Self-healing of fractured diamond.

Materials that possess the ability to self-heal cracks at room temperature, akin to living organisms, are highly sought after. However, achieving crack self-healing in inorganic materials, particularly with covalent bonds, presents a great challenge and often necessitates high temperatures and considerable atomic diffusion. Here we conducted a quantitative evaluation of the room-temperature self-healing behaviour of a fractured nanotwinned diamond composite, revealing that the self-healing properties of the composite stem from both the formation of nanoscale diamond osteoblasts comprising sp2- and sp3-hybridized carbon atoms at the fractured surfaces, and the atomic interaction transition from repulsion to attraction when the two fractured surfaces come into close proximity. The self-healing process resulted in a remarkable recovery of approximately 34% in tensile strength for the nanotwinned diamond composite. This discovery sheds light on the self-healing capability of nanostructured diamond, offering valuable insights for future research endeavours aimed at enhancing the toughness and durability of brittle ceramic materials.

SERS Detection of Trace Carcinogenic Aromatic Amines Based on Amorphous MoO3 Monolayers.

Aromatic amines are important commercial chemicals, but their carcinogenicity poses a threat to humans and other organisms, making their rapid quantitative detection increasingly urgent. Here, amorphous MoO3 (a-MoO3) monolayers with localized surface plasmon resonance (LSPR) effect in the visible region are designed for the trace detection of carcinogenic aromatic amine molecules. The hot-electron fast decay component of a-MoO3 decreases from 301 fs to 150 fs after absorption with methyl orange (MO) molecules, indicating the plasmon-induced hot-electron transfer (PIHET) process from a-MoO3 to MO. Therefore, a-MoO3 monolayers present high SERS performance due to the synergistic effect of electromagnetic enhancement (EM) and PIHET, proposing the EM-PIHET synergistic mechanism in a-MoO3. In addition, a-MoO3 possesses higher electron delocalization and electronic state density than crystal MoO3 (c-MoO3), which is conducive to the PIHET. The limit of detection (LOD) for o-aminoazotoluene (o-AAT) is 10-9 M with good uniformity, acid resistance, and thermal stability. In this work, trace detection and identification of various carcinogenic aromatic amines based on a-MoO3 monolayers is realized, which is of great significance for reducing cancer infection rates.

Defect-Induced Enhancement Emission Intensity of Ca4.85(BO3)3F(C4.85BF):0.15Bi3+ by Introducing Cation (Na+, Sr2+, Ba2+) or Anion (Cl-).

Generally, the emission intensity of phosphors can be enhanced by introducing a proper number of defects. To enhance the emission intensity of Ca4.85(BO3)3F(C4.85BF):0.15Bi3+, more Frenkel defects were introduced by Na+, Sr2+, and Ba2+. It is found that the number of Frenkel defects is related to volume and covalence of the crystal, in which the covalence has a greater effect than the volume. Furthermore, the larger the volume of the crystal is, the stronger the covalence of the crystal is, the more Frenkel defects will be produced. The volume of Ca4.85- xSr x(BO3)3F(C4.85- xSr xBF):0.15Bi3+ is larger than that of Ca4.85- xNa x(BO3)3F(C4.85- xNa xBF):0.15Bi3+; however, the covalence of Na+ is similar to that of Sr2+, which leads to the same trap depth ( Eα) and defect density (µg) in the quenching concentration. The results also confirmed that the number of Frenkel defects is mainly influenced by the covalence of crystal. Furthermore, crystal distortion also affects the number of Frenkel defects. C4.85- xSr xBF:0.15Bi3+ and C4.85- xNa xBF:0.15Bi3+ have the same distortion at quenching concentration, which results in the same emission intensity in the quenching concentration. Ca4.85- xBa x(BO3)3F (C4.85- xBa xBF):0.15Bi3+ has a larger volume and stronger covalence; meanwhile, it has deeper trap depth ( Eα) and larger defect density (µg) at the quenching concentration, comparing with C4.85- xSr xBF:0.15Bi3+ and C4.85- xNa xBF:0.15Bi3+. However, the distortion of C4.85- xBa xBF:0.15Bi3+ is in agreement with C4.85- xNa xBF:0.15Bi3+ and C4.85- xSr xBF:0.15Bi3+, which leads to the emission intensity of C4.85- xBa xBF:0.15Bi3+ basically the same as that of C4.85- xNa xBF:0.15Bi3+ and C4.85- xSr xBF:0.15Bi3+ in quenching concentration. And the different rates of distortion result in the different quenching concentrations of C4.85- xNa xBF:0.15Bi3+, C4.85- xSr xBF:0.15Bi3+, and C4.85- xBa xBF:0.15Bi3+. Moreover, for Ca4.85- xMg x(BO3)3F(C4.85- xMg xBF):0.15Bi3+ and Ca4.85(BO3)3F1- yCl y(C4.85BF1- yCl y):0.15Bi3+, there are no Frenkel defects due to weaker covalence and smaller volume of the crystal in C4.85- xMg xBF:0.15Bi3+. However, Frenkel defects can be observed in C4.85BF1- yCl y:0.15Bi3+ due to stronger covalence and larger volume of the crystal, furthermore, and the emission spectra and thermoluminescence spectra of C4.85BF1- yCl y:0.15Bi3+ are similar to those of 0.15Bi3+ doped C4.85- xNa xBF:0.15Bi3+, C4.85- xSr xBF:0.15Bi3+, and C4.85- xBa xBF:0.15Bi3+.

Mechanism of Crystal Structure Transformation and Abnormal Reduction in Ca5- y(BO3)3- x(PO4) xF (CBP xF): yBi3.

Tricoordinated planar triangle (PO4)3- may be formed due to the structural differences between planar triangular (BO3)3- and tetrahedral (PO4)3- when (BO3)3- is gradually substituted by (PO4)3-. This transformation of structure may affect the luminescence properties of phosphor. Therefore, a series of Ca5- y(BO3)3- x(PO4) xF (CBP xF): yBi3+ ( y = 0.05, 0.15; x = 0-3), Ca5- y(PO4)3- X(BO3) XF (CPB XF): yBi3+ ( y = 0.05, 0.15; X = 0-1), Ca4.9(PO4)3F (CPF):0.1Eu3+, Ca4.95(PO4)3F (CPF):0.05Bi3+, and nCaF2/CaCl2 ( n = 0-0.1) are synthesized to explore transformation of the crystal structure on luminescence properties. In CBP xF:0.15Bi3+ ( x = 0-3), (PO4)3- is doped to substitute for (BO3)3-, the position of emission spectra remains unchanged and the emission intensity decreases rapidly with increasing x. The underlying main reason for that is formation of the triangular plane (PO4)3-, which has been verified by performing a series of verification experiments of CPB XF: yBi3+ ( y = 0.5, 0.15; X = 0-1). In CPB XF: yBi3+ ( y = 0.5, 0.15; X = 0-1), (BO3)3- is doped to substitute for (PO4)3-, P-O2 bond breaks and the coordination of (PO4)3- varies from four to three when 0.5 < X < 1; meanwhile, the crystal structure transforms from Ca5(PO4)3F (ICSD-9444) to Ca5(PO4)3F (ISCD-30261), which impedes abnormal reduction from Bi3+ to Bi2+. Furthermore, Bi3+ should non-luminance in the plane triangular (PO4)3-, but luminescence in (BO3)3-. Therefore, the emission intensity starts to increase and the emission position suddenly changes from 553 to 474 nm in CPB XF: yBi3+ ( y = 0.05, 0.15; 0.5 < X < 1). From this, the crystal structures of CBP xF: yBi3+ ( y = 0.05, 0.15; x = 0-3) has been inferred to transform from Ca5(BO3)3F (ISCD-65763) to Ca5(PO4)3F (ISCD-30261), and then to Ca5(PO4)3F (ISCD-9444) with x increasing. Emission position remains unchanged and the emission intensity decreases rapidly in CBP xF: yBi3+ ( y = 0.05, 0.15; x = 0-3) do to formation of the triangular plane (PO4)3-. In addition, the rate of abnormal reduction from Bi3+ to Bi2+ can be improved by reducing the electronegativity of the environment around the activator or increasing the ionization energy of the activator, which has been confirmed by verification experiments of CPF:0.05Bi3+, nCaF2/CaCl2 ( n = 0-0.1), and CPF:0.1Eu3+.

Low-Temperature High-Areal-Capacity Rechargeable Potassium-Metal Batteries.

High mass loading and high areal capacity are key metrics for commercial batteries, which are usually limited by the large charge-transfer impedance in thick electrodes. This can be kinetically deteriorated under low temperatures, and the realization of high-areal-capacity batteries in cold climates remains challenging. Herein, a low-temperature high-areal-capacity rechargeable potassium-tellurium (K-Te) battery is successfully fabricated by knocking down the kinetic barriers in the cathode and pairing it with stable anode. Specifically, the in situ electrochemical self-reconstruction of amorphous Cu1.4 Te in a thick electrode is realized simply by coating micro-sized Te on the Cu collector, significantly improving its ionic conductivity. Meanwhile, the optimized electrolyte enables fast ion transportation and a stable K-metal anode at a large current density and areal capacity. Consequently, this K-Te battery achieves a high areal capacity of 1.25 mAh cm-2 at -40 °C, which greatly exceeds those of most reported works. This work highlights the significance of electrode design and electrolyte engineering for high areal capacity at low temperatures, and represents a critical step toward practical applications of low-temperature batteries.

A novel red-emitting phosphor Mg2Y2Al2Si2O12:Ce3+/Mn2+ for blue chip-based white LEDs.

Traditional white light-emitting diodes (LEDs) (blue chip + YAG:Ce3+ yellow phosphor) have the limitation of red deficiency, which limits their application in the illumination field. The single cation/anion substitution or co-doping of activators can increase the red component; however, the large energy loss is attributed to the ultra-long Stokes shift and energy transfer. This work attempts to utilize the short-distance Stokes shift and a small amount of energy transfer to increase the red component in two steps. First, based on a large number of previous research results, the Mg2Y2Al2Si2O12:Ce3+ phosphor is selected. Second, additional enhancement of the red component in the emission spectrum was achieved by ion co-doping Mn2+ into Mg2Y2Al2Si2O12:Ce3+. The emission peaks for samples Mg2Y2Al2Si2O12:Ce3+,Mn2+ shift from 600 to 635 nm with increase in the concentration of Mn2+, and the emission spectra intensity of Mg1.97Y1.93Al2Si2O12:0.07 Ce3+,0.03 Mn2+ anomalously increased by ∼37%, which was attributed to the increase in the distance between Ce3+ ions because of the doping of Mn2+ ions, and reduction in the concentration of defects in the crystal, resulting in the energy loss decreases of Ce3+. The emission peak of Mg1.97Y1.93Al2Si2O12:0.07 Ce3+,0.03 Mn2+ shifts to 618 nm and the quantum efficiency was as high as 83.07%. Furthermore, this sample has high thermal stability and the emission intensity was still 80.14% at 120 °C. As such, it has great potential in the application of white LEDs.

Designing a super broadband near infrared material Mg3Y2Ge3O12:Cr3+ using cation inversion for future light sources.

A series of broad emission band near infrared materials Mg3Y2Ge3O12:Cr3+ (650-1200 nm) was prepared based on cation inversion. For trivalent chromium ions (Cr3+), garnet structural components can provide conditions for the occurrence of cation inversion. With an increase in Cr3+ concentration, the Mg2+ and Ge4+ cations are inverted to ensure valence equilibrium, which was explained by recording the low temperature spectrum of the structure and carrying out structural refinement. As a result, this structure provides a new luminescent center [GeO6] for Cr3+, leading to a secondary enhancement in emission intensity. The wavelength of the main peak was found to move from 771 to 811 nm, and the full width at half maximum (FWHM) was broadened from 180 to 226 nm. The lattice occupation, luminescence mechanism and the reasons behind the red-shift and broadening of the spectra were studied in detail. By analyzing the crystallinity and particle size distributions of the samples, as well as the Cr3+ ion energy level shift, it was determined that cation inversion is an effective method that can be used to tune the luminescence performance. Meanwhile, a super broad near infrared light emitting diode (LED) with a FWHM of 260 nm was obtained by combining a GaN chip with MYG:0.40Cr3+.

A single-phase white light emitting phosphor Ba3Y(PO4)3:Ce3+/Tb3+/Mn2+: luminescence, energy transfer and thermal stability.

A series of Ce3+/Tb3+, Tb3+/Mn2+ and Ce3+/Tb3+/Mn2+ doped Ba3Y(PO4)3 were synthesized by the high temperature solid state method. Phase formation, energy transfer, luminescence properties and thermal quenching properties of phosphors were analyzed in detail. For the co-doped samples, the energy transfer from Ce3+ to Tb3+ and Tb3+ to Mn2+ was proved by analyzing the spectra and fluorescence lifetime, and the energy transfer mechanism was calculated to be dipole-dipole interaction. A series of color-tunable phosphors were obtained by the energy transfer from Ce3+ to Tb3+ and Tb3+ to Mn2+. For the tri-doped samples, it was confirmed that the energy transfers from Ce3+ to Tb3+, Tb3+ to Mn2+ and Ce3+ to Mn2+ exist at the same time by analyzing the spectra properties, and it can emit warm-white light with extensive color temperature regulability. In addition, the thermal stability was abnormal and outstanding because the defects exist in the samples. The results show that the phosphors may be novel warm white emitting phosphors for white light emitting diodes.

Design and improve of the near-infrared phosphor by adjusting the energy levels or constructing new defects.

Ca3Ga2Ge4O14:Cr3+ phosphors with a broad emission band are prepared by the high temperature solid state method. The emission peak position of Ca3Ga(2-x)Ge4O14:Cr3+ is located at 745 nm. Considering that the biological detection needs a widely spectra matching with the first biological window (650 nm-900 nm), Al3+ and In3+ are introduced into the Ga3+ sites to tune the peak position. When the Ga3+ (0.62 Å) is substituted by smaller Al3+ (0.535 Å), the crystal field around Cr3+ is enhanced, the energy level 4T2(4F) will move up and overlap with 2E(2G) level. As a result, the emission peak of Cr3+shift from 745 nm to 730 nm with an enhancement in the intensity about 19 times due to the electro transfer from 2E(2G) level to 4T2(4F) level. However, the energy level 4T2(4F) will move down when the Ga3+ is replaced by the larger In3+ (0.8 Å), which leads to the red shift of the emission peak from 745 nm to 780 nm. Meanwhile, the intensity is enhanced about 17 times with constructing the defects. In summary, the wide emission spectra of these samples can be tuned from730nm to 780 nm continuously by controlling the concentration of Al3+ and In3+.

Reverse effect of Sm3+ on Ce3+ in Ca2BO3Cl:Ce3+/Tb3+/Sm3+ phosphor: Luminescence, energy transfer and occupation site.

A series of Ca2BO3Cl:Ce3+, Tb3+, Sm3+ are successfully synthesized by a high temperature solid state reaction. And the crystal structure, luminescence property and energy transfer mechanism of Ce3+/Sm3+, Tb3+/Sm3+ and Ce3+/Tb3+/Sm3+ in Ca2BO3Cl are investigated. There is an interesting phenomenon that the right side of the Ce3+ emission spectra in Ca2BO3Cl:Ce3+, Sm3+ compresses gradually with increasing the Sm3+ concentration. By means of refinement, it can be found that Sm3+ ions are mainly occupied in the Ca2 sites, because the cell of the Ca2 lattice is easily occupied. Then, the emission peak2 of Ce3+ in Ca2 sites occurs to blue shift. While the emission peak1 of Ce3+ in Ca1 sites is basically stability. However, the emission of Ce3+ in Ca2BO3Cl:Ce3+, Tb3+, Sm3+ have different changes with increasing the Sm3+ concentration that the emission peaks of Ce3+ shift to long wave at first then to short wave and the FWHM remains stability. This can be attributed to the existence of Tb3+. For the energy transfer mechanism, according to Dexter's energy transfer theory and Reisfeld's approximation, the energy transfer process of Ce3+/Sm3+ and Tb3+/Sm3+ should be the dipole-dipole interaction. And white emitting phosphor is achieved by the efficient energy transfer.

Trap distribution and mechanism for near infrared long-afterglow material AlMgGaO4:Cr3.

Near infrared (NIR) long-afterglow materials have attracted much attention due to their high penetration and low destruction in biological tissues. Here, a series of deep red and near infrared materials, AlMgGaO4:xCr3+, were successfully synthesized by a high temperature solid state method. AlMgGaO4 was selected as the host considering its rich antisite defects, which can effectively capture electrons. The emission spectra of AlMgGaO4:xCr3+ range from 680 nm to 1100 nm, which can be nicely decomposed into four Gaussian bands with peaks centered at 706 nm, 723 nm, 916 nm, and 938 nm, respectively. At low temperature (10 K), the emission spectra show there are four emission peaks: a sharp line (peak 1) and broad emission band (peak 2) come from Cr3+ substituting for the regular octahedron [AlO6], and two broad emission bands (peaks 3 and 4) which originate from the spin-allowed transition 4T2(4F) → 4A2(4F) of Cr3+ in the disordered [GaO6] and [MgO6] octahedra, respectively. Remarkably, after removing the excitation source, it exhibited more than 10 hours of afterglow emission which decreased sharply in the first 30 min and then decreased slowly. With an increase in the Cr3+ concentration, the trap depth became shallower due to the generation of the electronic trap centers . The distribution of trap centers and the mechanism of the persistent luminescence have been carefully analyzed and are also discussed.

Crystal structure, luminescence properties, energy transfer, tunable occupation and thermal properties of a novel color-tunable phosphor NaBa1-zSrzB9O15:xCe3+,yMn2.

A series of color-tunable NaBa1-zSrzB9O15:Ce3+,Mn2+ phosphors were synthesized by a high temperature solid state method. Luminescence property, energy transfer, thermal stability and cation substitution were investigated in detail. Due to energy transfer, NaBaB9O15:Ce3+,Mn2+ presents violet to green luminescence and manifest a broad excitation range from 200 to 350 nm. The energy transfer mechanism of Ce3+-Mn2+ is identified as a dipole-dipole interaction. NaBa1-zSrzB9O15:Ce3+,Mn2+ displays both Ce3+ violet and Mn2+ green and orange emissions under ultraviolet excitation. It is observed that Sr2+ partial substitution for Ba2+ could adjust the ratio of Mn2+ emission intensity in different cation sites, which results from preferred sites' occupation with modification of the crystal structure. Furthermore, increase in temperature can enhance the energy transfer from Ce3+ to Mn2+, which enhances the Mn2+ emission intensity sharply. The highly thermal-sensitive property of NaBa1-zSrzB9O15:Ce3+,Mn2+ makes it feasible for its potential application in luminescent ratiometric thermometers with wide temperature range.