Search

Vibrational sum frequency generation can provide valuable structural information at surfaces and buried interfaces. Relating the measured spectra to the complex-valued second-order susceptibility χ(2) is at the heart of the technique and a requisite step in nearly all subsequent analyses. The magnitude and phase of χ(2) as a function of frequency reveal important information about molecules and materials in regions where centrosymmetry is broken. In this tutorial-style perspective, the origins of the χ(2) phase are first described, followed by the utility of phase determination. Finally, some practical methods of phase extraction are discussed. [ABSTRACT FROM AUTHOR]

Within cell plasma membranes, unsaturated lipids are asymmetrically distributed over the inner and outer leaflets, offering an attractive local structural feature. However, the mechanism to keep lipid transmembrane asymmetry and the closely related transmembrane movement (flip-flop) for unsaturated lipids remain poorly understood. Here, we applied sum frequency generation vibrational spectroscopy to investigate this lipid transmembrane asymmetry upon mimicking the cell membrane homeostatic processes. On the one hand, unsaturated lipids were found to hinder the flip-flop process and preserve lipid transmembrane asymmetry in model cell membranes, owing to the steric hindrance caused by their bent tails. On the other hand, local unsaturated lipids in the mixed unsaturated/saturated lipid bilayer were conducive to the formation of the local asymmetry. Therefore, lipid unsaturation can be recognized as an intrinsic key factor to form and maintain lipid transmembrane asymmetry in cell membranes. [ABSTRACT FROM AUTHOR]

Surface-specific sum frequency generation vibrational spectroscopy is applied to study the molecular configuration of short-chain n-alkanethiol self-assembled monolayers (SAMs with n = 2–6) on the Au surface. For monolayers with n ≥ 3, the alkanethiols are upright-oriented, with the CH3 tilt angle varying between ∼33° and ∼46° in clear even–odd dependency. The ethanethiol monolayer (n = 2) is, however, found to exhibit a distinct lying-down configuration with a larger methyl tilt angle (67°–79°) and a smaller CH2 tilt angle (56°–68°). Such a unique configurational transition from n = 2 to n ≥ 3 discloses the steric effect owing to chain–chain interaction among neighboring molecules. Through density functional theory calculations, the transition is further confirmed to be energetically favorable for thiols on a defective reconstructed Au(111) surface but not on the pristine one. Our study highlights the roles of the chain–chain interaction and the substrate surface atomic structure when organizing SAMs, offering a strategic pathway for exploiting their applications. [ABSTRACT FROM AUTHOR]

Lanthanide-doped upconversion (UC) luminescent materials display multicolor emissions, making them ideal for a variety of applications, such as multi-channel biological imaging, fluorescence encryption, anti-counterfeiting, and 3D display. Manipulating the UC emissions of the luminescent materials with a fixed composition is crucial for their applications. Herein, we propose a facile strategy to achieve pulse-width-dependent multicolor UC emissions in NaYF4:Yb/Er/Tm nanocrystals. Upon excitation with a 980 nm continuous-wave laser diode, Er3+ ions in NaYF4:20%Yb,15%Er,1%Tm nanocrystals exhibited UC emissions with a red-to-green (R/G) ratio of 11.3. Nevertheless, by employing a 980 nm pulse laser with pulse widths from 0.1 to 10 ms, the UC R/G ratio can be easily adjusted from 0.9 to 11.3, resulting in continuous and remarkable color transformation from green, yellow, orange, to red. By virtue of the dynamic luminescence color variation of these NaYF4:20%Yb,15%Er,1%Tm nanocrystals, we demonstrated their potential applications in the areas of anti-counterfeiting and information encryption. These findings provide deep insights into the excited-state dynamics and energy transfer of Er3+ in NaYF4:Yb/Er/Tm nanocrystals upon 980 nm pulse excitation, which may pave the way for designing multicolor UC materials toward versatile applications. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is a two-dimensional, mechanically strong, and chemically tunable material for separations. Elucidating GO–ion–water interactions at the molecular scale is highly important for predictive understanding of separation systems. However, direct observations of the nanometer region by GO surfaces under operando conditions are not trivial. Therefore, thin films of GO at the air/water interface can be used as model systems. With this approach, we study the effects of alkali metal ions on water organization near graphene oxide films at the air/water interface using vibrational sum frequency generation (SFG) spectroscopy. We also use an arachidic acid Langmuir monolayer as a benchmark for a pure carboxylic acid surface. Theoretical modeling of the concentration-dependent sum frequency signal from graphene oxide and arachidic acid surfaces reveals that the adsorption of monovalent ions is mainly controlled by the carboxylic acid groups on graphene oxide. An in-depth analysis of sum frequency spectra reveals at least three distinct water populations with different hydrogen bonding strengths. The origin of each population can be identified from concentration dependent variations of their SFG signal. Interestingly, an interfacial water structure seemed mostly insensitive to the character of the alkali cation, in contrast to similar studies conducted at the silica/water interface. However, we observed an ion-specific effect with lithium, whose strong hydration prevented direct interactions with the graphene oxide film. [ABSTRACT FROM AUTHOR]

The intriguing network of antibody–antigen (Ab–Ag) interactions is highly governed by environmental perturbations and the nature of biomolecular interaction. Protein–protein interactions (PPIs) have potential applications in developing protein-adsorption-based sensors and nano-scale materials. Therefore, characterizing PPIs in the presence of a nanomaterial at the molecular level becomes imperative. The present work involves the investigation of antiferritin–ferritin (Ab–Ag) protein interactions under the influence of tungsten disulfide quantum dots (WS2 QDs). Isothermal calorimetry and contact angle measurements validated the strong influence of WS2 QDs on Ab–Ag interactions. The interfacial signatures of nano–bio-interactions were evaluated using sum frequency generation vibration spectroscopy (SFG-VS) at the air–water interface. Our SFG results reveal a variation in the tilt angle of methyl groups by ∼12° ± 2° for the Ab–Ag system in the presence of WS2 QDs. The results illustrated an enhanced ordering of water molecules in the presence of QDs, which underpins the active role of interfacial water molecules during nano–bio-interactions. We have also witnessed a differential impact of QDs on Ab–Ag by raising the concentration of the Ab–Ag combination, which showcased an increased inter-molecular interaction among the Ab and Ag molecules and a minimal influence on the methyl tilt angle. These findings suggest the formation of stronger and ordered Ab–Ag complexes upon introducing WS2 QDs in the aqueous medium and signify the potentiality of WS2 QDs relevant to protein-based sensing assays. [ABSTRACT FROM AUTHOR]

Chirality-selective vibrational sum frequency generation (chiral SFG) spectroscopy has emerged as a powerful technique for the study of biomolecular hydration water due to its sensitivity to the induced chirality of the first hydration shell. Thus far, water O–H vibrational bands in phase-resolved heterodyne chiral SFG spectra have been fit using one Lorentzian function per vibrational band, and the resulting fit has been used to infer the underlying frequency distribution. Here, we show that this approach may not correctly reveal the structure and dynamics of hydration water. Our analysis illustrates that the chiral SFG responses of symmetric and asymmetric O–H stretch modes of water have opposite phase and equal magnitude and are separated in energy by intramolecular vibrational coupling and a heterogeneous environment. The sum of the symmetric and asymmetric responses implies that an O–H stretch in a heterodyne chiral SFG spectrum should appear as two peaks with opposite phase and equal amplitude. Using pairs of Lorentzian functions to fit water O–H stretch vibrational bands, we improve spectral fitting of previously acquired experimental spectra of model β-sheet proteins and reduce the number of free parameters. The fitting allows us to estimate the vibrational frequency distribution and thus reveals the molecular interactions of water in hydration shells of biomolecules directly from chiral SFG spectra. [ABSTRACT FROM AUTHOR]

Doubly resonant sum frequency generation (DR-SFG) serves as a potent characteristic technique for probing the electronic spectra and vibronic coupling of molecules on surfaces. In this study, we successfully developed a novel infrared (IR)–white light (WL) DR-SFG spectroscopy based on narrowband IR and tunable broadband WL. This novel method was employed to explore the excitation spectrum and vibronic couplings of sub-monolayer Rhodamine 6G molecules. Our findings elucidate that the xanthene skeleton vibrational modes exhibit strong coupling with the S0–S1 electronic transition. Notably, we observed not only the 0–0 transition of the S0–S1 electronic continuum but also the 0–1 transition, a first time observation in the realm of DR-SFG spectroscopy. This advanced DR-SFG spectroscopy methodology facilitates a more sensitive examination of electronic spectra and the coupling between electronic transitions and vibrational modes, heralding a significant advancement in the understanding of molecular interactions on surfaces. [ABSTRACT FROM AUTHOR]

Polymer chains at a buried interface with an inorganic solid play a critical role in the performance of polymer nanocomposites and adhesives. Sum frequency generation (SFG) vibrational spectroscopy with a sub-nanometer depth resolution provides valuable information regarding the orientation angle of functional groups at interfaces. However, in the case of conventional SFG, since the signal intensity is proportional to the square of the second-order nonlinear optical susceptibility and thereby loses phase information, it cannot be unambiguously determined whether the functional groups face upward or downward. This problem can be solved by phase-sensitive SFG (ps-SFG). We here applied ps-SFG to poly(methyl methacrylate) (PMMA) chains in direct contact with a quartz surface, shedding light on the local conformation of chains adsorbed onto the solid surface. The measurements made it possible to determine the absolute orientation of the ester methyl groups of PMMA, which were oriented toward the quartz interface. Combining ps-SFG with all-atomistic molecular dynamics simulation, the distribution of the local conformation and the driving force are also discussed. [ABSTRACT FROM AUTHOR]

Sum frequency generation (SFG) spectroscopy is an interface-selective spectroscopic technique that enables us to selectively observe the vibrational or electronic resonances of molecules within a very thin interface layer. The interfacial properties probed by SFG are contained in a complex quantity called the second-order nonlinear susceptibility ( χ 2 ). It is usually believed that the imaginary part of χ 2 (Im χ 2 ) exhibits the resonant responses of the system, whereas the nonresonant responses appear solely in the real part of χ 2 (Re χ 2 ). However, it was recently theoretically pointed out that a portion of the nonresonant responses actually contributes to the observed Im χ 2 spectra when the finite thickness of the interface layer is taken into account. In this study, by considering a simple air/liquid interface without any solutes as a model system, we theoretically evaluate the nonresonant contribution to experimentally accessible Im χ 2 as well as to Re χ 2 , from which the complex phase of the nonresonant background is estimated. It is shown that the deviation of the complex phase from 0° or 180° is less than 1° even if the thickness of the interface layer is taken into account. This means that the nonresonant contribution to Im χ 2 is practically negligible, and it is a very good approximation to think that the nonresonant background appears solely in Re χ 2 in the case of air/liquid interfaces. This result implies that Im χ 2 practically contains only the resonant responses of the system, and molecular resonances at the interface can be conveniently studied using Im χ 2 spectra at such interfaces. [ABSTRACT FROM AUTHOR]

Nonlinear optical methods, such as vibrational sum frequency generation (vSFG) and second harmonic generation (SHG), are powerful techniques to study elusive structures at charged buried interfaces. However, for the separation and determination of the Stern and diffuse layer spectra at these charged interfaces, complex vSFG spectra and, hence, the absolute phase need to be retrieved. The maximum entropy method is a useful tool for the retrieval of complex spectra from the intensity spectra; however, one caveat is that an understanding of the error phase is required. Here, for the first time, we provide a physically motivated understanding of the error phase. Determining the error phase from simulated spectra of oscillators with a spectral overlap, we show that for broadband vSFG spectra, such as for the silica/water interface, the diffuse and Stern layers' spectral overlap within the O–H stretching window results in a correlation between the error phase and the phase shift between the responses of these layers. This correlation makes the error phase sensitive to changes in Debye length from varying the ionic strength among other variations at the interface. Furthermore, the change in the magnitude of the error phase can be related to the absolute SHG phase, permitting the use of an error phase model that can utilize the SHG phase to predict the error phase and, hence, the complex vSFG spectra. Finally, we highlight limitations of this model for vSFG spectra with a poor overlap between the diffuse and Stern layer spectra (silica/HOD in D2O system). [ABSTRACT FROM AUTHOR]

In view of the current situation in which non-polarizable rigid water models have been scarcely examined against surface-specific properties, we appraise TIP4P-type models at the liquid water surface on the basis of heterodyne-detected sum frequency generation (HD-SFG) spectroscopy. We find in the HD-SFG spectrum of the water surface that the peak frequency of the hydrogen-bonded OH band, the half width at half maximum of the hydrogen-bonded OH band, and the full width at half maximum of the free OH band are best reproduced by TIP4P, TIP4P/Ew, and TIP4P/Ice, respectively, whereas it is already well known that TIP4P/2005 best reproduces the surface tension. These TIP4P-type models perform better at the water surface in terms of the present appraisal items than some polarizable models in the literature. [ABSTRACT FROM AUTHOR]

Recent vibrational sum frequency generation spectroscopic experiments [Sengupta et al., J. Phys. Chem. Lett. 13, 11391–11397 (2022)] demonstrated synergistic interfacial adsorption effects between the anionic dodecyl sulfate (DS−) and the polar, but charge-neutral hexaethylene glycol monododecyl ether (C12E6), surfactants. In this study, the interfacial adsorption thermodynamics underlying these synergistic effects are analyzed through free energy decompositions. A general decomposition method utilizing alchemical intermediate states is outlined. Combining free energy decompositions with the potential distribution theorem illuminates the statistical interpretations of correlated effects between different system components. This approach allows for the identification of the physical effects leading to synergistic adsorption thermodynamics of DS− binding to the air-C12E6-water interface. The binding properties are found to result from a combination of effects predominantly including energetic van der Waals stabilization between DS− and C12E6, as well as competing energetic and entropic effects due to changes in the interfacial water structure as a result of introducing a C12E6 monolayer into the bare air–water interface. [ABSTRACT FROM AUTHOR]

Understanding the electric double layer (EDL) of the metal electrode–electrolyte interface is essential to electrochemistry and relevant disciplines. In this study, potential-dependent electrode Sum Frequency Generation (SFG) intensities of polycrystalline gold electrodes in HClO4 and H2SO4 electrolytes were thoroughly analyzed. The potential of zero charges (PZC) of the electrodes was −0.06 and 0.38 V in HClO4 and H2SO4, respectively, determined from differential capacity curves. Without specific adsorption, the total SFG intensity was dominated by the contribution from the Au surface and increased similar to that of the visible (VIS) wavelength scanning, which pushed the SFG process closer to the double resonant condition in HClO4. However, the EDL contributed about 30% SFG signal with specific adsorption in H2SO4. Below PZC, the total SFG intensity was dominated by the Au surface contribution and increased with potential at a similar slope in these two electrolytes. Around PZC, as the EDL structure became less ordered and the electric field changed direction, there would be no EDL SFG contribution. Above PZC, the total SFG intensity increased much more rapidly with potential in H2SO4 than in HClO4, which suggested that the EDL SFG contribution kept increasing with more specific adsorbed surface ions from H2SO4. [ABSTRACT FROM AUTHOR]

Infrared upconversion devices (UCDs) enable NIR imaging without array and readout circuits, making them desirable for portable sensor, imaging and monitoring. However, the exorbitant cost and difficulties in fabrication associated with vacuum‐deposited materials, which are usually employed in high‐performance UCDs, restrict their application in flexible‐stretchable systems. Here, a solution‐processed upconversion device (s‐UCD), which is composed of detector and emitter, with high conversion efficiency and low turn‐on voltage achieved by device structure design and interlayer engineering is reported. The role of the electron blocking layer is investigated in s‐UCDs, and a peak luminance of 5,500 cd m−2 @7 V and a luminance on‐off ratio of 110000 @5.25 V are achieved. The s‐UCDs exhibit high resolution, microsecond response time and are compatible with flexible substrates. With the high‐performance large‐area s‐UCDs, direct non‐invasive transmission‐based bioimaging applications with high quality of bioimaging are further performed. It is believed that the s‐UCD imaging system offers potential applications for portable low‐cost non‐invasive tissue analysis, disease diagnosis, and virtual reality. [ABSTRACT FROM AUTHOR]

Molecular scaffolds are ideal for investigating upconversion (UC) at the highest spatial resolution and to create precisely controllable luminescent materials. Such control may be the key to overcoming the limitations of brightness and reproducibility found in UC micro‐ and nanoparticles. Cooperative UC can significantly increase luminescence brightness and bulk studies showed that highest efficiencies can be obtained by sensitizer‐to‐activator ion ratios ≥ 2, that is, via high probabilities of sensitizing the emitting lanthanide ion. Using nonanuclear molecular complexes, the authors demonstrate both experimentally and theoretically that interion distances are more relevant and that the highest UC efficiencies are actually attained for sensitizer‐to‐activator ion ratios around 1. By modeling accretive and cooperative sensitization UC, energy migration, and fitting experimental data, it is revealed that cooperative sensitization is predominant for the determination of UC luminescence intensities, whereas energy migration defines UC luminescence kinetics. The implementation of interion distances and different energy transfer mechanisms into advanced modeling of experimental UC data will be paramount for designing brighter and better UC materials. [ABSTRACT FROM AUTHOR]

The commonly used automotive head‐up display (HUD) technology is confronted with the problems of poor stability in organic resin counterpart and the unsatisfactory display effect of projection lighting source. To solve these issues, developing state‐of‐the‐art materials and designing new HUD schemes with a wide color gamut is of necessity. Herein, a series of pure red/green/blue (R/G/B) upconverting (UC) nano‐glass‐ceramics (GCs) containing lanthanide‐doped NaLuF4 nanocrystals (NCs) are synthesized in a cost‐effective, environment‐friendly, and scalable manner, simultaneously achieving high crystallinity (≈45.44%) and high transparency (>80%). Yb3+ is chosen as the sensitizer to Tm3+ (blue UC)/Ho3+ (green UC), due to its large absorption cross section from ground state 2F7/2 to excited state 2F5/2; meanwhile Er3+, Tm3+ co‐doped into NCs can obtain pure red UC emission via promoting the population of Er3+ red‐emitting 4F9/2 state. Consequently, the as‐prepared materials exhibit high R/G/B color purity of > 80% owing to the energy transfer between different lanthanide ions (Yb3+, Tm3+, Ho3+, and Er3+) upon 980 nm near‐infrared (NIR) laser excitation, and possess superior thermal reversibility/water resistivity. Remarkably, two unprecedented HUD prototypes are constructed to demonstrate the application feasibility of developed pure R/G/B UC GCs. [ABSTRACT FROM AUTHOR]

Visible‐to‐ultraviolet (UV) upconversion provides a fascinating strategy to achieve deep UV emission through readily accessible visible light. However, the intensity of deep UV emission obtained through visible‐to‐UV upconversion progress is still far from satisfactory, severely constraining its practical applications. Herein, a novel class of praseodymium ion (Pr3+)‐doped rare‐earth oxyhalides (YOCl, YOBr, and LuOBr) to achieve efficient upconverted deep UV emission in the spectral range of 250–350 nm is developed. The upconverted UV emission intensity of LuOBr:Pr3+ is determined to be 56.7 times stronger than that of the well‐established Lu7O6F9:Pr3+. When employed as a photon‐converter to activate photocatalytic water splitting reactions, upconverted deep UV emission enables H2 generation under visible light (λ > 420 nm) excitation from a xenon lamp. The efficient deep UV upconversion stems from tuning 4f15d1 state of Pr3+ by oxyhalide constituent which both facilitates the absorption of excitation photons in long‐lived intermediate 4f2 states and suppress the probability of nonradiative relaxation from 4f15d1 state. These findings not only provide new insights into a mechanistic understanding of the host effect on upconversion process but also make a breakthrough in developing efficient deep upconversion materials that will expand their further applications. [ABSTRACT FROM AUTHOR]

Organic upconverters made by integrating an infrared‐sensitive photodetector with a light‐emitting diode offer a low‐cost route to visualize images taken in the infrared. However, making such devices sufficiently efficient is challenging. Here, upconversion devices are demonstrated with an efficiency of 13.9% for converting infrared photons (980 nm, 5 mW cm−2) to visible photons (575 nm). Infrared photons are detected with a photomultiplication photodetector that includes a copper thiocyanate electron‐blocking/injection layer and an infrared‐sensitive squaraine dye dispersed (3 wt−%) in a fullerene matrix. At turn‐on, the detector achieves an external quantum efficiency of 1200% (at 1020 nm, −10 V, 44 µW cm−2). Photomultiplication occurs via hole trap‐induced injection of electrons. In the upconverter, these electrons are driven into the emitter and recombine with holes under visible light emission. During operation the photodetector current increases because, presumably, rearranging mobile ions in copper thiocyanate narrows the injection barrier. Thereby, the upconverter photoconversion efficiency gradually increases to 18.7%. The performance of the present upconverter is limited by the not‐yet‐ideal charge‐blocking/injection layer, which is too thick and blocks electrons in the dark insufficiently. With thin and compact charge‐blocking layers at hand, the device concept paves the way for widespread use in sensitive infrared imaging. [ABSTRACT FROM AUTHOR]

A series of phosphine oxide‐containing gold(III) complexes with tunable emission colors spanning from sky‐blue to near‐infrared region is reported. This is accomplished by the switching of the excited state characters from intraligand to ligand‐to‐ligand charge transfer through the replacement of the auxiliary ligand from aryl to nitrogen‐based ligands. In addition to high photoluminescence quantum yields in both solution and solid‐state thin films, these complexes exhibit large radiative decay rate constants of the order of 106 s−1, much larger than those commonly found for other gold(III) complexes. The origin of such enhanced performance is believed to be arising from the occurrence of both thermally activated delayed fluorescence and thermally stimulated delayed phosphorescence processes within the emitters. This is probed by ns‐ and fs‐transient absorption spectroscopy, time‐resolved, and temperature‐dependent emission spectroscopy. In particular, the direct observation of the upconversion processes and the determination of the activation barriers are achieved in the variable‐temperature fs‐transient absorption spectroscopic studies. Solution‐processed organic light‐emitting devices with satisfactory external quantum efficiencies of up to 15.2% are achieved, which could be ascribed to the presence of thermally activated delayed fluorescence and/or thermally stimulated delayed phosphorescence processes. [ABSTRACT FROM AUTHOR]

Transparent glass with photochromic and luminescent properties has recently garnered considerable interest in optical storage, while the photochromic transparent glass system is still limited. Herein, it is proposed that combining transparent glass matrix with photochromic nanocrystals is an efficient strategy to develop a broader range of photochromic luminescent glass systems. The Yb3+/Tb3+ co‐doped BaMgSiO4 glass ceramics are successfully prepared by a two‐step melt‐quenching approach followed by a thermal treatment in a reducing atmosphere. The glass ceramics exhibit high transparency and distinct coloration, showing a color change between colorless and pink by alternating irradiation between 365 nm ultraviolet light and 473 nm laser. The formation of color centers in the BaMgSiO4 nanoparticles drives the coloration of such glass ceramics. Based on their photochromic and photobleaching behavior, the efficient reversible upconversion luminescence modulation can be implemented with the maximum luminescence modulation rate of 79.83%. The excellent reproducibility and anti‐fatigue of such upconversion luminescence modulation demonstrate the promising application of Yb3+/Tb3+ co‐doped BaMgSiO4 glass ceramics as an optical storage medium. [ABSTRACT FROM AUTHOR]

An upconversion fluorescence sensing platform was developed with upconversion nanoparticles (UCNPs) as energy donors and gold nanoparticles (AuNPs) as energy acceptors, based on the FRET principle. They were used for quantitative detection of uranyl ions (UO22+) by amplifying the signal of the hybrid chain reaction (HCR). When UO22+ are introduced, the FRET between AuNPs and UCNPs can be modulated through a HCR in the presence of high concentrations of sodium chloride. This platform provides exceptional sensitivity, with a detection limit as low as 68 pM for UO22+ recognition. We have successfully validated the reliability of this method by analyzing authentic water samples, achieving satisfactory recoveries (89.00%–112.50%) that are comparable to those of ICP-MS. These results indicate that the developed sensing platform has the capability to identify trace UO22+ in complex environmental samples. [ABSTRACT FROM AUTHOR]

Real-time monitoring of temperature changes in substation equipment is crucial for preventing failures and ensuring a stable power supply. Currently, temperature monitoring of substation equipment primarily relies on manual infrared thermometry, which has limitations such as strong operational dependence, susceptibility to interference, and difficulty in detecting internal faults. The luminous intensity ratio (LIR) is a stable optical parameter unaffected by factors such as spectral loss and environmental influences, making it suitable for temperature detection. The multi-emission characteristics of rare-earth-doped upconversion (UC) materials are highly compatible with LIR technology, demonstrating their potential in high-precision temperature monitoring. Here we introduces a non-contact temperature monitoring method for substation equipment based on NaErF4@ NaYF4 core-shell UC materials and LIR technique. Experiments show that the method has high accuracy and sensitivity within temperature range of 25 °C to 225 °C, with a sensitivity as high as 35 x 10-3 °C-1, effectively monitoring temperature changes both inside and outside the equipment. This provides a new technical solution for temperature monitoring of substation equipment. [ABSTRACT FROM AUTHOR]

Photoactivatable carbon monoxide‐releasing molecules (CORMs), typically based on transition‐metal carbonyl complexes, have reliance on activation by UV or visible light that restricts their biomedical applications. To address this limitation, a near‐infrared (NIR)‐responsive nanoplatform is presented based on upconversion nanoparticles (UCNPs) loading with manganese carbonyl complex Mn2(CO)10 that concurrently releases CO and manganese ion (Mn2+). With the UCNPs, the more tissue‐penetrable NIR is used to locally generate UV light for photodecomposition of Mn2(CO)10 into CO and manganese oxide (MnOX), after which MnOX is reduced to Mn2+ by the overexpressed glutathione in cancer cells. Moreover, the released Mn2+ can serve as a magnetic resonance imaging contrast agent to monitor the NIR‐controlled corelease of CO and Mn2+ in real time. Therefore, this nanoplatform can provide a potential strategy for NIR‐enabled spatiotemporally release of CO and Mn2+, enhancing the controlled delivery and biomedical application of CORMs. [ABSTRACT FROM AUTHOR]

To investigate a near-infrared-to-blue luminescence upconversion curing method for polymerizing resin cements under zirconia discs. Lava zirconia discs of different thicknesses (0.5–2.0 mm) were manufactured. First, the transmittances of the NIR and two blue lights (BLs) (LED and halogen lights) through these discs were measured. Second, NaYF 4 :Yb3+/Tm3+ upconversion phosphor (UP) powder was milled into 0.5-μm particle sizes. A light-curable resin cement VariolinkII base was chosen as the control (UP0), and an experimental cement (UP5) was prepared by adding 5 % UPs. These two cements were examined using multiphoton excitation microscopy for particle distribution. UP5 and UP0 were polymerized with or without zirconia shielding then subjected to a microhardness test. A multifold analysis was performed to examine the effects of zirconia thickness, curing protocols (pure BL or combined BL and NIR curing), and cement type. The transmittance of NIR was superior to that of BL through zirconia discs of all thicknesses. UP particles were homogeneously distributed in UP5 and emitted blue luminescence under 980-nm NIR excitation. UP5 showed higher microhardness values than UP0 under any curing protocol or zirconia shielding condition. The combination of 20-s BL and 40-s NIR curing yielded the highest microhardness in uncovered UP5. However, combining 40-s BL and 20-s NIR curing surpassed the other groups when the zirconia discs were thicker than 0.5 mm. NIR exhibits higher transmission through zirconia than BL. UP particles work as strengthen fillers and photosensitizers in cements. NIR upconversion curing could be a new strategy for polymerizing resin cements under thick zirconia restorations. • An NIR activated upconversion reaction was used to induce blue light (BL) emission. • The transmittance of NIR through zirconia discs is higher than conventional BL. • Phosphor particles work as photosensitizers and strengthen fillers in cements. • Combining BL and NIR effectively enhanced polymerization of cements under zirconia. [ABSTRACT FROM AUTHOR]

Yb3+ doped CsPbCl3 metal halide perovskite photodetectors (PDs) in the structure of CsPbCl3(50 nm)/YbCl3(x nm)/CsPbCl3(50 nm), in which x ranges from 10 to 40 nm corresponding to the molar ratio from 6.3% to 25.2%, are fabricated by thermal evaporation on Si/SiO2 substrate. Photoresponse from 350 to 980 nm have been achieved with the optimal responsivity (R) of 3959, 5425, 955 A W−1 for the case of 20 nm YbCl3 at the wavelength (λ) of 420, 680 and 980 nm, respectively. A series of photophysical and electrical characterization has been performed and it is found that the remarkably improved photoresponse originates from the combining effects of upconversion and defects passivation from Yb3+. Moreover, the optimal YbCl3 thickness of 20 nm can be ascribed to the balance between upconversion and concentration quenching of Yb3+. The influence of the YbCl3 doping on the CsPbCl3 electronic structure is investigated and downshifting and stabilization of valence band maximum (VBM) can be attributed to the p-type doping and counteracting effect of Yb3+ and Cl−, respectively. [ABSTRACT FROM AUTHOR]

Recent reports of upconversion and white light emission from graphitic particles warrant an explanation of the physics behind the process. A model is offered, wherein the upconversion is facilitated by photoinduced electronic structure modification allowing for multiphoton processes. As per the prediction of the model, it is experimentally shown that graphite upconverts infrared light centered around 1.31 μm (0.95 eV) to broadband white light centered around 0.85 μm (1.46 eV). The results suggest that upconversion from shortwave infrared (≈3 μm, 0.45 eV) to visible region may be possible. The experiments show that the population dynamics of the electronic states involved in this upconversion process occur in the timescale of milliseconds. [ABSTRACT FROM AUTHOR]

This work presents a novel paradigm for upconversion‐assisted ferroelectric photovoltaic devices. The system comprises a ferroelectric active layer (BiFeO3), an upconverter layer (Yb; Er‐doped ZnO), a conductive ITO‐coated glass substrate, and a reflective coating (Al) at the rear end of the glass substrate. The photovoltaic efficiency of the single‐layer BFO was found to be 0.71%. With the prescribed device model, the total solar efficiency of BiFeO3 improved significantly and touched solar conversion efficiency of 2.21%. This model's projection widens the future perspectives of device performance in emerging photovoltaic technology, mainly perovskite‐based solar cells. [ABSTRACT FROM AUTHOR]

Weak luminescence of the small‐sized lanthanide‐doped nanoparticles has limited their applications long. In recent years, there is a growing interest in luminescence thermal enhancement in small‐sized upconversion nanoparticles (UCNPs). The mitigation of surface quenching effects and the improvement of energy transfer (ET) are two convincing explanations for this phenomenon. A systematical investigation on the luminescence dynamics of Yb3+ is implemented. ET rate and then the proportion of ET increases greatly with rising temperatures in Yb3+/Tm3+ codoped system, while an alternative trend can be summarized in Yb3+/Er3+ one. Based on these findings, therefore it can be concluded that the surface quenching mitigation related to the desorption of water molecules on the surface is a common mechanism of the luminescence thermal enhancement. But ET related to the thermally‐activated surface phonons is a special case, it does play a positive role in Yb3+/Tm3+ system. These findings not only explain the upconversion luminescence thermal enhancement in Yb3+/Tm3+ system is more significant but also help to understand thermal enhancement and benefit highly‐sensitive temperature probe design. [ABSTRACT FROM AUTHOR]

We develop a new all-dielectric metasurface for designing high quality-factor (Q-factor) quasi-bound states in the continuum (quasi-BICs) using asymmetry kite-shaped nanopillar arrays. The Q-factors of quasi-BICs follow the quadratic dependence on the geometry asymmetry, and meanwhile their resonant spectral profiles can be readily tuned between Fano and Lorentzian lineshapes through the interplay with the broadband magnetic dipole mode. The third-harmonic signals of quasi-BIC modes exhibit a gain from 43.4- to 634-fold enhancement between samples with an axial-length difference of 15 nm and 75 nm when reducing the numerical aperture of the illuminating objective lenses in nonlinear measurement, which is attributed to the increasing illumination spot size and the less contribution from the large oblique incident light for establishing quasi-BIC modes with high-Q spectral profile and strong near-field intensity. The silicon-based metasurfaces with their simple geometry are facile for large-area fabrication and open new possibilities for the optimization of upconversion processes to achieve efficient nonlinear devices. [ABSTRACT FROM AUTHOR]

Although interfacial solvation plays an important role in determining carbon dioxide reduction (CO2R) kinetics, present understanding of the potential dependent properties of the electrochemical double layer under conditions relevant for CO2R remains limited. This article summarizes the development and recent applications of plasmon‐enhanced vibrational sum frequency generation (VSFG) spectroscopy to study the effects of cation hydration and interfacial solvation on CO2R using CO as a vibrational Stark reporter. Results show that electrolyte cations retain their entire solvation shell upon adsorption to inactive sites, while active sites retain only a single water layer between the gold surface and the cation. Measurements also show that the total interfacial electric field can be separated into two contributions: one from the electrochemical double layer (Stern field) and another from the polar solvation environment (Onsager field). Surprisingly, correlating VSFG spectra with reaction kinetics reveals that it is the solvation‐mediated Onsager field that governs the chemical reactivity at the electrode/electrolyte interface. Measuring the interfacial water spectra during electrocatalysis also provides evidence for the proton source during H2 evolution, which competes with CO2R in aqueous electrolyte. These findings highlight the importance of directly probing cation hydration and interfacial solvation, which mediates reaction kinetics at electrochemical interfaces. [ABSTRACT FROM AUTHOR]

In this work, we investigate trion dynamics occurring at the heterojunction between organometallic molecules and a monolayer transition metal dichalcogenide (TMD) with transient electronic sum frequency generation (tr‐ESFG) spectroscopy. By pumping at 2.4 eV with laser pulses, we have observed an ultrafast hole transfer, succeeded by the emergence of charge‐transfer trions. This observation is facilitated by the cancellation of ground state bleach and stimulated emission signals due to their opposite phases, making tr‐ESFG especially sensitive to the trion formation dynamics. The presence of charge‐transfer trion at molecular functionalized TMD monolayers suggests the potential for engineering the local electronic structures and dynamics of specific locations on TMDs and offers a potential for transferring unique electronic attributes of TMD to the molecular layers. [ABSTRACT FROM AUTHOR]

Early-stage diagnosis of prostatic carcinoma is essential for successful treatment and, thus, significant prognosis improvement. In laboratory practice, the standard non-invasive diagnostic approach is the immunochemical detection of the associated biomarker, prostate-specific antigen (PSA). Ultrasensitive detection of PSA is essential for both diagnostic and recurrence monitoring purposes. To achieve exceptional sensitivity, we have developed a microfluidic device with a flow-through cell for single-molecule analysis using photon-upconversion nanoparticles (UCNPs) as a detection label. For this purpose, magnetic microparticles (MBs) were first optimized for the capture and preconcentration of PSA and then used to implement a bead-based upconversion-linked immunoassay (ULISA) in the microfluidic device. The digital readout based on counting single nanoparticle-labeled PSA molecules on MBs enabled a detection limit of 1.04 pg mL−1 (36 fM) in 50% fetal bovine serum, which is an 11-fold improvement over the respective analog MB-based ULISA. The microfluidic technique conferred several other advantages, such as easy implementation and the potential for achieving high-throughput analysis. Finally, it was proven that the microfluidic setup is suitable for clinical sample analysis, showing a good correlation with a reference electrochemiluminescence assay (recovery rates between 97% and 105%). [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. It includes a range of papers on various topics, such as photon upconversion, catalytic activity, structural diversity, and crystal stability. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document provides a list of papers and their authors, allowing library patrons to quickly identify articles of interest for their research. [Extracted from the article]

808 nm excited Nd3+ doped upconversion nanoparticles (UCNPs) have become a new research hotspot due to their reduced thermal effect when applied in a water-rich system. Different from Tm3+-mediated energy migration upconversion of Tb3+, in this work, NaYF4:Yb/Tb@NaYF4:Yb@NaNdF4:Yb@NaYF4 core–shell–shell–shell nanoparticles were designed based on the Yb3+ sensitized cooperative energy-transfer process to realize photon upconversion. NaYF4:Yb served as the migration layer, separating the activator Tb3+ from the sensitizer Nd3+ and minimizing the deleterious cross-relaxation between them. At 40% Yb3+ doping concentration in the NaYF4:Yb layer, bright green luminescence was achieved under 808 nm excitation. Meanwhile, the presence of Yb3+ in the sensitization layer (NaNdF4:Yb) reduced Nd3+ cross-relaxation, leading to improved energy migration efficiency of Nd3+ → Yb3+. Finally, the incorporation of an inert NaYF4 shell resulted in a significant luminescence boost. These nanoparticles can be dispersed in water after surface modification and could be effectively excited after laser penetration of 3 cm of water, indicating the enormous potential of the designed UCNPs in the biological system. [ABSTRACT FROM AUTHOR]

A near‐infrared luminescent complex Er(DBTTA)3(DBFDPO) [where DBTTA = dibenzotetrathienoacene; DBFDPO = 4,6‐bis (diphenylphosphoryl) dibenzofuran] is synthesized. Based on the intramolecular energy transfer between organic ligands and Er3+ ions, optical gains at 1535 nm are demonstrated in Er(DBTTA)3(DBFDPO)‐doped polymer waveguides under the excitation of light‐emitting diodes (LEDs) instead of laser pumping. Relative gains of 6.4, 8.2, and 10.6 dB are obtained in 1 cm long waveguides with cross‐sectional dimensions of 6 × 4, 4 × 4, and 2 × 3 µm2 respectively, using the vertical top‐pumping mode of a 365 nm LED with 462 mW. Incorporating an ≈100 nm thick aluminum reflector grown under the lower cladding, enhanced the optical gain to 11.6 dB cm−1 in a waveguide with a cross‐section of 4 × 4 µm2, and an internal gain of ≈7.4 dB cm−1 is achieved. By relying on the intramolecular energy transfer and LED top‐pumping technology, the upconversion luminescence of Er3+ ions and thermal damage to polymer waveguides caused by the high power density of laser pumping can be effectively reduced. The complex Er(DBTTA)3(DBFDPO)‐doped polymer can be spin‐coated on different types of waveguides to compensate for optical losses at 1.5 µm and is expected to have a critical role in planar photonic integration. [ABSTRACT FROM AUTHOR]

A novel force sensor exploiting the interaction between plasmonic nanostructures and upconversion nanoparticles (UCNPs) is reported. The nanosensor is composed of a gold nanodisk and UCNPs separated by a flexible polymer layer. The gold nanodisk is designed to exhibit a plasmon resonance that selectively enhances one of the emission bands of the UCNPs while leaving the other ones largely unaffected. As the nanosensor is compressed or stretched by an external force, the polymer layer thickness changes, modulating the plasmon‐UCNP coupling. The resulting changes in the luminescence intensity provide the basis for sensing. Furthermore, the nanosensor employs ratiometric sensing, which makes it highly robust against any environmental variations. The nanosensors exhibit two orders of magnitude higher responsivity than previously reported UCNP‐based force sensors. They can be prepared as an on‐chip sensor array or in a colloidal solution, making them suitable for a variety of applications in biology and robotics. [ABSTRACT FROM AUTHOR]

Fluoride-upconversion transparent ceramic materials doped with Er ions have attracted extensive interest due to their higher stability, lower phonon energy, and higher upconversion efficiency. xEr:Sr 5 (PO 4) 3 F (S-FAP) (x=0.5–5 at%) transparent ceramics have been synthesized by hot pressing sintering in this work, and the maximum optical transmittance of the sample reached 74.52 and 82.45% at 500 and 1000 nm, respectively. The XRD results of the powder and ceramic samples were consistent with the diffraction characteristics of the hexagonal S-FAP crystal structure. The SEM and TEM images of powder revealed that the morphology of the sample was composed of mostly rice grains with a diameter of around 20 nm. The XPS and EDS results confirmed the presence of Er3+ and the uniform distribution of Er elements. The thermally etched surface and cross section of ceramics revealed residual pores as the most important scattering source, and the SEM images of the ceramics show that Er doping can obviously promote the growth of the average grain size of S-FAP transparent ceramics. Furthermore, the upconversion luminescence characteristics and fluorescence lifespan of S-FAP transparent ceramics with varied Er doping concentrations were examined, as well as the upconversion luminescence process. The findings in this work indicate that Er:S-FAP transparent ceramics can be employed as a potential upconversion fluorescent material in display technology, biomedicine, temperature sensing, and other applications. • The xEr:S-FAP (x=0–0.05) transparent nanostructured ceramics with highly optical quality were prepared by hot-pressed sintering for the first time. • The microstructural characteristics, upconversion luminescence property, and mechanism of as-synthesized xEr:S-FAP transparent ceramics were investigated for the first time. • The wide visible light spectrum from red light to green light was achieved by changing the doping amount of Er3+ from 0.5 to 5 at%. [ABSTRACT FROM AUTHOR]

Lanthanide‐doped upconversion nanoparticles (UCNPs) have attractive emission properties but suffer from weak light‐absorbing capacities and thereby relatively low brightnesses. This motivates using strongly absorbing dye molecules as antennas and sensitizers. However, despite much effort, understanding of this dye‐UCNP interplay is still limited. Major sensitization mechanisms are still under discussion, largely because there is a lack of effective means to observe key factors such as dark state transitions within the dyes. Here, a combined spectroscopic procedure is established to systematically investigate the photophysics behind the dye‐UCNP interaction, embracing fluorescence‐based transient‐state excitation‐modulation, lifetime and correlation spectroscopy, and spectrofluorometry/spectrophotometry. With this procedure the heptamethine cyanine dye IR806, a typical UCNP sensitizer is studied, its photophysical model is established, its photophysics in UCL‐sensitization‐related environments is deciphered, and the energy transfer from the IR806 singlet excited state to Yb3+ (UCNP sensitizer ion) can be identified as the dominant sensitization mechanism. These studies suggest that IR806 can form non‐emissive H‐aggregates at the nanoparticle surfaces, which can be dissociated after certain light excitation duration (typically>100 µs). Moreover, buildup of a non‐fluorescent, photo‐redox state of IR806 after longer irradiation times (10–100 ms) can deleteriously affect its UCL sensitization effect, inferring an optimal excitation duration for dye‐sensitized UCNPs, relevant for, e.g., optical imaging applications. [ABSTRACT FROM AUTHOR]

Solid-state infrared-to-visible photon up-conversion is important for spectral-tailoring applications. However, existing up-conversion systems not only suffer from low efficiencies and a need for high excitation intensity, but also exhibit a limited selection of materials and complex fabrication processes. Herein, we propose a sensitizer with a bulk-heterojunction structure, comprising both an energy donor and an energy acceptor, for triplet-triplet annihilation up-conversion devices. The up-conversion occurs through charge separation at the donor-acceptor interface, followed by the formation of charge transfer state between the energy donor and annihilator following the spin statistics. The bulk-heterojunction sensitizer ensures efficient charge generation and low charge recombination. Hence, we achieve a highly efficient solid-state up-conversion device with 2.20% efficiency and low excitation intensity (10 mW cm−2) through a one-step solution method. We also demonstrate bright up-conversion devices on highly-flexible large-area substrates. This study introduces a simple and scalable platform strategy for fabricating efficient up-conversion devices. Using donor-acceptor bulk heterojunction as sensitiser for efficient charge generation and low charge recombination in triplet-triplet annihilation upconversion, Bi et al report solid-state one-step printed device with upconversion efficiency of 2.2% and threshold excitation intensity of 10 mW cm−2. [ABSTRACT FROM AUTHOR]

Transparent glass ceramics embedded with YbOF: Er3+ nanocrystals were successfully prepared by melt quenching and cooling methods. The structure and morphology of the YbOF nanocrystals were confirmed by X-ray diffraction, selected area electron diffraction, and transmission electron microscopy. The significant enhancement of upconversion luminescence confirms the doping of Er3+ into the precipitated YbOF nanocrystals. Furthermore, the temperature dependence of the upconversion luminescence was systematically investigated using the fluorescence intensity ratio (FIR) technique under 980 nm excitation. The FIR of the two thermally coupled energy levels of Er3+ ion was validated to be suitable used as temperature probes. The maximum thermal relative sensitivity is about 1.02% K− 1 at 300 K. The results indicate that glass ceramics embedded with YbOF: Er3+ nanocrystals can be used as candidates for temperature sensing. [ABSTRACT FROM AUTHOR]

Tri-doped phosphor YNbO4:Er3+/Tm3+/Yb3+ was prepared by solid-state reaction method. The XRD and SEM results reveal that the product is a monoclinic phase of YNbO4 with high crystallinity and the particles presenting grains with well-defined boundaries with average size is about 1–5 μm. The temperature-dependent luminescence is investigated with 980 nm laser excitation, whereas temperature sensing behaviour was studied in the range of 300–500 K based on Stark sublevels 1G4(a)/1G4(b) (Tm3+), thermal coupling levels 2H11/2/4S3/2 (Er3+) and non-thermal coupling levels 4F9/2 → 4I15/2 (Er3+) /3F2 → 3H6 (Tm3+), 2H11/2 → 4I15/2 (Er3+) / 4F9/2 → 4I15/2 (Tm3+) and 4S3/2 → 4I15/2 (Er3+) /3F2 → 3H6 (Tm3+), utilizing fluorescence intensity ratio (FIR) technique. It is worth highlighting that 1G4(a)/1G4(b) ratio as is not much employed in thermometry. Regarding, NTCL 3F2/1G4(b) pair exhibited the highest absolute sensitivity (SA) is about 110.2 × 10− 3 K− 1 at 500 K, whereas NTCL 3F2/4F9/2 pair presented the highest relative sensitivity (SR) is 2.1% K− 1 at 339 K. Meanwhile, the temperature-dependent emission colours are discussed in detail. High sensitivity indicates that YNbO4:Er3+/Tm3+/Yb3+ white-light phosphor can be used in non-contact temperature sensors applications. [ABSTRACT FROM AUTHOR]

The current works explores the optical contrast property and nanaotheranostic capabilities of the rare earth based Upconversion nanoparticles. Optical coherence tomography (OCT) has been used to explore the particles ability to increase contrast and improve signal intensity. Photo thermal OCT, a function extension of OCT has been used to gauge the photo thermal potential of the nanoparticles. The nanoparticles successfully improved contrast and information from the deeper layers of the sample. The particles also showed excellent capability for use as photo thermal agents. [ABSTRACT FROM AUTHOR]

Current research of triplet–triplet annihilation upconversion (TTA-UC) faces difficulty such as overuse of organic solvents and quenching of excited triplet sensitizers by molecular oxygen. Herein, we propose an efficient and facile preparation strategy of TTA-UC microemulsion to overcome these issues. With simple device and short preparation process, air-stable TTA-UC with a high upconversion efficiency of 16.52% was achieved in microemulsion coassembled from TritonX114, tetrahydrofuran and upconverting chromophores (platinum octaethyl-porphyrin and 9,10-diphenylanthracene). This is comparable to the highest UC efficiency ever reported for TTA-UC microemulsion systems. The excellent UC performance of TX114–THF could be attributed to two perspectives. Firstly, small-size micelle accommodated chromophores up to high concentrations in organic phase, which promoted efficient molecular collision. Additionally, high absorbance at 532 nm ensured full use of excitation light, getting more long wavelength photons involved in the TTA-UC process. Moreover, air-stable TTA-UC also performed well in microemulsion with various surfactants, including nonionic surfactants (Tween 20, Tween 80, Triton X-110, Triton X-114), ionic surfactants (sodium dodecyl sulfate, cetyltrimethyl ammonium bromide) and block copolymers (pluronic F127, pluronic P123), through three conjectural assembly models according to the structural characteristics of surfactant molecules (concentrated, uncompacted and scattered). These discoveries could provide estimable reference for selection of surfactants in relevant fields of TTA-UC. [ABSTRACT FROM AUTHOR]

Circularly polarized luminescence (CPL)‐active materials are increasingly recognized for their potential applications such as 3D imaging, data storage, and optoelectronic devices. Typically, CPL materials have required high‐energy (HE) photons for excitation to emit low‐energy (LE) circularly polarized light, a process known as downshifting CPL (DSCPL). However, the emergence of upconverted CPL (UCCPL), where the absorption of multi LE photons results in the emission of a single HE photon with circular polarization, has recently attracted considerable attention. This minireview highlights the intricate relationship between upconversion and CPL phenomena. During upconversion, the dissymmetry factor (glum) value can be improved in certain systems. Additionally, the integration of both LE and HE photons in upconversion‐downshifting‐synergistic systems offers avenues for dual‐excitation or dual‐emission CPL functionalities. More in detail, the emerging UCCPL based on various photon upconversion mechanisms and their synergy with DSCPL are introduced. Additionally, several examples that demonstrate the applications of UCCPL are presented to highlight the future opportunities. [ABSTRACT FROM AUTHOR]

Spatial and temporal precisely control of direction and speed is crucial for nanomotors to enable complex operations and applications in microsurgery, drug delivery, isolation of biological targets, and so on. Judicious material design involving Janus nanoparticles has been popular over the past decades, however, precise and customizable modulation of Janus structure with a specific asymmetric ratio for motion control is still challenging. In this study, a universal “interface allocation” strategy is developed for efficient and controllable preparation of Janus mesoporous silica‐coated upconversion nanoparticles (Janus UCNP@mSiO2) with precisely tuned asymmetric ratio to achieve near‐infrared (NIR)‐controlled active mobility for relieving vessel plaque. Mesoporous silica with a thickness of 50 nm is precisely coated onto the nanoparticles’ surface with an optimal coverage ratio of 50% to encapsulate gas propellant. Upon exposure to upconverted blue light, the nanomotors release nitric oxide, facilitating their motion and pathologically improving atherosclerosis through endothelium‐dependent vasodilation. Experimental and theoretical simulation results demonstrate the advantages of NIR‐controlled Janus upconversion nanomotors in atherosclerosis treatment, including enhanced nanoparticle‐transmittance rate (34.83% to 85.57%) and excellent in vivo therapeutic efficacy. [ABSTRACT FROM AUTHOR]

In this work, Yb3+ and Er3+-co-doped Sr 9 In(PO 4) 7 upconversion fluorescent materials with dual functionality were synthesized though simple high-temperature solid state method. Based on International Commission on Illumination (CIE) color coordinates, the calculation of color purity at different temperatures demonstrates the attainment of highly pure green luminescence (color purity >90 %) for the synthesized materials. The analysis of activation energy proves that synthesized materials are stable. Utilizing the fluorescence intensity ratio (FIR) of the thermally coupled energy levels (2H 11/2 , 4S 3/2) as a metric for optical sensing performance, absolute sensitivity and relative sensitivity are determined, and their maximum values are 0.44 % and 1.13 %, respectively. Inspired by the variation in CIE coordinates with temperature, thermally responsive two-dimensional barcode image was developed, demonstrating the practical application of Sr 9 In(PO 4) 7 :Yb/Er materials in the field of information security and anti-counterfeiting. [ABSTRACT FROM AUTHOR]

In this review, the developments of efficient high-power CW orange-lime-green lasers by using intracavity stimulated Raman Scattering (SRS) in Nd-doped vanadate lasers are systematically discussed. The overall properties of the spontaneous Raman spectra in Nd:YVO4 and Nd:GdVO4 crystals are overviewed. The critical phase matchings of using the lithium triborate (LBO) crystals for sum frequency generation (SFG) and second harmonic generation (SHG) are thoroughly reviewed. We make a detailed review for achieving the individual green-lime-orange emissions from the self-Raman Nd:YVO4 and Nd:GdVO4 lasers with LBO crystals. The following is to review the dual-wavelength operations of the lime-green and orange-green lasers. Finally, the procedure for generating the triple-wavelength operation of orange-lime-green simultaneous emissions is completely described. The present review is expected to be useful for developing compact, efficient, high-power CW visible lasers for applications including medical treatment, biology, spectroscopy, and remote sensing. [ABSTRACT FROM AUTHOR]

Photonic-integrated circuits based on erbium-doped thin film lithium niobate on insulator has attracted broad interests with insofar various waveguide amplifiers and microlasers demonstrated. Wideband operation facilitated by the broadband absorption and emission of erbium ions necessitates the functional integration of wavelength filter and multiplexer on the same chip. Here, a low-loss wavelength division multiplexer at the resonant pumping and emission wavelengths (∼1480 nm and 1530–1560 nm) of erbium ions based on angled multimode interferometer is realized in the erbium-doped thin film lithium niobate on insulator fabricated by the photolithography assisted chemomechanical etching technique. The minimum on-chip insertion losses of the fabricated device are <0.7 dB for both wavelength ranges, and a 3-dB bandwidth of >20 nm is measured at the telecom C-band. Besides, direct visualization of the multimode interference pattern by the visible upconversion fluorescence of erbium ions compares well with the simulated light propagation in the multimode interferometer. Spectral tuning of the wavelength division multiplexer by structural design is also demonstrated and discussed. [ABSTRACT FROM AUTHOR]