Luminescence Properties Research Articles

Synthesis of quadruply boron-doped acenes with stimuli-responsive multicolor emission

Boron-doped acenes have attracted attention due to their unique structures and intriguing luminescent properties. However, the hitherto known boron-doped acenes have only one or two boron atoms, limiting the chemical space of this unique family of compounds and the capability to tune their optical properties. Herein, we report the synthesis of quadruply boron-doped acenes, including pentacene, heptacene, and nonacene. The importance of the boron doping level on the luminescent properties of acenes is demonstrated. The title compounds manifest enhanced Lewis acidity as compared with dihydrodiboraacenes, leading to Lewis-base-responsive emission in the solid state. Moreover, quadruply boron-doped nonacene displays mechanochromic luminescence in addition to Lewis-base-responsive properties, realizing high-contrast solid-state multicolor emission. This work greatly expands the chemistry of boron-doped acenes and offers opportunities for developing boron-based luminescent materials.

α-Sr2SiO4:Ce3+, Dy3+, Na+ phosphors with abnormal thermal quenching properties for solid-state lighting applications

There is urgent need of thermally stable phosphors for fabricating high-performance white light emitting diodes (LEDs). In this paper, Sr2SiO4:0.02Ce3+,xDy3+, (0.02+x)Na+ phosphors were successfully synthesized by the solid-state reaction method and their luminescence properties were studied. Phase analysis shows that single-phasic α-Sr2SiO4 was prepared when x was greater than 0.006, while a mixed phase of α-Sr2SiO4 and β-Sr2SiO4 were obtained in the samples with x of 0.006 or less. When excited at 344 nm, there is a major emission band at 380–500 nm corresponding to the 5d-4f transition of Ce3+, and other emission peaks with a dominated one at 575 nm corresponding to the 4F9/2-6H13/2 transition of Dy3+. The as-developed Sr2SiO4:Ce3+,Dy3+,Na+ phosphors exhibit excellent thermal stability. To be specific, the intensity retention rate of 425 and 572 nm at 300 °C is as high as 103.6 % and 89.2 %, respectively. Furthermore, near-ultraviolet (nUV) chip-pumped white LED prototypes were assembled using the co-activated phosphor and commercial green and red phosphors, which demonstrate its great potential in high-power white LEDs for solid-state lighting applications.

Novel Eu3+-Doped Glasses in the MoO3-WO3-La2O3-B2O3 System: Preparation, Structure and Photoluminescent Properties.

Novel multicomponent glasses with nominal compositions of (50-x)MoO3:xWO3:25La2O3:25B2O3, x = 0, 10, 20, 30, 40, 50 mol% doped with 3 mol % Eu2O3 were prepared using a conventional melt-quenching method. Their structure, thermal behavior and luminescent properties were investigated by Raman spectroscopy, differential thermal analysis and photoluminescence spectroscopy. The optical properties of the glasses were investigated by UV-vis absorption spectroscopy and a determination of the refractive index. Physical parameters such as density, molar volume, oxygen molar volume and oxygen packing density were determined. The glasses are characterized by a high glass transition temperature. Raman analysis revealed that the glass structure is built up mainly from tetrahedral (MoO4)2- and (WO4)2- units providing Raman bands of around 317 cm-1, 341-352 cm-1, 832-820 cm-1 and 928-935 cm-1. At the same time, with the replacement of MoO3 with WO3 some fraction of WO6 octahedra are produced, the number of which increases with the increasing WO3 content. A strong red emission from the 5D0 level of Eu3+ ions was registered under near-UV (397 nm) excitation using the 7F0 → 5L6 transition of Eu3+. Photoluminescence (PL) emission gradually increases with increasing WO3 content, evidencing that WO3 is a more appropriate component than MoO3. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. All findings suggest that the investigated glasses are potential candidates for red light-emitting phosphors.

Effects of acoustic shock waves on the structural and optical properties of cadmium borate

Cadmium borate (CdB₂O₄), an inorganic compound combining transition metals and non-metals, has a broad range of optical applications. In this study, CdB₂O₄ was subjected to acoustic transient pressure using a semi-automatic Reddy tube, with shock pulses applied at counts of 100, 200, 300, and 400 at a Mach number of 1.5, corresponding to a transient pressure of 0.59 MPa and a temperature of 520 K. Control and shock-treated samples were analyzed using XRD, Raman, FTIR, SEM, UV-DRS, and photoluminescence spectroscopy to investigate shock wave effects. The XRD analysis revealed peak disappearance, the formation of new peaks, increased crystallinity, and instability in crystallite size. Raman spectroscopy showed peak disappearance, shifts, and broadening of lattice modes. SEM indicated increased particle size and agglomeration under shock conditions, consistent with changes in crystallinity. UV-DRS analysis shows a slight change in their band gap. Photoluminescence exhibited fluctuating trends in luminescent properties after the shock treatment. The findings reveal that CdB₂O₄'s structural and optical properties are sensitive to acoustic pressure, suggesting its potential for tailored optical behavior in specific applications. These results enhance our understanding of how acoustic pressure affects CdB₂O₄ and open new possibilities for optimizing its use in high-pressure applications.

Overcoming surface quenching in persistent luminescence nanoparticles with organic ligand coordination: Implications for enhanced optical imaging

Persistent luminescence nanoparticles (PLNPs) have been considered as excellent luminescent tools for sensitive optical imaging. However, the persistent luminescence (PL) properties of PLNPs are usually suppressed due to severe surface quenching caused by nanoscale size. Despite considerable efforts, the understanding of surface quenching mechanisms remains a challenge. Here we report a surface ligand coordination method to enhance the PL properties of ZnGa2O4:Al,Cr (ZGO:AC) PLNPs. ZGO:AC PLNPs coated with organic ligands containing carboxyl groups show enhanced PL intensity and prolonged decay time. Among the six ligands, the phthalic acid (PA) ligands yielded the largest luminescence enhancement effect, on which the PL intensity and decay time increased 3 and 2 times compared with ligand-free ZGO:AC PLNPs, respectively. Density functional theory (DFT) calculations and detailed characterizations demonstrated that surface quenching is suppressed due to the coordination of non-saturated Ga ions and -COO- of ligands. Finally, ZGO:AC@PA PLNPs were applied in autofluorescence-free bioimaging and exhibited high imaging sensitivity and contrast ratio. These findings provide insights into the surface quenching mechanisms of PLNPs and offer a platform for developing highly emissive PLNPs on nanoscale.

Modification of an AIE Fluorescent Probe for Monitoring the Polarity of Lipid Droplets Based on a Series of Synthesized Aryl Naphthalizes.

Lipid droplets (LDs) are subcellular organelles that are dynamic and play a central role in energy homeostasis and lipid metabolism. They also contribute to the transport and maturation of cellular proteins and are closely associated with several diseases. The important role of the cellular microenvironment in maintaining cellular homeostasis. Changes in cell polarity, particularly in organelles, have been found to be strongly linked to inflammation, Alzheimer's disease, cancer, and other illnesses. It is essential to check the polarity of the LDs. A series of arylated naphthalimide derivatives were synthesized using the Suzuki reaction. Modification of synthesized aryl naphthalimides using oligomeric PEG based on intramolecular charge transfer (ICT) mechanism. A series of fluorescent probes were designed to target LDs and detect their polarity. Nap-TPA-PEG3 probe exhibited high sensitivity to polarity. The addition of oligomeric polyethylene glycol (PEG) to the probe not only significantly improved its solubility in water, but also effectively reduced its cytotoxicity. In addition, the probe exhibited excellent aggregation-induced luminescence (AIE) properties and solvent discolouration effects. Nap-TPA-PEG3 probe exhibited high Pearson correlation coefficient (0.957163) in lipid droplet co-localization in cells. Nap-TPA-PEG3 could be used as an effective hand tool to monitor cell polarity.

Combining SSVD and subsequent heat treatment processes to fabricate high-quality CsPbBr3 perovskite films

Perovskites, known for their excellent photoluminescence efficiency and color purity, have seen widespread application in flat panel displays and lighting in recent years. Here, we present a process for fabricating CsPbBr3 perovskite film (PeFilm) with high luminescent properties and remarkable weather resistance. By combining single-source vapor deposition (SSVD) with subsequent heat treatment, the quality of PeFilms has been significantly improved. We enhanced the quality of PeFilms by using a thermal annealing process to remove PbBr2 from CsPb2Br5. During annealing, PbBr2 evaporates from PeFilms, changing the crystal phase to CsPbBr3. The heat treatment rearranges atoms between grains, promoting grain growth and fusion, producing larger crystals and reducing defects. The research results demonstrate that the integration of SSVD and appropriate heat treatment enables the fabrication of the CsPbBr3 PeFilm with an emission wavelength of 533 nm, CIE coordinates of (0.1842, 0.7797), and a photoluminescence quantum yield (PLQY) of 52.1%, and even after storing it in atmospheric conditions for 100 days, the PLQY of the CsPbBr3 PeFilm remains above 52%, demonstrating excellent stability.

INVESTIGATION OF VARIOUS MECHANISMS OF RADIATIVE RECOMBINATION OF SILICON NITRIDE AS AN EFFECTIVE WAY TO BROADENING THE PHOTOLUMINESCENCE SPECTRUM

The development of devices combining optical and electrical functions based on silicon-containing materials is one of the challenges in microelectronics. By plasma enhanced chemical vapor deposition synthesis and subsequent annealing, silicon nitride samples with both excess silicon and excess nitrogen were formed. The high concentration of Si-H and N-H bonds was determined by Raman spectroscopy in samples before annealing. By the transmission electron microscopy, it was determined that in addition to silicon nitride, silicon clusters were formed in the sample’s matrix. The photoluminescence spectra changed significantly for both types of samples during annealing in different gas atmospheres. Heat treatment of samples at 1100 °C after synthesis led to the disappearance of the PL spectrum, and after annealing at 800 °C, photoluminescence increases. It is noted that the highest intensity of photoluminescence was detected after annealing in the air atmosphere and the lowest in the nitrogen. The participation of N centers in recombination processes was confirmed by the method of electron paramagnetic resonance. The different mechanisms of particle interaction leading to photoluminescence and charge storage are considered. Thus, the conditions for the synthesis and annealing of silicon nitride layers are selected to obtain controlled luminescent properties in various spectral ranges.

Luminescence and Faraday rotation properties of Tb2O3 and Tb:Y2O3 single crystals

Heavily-doped and fully concentrated 2.78% Tb:Y2O3 and Tb2O3 single crystals with high optical quality and very low levels of impurities have been grown and studied for their luminescence and Faraday rotation properties. Absorption, emission and fluorescence decay measurements performed vs excitation wavelength and temperature and their confrontation with Judd-Ofelt and crystal-field calculations show the contributions of two types of luminescent centers: dominant ones with a 5D4 emission lifetime of 23 μs corresponding to coupled near-neighbor Tb3+ ions, all in C2 symmetry sites, and minority ones with a 5D4 emission lifetime of about 2 ms corresponding to coupled Tb3+ ions in C2 and C3i near-neighbor symmetry sites. Faraday rotation measurements confirm Tb2O3 as the Tb-based Faraday crystalline material with the largest ever measured Verdet constant, at all temperatures and from the visible to the near-infrared. They also show that the dominant luminescent centers contribute more particularly to this large Verdet constant thanks to a favorable crystal-field splitting of their 7F6 ground multiplet and also to the contributions of both types of spin-allowed and spin-forbidden 4f-5d absorption bands.

Gamma-ray irradiation-induced effects on Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glass: Structural, optical, luminescence, and radiation shielding properties

In the present study, we report the gamma (γ) ray irradiation-induced structural, optical, luminescence and radiation shielding properties of Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glasses prepared by melt-quenching technique. It was evidence of the slight reductions in density and refractive index while maintaining stable optical properties upon the γ irradiation. Additionally, increased molar volume and polarizability indicated a less compact network. Raman spectroscopy shows broadened peaks and intensity reductions at key vibrational modes. The UV–Vis–NIR absorption spectra reveal the shift in the absorption edge and reduction in the intensities of Er³⁺ absorption bands (around 450, 520, 550, and 650 nm) with higher radiation doses, indicating radiation-induced damage. It was found that the band gap values decreased from 2.58 eV to 1.30 eV for un-irradiated glass to 90 kGy irradiated glass, and Urbach energy was found to increase from 0.18 to 1 eV respectively, indicating structural disorder and localized states within the band gap. PL emission spectra demonstrated intensity changes and peak shifts with γ radiation dose while maintaining a dominant green emission from 4S3/2 → 4I15/2 and 2H11/2 → 4I15/2 transitions, supported by the CIE diagram analysis. The NIR emission spectra also displayed a peak at 1530 nm with decreasing intensity, indicating defect-induced non-radiative recombination centres. Luminescence lifetime decay profiles indicated reduced lifetimes at higher γ doses, suggesting introduced non-radiative decay pathways. Furthermore, Phy-X software analysis highlighted effective γ-ray shielding influenced by chemical composition and photon flux, with MAC sharply decreasing to 1.8 cm2/g at 0.1 MeV and stabilizing, while LAC showed reduced attenuation efficiency at higher energies. HVL and TVL increased with energy, stabilizing around 4–5 cm and 15–16 cm, respectively, necessitating thicker materials for effective shielding at higher photon energies. MFP rapidly increased to 6–7 cm at 2 MeV, stabilizing at higher energies, while Zeff decreased sharply before stabilizing around 1 MeV. The EBF and EABF trends exhibited higher values at low energies, stabilizing at higher energies, indicating effective photon interaction and resonance effects.

Influence of the synthesis route on optical and luminescence properties of glass-ceramic doped with europium ions

The production of transparent glass-ceramic materials often faces challenges, such as inhomogeneities, inclusions, uncontrolled crystallization and other defects that make glass ceramics unsuitable for fiber optics, for example. At the same time, the chosen chemical composition is valuable for its unique properties. The present study investigated the effect of different methods of synthesizing glass-ceramic silica-germanium-antimony matrices on their transmittance optimization and luminescence properties where the conventional melt-quenching route is insufficient in terms of the transparency and homogeneity of the material obtained. The effect of heat treatment on the studied properties was also considered. Full Text: PDF References G.A. Khater, E.M. Safwat, J. Kang, Y. Yue, A.G.A. Khater, "Some Types of Glass-Ceramic Materials and their Applications", Int. J. Res. Stud. Sci. 7(3), 1 (2020). DirectLink J. Deubener, M. Allix, M.J. Davis, A. Duran, T. Höche, T. Honma, et al., "Updated definition of glass-ceramics", J. Non-Crystalline Solids 501, 3 (2018). CrossRef W. Blanc, Y. Gyu Choi, X. Zhang, M. Nalin, K.A. Richardson, G.C. Righini, et al., "The past, present and future of photonic glasses: A review in homage to the United Nations International Year of glass 2022", Progr. Mat. Sci. 134, 101084 (2023). CrossRef P. Golonko, M. Kochanowicz, P. Miluski, M. Kuwik, J. Pisarska, W. Pisarski, J. Dorosz, M. Leśniak, D. Dorosz, A. Basa, J. Żmojda, "Glass-ceramic optical fibers with controlled crystallization of core doped with europium ions", Ceram. Int. S0272884224002955 (2024). CrossRef J. Zmojda, M. Kochanowicz, P. Miluski, A. Baranowska, A. Basa, R. Jadach, M. Sitarz, D. Dorosz, "The influence of Ag content and annealing time on structural and optical properties of SGS antimony-germanate glass doped with Er3+ ions", J. Mol. Struct. 1160, 428 (2018). CrossRef X. Liu, J. Zhou, S. Zhou, Y. Yue, J. Qiu, "Transparent glass-ceramics functionalized by dispersed crystals", Progr. Mat. Sci. 97, 38 (2018). CrossRef T.N.L. Tran, A. Chiasera, A. Lukowiak, M. Ferrari, "Eu3+ as a Powerful Structural and Spectroscopic Tool for Glass Photonics", Materials 15, 1847 (2022). CrossRef Z. Li, L. Tan, C. Chen, D. Zhou, L.R. Jensen, J. Ren, Y. Zhang, J. Qiu, Y. Yue, "The effect of melt-homogenization and heat-treatment on the optical properties of the rare earth doped oxyfluoride glass-ceramics", J. Non-Cryst. Solids 593, 121773 (2022). CrossRef D. Dorosz, M. Kochanowicz, R. Valiente, A. Diego-Rucabado, F. Rodríguez, N. Siñeriz-Niembro, et al., "Pr3+-doped YPO4 nanocrystal embedded into an optical fiber", Sci Rep. 14, 7404 (2024). CrossRef

Crystal structure and optical properties of a new 0D Sb-based hybrid metal halide: (3,5-DMP)3Sb2Br9

Zero-dimensional (0D) lead-free hybrid organic-inorganic metal halides (OIMHs) have recently garnered tremendous attention due to their diversified structures and unique structure-dependent photoluminescent (PL) properties. Herein, we report a novel Sb-based 0D hybrid organic-inorganic metal halide (OIMH), with the chemical formula (3,5-DMP)3Sb2Br9 [3,5-DMP+ = 3,5-dimethyl piperidinium cation, C7H16N+]. The (3,5-DMP)3Sb2Br9 compound crystallizes in the triclinic crystal system (P1‾ space group), possessing a typical zero-dimensional (0D) structure with isolated face-sharing (Sb2Br9)3− bi-octahedral units encased by (3,5-DMP)+ organic cations. The isolated bi-octahedral units are distorted due to the strong stereochemical expression of the 5s2 lone pair on Sb3+ and intermolecular H-bonding between the organic moieties and inorganic clusters. The compound exhibited good thermal and environmental stability and possessed an indirect band gap of 2.92 eV. Upon 390 nm UV light excitation, the compound displayed a broad emission band centred at 555 nm, which was attributed to the self-trapped excitons (STEs) formed due to strong electron-phonon coupling in this compound. This study suggests the possibility of new types of 0D OIMHs by introducing different metal centers and bulky organic cations and provides a reference for the structure-property relationship in these compounds, thus, offering guidance for examining the structural evolution and improving their luminescent properties.

Synthesis and Thermoluminescence Characterization of Ba₆Y₂W₃O₁₈ Perovskite Nanosensors for Dosimetry

Through the citrate-assisted sol-gel method, barium gadolinium tungstate (Ba6Y2W3O18) perovskite samples were synthesized, and their luminescence properties were investigated. Through X-ray diffraction (XRD) the crystal structure of the prepared samples was examined. The tunnelling electron microscopy (TEM) analysis has confirmed the agglomeration of the nanoparticles into rods with an average diameter and length of 71 and 214 nm, respectively. The thermoluminescence (TL) properties were investigated by; first, estimating the number of composing TL components using both experimental and computational methods; second, studying the dose-response of the glow curves in response to the irradiated beta dose. The third step in the study of the TL properties was to assess the reusability of the prepared samples in TL dosimetry and the fourth step was to estimate the minimum detectable dose of the phosphor samples. The Computerized Glow Curve Deconvolution (CGCD) method was then used to extract the kinetic parameters of the composing TL peaks.

Alpha sensing, NIR to green light emission in Er3+ doped PbWO4 nanoparticles with modification of calcination atmosphere

In this study, various concentrations (0.5, 1, and 1.5 at%) of Er3+ PbWO4 nanoparticles (PWO: Er NPs) were prepared using a co-precipitation procedure, and the effect of the calcination atmosphere (air and argon) on the luminescence properties and scintillation responses were investigated. Different characterization analyses were carried out to study the structural and optical characteristics of prepared samples. We found evidence of the transformation of the PWO Scheelite structure into a non-centered group, which effectively influences the symmetry properties of the structure and subsequently its luminescence and sensing properties. Both Ar atmosphere and Er concentration contribute to the distortion of the scheelite structure and the symmetry breaking. However, with increasing dopant concentrations, the lattice becomes more homogeneously distorted, causing the structure to re-symmetrize and, as a result, the intensity of luminescence increases, particularly magnetic dipolar (MD) transitions that correspond to NIR emission. The ideal conditions are given when the impurity percentage reaches 1.5 at%, in the Ar atmosphere. Our PWO: Er (1.5 at%-Ar) sample had a maximum count rate of 1388 and 2082 and detection efficiency of 0.216 and 0.170 cps/Bq under 241Am sources with 0.22 and 0.26 μc activities, respectively. By exceeding the efficiency of the commercial ZnS(Ag), it showed promising potential for practical applications in future optoelectronic domains.

Double perovskite CaSrMSbO6(M = La, Gd, Y): Bi3+ phosphors for multifunctional application

Bi3+-doping luminescent materials have recently evoked considerable interest in versatile applications. In this work, we have developed a series of Bi3+-activated CaSrMSbO6(M = La, Gd, Y) phosphors with double perovskite structures, exhibiting blue emission from 350 nm to 500 nm. The emission spectral position and intensity of Bi3+ ions can be tuned by changing excitation wavelength and doping concentrations. The relationship between the local crystal field environment and the luminescence properties is comprehensively analyzed. Importantly, optical temperature properties of CaSrLaSbO6: Bi3+ were investigated and were found to reach a maximum relative sensitivity of 4.57 % K−1 at 298 K. Furthermore, the anti-counterfeiting ink was prepared using CaSrLaSbO6: Bi3+ phosphors, and it showed tunable emission under different light stimulation. These results indicate that CaSrLaSbO6: Bi3+ phosphors have application potential in optical temperature sensing and anti-counterfeiting.

Piezoelectric-induced mechanoluminescence in centrosymmetric Lu3Al5O12: Properties of self-recoverable and tunable near-infrared luminescence

Mechanoluminescence (ML) materials with long-wavelength emission bands are essential for future in vivo bioimaging, non-destructive testing. However, most of the near-infrared (NIR) ML materials require pre-irradiation, which may limit their further applications. Generally, piezoelectric-induced ML materials were considered to be related to the piezoelectric effect from non-centrosymmetric structure. Innovatively in this work, a novel piezoelectric-induced near-infrared ML material Lu3Al5O12:Cr3+ with centrosymmetric structure is obtained. In Lu3Al5O12:Cr3+, piezoelectric effect is generated from the distortion of the centrosymmetric structure of the host due to the uneven electron distribution of Cr3+. Here, highly tunable ML FWHM from 7 nm to 118 nm is realized by introducing different content Ga3+ ions to Lu3Al5O12:Cr3+. The ML film fabricated by composite polydimethylsiloxane and Lu3Al2Ga3O12:Cr3+ can penetrate 20 mm pork tissue, which suggests the potential applications of the NIR ML material in the field of optical imaging of stress distribution in organisms. The discovery of distorted crystal structure to induce piezoelectric effect provides a new thinking for exploring ML in centrosymmetric materials. In addition, LuAl5-xGaxO:Cr3+ phosphors have broad prospects in self-powered sensing, temporomandibular disorders diagnosis, information security, and biomedical fields.

Temperature dependence of Ce luminescence characteristics in LaBr3: Ce crystal

Despite the large interest in the scintillation properties of LaBr3:Ce, a detailed understanding of the underlying mechanism of temperature-dependence properties of Ce luminescence remains elusive. This study introduces a self-designed spectral apparatus to explore these properties in LaBr3:5%Ce. We observed a redshift phenomenon and band changes in the emission peak bands, indicating a reduction of the bond length between Ce and the host with increasing temperature. Moreover, the probability of low-energy peak emission decreases and the probability of high-energy peak emission increases, with increasing temperature was observed, suggesting a correlation with the proximity of Ce's 4f energy level to the valence band. Utilizing intensity parameters from the spectra, we identified the impact of temperature on LaBr3:Ce's self-absorption effect, revealing a significant self-absorption effect at the high-energy peak for the first time. A simple self-absorption model indicated that, despite high quantum efficiency of Ce, the overall self-absorption is minimal, establishing a correlation between the self-absorption coefficient of the high-energy peak and overall absorption. This research offers insights for developing radiation-resistant high-temperature luminescent devices and advances the field of high-temperature luminescent materials.

Nonlinear scintillation effects in the intrinsic luminescence from Sc1.318Y0.655Si1.013O4.987 crystal excited by electrons and γ-quanta

The spectral and kinetic properties of intrinsic luminescence from (Y2Sc1)0.(3)(Sc)[Si]O5 crystal are studied. The emission is excited by electrons and γ-quanta. The composition (Y2Sc1)0.(3)(Sc)[Si]O5 is the congruent one for Sc2SiO5-Y2SiO5 solid solutions. It is found, that the crystal emits fairly bright intrinsic cathodololuminescence (CL) and radioluminescence (RL) at room temperature. In particular, the light yield of scintillation excited by γ-quanta with the energies of 661.7 keV is of 12000 photons/MeV. An increase in the beam flux by ∼20 times leads to the shift in the maximal CL energy spectral density from 315 to 340 nm and to the decrease in the CL decay time at 415 nm from 1377 ± 3 ns to 1165 ± 1 ns. Simultaneously, the decay time of RL excited by a photoelectron with the energy of 644.7 keV is of 1310 ± 10 ns while a Compton electron with the energy of 477 keV excites RL with the decay time of 1050 ± 10 ns. Also, we observed differences in the CL yield dependencies on the volume-averaged density of electronic excitations (EEs) at different wavelengths. An explanation of the results is given considering the nonlinear scintillation phenomena induced by an interaction between EEs. It is based on a conception that an increase in EE volume density leads to an increase in EEs nonradiative quenching due to these interactions.

Biomolecule-functionalized exfoliated-graphene and graphene oxide as heteronucleants of nanocrystalline apatites to make hybrid nanocomposites with tailored mechanical, luminescent, and biological properties

Nanocrystalline apatite (Ap), known for its exceptional biological properties, faces limitations in hard tissue engineering due to its poor mechanical properties. To overcome this limitation, we investigated the preparation of nanocomposites through heterogeneous nucleation of calcium phosphate on exfoliated graphene (G) and graphene oxide (GO) flakes, selected for their outstanding mechanical properties. The flakes were treated (functionalized) with amino acids of varying isoelectric points—namely L-Arginine (Arg), L-Alanine (Aln) and L-Aspartic acid (Asp)— as well as citrate (Cit) molecules. Furthermore, Tb3+ was incorporated into the formulations to introduce luminescence and further enrich the functionality of the composite. The synthesis was conducted using the sitting drop vapor diffusion method. Functionalized GO/Ap nanocomposites significantly improved roughness, adhesion forces and elastic modulus compared to Ap and G-based particles. GO-Asp-Ap-Tb nanocomposites exhibited the highest roughness (163.8 ± 116.2 nm), while G-Cit-Ap had the lowest (6.8 ± 5.6 nm). In terms of adhesion force, GO-Cit-Ap-Tb reached the highest value (31.06 ± 13.3 nN), while G-Arg-Ap had the lowest (3.7 ± 1.8 nN) compared to Ap (13.6 ± 3.2 nN). For the elastic modulus, GO-Aln-Ap-Tb demonstrated the greatest stiffness (3489 ± 101.01 MPa) compared to Ap (30.2 ± 6.5 MPa), while G-Aln-Ap-Tb showed the lowest (17.2 ± 8.4 MPa). Concerning their luminescence, regardless of G/Ap and GO/Ap, the relative luminescence intensities depended on the biomolecule used and decreased in the order Arg > Aln >Asp and Cit. Furthermore, G/Ap and GO/Ap nanocomposites demonstrated good biocompatibility on murine mesenchymal stem cells at low concentrations, showing cell viabilities exceeding 80% at 0.1 μg/mL. This research offers a novel approach to enhancing the mechanical properties of apatites while preserving their good biocompatibility properties and introducing new functionalities (i.e. luminescence) in the composites, thereby expanding their range of applications in hard tissue engineering.

Ca2HfSi4O12:Eu2+: A novel blue phosphor with excellent temperature sensitivity for temperature sensor and cathodoluminescence properties for field-emission displays

A new silicate blue phosphor Ca2HfSi4O12:Eu2+ (CHSO:Eu2+) was designed and synthesized via a solid-state reaction. The structure of CHSO:Eu2+ was analyzed by structure refinement. The electronic structure of CHSO was calculated using first-principles calculations, revealing its effect on luminescence and long-persistent properties. Owing to the O vacancies in the crystal structure, undoped CHSO showed wide blue emission (400–650 nm, λmax = 486 nm) under 296 nm excitation. After being irradiated with a UV lamp for 10 min, the CHSO sample showed obvious afterglow properties that could persist for approximately 50 min above the recognizable intensity level (≥0.32 mcd m−2). CHSO:Eu2+ exhibited excellent temperature sensitivity with a relative sensitivity of 4.5 % K−1@473K, which is higher than those of other Eu2+-based temperature sensor materials. The mechanism between thermal quenching and electronic structure was proposed. Moreover, CHSO:Eu2+ shows excellent cathode ray saturation and aging resistance. This study provides a potential temperature sensor, field-emission-display material, and theoretical reference for developing high-sensitivity temperature-sensing materials.