Strongest Emission Intensity Research Articles

Theoretical and experimental investigation of BaY2(MoO4)4:xSm3+ phosphors

In this paper, the novel BaY2(MoO4)4:xSm3+ phosphors with strong red emission and high thermal stabilization were prepared by a conventional method of high temperature solid state reaction in air atmosphere. Morphology, phase purity, element distribution, UV–Vis–NIR diffuse reflectance spectroscopy (DRS), and luminescence properties were investigated in detail. The crystal structure of the BaY2(MoO4)4 host was refined with the aid of the Rietveld refinement method by the GSAS program. The electronic band structure and phonon dispersion were performed using plane-wave density functional theory (DFT). The prepared BaY2(MoO4)4:Sm3+ phosphor exhibits excellent red emission under near-ultraviolet excitation. Strong red emission intensity and high thermal stability suggest potential application in backlighting or phosphor-covered white light-emitting diodes (pc-LEDs).

Chiral Emission from Optical Metasurfaces and Metacavities

Chiral emission exhibiting a large degree of circular polarization (DCP) is important in diverse applications ranging from displays and optical storage to optical communication, bioimaging, and medical diagnostics. Although chiral luminescent materials can generate chiral emissions directly, they frequently suffer from either low DCP or low quantum efficiencies. Achieving high DCP and quantum efficiencies simultaneously remains extremely challenging. This review introduces an alternative approach to chiral emission. Chiral emission with large DCP can be readily achieved by combining conventional achiral emitters with chiral metasurfaces. Particularly, this article focuses on recent experimental and theoretical studies on perovskite metasurfaces and metacavities that employ achiral perovskite materials. First, chiral photoluminescence from extrinsic and intrinsic perovskite metasurfaces is explained together with theoretical discussions on metasurface design based on reciprocity and critical coupling. Chiral photoluminescence from other achiral materials is also explained. Subsequently, chiral electroluminescence from perovskite metacavities and other achiral materials is discussed. Finally, it is concluded with future perspectives. This review provides physical insights into how ideal chiral emission can be realized by optimizing the design of metasurfaces and metacavities. Compact chiral light sources with both near‐unity DCP and strong emission intensities can have far‐reaching consequences in a wide range of future applications.

Structural and photoluminescence properties of SrNb2O6: RE3+ (RE = Sm, Tb) phosphors for solid state lighting

The phosphors for pc-LEDs have high thermal stability requirements due to the high operating temperature of LEDs. In addition, there are many phosphors based on SrNb2O6, but no one has studied Sm3+ or Tb3+ as the luminescent center of SrNb2O6 host. Therefore, two new phosphors based on SrNb2O6 host are proposed in this work. One is an orange phosphor with negative thermal quenching phenomenon using Sm3+ as the luminescent center, and the other is a green phosphor with Tb3+ as the luminescent center. In this work, a series of SrNb2O6:Sm3+ and SrNb2O6:Tb3+ phosphors were prepared by the solid-state reaction method. The structure, morphology, chemical composition, absorption properties and luminescence properties of Sm3+ and Tb3+ doped SrNb2O6 samples were studied. Under 405 nm excitation, the SrNb2O6:Sm3+ samples exhibit the 4f-4f transition of Sm3+ with the strongest emission intensity at 607 nm, the emission intensity of SrNb2O6:0.03Sm3+ phosphor at 150 °C remains at 100.56% of its room temperature value and the chromaticity coordinates are located in the orange region, with a color purity of 88.19%. Under 307 nm excitation, the SrNb2O6:Tb3+ samples exhibit the 4f-4f transition of Tb3+ with the strongest emission intensity at 544 nm, the emission intensity of SrNb2O6:0.09Tb3+ phosphor at 150 °C remains at 7.68% of its room temperature value and the chromaticity coordinates are located in the green region with a color purity of 74.29%. Additionally, Na+ is introduced as a charge compensator in the Sm3+ or Tb3+ doped phosphors, which enhances their luminescence intensity. These results indicate that the two phosphors synthesized in this work have the prospect of application in the field of solid-state lighting.

An Organophosphorescence Probe with Ultralong Lifetime and Intrinsic Tissue Selectivity for Specific Tumor Imaging and Guided Tumor Surgery.

Organic phosphorescent materials are excellent candidates for use in tumor imaging. However, a systematic comparison of the effects of the intensity, lifetime, and wavelength of phosphorescent emissions on bioimaging performance has not yet been undertaken. In addition, there have been few reports on organic phosphorescent materials that specifically distinguish tumors from normal tissues. This study addresses these gaps and reveals that longer lifetimes effectively increase the signal intensity, whereas longer wavelengths enhance the penetration depth. Conversely, a strong emission intensity with a short lifetime does not necessarily yield robust imaging signals. Building upon these findings, an organo-phosphorescent material with a lifetime of 0.94 s was designed for tumor imaging. Remarkably, the phosphorescent signals of various organic nanoparticles are nearly extinguished in blood-rich organs because of the quenching effect of iron ions. Moreover, for the first time, we demonstrated that iron ions universally quench the phosphorescence of organic room-temperature phosphorescent materials, which is an inherent property of such substances. Leveraging this property, both the normal liver and hepatitis tissues exhibit negligible phosphorescent signals, whereas liver tumors display intense phosphorescence. Therefore, phosphorescent materials, unlike chemiluminescent or fluorescent materials, can exploit this unique inherent property to selectively distinguish liver tumor tissues from normal tissues without additional modifications or treatments.

An Organophosphorescence Probe with Ultralong Lifetime and Intrinsic Tissue Selectivity for Specific Tumor Imaging and Guided Tumor Surgery

AbstractOrganic phosphorescent materials are excellent candidates for use in tumor imaging. However, a systematic comparison of the effects of the intensity, lifetime, and wavelength of phosphorescent emissions on bioimaging performance has not yet been undertaken. In addition, there have been few reports on organic phosphorescent materials that specifically distinguish tumors from normal tissues. This study addresses these gaps and reveals that longer lifetimes effectively increase the signal intensity, whereas longer wavelengths enhance the penetration depth. Conversely, a strong emission intensity with a short lifetime does not necessarily yield robust imaging signals. Building upon these findings, an organo‐phosphorescent material with a lifetime of 0.94 s was designed for tumor imaging. Remarkably, the phosphorescent signals of various organic nanoparticles are nearly extinguished in blood‐rich organs because of the quenching effect of iron ions. Moreover, for the first time, we demonstrated that iron ions universally quench the phosphorescence of organic room‐temperature phosphorescent materials, which is an inherent property of such substances. Leveraging this property, both the normal liver and hepatitis tissues exhibit negligible phosphorescent signals, whereas liver tumors display intense phosphorescence. Therefore, phosphorescent materials, unlike chemiluminescent or fluorescent materials, can exploit this unique inherent property to selectively distinguish liver tumor tissues from normal tissues without additional modifications or treatments.

Red‐Shifting ESIPT Fluorescence by Site‐Specific Functionalization in 2‐(2’‐hydroxyphenyl)benzazole Derivatives

AbstractWe describe the synthesis, full photophysical study, and ab initio calculations of 2‐(2’‐hydroxyphenyl)benzazole (HBX) fluorophores substituted, at the meta position of the phenol group, by pyridine derivatives. HBX are commonly used as model dyes to study the stimuli‐induced modulation of the Excited State Intramolecular Proton Transfer (ESIPT) process. The meta‐substituted fluorophores reported herein, display a photophysical profile different from the previously reported ortho‐ and para‐substituted HBO pyridine isomers. Indeed, while all dyes undergo spontaneous deprotonation in neutral conditions, leading to highly emissive anionic species; upon protonation, ortho‐ and para‐pyridine substitution leads to resonance‐stabilized keto isomers, formed after ESIPT. Protonated meta derivatives, unable to stabilize their excited structure by such electronic delocalization process, display sizable intramolecular charge transfer (ICT) processes, translating into significantly redshifted emission. In addition, all dyes present a strong emission intensity, not only in neutral and acidic solutions, but also in the solid‐state. The nature of the emissive transitions was confirmed in each case by theoretical calculations combining Time‐Dependent Density Functional Theory (TD‐DFT) and second‐order Coupled Cluster (CC2) methods.

Application of Sm3+ doped Gd2O3–Y2O3–ZnO–B2O3 glass for development of X-ray imaging scintillator

The X-ray scintillator materials are mostly made from single crystal. The limitations are high productive cost, and the process of producing is complex. There are numerous studies about developing new scintillators by using glass that are easier preparation and lower cost. This study tries to produce a new series of borate glass doped with Sm3+ in 20Gd2O3:10Y2O3:10ZnO: (60-x)B2O3:xSm2O3 formula with varying concentrations of Sm2O3. The samples were measured and analyzed by physical, optical, luminescence and scintillation properties. The results showed that the density increased after increasing the Sm2O3 concentration. The strong emission intensity was observed from photoluminescence and radioluminescence measurements, and the concentration quenching was observed at 0.5 and 1.0 mol% of Sm2O3 respectively. The strongest emission peak of Sm3+ ion is located at 600 nm that corresponds to f-f transition of 4G5/2 to 6H7/2 level. Moreover, we found that the Sm3+ luminescence at 600 nm emission wavelength increases (up to 0.5% mol), while the Gd3+ emission wavelength at 313 nm decreases, attributed to the energy transfer (ET) from Gd3+ ions to Sm3+ ions. X-ray imaging was also observed by using Synchrotron X-rays. These results suggest that the developed glasses could be applied to X-ray scintillators material, especially imaging applications.

Orotic acid-capped Tb(III)-doped calcium sulphate nanorods for the selective detection of tryptophan.

Lanthanide-based luminescent materials have gained huge attention due to their applications in optoelectronic devices, sensing, bio-imaging, anti-counterfeiting, and more. In this work, we report a luminescence-based sensor for the detection of tryptophan using orotic acid-capped Tb3+-doped CaSO4 nanorods (NRs). Orotic acid (OA) was found to play a dual role as a capping agent to control the growth of the nanorods and as a sensitizer for Tb3+ ions. The resulting nanorods exhibited excellent dispersibility and strong photoluminescence signals characteristic of Tb3+ ions in the visible region. Nearly 10-fold enhancement in the emission intensity was noted through OA sensitization compared to direct excitation of Tb3+ ions (acceptors). Interestingly, the strong emission intensity of the NRs reduced significantly with the addition of tryptophan. In contrast, hardly any change was noted with the addition of other amino acids and metal ions, suggesting greater selectivity for tryptophan. Moreover, there is barely any notable interference from other amino acids toward the detection of tryptophan. The limit of detection is found to be ∼0.61 μM. Finally, the sensing study was extended to biological samples to detect tryptophan present in blood plasma, urine, and saliva samples. The nanorods demonstrated high detection abilities, indicating the potential of the developed materials for biomedical applications.

Self-referenced dual-near-infrared emission-based sensor platform for the ultrasensitive discrimination of D2O and H2O

Due to its chemical and physical similarities, the ultrasensitive discrimination of D2O in the presence of H2O remains a practical challenge. In this study, we present an approach to utilize the near-infrared (NIR) optical properties of H2O. Specifically, the absorption coefficient of H2O at approximately 980 nm, which is derived from the second overtone of the O–H stretching mode of H2O, exhibits a notable distinction from that of D2O. To this end, we construct and optimize a dual-NIR emissive lanthanide-doped nanoprobe with a strong emission intensity at 980 nm. In addition, to enhance the reliability of the proposed sensor platform, we introduce a self-referenced signal at 865 nm, which shows a stable signal intensity in both H2O and D2O. Our self-referenced dual-NIR emission-based sensor platform successfully discriminates between D2O and H2O and shows ultrasensitive discrimination capabilities with a limit of detection of 0.17 nM, which has the highest sensitivity among that of previously reported D2O sensors.

Development of Highest Value of the Measured Efficiency of Mesoporous Petal Shaped Europium (III) Doped Cobalt Tetroxide@Cupric Oxide Hybrid Nanomaterials for Enhanced Room Temperature Photoluminescence and Fluorescence Decay Properties.

In our work, a novel series of europium (III) (Eu3+) (5, 10 and 15 wt %) doped cobalt tetroxide@cupric oxide (Co3O4@CuO) nanomaterials (NMs) were synthesized by facile coprecipitation method. The synthesized NMs were characterized by XRD (X-ray diffraction), FT-IR (Fourier transform infrared), UV (ultraviolet)-visible absorption spectra, XPS (X-ray photoelectron), BET (Brunauer-Emmett-Teller) analytical methods. Crystal structure studies revealed the formation of polycrystalline nature with monoclinic and cubic phase. The morphology studies of Eu3+x:Co3O4@CuO (x = 5, 10 and 15 wt %) showed petal shape nanoparticles (NPs) with agglomeration. Redshift in optical absorption spectra appeared with a significant impact on the optical band gap as Eu3+ concentration increases on Co3O4@CuO bimetallic oxide NMs. The chemical composition and valence state of the elements confirmed from XPS studies detected the presence of Eu, Cu, Co, O and C elements. An increase in the pore size and surface area resulted as the Eu3+ concentration increased on Co3O4@CuO NMs. However, room temperature photoluminescence (RTPL) spectra of Co3O4@CuO bimetallic oxide NMs at two different excitations (λ excitation = 280nm, 320nm) showed sharp, strong emission intensities located at near ultraviolet (NUV) region and weak emissions detected at far ultraviolet (FUV) regions of the RTPL spectrum. Further, visible range emission intensities were displayed by Eu3+:Co3O4@CuO (5, 10 and 15 wt %) NMs when exited at 280nm. The characteristic white light emission peaks in the visible range of the RTPL spectra showed intense blue, green and orange colours. Emission intensity increases with an increase in Eu3+ concentration on Co3O4@CuO bimetallic oxide NMs. The fluorescence (FL) decay spectra of Eu3+ 10wt% and 15 wt%: Co3O4@CuO NMs showed a decay lifetime of 2.54 and 2.31ns (ns) attributed to the dynamic, ultrafast excitation energy transfer between Eu3+ (dopant) and Co3O4@CuO (host) NMs. It is proposed that enhanced RTPL emission intensity and FL decay behavior of Eu3+x:Co3O4@CuO NMs closely related to the change in the optical band gap, variation in the crystallite size, formation of more number of oxygen vacancies in the crystal structure of hybrid nanomaterials.

Small Stokes shift and high thermostability in Ce3+ doped K2BaPO4F phosphors

Novel K2BaPO4F:Ce3+ phosphors with strong violet-emission and high thermostability were synthesized by a traditional high-temperature solid-state reaction method. The phase composition and crystal structure were investigated in detail by XRD refinement. DFT calculations based on refined crystal structure were performed. A bright emission in the range of 340–390 nm with a small Stokes shift has been observed when excited at about 323 nm in K2BaPO4F:Ce3+ phosphors. The temperature-dependent PL spectra from 80 to 500 K were investigated systematically. The best doping concentration of K2BaPO4F:xCe3+ phosphors was verified and the concentration quenching mechanism was also confirmed. When the temperature increased from 80 K to 500 K, the emission intensity still remains 53 %. The thermal quenching mechanism was explained using the crystal structure investigation and DFT calculation. The strong near-ultraviolet emission intensity and ultra-high thermal stability indicating that the prepared K2BaPO4F:Ce3+ phosphors have potential applications in anti-counterfeiting and solid-state lighting.

A biscoumarinyl hydrazone based nontoxic fluorescent dye for direct binding and imaging of actin in living cells and organism

The filamentous protein ‘actin’ plays an essential role in maintaining a proper cellular health and any disruption in its structure and dynamics may induce the growth and metastasis of cancerous cells. Recent studies have shown that, actin can serve as a potential therapeutic target and an indicator to examine the efficacy of modern chemotherapeutic agents. In this regard, the microscopy imaging of actin using fluorescent dyes can pave the way toward development of efficient drugs for cancer treatment. Herein, we report the synthesis of an organic fluorescent dye (BCH) which shows good selectivity toward F-actin at physiological pH. The dye displays a large Stokes shift (∼232 nm), strong emission intensity, good photostability and great sustainability over a wide pH range of 2–10. The dye can directly bind and localize in the actin-rich region of gut, testes and eye of a model organism, Drosophila melanogaster in both living and fixed cells and enable their confocal microscopy imaging without using any actin binding domain. Interestingly, the BCH dye is proved to be nontoxic in the tested organism and has been successfully employed as a potential tool to visualize cellular actin in living tissues of larva and pupa of the organism.

Effect of Ca2+ ions on structure and spectroscopic properties of Er3+: KBaY(MoO4)3 crystals

This study successfully grew KBaY(MoO4)3 crystals doped with single Er3+ ions and co-doped with Ca2+/Er3+ ions using the top-seeded solution growth method. Thermal analysis of the KBaY(MoO4)3 crystals was performed by differential scanning calorimetry, and their phase and structure were characterized using X-ray diffraction and Fourier transform infrared spectroscopy. The luminescent properties of the crystals in the visible and near-infrared wavelength ranges under different concentrations of Er3+ ions were analyzed through emission spectroscopy, and the concentration quenching mechanism was investigated in depth. The results showed that the strongest emission intensity was obtained at an Er3+ ion concentration of 5 mol%. Additionally, by substituting Ba2+ ions with Ca2+ ions, the emission intensity was significantly enhanced, especially when the Ca2+ ion doping concentration reached 6 mol%, resulting in the maximum emission intensity. Furthermore, we investigated the effects of matrix structure and lattice distortion on the spectral properties by employing Judd-Ofelt (J-O) theory and studying energy transfer mechanisms. The mechanisms of Ca2+-induced fluorescence quenching and factors influencing the fluorescence decay time were analyzed. Through the analysis of the absorption cross-section, emission cross-section, and gain cross-section of crystals with different Ca2+ ion concentrations, it was found that Ca2+, Er3+: KBYM crystals exhibited a low laser pump threshold. The results demonstrate that the 6 mol% Ca2+, 5 mol% Er3+: KBYM crystals possess excellent performance and are a promising laser gain medium.

Dynamics of laser-induced plasma and cavitation bubble at high pressures and the impacts on underwater LIBS signals

Characteristics of laser-induced plasma depends strongly on its ambient pressure, and a deeper understanding of the high pressure impact on the underwater plasma emission is essential for the application of LIBS in the deep-sea. In this work, we investigated the temporal evolution of underwater plasma and cavitation bubble at the high pressures up to 50 MPa, by using fast imaging and shadowgraph techniques. It showed that as the ambient pressure increases, the plasma expansion is much suppressed with a stronger emission intensity and a slower emission decay, but it quenches much earlier and ends with a sharp drop at the higher pressures. From the shadowgraph imaging results, it showed that the increase in pressure has a great impact on the bubble evolution. Both the bubble maximum radius and the bubble lifetime decrease dramatically with the pressure as a consequence of faster dynamics. By comparing between the plasma and bubble results, we demonstrated the critical role of bubble dynamics on the characterization of plasma emission at high pressures. At relatively low pressures, the bubble expansion time is long enough to finish the plasma radiation. While at high pressures, strong bubble-plasma interaction occurs that will guide the plasma evolution behavior at the late stage. The plasma can gain energy from the confinement effect caused by the bubble shrinking process which leads to an increase in the emission intensity, but it will quench immediately after the bubble collapse. Such effects caused by bubble dynamics at high pressures explain well the evolution behaviors of underwater LIBS signals of OH, Ca II, Ca I, and CaOH, considering the different lifetimes of these emitting species in the plasma. This work reveals the complex impacts of high pressure on underwater plasma emissions and underwater LIBS signals.

Structural, morphological and luminescence properties of hafnia nanoparticles obtained by hydrothermal synthesis

Hafnia is a novel material for optoelectronic applications, fabrication methods are focused to obtain hafnium oxide nanomaterials included thin films and nanoparticles. HfO2 nanoparticles synthesized and studied in this work are crystalline without subsequent heat treatment and were processed by hydrothermal method at 200 °C during 1.3, 2 and 4 h. SEM and TEM analysis revealed the presence of spherical and oval nanoparticles, with range size from 60 to 70 nm and 90–110 nm for spherical and oval nanoparticles, respectively. Raman spectroscopy and X-ray diffraction confirmed that nanoparticles exhibit a stable monoclinic phase. Crystal growth is typical with the presence of the characteristic monoclinic plane (1‾11) but for reaction times of 2 and 4 h and pH over 12 it turns in the plane (220) which is perpendicular to typical growth. Cathodoluminescence measurements revealed strong blue emission intensity showing a broadband in all visible range and a maximum peak at 460 nm. The presences of VO3 and VO4 in HfO2 crystalline structure are responsible for this inherent CL emission corroborated by photoluminescence studies.

Quantitative detection of citrate for early stage diagnosing of prostate cancer: Discriminating normal to cancer in prostate tissues

Prostate cancer (PC) biomarker-citrate detection is clinically important to diagnose PC in early stages. Methylquinolinium iodide (Q) conjugated indole-phenylboronic acid (IB) was designed as a red-emissive QIB probe for the detection of citrate through Lewis acid–base reaction and intramolecular charge transfer (ICT) sensing mechanisms. Boronic acid acts as Lewis acid as well as citrate (Lewis base) recognition unit. The probe reacted with citrate, showing enhanced red emissions. Since the probe has excellent water solubility and great biocompatibility, practical application in biological systems is possible. Citrate was monitored precisely in the mitochondria organelle (in vitro) of living cells with a positive charge on QIB. Also, endogenous (in situ) citrate was detected quantitatively to discriminate non-cancerous and PC mice, observed strong and lower (negligible) emission intensity on non-cancerous and cancerous prostate tissues, respectively. Because, the concentration of citrate is higher in healthy prostate compared with PC prostate. Furthermore, the analysis of sliced prostate tissues can give PC-related information for clinical diagnosis to prevent and treat PC in the initial stages. Therefore, we believe that the present probe is a promising biochemical reagent in diagnosing PC.

Single-dislocation ultraviolet light emission

Micro-nano ultraviolet light sources have recently attracted great attention due to their promising applications in future quantum display, photoelectric detection sensors, biomedical devices, and so on. Design of ultraviolet light sources with smaller size, stronger emission intensity, and higher integration, are the key aspects for the development of high-performance micro-nano ultraviolet devices. Here, we demonstrate that unidirectional threading dislocation arrays in an AlN thin film can emit ultraviolet light with wavelength of ∼ 317 nm. The density of AlN dislocations is ∼ 4 × 1010 cm−2, and the light emission intensity of AlN dislocations is comparable to the intrinsic emission of the AlN thin film. By combining aberration-corrected transmission electron microscopy, atomic-resolution valence electron energy-loss spectroscopy, and first-principles calculations, the atomic and electronic structures and the band gaps of the AlN threading dislocations are determined. It is found that the AlN threading dislocations are comprised of edge, screw, and mixed dislocations. All the AlN dislocations exhibit smaller band gaps compared to the AlN bulk due to the increase of the Al-N bond length at the dislocation cores. The dangling bonds of Al and N at the edge dislocations, Al-Al and NN bonds at the screw dislocations cause the defect states in the band gaps. This study not only has clarified the atomic origin of dislocation nano-optics, but also will encourage the development of microelectronics and optoelectronic devices based on dislocation ultraviolet light emission.

The blue fluorescence luminescence properties of hyperbranched polysiloxane containing halogen atom

AbstractIn order to obtain a new class of aggregation‐induced emission (AIE) polymers without common conjugated chromophores in their structures, hyperbranched polysiloxanes (HBPSi) containing halogen elements were obtained by introducing chlorine and bromine atoms into HBPSi (Cl‐HBPSi, Br‐HBPSi) through one‐step polycondensation reaction. The relationship between the chemical structure and fluorescence properties of the two types of HBPSi was studied. The results show that both Cl‐HBPSi and Br‐HBPSi prepared in this study can emit bright blue light under a UV lamp of 365 nm wavelength, and appropriate ratio of raw materials can endow the halogenated HBPSi with moderate degree of polymerization, and give it strong excitation intensity and emission intensity. Meanwhile, Br‐HBPSi exhibits a higher fluorescence intensity, which is due to the ‘heavy atom effect’ of halogen atoms. In addition, for different concentrations of tetrahydrofuran (THF) solutions with the same addition of HBPSi, the luminescence intensity increases gradually with the decrease of THF concentration. These results indicate that the emission intensity is affected by the molecular weight and concentration of polymers, and that the AIE properties of halogenated HBPSi are related to the ‘impurity atomic clusters’ formed by halogenated atoms and the hydroxyl groups formed by the heterogeneity of HBPSi. © 2023 Society of Industrial Chemistry.

Serial Dynamics, Spatial Spillover and Common Factors of Carbon Emission Intensity in China’s Bohai Economic Rim

The Bohai Economic Rim (BER) is an important economic Rim in north China. Since the implementation of the Beijing−Tianjin−Hebei Coordinated Strategy in 2014, the provinces have become more closely connected in economic development and environmental governance. This paper investigates the dynamics and spillover effects of carbon emission intensity in the BER before and after removing the common factors, and analyzes the reasons for the difference. In this study, the serial dynamics characteristics and spatial spillover effects of the carbon emission intensity of provinces were analyzed in the BER provinces between 2000 and 2019. Based on the Moran index and the spatial Durbin model, the provincial carbon emission intensity and influence factors were examined. CD (Correlation Dependence) tests were then applied, with the test results indicating that the carbon intensities had strong spatial correlation. Therefore, the dynamic spatial Durbin common factor model was introduced, characterizing the dynamic characteristics of the carbon emission intensity and the spatial spillover effect in the BER. The consequences obtained are as follows: (1) The carbon emission intensities in the BER were influenced by the energy intensity, urbanization level, economic growth, and population density. There was a significant spatial spillover effect between a province and its neighboring provinces. (2) The carbon emission intensities of the provinces exhibited a strong correlation. (3) The reason for the strong carbon emission intensity correlation is associated with environmental protection policies that are similar and the common external development environment. Combining the above findings and study conclusions, the authors offer the following policy suggestions: (1) optimize the energy structure; (2) improve the industrial structure; (3) construct a regional collaborative governance mechanism for carbon emissions; and (4) formulate a precise policy. This study is crucial for reducing regional carbon emissions, promoting the transition to a green economy and society, and achieving the “carbon peaking” and “carbon neutrality” targets in China.

Synthesis and surface modification of ultrasmall monodisperse NaYF4:Yb3+/Tm3+ upconversion nanoparticles

The emerging upconversion nanoparticles (UCNP) have gained substantial consideration in the field of bioanalytical as well as diagnostic applications. Therefore, great progress has been made in the synthesis and surface modification of luminescent UCNPs over the last two decades. In this paper, we have reported monodispersed and high luminescent upconversion nanoparticles NaYF4: 20%Yb3+, 2%Tm3+ have been synthesized using a solvothermal method, followed by a coating of the NaYF4 shell with a thin layer of SiO2 on the surface to afford the core-shell NaYF4:Yb3+, Tm3+@SiO2 nanoparticles (NP@SiO2). The prepared nanoparticles were of strong upconversion fluorescent emission intensity, hexagonal phase, and with an average size of about 8 ± 1 nm, which have been characterized by luminescence spectroscopy, powder X-ray diffraction (P-XRD), Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). The results indicate that the NP@SiO2 can be used for the conjugation of fluorescent probes for various biomolecules and can find applications in cancer cell imaging and disease diagnosis.