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Large‐scale production of two‐dimensional (2D) materials still is a crucial point toward its practical applications. Violet phosphorus (VP) with a wide bandgap accelerates and broadens the potential applications of elemental phosphorus in optoelectronics. Here, we demonstrate the scalable production of solution‐processable violet phosphorus flakes stably dispersed in several solvents. The exfoliated VP flakes exhibit thickness‐dependent visible photoluminescence characteristics, which covers the shortcoming of black phosphorus. Meanwhile, the VP‐based field‐effect transistor reveals relatively competitive electrical properties to other liquid‐phase exfoliated 2D materials. Our study paves the way for a wide range of applications of optical devices, energy storage, catalysis, and sodium batteries based on large‐scale VP flakes.

Realizing multicolored luminescence in two-dimensional (2D) nanomaterials would afford potential for a range of next-generation nanoscale optoelectronic devices. Moreover, combining fine structured spectral line emission and detection may further enrich the studies and applications of functional nanomaterials. Herein, a lanthanide doping strategy has been utilized for the synthesis of 2D ZnSe:Er

Ultrathin two-dimensional (2D) materials have drawn great attention in recent years due to their promising applications in biomedicine and atomically optoelectronic devices. In this work, we have fabricated a 2D In2Se3 nanosheet doped with Nd3+ ions via the two-step method of solid phase synthesis and liquid exfoliation. Owing to the special inner 4f-4f energy level transitions, lanthanide ions can emit photons with almost the same energy in different environments. Here, a stable near-infrared luminescence from Nd3+-doped 2D In2Se3 nanosheets has been realized, which includes emission bands around 910, 1057, and 1324 nm. The doping of Nd3+ ions extends the emission region of In2Se3 nanosheets. Moreover, the photoluminescence mechanism of Nd3+ ions was investigated through a series of optical measurements. This work not only provides a reliable method to fabricate lanthanide ion-doped 2D materials but also possesses a great significance for luminescence study of lanthanide ions in the 2D matrix.

Lanthanide ions have attracted great attention due to their distinct photonic properties. The optoelectronic properties and device performance are greatly affected by the interfacial coupling between the layered van der Waals heterostructure, fabricated with two or more transition metal dichalcogenide (TMD) layers. In this work, lanthanide-doped WS2/MoS2 layered heterostructures have been constructed through two synthesis steps. The doped thin films are highly textured nanosheets on wafers. Importantly, the as-prepared heterostructure exhibits efficient near-infrared emission in the range of the telecommunication window, owing to energy transfer between lanthanide ions in the two TMD layers. The use of the layered heterostructure allows the decrease of deleterious cross-relaxation due to homogeneous doping or concentration quenching. The energy transfer process was further elaborated in this work. The results suggest that lanthanide ions can effectively extend the emission band of TMD thin films and their heterostructures. The doped TMD heterostructure is highly favourable for constructing atomically thin near-infrared photonic devices.

The sensing of temperature is closely related to human life. The noncontact ratio temperature measurement method has extensive applications in biochemical monitoring and industrial production. Howe...

Ferroelectric oxide nanocrystals, in combination with the robust coupling of an electric field with crystal structure symmetry, makes such systems agreeable to field-induced crystal structural transformation. The luminescent properties of rare earth ions are sensitive to the symmetry of the surrounding crystal field. The luminescence tuning of rare earth ions is an important assignment in the research of luminescent materials. However, the current conditional feasibility and reversibility in the exploration of luminescence modification remain major challenges. In this article, the luminescence modulation of rare earth ions has been developed in Yb3+/Er3+ codoped ferroelectrics glass ceramics containing Bi4Ti3O12 nanocrystals through an electric field. The inclusion of nanocrystals in the glass matrix greatly enhances the electrical resistance. Both upconversion and near-infrared emissions of rare earth ions are effectively enhanced more than twice via polarization engineering. The electric field regulates the photonic properties of rare earth ions with excellent reversibility and nonvolatility in ferroelectrics. The effective modification by electric field provides a new scheme for optical storage and optoelectronic devices.

Luminescence modification of lanthanide ions has attracted great attention due to its applications in sensing, colorful display, information transmission and anti-counterfeiting. Traditional methods of tuning fluorescence typically employ tuning compositions that are not conducive to the development of multi-environment detection and anti-counterfeiting. In this study, lanthanide ions doped ferroelectric nanocomposite was exploited with external stimuli. The upconversion luminescence modification was preformed via both the thermal and electric fields. The anti-thermal quenching phenomenon was observed in the prepared nano-composite, which could effectively enhance the upconversion luminescence of lanthanide ions. Based on the electromechanical softness of the ferroelectric lattice, exceptional luminescence modification was realized through electric polarization. The luminescence modifications by thermal and electric fields exhibited excellent reversibility and non-volatility. These results provide unique insights into the development of integrated stimulus responsive smart devices, colorful display and advanced multi-mode sensing materials.

Manipulating the energy transfer process between the dopants can realize efficient modulation of photoluminescence, which is essential for fabricating optoelectronic devices. This work presents the polarization-assisted energy transfer process between Er3+ and Dy3+ ions in borate glass-ceramics system for the first time. The overall photoluminescence intensities increased gradually as undergoing polarization engineer. The promoted energy transfer process from Er3+ to Dy3+ is obtained by emission spectra and verified by decay dynamics, which can be attributed to the slight tuning of ionic environment around doping ions. Herein, the tunable energy transfer process inspired by polarization may provide guidance for fabricating high-performance optoelectronic devices.

With 980 nm laser diode (LD) pumping sources, 2.7 µm emission of Er3+-doped tungsten-tellurite (TWL) glasses were investigated. Absorption spectra were measured and an irregularly increased absorption predicted the phenomena of concentration quenching or clustering at 4 mol% Er2O3 concentration. Emission properties of 2.7 µm, 1.5 µm and visible regions were tested to evaluate the energy transfer process of Er3+ ions. With the increment of Er3+ ions, the excited-state absorption (ESA) from Er3+: 4I13/2 level was becoming more apparent and the lifetime of 1.5 µm emission was decreased. At the same time, the up-conversion emissions at green and red regions were decreased. These phenomena gave the evidence of concentration quenching or clustering. Thus, the best concentration of Er3+ ions in this tungsten-tellurite glass was about 3 mol%. Based on its advantages on high solubility of Er3+ ions, strong emission and good thermal stability, tungsten-tellurite glass is a good candidate for mid-infrared laser matrix.

Two-dimensional inorganic semiconductor materials have aroused tremendous research interest and found their potential in resolving the present urgent global issues, such as cancer therapy and fresh water shortage. Particularly, the near-infrared (NIR) photothermal conversion efficiency is a significant parameter in photothermal therapy. However, lack of an effective improvement strategy and their relatively low NIR phothermal conversion efficiency would restrict their wide and further application. Here, this work reports that enhanced NIR photothermal conversion is achieved in topological Bi2Se3 nanosheets by introducing a lanthanide dopant. Specifically, lanthanide Pr-doped Bi2Se3 nanosheets possess a photothermal conversion efficiency of 49.5%, which is higher than those of undoped Bi2Se3 nanosheets (31.0%) and numerous reported photothermal materials. The electronic structure of Pr-doped Bi2Se3 nanosheets was also analyzed by first-principles simulation. Furthermore, an interfacial evaporation system based on the developed nanosheets has been established, demonstrating a superior solar-thermal conversion efficiency of 91.5% and a water evaporation rate of 1.669 kg m-2 h-1 under 1 sun irradiation. The present work would provide new insights for the increase in the efficiency of photothermal materials.

The development of integrated multifunctional materials with transparent characteristics meets the requirements of optoelectronics and communication. The coupling of stimuli-responsive materials has become a frequently considered strategy. Experimentalists not only search for photonic materials with excellent physical and chemical properties, but also pursue precise and reversible spectral modification. In this study, the luminescent center Ni2+ is artificially introduced into the transparent LiNbO3 nanoferroelectric photonic materials. The Ni2+ ion-based transparent photonic materials exhibit novel complete ultra-broadband emission in the whole near-infrared region. Until now, the ultra-broadband emission was realized by codoping of several active doping ions. In addition, the emission intensity and wavelength of the luminescent center are modified accurately and reversibly by field-induced nanoscale structural transformation. The Ni2+ ion-based transparent nanoferroelectric photonic materials provide an easy way to develop tunable lasers and ultra-broadband optical amplifiers.

Lanthanide ion doped ferroelectric oxides have unique ferroelectric and luminescence properties, which show great promise for future optoelectronic applications. Moreover, it is of great interest that the luminescence of ferroelectric materials can be effectively modulated by an external electric field. In this work, Nd3+ doped ferroelectric nanocomposites with near-infrared emission have been developed to study their optoelectronic properties and reversible tuning. At room temperature, the near-infrared emission has been enhanced over 4.6 times and the intensity can be controllably modulated by tuning the electric field. The mechanism behind the enhancement and reversible modulation has been investigated for designing luminescence memory or optoelectronic sensors. This work suggests a way for not only studying the luminescence properties of optical materials via polarization engineering, but also for potentially developing multifunctional materials for optoelectronic applications.

The emission properties of lanthanide ions have been extensively investigated for their interesting physical processes and enormous applications. Conventional strategies have been used to modify luminescence properties such as temperature, pressure, and modifying components. However, the traditional methods are volatile and irreversible, which is unconducive for some optoelectronic applications. In this article, the electromechanical softness of the ferroelectric lattice is employed, which makes the strong coupling relationship between the electric field and the photonic properties of lanthanide ions. The emission intensity of the Tm3+:3H4-4H6 and 3F4-4H6 transitions was exceptionally enhanced by 2.6 and 3.2 times via ferroelectric polarization, respectively. Meanwhile, the luminescence response presents excellent reversibility and nonvolatility. This study provides a unique proposal for designing highly integrated stimuli-responsive photonic materials toward a variety of applications.

Control over porosity and crystal orientation is a huge challenge in the field of materials science. Cathode materials with high porosity and reactivity of exposed crystal planes contribute to the charge transfer kinetics, structural stability and interfacial compatibility between electrode and electrolyte. In this paper, hierarchically porous urchin-like LiNi0.5Mn1.5O4 hollow spheres comprising aggregated nanosheets with highly exposed {111} facets have been successfully synthesized with ultrathin MnO2 nanosheets encapsulating poly styrene spheres as precursor. Transmission electron microscopy results present the crystal orientation of target cathode material is exposed with dominant {111} facets, which could effectively relieve the dissolution of manganese from the lattice, thus leading to an excellent cycling stability. The charge-discharge characterizations demonstrate that the resultant urchin-like LiNi0.5Mn1.5O4 hollow spheres exhibits excellent rate capability and high-rate cyclic stability. Notably, even at a high rate of 30 C, the battery can deliver about 92% of the initial discharge capacity retention after 1500 cycles. Experiment results and theoretical calculation indicate that the superior performance of the synthesized product can be ascribed to its intrinsic structure and preferred orientation growth of {111} facets. Therefore, hierarchically porous urchin-like LiNi0.5Mn1.5O4 with highly exposed {111} plane is a promising cathode material for high-energy density lithium-ion batteries.

Ferroelectrics doped with active luminescent ions have gradually paved the path of optoelectronic industry due to their multifunctionality and the dynamic modulation of luminescent properties through electric method widely broadens their application prospect in future devices. In this work, a novel strategy without compositional change is employed on the Er3+ doped transparent hybrid enriched with nano-sized ferroelectric LiNbO3 crystals to investigate the tunable photoluminescence performance. The results demonstrate that the photoluminescence acquires a tremendous boost after polarization engineering, that is, a six times enlargement. This notably light amplification effect is propelled by the reduction of environmental symmetry around luminescent Er3+ ions that is originated from electric polarization. Additionally, the prepared samples are proved to possess optical and electric properties simultaneously. Therefore, this multifunctional material with tunable luminescent properties is beneficial for regulating the physical couplings of electric and optics, which highlights the prospect in future optoelectronic industry.

Methylammonium lead iodide perovskite (MAPbI 3), as a new type of light absorber for optoelectronic devices, has attracted much interest and served as foundation for new device concepts. However, most studies to date are mainly focusing on the fabrication of MAPbI3 -based solar cells and photodetectors . Here we report a facile method to prepare a large-scale MAPbI 3 photocatalyst through atmospheric pressure physical vapor deposition . The photocurrent density of the MAPbI 3 coated with an Au layer can reach 30.8 and 85.5 μA/cm2 in ethanol and H2SO4 electrolytes, respectively. Meanwhile, the strong interaction between H2O orbitals and the conduction band of MAPbI3 is revealed by density functional theory calculations. Our study opens a new pathway for the development of perovskite-based photo-electrochemical reaction systems.

The non-contact thermometry based on fluorescence intensity ratio of phosphors has been extensively investigated owing to its high sensitivity and fast response. However, most of them only use a single mode of upconversion or downconversion emission for temperature sensing and ignore the affection of the humidity. In this work, the Yb/Er ions doped La2Mo3O12 microcrystals with nonhygroscopic property and multimode luminescence have been developed for temperature sensing. The optical thermometer could be based on not only luminescent intensity ratio of upconversion and downconversion, but also average fluorescence decay lifetime. The maximal absolute sensitivity can reach up to 6.2% K−1 and the maximal relative sensitivity is 1.63% K−1. Moreover, the fluorescence emission intensity of the doped La2Mo3O12 microcrystals will not be affected by the humidity compared to some doped molybdate and tungstate. These excellent performances suggest that the La2Mo3O12:Yb/Er microcrystals possess great potential for practical applications in temperature sensing.

Luminescent materials with negative thermal quenching effects show superior potentials in temperature sensing and anti-counterfeiting fields. Normally, smaller nanocrystals (NCs) with higher surface-to-volume ratios are used to achieve larger thermal-induced intensification of upconversion (UC) emission intensity. Herein, confining sensitizers and activators to the shell layer with two-dimensional space and introducing defect energy levels via doping low-valence ions are simultaneously applied to enhance the negative thermal quenching effect. By increasing the temperature from 293 K to 413 K, the integral UC emission intensity of 20Yb/2Er:NaGdF4 increases only by ∼2.2 times, whereas that of NaGdF4@20Ca/20Yb/2Er:NaGdF4 core–shell NCs with a similar particle size increases by ∼10.9 times.

Atomically thin layers of transition metal dichalcogenides (TMDs) have recently drawn great attention. However, doping strategies and controlled synthesis for wafer-scale TMDs are still in their early stages, greatly hindering the construction of devices and further basic studies. In this work, we develop the fast deposition of wafer-scale layered lanthanide ion Yb/Er co-doped WSe2 using pulsed laser deposition. WSe2 nanosheets were chosen as the host, while Yb3+ and Er3+ ions served as the sensitizer and activator, respectively. The obtained Yb/Er co-doped WSe2 layers exhibit good uniformity and high crystallinity with highly textured features. Under the excitation of a diode laser at 980 nm, down-conversion emission is observed at around 1540 nm, assigned to the emission transition between the 4I13/2 and 4I15/2 states of Er3+. Considering the significance of 1540 nm luminescence in the application of photonic technologies, this observation in the WSe2:Yb/Er nanosheets down to the monolayer provides a new opportunity for developing photonic devices at the 2D limit. Our work not only offers a general method to prepare wafer-scale lanthanide doped TMDs, but also to widely modulate the luminescence of atomically layered TMDs by introducing lanthanide ions.

At present, the shortage of potable water is still a critical issue. The emerging of solar-driven evaporation technique offers a promising way to solve freshwater scarcity. However, developing highly efficient evaporation system is still a challenge. Herein, this work developed two-dimensional heterostructure nanosheets as the photothermal agent. We used the WSe2 nanosheets to enhance the absorption of graphene and facilitate the heat localization due to its higher visible light absorption and ultralow thermal conductivity. And graphene provided the low surface reflection and a broad absorption spectrum. Moreover, the enhanced near infrared photothermal conversion of the heterostructure nanosheets is realized to be 41.4% higher than some previous works by introducing lanthanide ions. A series of experiments are performed to determine its heterostructure. Besides, the interfacial evaporation system has been constructed based on as-prepared nanosheets, exhibiting excellent solar-to-heat efficiency of 91.8% and water evaporation rate of 1.672 kg m−2h−1 under stimulated 1 sun irradiation. It is suggested that developed nanosheets have the potential application for highly effective solar-driven evaporation.

The dual-functional optical materials that can achieve accurate temperature sensing and effective photothermal conversion have aroused great concern in biomedical and industrial fields. However, the lack of optical functional materials limits the photothermal devices in practical applications. In this work, the pure monoclinic Ho3+/Yb3+ codoped La2Ti2O7 microcrystals have been successfully synthesized for optical thermometry and photothermal conversion. Different from the partial overlap of thermal coupling energy levels in Er3+, the wide separation of emission bands in Ho3+ reduce the calculation error of ratio-metric thermometry. The maximum value of sensitivity reaches 1.41% K−1. And the light-to-heat energy conversion of the sample has been explored by some photothermal experiments. It is confirmed that the sample can be heated to the specified temperature by adjusting the power of the heating light source. Meanwhile, the photothermal imaging can be achieved because of the high photothermal conversion of the material. Besides, the dual-functional prototype probe based on La2Ti2O7:Ho3+/Yb3+ microcrystals has been made to investigate the temperature sensing and photothermal conversion performance. These results illustrated the sample has potential applications in optical thermometry and biological photothermal therapy.

Room-temperature magnetoresistance (MR) effect is observed in heterostructures of wafer-scale MoS2 layers and ferromagnetic dielectric CoFe2O4 (CFO) thin films. Through the ferromagnetic gating, an MR ratio of −12.7% is experimentally achieved in monolayer MoS2 under 90 kOe magnetic field at room temperature (RT). The observed MR ratio is much higher than that in previously reported nonmagnetic metal coupled with ferromagnetic insulator, which generally exhibited MR ratio of less than 1%. The enhanced MR is attributed to the spin accumulation at the heterostructure interface and spin injection to the MoS2 layers by the strong spin–orbit coupling effect. The injected spin can contribute to the spin current and give rise to the MR by changing the resistance of MoS2 layers. Furthermore, the MR effect decreases as the thickness of MoS2 increases, and the MR ratio becomes negligible in MoS2 with thickness more than 10 layers. Besides, it is interesting to find a magnetic field direction dependent spin Hall mag...

International audience; In this work, Er3+ doped ferroelectric glass ceramics containing high-content BaTiO3 nanoperovskite have been prepared successfully. Optical behaviors with structural dependence indicate that the perturbation of ligand field by tunable thermal condition in glass-ceramics is beneficial to boost upconversion efficiency, that is, the emission intensity possesses multifold improvement in both green band (2H11/2, 4S3/2 → 4I15/2) and red band (4F9/2 → 4I15/2). And adding voltage to stimulate polarization reversal of ferroelectric domains has been investigated as a physical mode to broaden luminescence emissions in visible range. Compared with the unpolarized glass-ceramics, over 1.5 folds higher luminescence intensity can be obtained by polarizing the samples. The multiple mechanisms to achieve upconversion enhancement in ferroelectric materials will stimulate and expand the use of innovative optoelectronic devices.

The phosphorus-doped carbon nitride nanosheets (P-g-C3N4 nanosheets) were prepared by ultrasonic stripping. Through the performance characterization, it was found that the P-g-C3N4 nanosheets emitted pure blue light with stable performance. Compared with other metal ions, it was found that the quenching reaction between P-g-C3N4 nanosheets and Fe3+ was the strongest. The detection limit of Fe3+ was found to be about 1.63 μM. P-doped g-C3N4 is expected to be an efficient fluorescent probe for Fe3+ detection.

Multifunctional optical sensing devices are of decisive significance to the miniaturization and integration of optoelectronic devices. However, the development of stimuli responsive materials with multimode emission is still in the early stage, limiting the application of integrated optical sensing. Here, we report the multimode emission piezophotonic material fabricated by doping lanthanide ions into the quaternary piezoelectric semiconductor SrZnOS, achieving multimode emission under various stimulus/excitation sources (ultraviolet, near-infrared laser, X-ray, and force), due to its multifunctional optical properties. Particularly the mechanoluminescence has been realized covering both the visible and near-infrared spectral bands. Optical stress sensing was achieved by establishing a quantitative relationship between force and light conversion. Moreover, near-infrared mechanoluminescence can effectively resist the interference of ambient light. The temperature detection performance and the power-dependent color tunability of the sample were also evaluated for multifunctional applications. All the results indicate that the developed multifunctional optical materials with inherent multimode light-emitting characteristics have the potential in advanced optical sensing and anti-counterfeiting applications.

The optical thermometer materials have drawn tremendous attention for their excellent performances, such as fast response, well-adapted, and non-contact. However, most phosphors present thermally quenched emissions, which greatly weakens temperature sensing. In this work, we synthesized Yb3+/Nd3+ codoped CaTiO3 microcrystals by solid state reaction. Under the excitation of 980 nm, the developed perovskite particles present anti-Stokes emissions at the near-infrared range. More importantly, the near-infrared anti-Stokes emissions gradually get enhanced as the temperature rises. An optical ratiometric thermometer has been constructed based on the energy level transitions of Nd3+ ions (4F7/2/4F5/2 →4I9/2). On account of the thermally enhanced emissions, the prepared thermometer only needs 16 mW/mm2 power density, and has a relatively high sensitivity of 1.52 % K−1. Therefore, the prepared Yb3+/Nd3+ codoped CaTiO3 crystal is a promising optical thermometer material with great application prospects.

Two-dimensional transition metal dichalcogenides (2D TMDs) have drawn considerable attention due to their promising applications in biomedical and optoelectronic areas. However, the emission of 2D TMDs materials and devices is mostly limited from visible to the edge of near-infrared (NIR), which restricts their wide applications. Herein, we develop Er doped WSe2 nanosheets through cation exchange and ultrasonication-assisted liquid-phase exfoliation. Thanks to the Er ions, the luminescence of 2D nanosheets can be extended to NIR II window. The emission at NIR II range can effectively penetrate several centimeters thick biological tissue. Furthermore, a series of photothermal experiments is also performed with 808 nm laser. The photothermal conversion efficiency of as-produced nanosheets is determined to be as high as 35.2%, which is greatly higher than many previous reports. It suggests that as-prepared nanosheets combining NIR II emission and highly effective photothermal conversion property may be promising as a bifunctional agent for bioimaging and photothermal therapy.

Lanthanide-doped luminescent materials have drawn great attention due to their lighting, display, and sensing applications. However, their emission intensity usually decreases with increasing temperature, leading to a weaken performance. In this work, the Er3+-doped Yb2Mo3O12 microcrystals with optical temperature sensing properties have been synthesized by a solid-phase sintering route. Under the excitation of a 980 nm laser, the sample shows enhanced upconversion emissions as temperature rises, which is attributed to the negative thermal expansion in the crystal structure and enhanced crystal field strength. At the same time, based on the luminous intensity ratio of two thermally coupled energy levels (Er3+:2H11/2,4S3/2), the temperature sensing properties of the prepared microcrystals were studied. This work achieves high SR (1207.4/T) in the range from 313 to 573 K, and it is accompanied by a 21-fold enhancement of the upconversion emission intensity. As a whole, this is an excellent material that can be used for optical temperature sensing with highly sensitive and enhanced upconversion emission.

Triboelectric nanogenerator (TENG) as a promising approach has attracted extensive attentions from academic and industry. Herein, a novel strategy of wind and blue energy harvesting based on magnetic-assisted noncontact TENG has been demonstrated. Through the combination of magnetic responsive composite with TENG device, the wind and water forces could be converted into the contact-separation action between Al/Ni electrode and PDMS film. The influence of the relevant parameters (contact-separation frequency, wind speed and humidity, etc.) on the performances of the fabricated TENG has been systematically investigated. The results show the robust potential of magnetic-assisted noncontact TENG for wind and blue energy harvesting applications.

Luminescent ions doped materials have been widely applied in many areas, both scientific research and practical fields. Recently, incorporating luminescent ions and advanced materials into versatile and multifunctional systems seems to be a tendency, motivated by the stimulating desires of fundamental studies and technological applications. This feature article provides a general overview of the myriad of luminescent ions-based advanced composite materials recently investigated. It is demonstrated that the improved or additional properties may be achieved via implementing a strategy of incorporating luminescent ions (lanthanide, transition and main group metal ions) into various types of materials, such as flexible polymers, two-dimensional atomically thin layers, porous materials, and so on. We outline the design principles, synthesis and processing of various systems joined by luminescent ions doped phosphors. A number of recent works indicate that those novel composite materials allow one to conceive and develop multifunctional applications in a broad area, including optoelectronics, photonics, clean energy, biomedicine, and new types of sensors. Lastly, some challenging issues are discussed and potential directions are suggested for further developing advanced composite materials incorporated with luminescent ions.

Thin films of Yb3 +/Er3 + codoped Pb(Zr,Ti)O3 (PZT:Yb/Er) have been epitaxially grown on the SrTiO3 buffered Si wafer by pulsed laser deposition. Strong upconversion photoluminescence was observed in the PZT:Yb/Er thin film. Using piezoresponse force microscopy, polar domains in the PZT:Yb/Er film can be reversibly switched with a phase change of 180°. Ferroelectric hysteresis loop shape with a well-saturated response was observed. The epitaxially grown lanthanide-doped PZT on silicon opens up a promising route to the integration of luminescent functional oxides on the silicon platform.

International audience; Lanthanide-doped luminescent materials have been widely used in the field of information security and optical sensing, owing to their unique optical properties. However, conventional luminescent materials usually exhibit unicolor and single-peak emission, which leads to a decrease in the application efficiency of anti-counterfeiting and optical temperature sensing. In this work, we have successfully developed a series of novel multi-mode stimulation luminescent materials in the Ca2Nb2O7 system via the solid phase reaction. This luminescent material is synthesized by doping dual lanthanide ions to realize adjustable multi-mode luminescence, which simultaneously create luminescent centers and carrier traps in the host lattice. The multi-colored emission can be realized under different excitation wavelengths. Meanwhile, it has a combination of fluorescent phenomenon by upconversion, down-shifting and thermal stimulation. In addition, the fluorescence intensity ratio of lanthanide ions shows significant temperature dependence, and the maximum Sr is 0.0072 K−1 at 293 K. Hence, we have fabricated a novel material that can be used for multi-mode anti-counterfeiting and optical temperature sensing. © 2020 Elsevier B.V.

Optical thermometer based on luminescent materials plays a vital role in many fields due to its fast response and non-contact properties. However, most of the luminescent materials are primally affected by thermally quenching effect, which restricts the range and accuracy of optical temperature sensing. In this work, the Yb3+/Nd3+ codoped LiNbO3 ceramics with thermally enhanced emission have been fabricated for a fluorescent ratiometric thermometer. The temperature sensing is based on the two thermally coupled levels of Nd3+:4F7/2 and 4F5/2 under 980 nm excitation. Due to the anti-thermal quenching effect, the near-infrared emission intensity of the two levels increases as the temperature rises. The thermally enhanced anti-Stokes emission leads to an excellent temperature measurement performance. The relative sensitivity is determined to be as high as 0.5747% K−1. Besides, the ceramics also exhibit an excellent repeatability after five heat-cooling cycles. These results suggest that the Yb3+/Nd3+ codoped LiNbO3 ceramics could be a promising near-infrared thermometer in the temperature sensing fields.

Novel blue LED excitable Ce3+-doped alkaline-earth sulfide nanocrystals are exploited for selective and sensitive Fe3+ ions sensing in this work. The detection limit is calculated to be as low as 92.5 nM, which is better than most previous ultra-violet light excited fluorescence probes. The decreased radiative probability of the Ce3+: 5d by the NC surface environmental variation activates the sensing capability.

The beta-Ga2O3 with wide bandgap is an important semiconductor for optoelectronic applications. In this work, the Er3+-doped beta-Ga2O3 with upconversion emissions has been prepared for optical thermometry. The upconversion emission spectra include green bands around 522 and 554 nm, red emission band around 654 nm by a 980 nm laser excitation. A luminescence thermometer is constructed with the emission intensity ratio of the 2H11/2 → 4I15/2 and 2S3/2 → 4I15/2 transitions in Er3+ ions. The maximal relative and absolute sensitivities were 1.08% and 3.56 × 10−3 K−1, respectively. This work indicates that Er3+ doped beta-Ga2O3 could be a promising optical thermometer in integrated optoelectronics.

Lanthanides doped optical materials with temperature sensing property are of great interest for optical thermometry. However, most lanthanides doped luminescent materials for ratiometric thermometer are often accompanied by thermal quenching, which leads to a decrease in temperature sensing performance. Here, Nd3+ doped Yb2Mo3O12 phosphor with near-infrared upconversion emissions has been fabricated. A non-contact thermometer is constructed with the luminescence of Nd3+ ions and the change of the emission peak height ratio of 4F7/2-4I9/2 and 4F5/2-4I9/2 transitions. Interestingly, the intensity of the emission peaks in the prepared phosphor increases with increasing temperature. Avoiding thermal quenching, the thermally enhanced upconversion emission affords high sensing accuracy. The maximum relative and absolute sensitivity was 1.186% and 9.789 × 10−3 K−1, respectively. The results suggest that appropriate emission bands with thermal population are benefit for optical ratiometric thermometers.

In this study, a multi-color and multi-mode luminescence material has been developed for anti-counterfeiting and temperature sensing. The rare earth ions Er 3 + are selected as the luminescent center to be doped in the piezoelectric material ZnS. The prepared samples can generate multi-color (orange–yellow–green) and multi-mode (upconversion/down-shifting/energy transfer) emission through the energy transitions of lanthanide ions in the ZnS host. When the excitation wavelength or the temperature is selected to be different, the luminous color is obviously different due to different mode emission. Therefore, multiple anti-counterfeiting of a single compound can be realized, the security degree of the anti-counterfeiting can be improved and overcome the defect of the general fluorescent material in a single light-emitting mode. The work will establish experimental basis for the design and development of a new high-integration functional luminescence material, and is expected to use the developed materials in the fields of optical anti-counterfeiting and information encryption.

The huge consumption of rare-earth resources over the world requires the exploration of new deposits urgently. Comparing with traditional geochemical analysis and many alternative analytical techniques, photoluminescent (PL) sensing strategy possesses superior advantages, such as non-invasive, high sensitivity, fast response and remote operation, which has rarely been employed for the detection of rare-earth elements (REEs) -bearing minerals to date. Herein, Tb3+ (or Eu3+) ions doped oxysulfide nanocrystals are verified to be excellent candidates for Ce3+ ions sensing with a detection limit of ~3.9 nM. Moreover, considering cerium ions co-existes with other rare-earth elements (REEs) in most principal REEs-bearing minerals, the present studied NCs show great potential application in the exploration of REEs-bearing minerals with high sensitivity, i. e 0.1 g mineral could lead to more than 90% PL quenching degree. This work provides a new and convenient PL sensing route for Ce3+ ions and REEs-bearing minerals by the utilization of lanthanide-doped inorganic NCs.

Optical thermometer based on the non-contact fluorescence intensity ratio technique of two thermally-couple levels has huge potential applications in many fields, such as the electric power industry and in-situ physiological measurements. In the paper, the Yb3+/Nd3+ codoped Bi4Ti3O12 nanocrystal ratio thermometer has prepared by solid-phase sintering. The two thermally-couple levels are Nd3+:4F7/2 (emission peak around 753 nm) and Nd3+:4F5/2 (emission peak at 805 nm), respectively. The optical thermometer has based on the upconversion in near-infrared luminescence under 980 nm excitation with low power of 1.87 W/cm2. Due to the relatively low pump power, the effect of the excitation heat effect on the material is reduced. This resulted in a relatively high relative sensitivity (SR = 1% K−1) in the temperature range of 323–573 K. In addition to the characteristics, the excellent repeatability (σ = 1.5%) of the fluorescence intensity ratio between the two Nd3+ emission peaks makes Yb3+/Nd3+ codoped Bi4Ti3O12 microcrystals a promising non-contact near-infrared ratio thermometer.

Optical thermometry technology plays a significant role in plenty of fields owing to its unrivaled properties such as sensitive, noncontact, reliable and so on. In this work, Er3+/Yb3+ codoped lanthanum titanate (La2Ti2O7) microcrystals have been synthesized by solid state reaction for optical thermometry. This novel prepared material for thermometry is based on the fluorescence intensity ratio of thermally coupled levels from upconversion emission under 980 nm excitation. The sensitivity of thermometry is 5.7 × 10−3 K−1, and the input power density is only 8.3 mW/mm2. Furthermore, the result of repeatability test illustrates that the as-prepared microcrystals possess excellent stability at the temperature range from 333 to 553 K. Therefore, these demonstrated advantages of Er3+/Yb3+ codoped La2Ti2O7 microcrystals make it a promising material in optical thermometry area.

Optical thermometry has drawn great attention due to its sensitive and noncontact properties. Herein, Yb3+/Er3+ codoped Bi4Ti3O12 phosphor microcrystals have been synthesized by solid phase reaction for optical temperature sensing. The phase, microscopic structure and morphology of the prepared sample have been studied by the X-ray diffraction, transmission electron microscopy, etc. The process of upconversion emission has been researched with different environmental temperature and excitation power under 980 nm laser excitation. Meanwhile, the temperature sensing nature of the as-prepared microcrystals has been investigated based on the luminescence intensity ratio of two thermally coupled energy levels (Er3+:2H11/2, 4S3/2). The excitation laser power density is 3.95 mW/mm2, and the absolute sensitivity reaches 0.0046 K-1. The result demonstrates potential of the Bi4Ti3O12:Yb3+/Er3+ microcrystals in making optical sensing device under low excitation power density.

A magnetic-assisted noncontact triboelectric nanogenerator (TENG) is developed by combining a magnetic responsive layer with a TENG. The novel TENG device is applied to harvest mechanical energy which can be converted into electricity and light emissions. This work has potential for energy harvesting, magnetic sensors, self-powered electronics and optoelectronics applications.

The phosphors of Ca3Ga2Ge3O12 (CGGG) co-doped with Nd3+ and Cr3+ ions were synthesized using conventional solid-state reaction techniques. Steady-state and time-resolved near-infrared (NIR) photoluminescence (PL) and long-lasting phosphorescence (LLP) properties are investigated in the Nd3+-doped CGGG samples. An increase in NIR luminescence traps can be realized in Nd3+/Cr3+ co-doped samples. Energy transfer from Cr3+ to Nd3+ with an efficiency of up to 57.5% is evident for Ca3−xNdxGa1.99Cr0.01Ge3O12 at x = 0.09. A cross relaxation scheme related to 4T2–4A2 of Cr3+ and 4I9/2–4F3/2 transitions of Nd3+ is discussed. We have presented the luminescence mechanism involving the competing processes of NIR PL and LLP, which is in accordance with our measurements. The results show that the NIR persistent luminescence of CGGG co-doped with Nd3+ and Cr3+ is more efficient compared to the single Nd3+ ion doped CGGG.

The development of energy harvesting white light sources converted from multiple stimuli especially mechanical strain requires the search of new types of phosphors and devices. In this work, various flexible composites of single-phase metal ion-doped ZnS mixed to polydimethylsiloxane (PDMS) matrix have been prepared. The synthesized composites possess flexible, durable, easy fabrication, and compatible with arbitrary substrate characteristics. With the advantages of the flexible composite, we have fabricated two kinds of light-emission devices, namely flexible electroluminescence device with graphene electrode, and piezo-phototronic luminescence device composed of polymer phosphor layer coated on the top of piezoelectric actuator. Such composite phosphors and the related hybrid devices are capable of responding to different types of external stimuli, including electric field, uniaxial strains of stretch and mechanical writing, and piezoelectric biaxial strain, resulting in the observed white and green light emissions by the naked eyes. The stimulus excitation, resultant luminescence spectra, and their relations with color properties (color coordinates, color temperature, etc.) of the white light emission have been investigated. The observation is ascribed to the non-central symmetric crystal structure of wurtzite-type ZnS material, inherently producing piezoelectric effect under strain. Energy transitions of the observed white light emissions may originate from the donor-acceptor pairs recombination between Al Zn →Cu Zn , as well as the radiation transition between 4 T 1 and 6 A 1 of Mn 2+ ion. Our results show promise in constructing new types of flexible light source for applications in sustainable energy and so on.

We describe the use of a layer-by-layer hierarchical nanostructure to exploit the synergy of different lanthanide ions for converting single wavelength excitation into emissions spanning the whole spectral region. By lining up a set of lanthanide ions with matched energy levels in a core–shell nanostructure, we demonstrate well-defined cascades of energy transfer that gives access to optical emissions from a large collection of lanthanide ions (Tb3+, Eu3+, Dy3+, Sm3+, Nd3+, Yb3+, and Er3+) after excitation into a common sensitizer of Ce3+ featuring a broad absorption. Through optimization of the nanoparticle structure and surface coating, high quantum yields of up to 90% are achieved. Our results highlight that the controlled energy cascades at nanometer scale provide new opportunities for applications such as fighting against counterfeiting and sensing small molecules.

Porous micrometer-sized architecture that consists of aggregated single-crystalline nanoparticles is critical for LiMn2O4 to achieve good rate capacity and cycling stability, since it can increase the contact area between the electrolyte/electrode and shorten the transport paths for electrons and lithium ions. In this paper, hierarchical porous donut-shaped LiMn2O4 comprising aggregated single-crystalline nanoparticles has been successfully fabricated with MnO2 nanosheet coated polystyrene spheres as a precursor and characterized in terms of structure and performance as the cathode for lithium ion batteries. The charge/discharge tests show that the as-obtained donut-shaped LiMn2O4 exhibits excellent rate capability and high-rate cyclic stability. Surprisingly, even at a high charge/discharge rate of 10 C, the battery yields a capacity retention of over 95% after 500 cycles. The superior performance of the synthesized product can be attributed to its intrinsic structure: porous donut-shaped LiMn2O4 consisting of well-connected single-crystalline nanoparticles. The interpenetrating nanoparticle reduces the path of Li ion diffusion and increases the number of reaction sites for lithium insertion/extraction; the pores provide void space to buffer the volume changes during high-rate charge/discharge.

We report, for the first time, on the synthesis of perovskite films by thermal annealing of evaporated lead(II) iodide (PbI2)/methylammonium iodide (CH3NH3I) multilayers. Detailed characterization of the resulting films is presented. Our work demonstrates that compact, high quality and uniform perovskite films can be grown using this technique. Optimization of the device structure was achieved by careful design of the layer thickness and the number of PbI2/CH3NH3I pairs used in the formation of the absorber layer. Utilizing additional annealing steps in a controlled atmosphere was shown to result in significant improvement in the device performance. Our experimental data indicate that O2 treatments may result in substantial reduction in the trap density of the device and thereby significant improvement in the lifetimes of the carriers. A high power conversion efficiency (PCE) of 12.5% was recorded for the champion device.