized nano-crystals exhibit emissions at (i) 369nm, 392nm, 435nm and 477nm for an excitation wavelength of 280 nm and (ii) 540nm and 669nm for an excitation wavelength of 490nm. The emission wavelengths clearly indicate the blue light and green light generation, which is significant for developing luminescent materials of tungstate systems.

Tunable luminescence and energy transfer properties in novel fluoro-oxide glass ceramics containing KGd2F7:Dy3+/Tb3+ nanocrystals

Herein, a traditional melt-quenching technique was employed to fabricate borosilicate fluoro-oxide glass-ceramic (GC) containing Dy3+/Tb3+ co-doped KGd2F7 nanocrystals. The microstructural and spectroscopic characterizations demonstrated that the crystallites with composition-dependent properties were precipitated in glass matrix and the Dy3+ and Tb3+ ions were successfully incorporated into the lattices of monoclinic-phase KGd2F7 nanocrystals. The GC shows strong characteristic polychromatic yellow (Dy3+:576 nm) and green (Tb3+:544 nm) emissions upon excitations of both 389 nm and 278 nm lights. Moreover, the tunable emission from white to green combining Dy3+ and Tb3+ emissions can be adjusted effectively by incorporating concentrations of Tb3+ and exciting lights of 389 nm and 278 nm. Additionally, the energy transfer (ET) processes among Gd3+, Dy3+, and Tb3+ were systematically investigated by varied fluorescence emission spectra and decay curves. The results indicated that the Dy3+/Tb3+ co-doped fluoro-oxide GC with tunable multicolor emission have a great potential application in full-color displays.

Role of divalent Co2+ and trivalent Tb3+ incorporation in ZnO nanocrystals: Structural, optical, photoluminescence properties and enhanced ferromagnetism

Herein, we synthesized the series of cobalt (Co) and terbium (Tb) co-doped (Zn0.95-xTbxCo0.05O; x = 1–4%) nanocrystals by co-precipitation method and studied their multifunctional properties. X-ray photoelectron spectroscopy (XPS) results ensure the successful doping of Co and Tb ions in the ZnO lattice. X-ray diffraction (XRD) patterns reveal the formation of single-phase hexagonal wurtzite structure for all samples. Scanning electron microscopy (SEM) analysis shows the non-uniform distribution of spherical-shaped nanocrystals of 20–23 nm size. The UV–visible spectra show a marginal red shift in the absorption peak and a decrease in the bandgap energy. Photoluminescence (PL) spectra show a broad emission band identifying the presence of lattice defects in the visible region those act as trap centers. The magnetic measurements exhibit strong ferromagnetism (FM) at room temperature. The BMPs concentration (1021cm−3) in the co-doped samples is higher than the required threshold value. It is established that the observed FM is induced by the magnetic polarons.

Hydrothermal Synthesis and In Vivo Fluorescent Bioimaging Application of Eu3+/Gd3+ Co-Doped Fluoroapatite Nanocrystals.

In this study, Eu3+/Gd3+ co-doped fluoroapatitååe (Eu/Gd:FAP) nanocrystals were synthesized by the hydrothermal method as a fluorescent bioimaging agent. The phase composition, morphology, fluorescence, and biosafety of the resulting samples were characterized. Moreover, the in vivo fluorescent bioimaging application of Eu/Gd:FAP nanocrystals was evaluated in mice with subcutaneously transplanted tumors. The results showed that the Eu/Gd:FAP nanocrystals were short rod-like particles with a size of 59.27 ± 13.34 nm × 18.69 ± 3.32 nm. With an increasing F substitution content, the Eu/Gd:FAP nanocrystals displayed a decreased size and enhanced fluorescence emission. Eu/Gd:FAP nanocrystals did not show hemolysis and cytotoxicity, indicating good biocompatibility. In vivo fluorescent bioimaging study demonstrated that Eu/Gd:FAP nanocrystals could be used as a bioimaging agent and displayed stable fluorescence emitting in tumors, indicating an accumulation in tumor tissue due to the passive targeting ability. In addition, any adverse effects of Eu/Gd:FAP nanocrystals on major organs were not observed. This study shows that biocompatible rare earth co-doped FAP nanocrystals have the potential to be used as a bioimaging agent in vivo.

(Yb3+, Mn2+) Co-doped CdTe nanocrystals with enhanced quantum yields and red-shift emission

We prepared the nanocrystals (NCs) of CdTe, CdTe:Yb, and CdTe:Yb, Mn vis water phase synthesis and examined their structural, morphological, and optical properties. All NCs have a particle diameter of about 2–4 nm, and the monodispersed, uniform spherical, cubic structure of the CdTe NC remains largely unchanged after the doping with Yb and Mn. According to the X-ray diffraction results, the CdTe, CdTe:Yb, and CdTe:Yb, Mn NCs all have a cubic structure, and the diffraction peak of CdTe:Yb NC is at a lower 2θ angle compared with that of the CdTe NC. With the CdTe NC as the reference, the UV–Vis absorption of the CdTe:Yb and the CdTe:Yb, Mn NCs exhibits a blueshift and a redshift, and the emission of CdTe:Yb and CdTe:Yb, Mn has a blueshift of about 12 nm and a redshift of about 73 nm, respectively. The CdTe:Yb, Mn NCs have higher quantum yields than the CdTe:Yb NC, and the quantum yield is the highest when CdTe is doped with 1:1 Mn2+/Yb3+. In addition, both the CdTe:Yb and CdTe:Yb, Mn NCs have a shorter fluorescence lifetime than the CdTe NC.