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Targeted drug delivery has been extensively studied in the last decade, whereas both passive and active targeting strategies still face many challenges, such as off-target drug release. Light-responsive drug delivery systems have been developed with high controllability and spatio-temporal resolution to improve drug efficacy and reduce off-target drug release. Photoremovable protecting groups are light-responsive moieties that undergo irreversible photocleavage reactions upon light irradiation. They can be covalently linked to the molecule of interest to control its structure and function with light. In this review, we will summarize recent applications of photocleavage technologies in nanoparticle-based drug delivery for precise targeting and controlled drug release, with a highlight of strategies to achieve long-wavelength light excitation. A greater understanding of these mechanisms and emerging studies will help design more efficient photocleavage-based nanosystems to advance photoresponsive drug delivery.

Optical imaging is an indispensable tool in clinical diagnostics and fundamental biomedical research. Autofluorescence-free optical imaging, which eliminates real-time optical excitation to minimize background noise, enables clear visualization of biological architecture and physiopathological events deep within living subjects. Molecular probes especially developed for autofluorescence-free optical imaging have been proven to remarkably improve the imaging sensitivity, penetration depth, target specificity, and multiplexing capability. In this Review, we focus on the advancements of autofluorescence-free molecular probes through the lens of particular molecular or photophysical mechanisms that produce long-lasting luminescence after the cessation of light excitation. The versatile design strategies of these molecular probes are discussed along with a broad range of biological applications. Finally, challenges and perspectives are discussed to further advance the next-generation autofluorescence-free molecular probes for in vivo imaging and in vitro biosensors. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) K.P. thanks Singapore Ministry of Education, Academic Research Fund Tier 1 (2019-T1-002-045 and RG125/19), Academic Research Fund Tier 2 (MOE2018-T2-2-042), and A*STAR SERC AME Programmat

Photoacoustic imaging is a state-of-the-art technique that combines light excitation with ultrasound generation via the photoacoustic effect. Since sound waves at clinically relevant frequencies undergo minimal perturbation as they pass through the body, photoacoustic imaging is ideal for deep-tissue imaging applications in vivo. Despite its utility in the biomedical field, it is unlikely that undergraduate students will ever experience this technology firsthand in a classroom setting owing to the delicate and expensive nature of the instrumentation. Likewise, students will not be exposed to acoustogenic probes, which are specialized chemicals designed to detect biologically relevant analytes using photoacoustic imaging. With the goal of introducing new chemical analysis and imaging techniques to the undergraduate chemistry curricula, we present a simple and inexpensive setup (all materials were purchased for less than $48 USD) to demonstrate the photoacoustic effect through analyte sensing.

Near-infrared (NIR)-II light-excitable photonic agents capable of generating tumor hyperthermia and cytotoxic free radicals are promising for synergistic phototherapy of tumors. However, the lack o...

With the rapid development of the internet of things, light-excited gas sensors have aroused great attention to meet the increasing demand for room-temperature devices with high portability and low power consumption. However, there are still many issues that need to be addressed, especially the lack of tailored structures specifically designed for light-excited gas sensors. In this work, ∼2600 PIC micron-scaled gas sensors and LED UVC light sources were integrated on a 2-inch sapphire wafer. The integrated microchip exhibited an excellent gas-sensing response to NO2 under in situ light excitation. The response of the device to 500 ppb NO2 was S = 1.12 and its response to an ultra-low concentration of 10 ppb NO2 was S = 1.01. The device exhibited a low resistance at the kΩ-level and fast response and recovery time of 30 s and 88 s, respectively, to 500 ppb NO2, making it ideal for portable applications at room temperature. Moreover, its sensing properties could be tuned by adjusting the wavelength and irradiance of the LED layer. This work lays the foundation for the fabrication of integrated multi-functional devices.

Optimizing the stability and improving photoluminescence quantum yields (PLQYs) of all-inorganic halide perovskite nanocrystals has become an urgent and challenging task to promote its application ...

One of the most exciting applications of metaparticles and metasurfaces consists in the magnetic light excitation. However, the principal limitation is due to parasitic extra multipoles of electric family excited in magnetic dipole meta-particles characterized by a radiating nature and corresponding radiating losses. In this paper, we propose the “ideal magnetic dipole” with suppressed additional multipoles except of magnetic dipole moment in the scattered field from a cylindrical object by using mantle cloaking based on metasurface and on anapole concept. The considered metasurface consists of a periodic width modulated microstrip line, with a sinusoidally shaped profile unit cell printed on a dielectric substrate.

A 657 nm red emission from a novel rare earth free oxide-based CaO–0.5Al2O3–0.5Nb2O5:xMn4+ (0.001 ≤ x ≤ 0.008) phosphors with high water-resistance property were prepared by solid-state reaction method. The composition and structure of the as-prepared phosphors was studied. Under relative ultraviolet (331/365 nm) and blue (465 nm) light excitation, the as-prepared phosphor presents a 657 nm red emission that assigned to the 2Eg → 4A2g transition of Mn4+ ions. The red light source in CaO–0.5Al2O3–0.5Nb2O5:Mn4+ system was discussed, and the water resistance property of the phosphor was also investigated. The as-prepared phosphor presents more proper red emission position than those of similar oxide-based Mn4+-activated phosphors and shows excellent water-resistance property compared with commercial used K2SiF6:Mn4+ phosphor. With the further optimization of its photo-luminescent properties, the as-prepared CaO–0.5Al2O3–0.5Nb2O5:Mn4+ phosphors may find its potential application in the field of white LEDs.

Human mitochondrial matrix protein Miner2 hosts two [2Fe-2S] clusters via two CDGSH (Cys-Asp-Gly-Ser-His) motifs. Unlike other iron-sulfur clusters in proteins, the reduced CDGSH-type [2Fe-2S] clusters in Miner2 are able to bind nitric oxide (NO) and form stable NO-bound [2Fe-2S] clusters without disruption of the clusters. Here we report that the NO-bound Miner2 [2Fe-2S] clusters can quickly release NO upon the visible light excitation. The UV-visible and Electron Paramagnetic Resonance (EPR) measurements show that the NO-bound Miner2 [2Fe-2S] clusters are converted to the reduced Miner2 [2Fe-2S] clusters upon the light excitation under anaerobic conditions, suggesting that NO binding in the reduced Miner2 [2Fe-2S] clusters is reversible. Additional studies reveal that binding of NO effectively inhibits the redox transition of the Miner2 [2Fe-2S] clusters, indicating that NO may modulate the physiological activity of Miner2 in mitochondria by directly binding to the CDGSH-type [2Fe-2S] clusters in the protein.

Light excitation of the sensitizer [Ru(NH3)5(eina)](PF6)2, where eina is ethyl isonicotinate, anchored to anatase TiO2 nanocrystallites interconnected in a mesoporous thin film and immersed in CH3C...

We investigated the emission property of Ce3+ and Tb3+ co-doped CaHfO3 phosphor. Using photoluminescence and photoluminescence excitation spectroscopy, we found that as a result of the energy transfer from Ce3+ to Tb3+, the visible emission intensity of Tb3+ increased dramatically with near ultraviolet (UV) light excitation, and consequently, the colors of our phosphors were tuned from blue to green/yellow and through to white. The temperature dependent emission measurement revealed that the energy transfer from Ce3+ to Tb3+ in the near UV region could be more efficient at low temperatures.

Photoelectrochemical (PEC) cells offer a promising approach for developing a solar energy conversion system to resolve the increasingly serious energy crisis and environmental issues. However, the lack of stable and eco-friendly electrodes hampers their practical applications. Herein, we prepare an eco-friendly photoanode with enhanced PEC performance embedding AgInS2 quantum dots (QDs) into three-dimensional (3D) graphene nanowalls (GNWs). AgInS2 QDs with tunable PL emissions are synthesized using a facile hydrothermal method and then deposited on GNWs directly grown on silica by a catalyst-free method. Benefitting from the interconnected 3D conductive network, GNWs act as an outstanding electron acceptor to transport the photogenerated carriers of AgInS2 QDs. The experimental results demonstrate that the AgInS2/GNWs photoanodes exhibit rapid photoresponse upon light excitation with comparable short rise-time (0.23 s) and decay-time (0.41 s). By optimizing the reaction temperature of the QDs, a photo-current density of 145 μA cm−2 can be achieved due to the effective separation of the photogenerated carriers. Meanwhile, the as-prepared photoanodes exhibit excellent stability of the photoresponse for more than 4000 s of on–off switching and one-month duration. Our study provides a new strategy to construct an eco-friendly PEC system with high performance which shows potential applications for PEC-type devices.

Two new oxysulfides, AeGeS2O (Ae = Sr, Ba), were successfully synthesized via the molten salt method. The two isostructural compounds crystallize in the noncentrosymmetric space group P212121. Their structures feature 1∞[GeS2O]2- one-dimensional helical chains which are built up by [GeS2O2]4- heteroanionic tetrahedra via corner sharing of O atoms. The two oxysulfides are typical semiconductors with wide bandgaps (SrGeS2O: 3.9 eV and BaGeS2O: 4.1 eV) that are perfectly consistent with the first-principles calculation results. They show typical band emissions under UV light excitation (SrGeS2O: 375 nm and BaGeS2O: 360 nm). In addition, SrGeS2O also possesses an orange-yellow light emission (572 nm). SrGeS2O and BaGeS2O exhibit moderate second harmonic generation (SHG) intensities of 0.4 × AgGaS2 and 0.5 × AgGaS2, respectively.

We report on a strong persistent photoconductivity (PPC) induced appearance of conductor‑like behaviour in zinc-tin-oxide (ZTO) photo-thinfilm transistors (TFT). The active ZTO channel layer was prepared by remote-plasma reactive sputtering and possesses an amorphous structure. Under sub-bandgap excitation of ZTO with UV light, the photocurrent reaches as high as ~10-4 A (a photo-to-dark current ratio of ~107) and remains close to this high value after switching off the light. During this time, the ZTO TFT exhibits strong PPC with long-lasting recovery time, which leads the appearance of the conductor‑like behaviour in ZTO semiconductor. In the present case, the conductivity changes over six orders of magnitude, from ~10-7 to 0.92 Ω-1cm-1. After UV exposure, the ZTO compound can potentially remain in the conducting state for up to a month. The underlying physics of the observed PPC effect is investigated by studying defects (deep-states and tail-states) by employing a discharge current analysis (DCA) technique. Findings from the DCA study reveal direct evidence for the involvement of sub-gap tail-states of the ZTO in the strong PPC, while deep-states contribute to mild PPC.

In this study, Li-based blue- and green-emitting core@shell (C@S) upconversion nanophosphors (UCNPs) and NaGdF4-based red-emitting C@S UCNPs were synthesized, and IR-808 dyes were conjugated with the C@S UCNPs to enhance upconversion (UC) luminescence. The surface of the as-synthesized C@S UCNPs, which was originally capped with oleic acid, was modified with BF4&minus, to conjugate the IR-808 dye having a carboxyl functional group to the surface of the UCNPs. After the conjugation with IR-808 dyes, absorbance of the UCNPs was significantly increased. As a result, dye-sensitized blue (B)-, green (G)-, and red (R)-emitting UCNPs exhibited 87-fold, 10.8-fold, and 110-fold enhanced UC luminescence compared with B-, G-, and R-emitting Nd3+-doped C@S UCNPs under 800 nm near-infrared (NIR) light excitation, respectively. Consequently, dye-sensitized UCNPs exhibiting strong UC luminescence under 800 nm NIR light excitation have high applicability in a variety of biological applications.

Despite the outstanding optoelectronic properties of MoS2 and its analogues, synthesis of such materials with desired features including fewer layers, arbitrary hollow structures, and particularly specifically customized morphologies, via inorganic reactions has always been challenging. Herein, using predesigned lanthanide‐doped upconversion luminescent materials (e.g., NaYF4:Ln) as templates, arbitrary MoS2 hollow structures with precisely defined morphologies, widely variable dimensions, and very small shell thickness (≈2.5 nm) are readily constructed. Most importantly, integration of the near‐infrared‐responsive template significantly improves the photoresponse of up to 600 fold in device made of NaYF4:Yb/Er@MoS2 compared with that of MoS2 nanosheets under 980 nm laser illumination. Multichannel optoelectronic device is further fabricated by simply changing luminescent ions in the template, e.g., NaYF4:Er@MoS2, operating at 1532 nm light excitation with a 276‐fold photoresponse enhancement. The simple chemistry, easy operation, high reliability, variable morphologies, and wide universality represent the most important advantages of this novel strategy that has not been accessed before., A facile template‐based strategy for reliable construction of arbitrary MoS2 hollow architectures with widely varied morphologies and dimensions is reported. An up to 600‐fold improvement of photoresponse to 980 nm light illumination is obtained in the representative optoelectronic device made of NaYF4:Yb/Er@MoS2 composite, compared with that of MoS2 nanosheets.

We designed and realized non-concentric magnetoplasmonic-diskplasmonic-ring nanocavities. Free-space light excitation and hybridization of multipolar modes in the plasmonic nanoring with the dipolar plasmon of the magnetoplasmonic disk produce an unprecedented amplification of the magneto-optic response.

The photon activated quantum states yielding resonant tunneling characteristics have been studied from the electrical properties of CdSe nanosheets grown in solvothermal technique. Using metal-semiconductor junction properties, the observed current density –voltage (J-V) behaviors have been analyzed under ultra-violet (UV) light excitation. In comparison to the dark behavior, the J-V property under UV shows a peak bound feature attributed to quantum controlled resonant tunneling effect.

Liquid biopsy consists of a test or a series of tests carried out on a sample of blood to monitor circulating biomarkers, including nucleic acids. In cancer, a liquid biopsy approach can be useful not only for a rapid diagnosis, but also for therapy selection and cancer patient monitoring during treatment. However, the analytical assays need to be very sensitive (capable of detecting very small amounts of circulating analytes) as well as selective. Photoelectrochemistry is a powerful technique of developing an analytical biosensing assay, since it possesses advantages of both optical and electrochemical methods by coupling light excitation and electrochemical detection, and thus resulting in potentially very sensitive measurements due to the low background current. The aim of this review is to describe photoelectrochemical genosensors and to point out the potential of this class of genosensors in determining circulating nucleic acids as well as the challenges in the frame of a liquid biopsy approach.

Ce3+/Eu3+/Tb3+/Mn2+ ion single- or codoped Ca3Al4ZnO10 (CAZO) luminescent materials were successfully synthesized by the high-temperature solid-state reaction. We studied the photoluminescence properties in detail. Under UV radiation, the CAZO:Ce3+ phosphor displays a strong and wide blue emitting band from the doping Ce3+ ion. The CAZO:Eu3+/Tb3+/Mn2+ samples emit the orange, blue-green and yellow-green light due to their characteristic f-f and d-d emissions, respectively. Moreover, the Tb3+ and Mn2+ codoped CAZO samples give simultaneous emissions of Tb3+ and Mn2+, leading to the emission colors changing from green to yellow. Under UV light excitation, multi-color emissions can be obtained by modifying the relative doping concentration of Tb3+ and Mn2+. More importantly, a near white emission was obtained in CAZO:0.003Tb3+, 0.007Mn2+ samples.

In this paper the white-light-emitting Gd2P4O13:Tm3+-Dy3+ phosphors were synthesized via high temperature solid-state reaction method. The X-ray diffraction of the Gd2P4O13:Tm3+-Dy3+ phosphors were performed. Concentration quenching of Gd2P4O13 with Tm3+ - doped ions was studied in detail. The luminescence excitation, emission and decay measurements were performed. Energy transfer between Tm3+ and Dy3+ have been studied. The phosphor Gd2P4O13:Tm3+ exhibit strong blue emission ranging from 440 nm to 470 nm of Tm3+ (3H6 → 1D2) under 359 nm excitation. The emission peak at 456 nm is the luminescence of Tm3+ (1D2 → 3F4). Energy transfer process in the Dy3+-Tm3+ system is proved. This paper includes the color perception analysis of synthesized phosphors. The coordinates of Gd2P4O13:1%Tm3+-3%Dy3+ phosphor is very close to the white-lighting location.

The interaction between radionuclides and nanomaterials could generate Cerenkov radiation (CR) for CR-induced photodynamic therapy (PDT) without requirement of external light excitation. However, the relatively weak CR interaction leaves clinicians uncertain about the benefits of this new type of PDT. Therefore, a novel strategy to amplify the therapeutic effect of CR-induced PDT is imminently required to overcome the disadvantages of traditional nanoparticulate PDT such as tissue penetration limitation, external light dependence, and low tumor accumulation of photosensitizers. Herein, magnetic nanoparticles (MNPs) with (89)Zr radiolabeling and porphyrin molecules (TCPP) surface modification (i.e., (89)Zr-MNP/TCPP) were synthesized for CR-induced PDT with magnetic targeting tumor delivery. As a novel strategy to break the depth and light dependence of traditional PDT, these (89)Zr-MNP/TCPP exhibited high tumor accumulation under the presence of an external magnetic field, contributing to excellent tumor photodynamic therapeutic effect together with fluorescence, Cerenkov luminescence (CL), and Cerenkov resonance energy transfer (CRET) multimodal imaging to monitor the therapeutic process. The present study provides a major step forward in photodynamic therapy by developing an advanced phototherapy tool of magnetism-enhanced CR-induced PDT for effective targeting and treatment of tumors.

A series of Ce-doped phosphors K3Gd1-xB6O12:xCe3+ (x = 0, 0.005, 0.01, 0.02, 0.03, 0.04) were synthesized by high-temperature solid state reaction method. The luminescence properties were investigated under UV (333 nm) excitation. Under 333 nm light excitation, K3Gd1-xB6O12:xCe3+ exhibits intense blue emission centered at 405 nm, due to the 4f1(2F5/2)→4f°5d1 transition of Ce3+ activator. The optimum doping concentrations was found to be x = 2%. The bi-exponential behavior of the decay curves of phosphor K3Gd0.98B6O12:0.02Ce3+ reveals that the Ce3+ activators can reside in two unique crystallographic distinct sites (Gd3+ sites), which fits well with the XRD analysis. One may expect that K3Gd1-xB6O12:xCe3+ has the potential be used as a green phosphor activated by near near-UV light.

In this paper we report the photo-trapping effect of photogenerated charge in a few numbers of silicon nanocrystals (Si-NCs) embedded in SiO2 layer tunnel oxide of small area single electron photodetector (Photo-SET or nanopixel). Using Current-Voltage measurements under illumination (photo-I–V) we find the photo-active traps effect in inversion zone at room temperature. Random Telegraphic Signal under illumination (photo-RTS analysis) confirms that is a photo-generated active trap inside into tunnel oxide layer (Ephoto-act∼ 0.2 eV) and capture section: σ∼8.72 × 10−17 cm2). Moreover, an increasing about 10 pF in capacity’s values in the inversion region for inverse high voltage applied under photo-excitation at low temperature have been marked using photo-Capacitance-Voltage (photo-C–V) measurements. This result confirms the contribution of photo-active traps to better dots photo-charged. The increase of light excitation time-duration, increase the hysteresis width. At 100 μW optical power and 595 nm wavelength, the hysteresis width has their saturation for a 0,05V/s romp speed, and consequently, SiO2 will not behave a dielectric, but as a metal. So we make think that total capacity of structure no more corresponds to the capacity related to the oxide, but to all structure capacity values. The nanopixel photo-detection time (∼400 s) estimated from the flat band evolution in time is affected by photo-active oxide traps presence.

A transient negative photoconductance phenomenon is observed in n -type Czochralski silicon wafers. After a pulsed light excitation, the measured photoconductance drops to negative values and then increases to the original zero. The paper details how transient negative photoconductance is predicted by the Shockley–Read–Hall rate equations for a system of two defects. For this to occur, one defect must act as a majority carrier trap, and the other must be a relatively faster recombination channel. The specific conditions of these defects for a negative photoconductance to occur are derived analytically. Numerical modeling of this system shows good agreement with the experimental results. Finally, a method to extract the trap parameters from negative photoconductance for a sample with temperature-independent capture cross sections is demonstrated.

In present study, 2-(5-(9, 9-diethyl-9H-fluoren-2-yl) thiophen-2-yl)-1-(4isopropylphenyl)-1H-phenanthro [9,10-d] imidazole(PTF) − a multichromophoric hybrid molecule − was synthesized and evaluated as an efficient fluorescent powder for the development of latent fingermarks on non-porous and semi porous surfaces. PTF formulation with silica was applied to the fresh and old fingermarks deposited on non-porous and semi porous surfaces such as, glass, ceramic, steel, polythene and glossy papers. The fingermarks when observed under UV light excitation at 366 nm, developed clear, high contrast, stable, bluish green fluorescence, which can be visualized and photographed for comparison. Optimization studies were carried out on various porous, semi porous and non-porous surfaces with various diluent powders in different concentrations of PTF. The elapsed time and stability studies were also carried out. The fluorescence upon excitation at 366 nm was found to be intense and of comparable quality. The method was validated with reference to fluorescent powder available in the market. To the best of our knowledge this is the first ever report of employing the concept of delayed fluorescence to improve the efficiency of a dye for forensic purposes. The proposed method was found to be simple, stable and sensitive which can be adopted for the routine fingermark practice.

Herein, we report a facile, efficient and versatile method for the photo-regulation of pH-dependent activities of artificial enzymes by incorporating flash photolysis reagents. Under light excitation, a persistent pH shift is achieved by proton release from photosensitive 2-nitrobenzaldehyde. Following such change, the controlled activation of oxidase-like activity of nanoceria is successfully demonstrated.

Indocyanine green (ICG) emits fluorescence in the far-red domain under light excitation. ICG video angiography (ICG-VA) has been established as a useful method to evaluate blood flow in the operative field. We report the usefulness of ICG-VA for Sylvian fissure dissection in patients with subarachnoid hemorrhage (SAH). Subjects comprised 7 patients who underwent ICG-VA before opening the Sylvian fissure during neck clipping for ruptured cerebral aneurysm. We observed contrasted Sylvian veins before opening the Sylvian fissure using surgical microscopes. This procedure was termed "Sylvian ICG". We observed ICG fluorescence quickly in all cases. Sylvian veins that appeared unclear in the standard microscopic operative field covered with subarachnoid hemorrhage were extremely clearly depicted. These Sylvian ICG findings were helpful in identifying entry points and the dissecting course of the Sylvian fissure. At the time of clipping, no residual fluorescence from Sylvian ICG was present, and aneurysm clipping was not impeded. Sylvian ICG for SAH patients is a novel technique to facilitate dissection of the Sylvian fissure. We believe that this technique will contribute to improved safety of clipping surgery for ruptured aneurysms.

To study chemical and biological processes, spatially resolved determination of the concentrations of one or more analyte species is of distinct interest. With a light-addressable potentiometric sensor (LAPS), chemical images can be created, which visualize the concentration distribution above the sensor plate. One important challenge is to achieve a good lateral resolution in order to detect events that take place in a small and limited region. LAPS utilizes a focused light spot to address the measurement region. By moving this light spot along the semiconductor sensor plate, the concentration distribution can be observed. In this study, we show that utilizing a pulse as light excitation instead of a traditionally used continuously modulated light excitation, the lateral resolution can be improved by a factor of 6 or more.

The ability of plasmonic nanoparticles to harness visible light can be being combined with their catalytic activity to drive photocatalytic transformations. This Review introduces the promise of this new class of photocatalysts for fulfilling the quest for sunlight-driven recycling of CO2 into transportable liquid fuels. We discuss the prospects and challenges of such an approach. Despite considerable advances, a selective, stable, and efficient CO2 reduction reaction (CO2RR) catalyst has been elusive. These open challenges may be addressable by the strategic utilization of plasmonic light excitation. Plasmonic catalysts have exhibited the ability to drive a rich milieu of CO2RR processes under visible light excitation. At this stage, improved mechanistic understanding and reaction control are needed. To motivate rational design of photocatalytic materials and processes by a future generation of researchers, we suggest potential pathways by which plasmonic-assisted CO2RR can take place. We describe unique...

In this work, a series of Eu2+-doped (Ca1−xSrx)8MgLu(PO4)7 and Eu2+/Mn2+-codoped Ca6.5Sr1.5MgLu(PO4)7 phosphors were prepared via the combustion-assisted solid-state reaction process. XRD patterns and Rietveld refinements were used to verify the incorporations of Sr into Ca8MgLu(PO4)7:Eu2+. Upon the same excitation wavelength of 380 nm, the emission peaks of Eu2+-doped (Ca1−xSrx)8MgLu(PO4)7 (0≤x≤1) phosphors red-shifted from 453 to 519 nm with increasing Sr/Ca ratio. The red-shift of the Eu2+ emission with increasing Sr/Ca ratio was ascribed to the change of Eu2+ emission at different lattice sites. With variation of the Mn2+ content, the emission color of Eu2+/Mn2+ codoped Ca6.5Sr1.5MgLu(PO4)7 phosphors exhibited the luminescence tunable from greenish blue to white and eventually to red. The energy transfer from Eu2+ to Mn2+ in Ca6.5Sr1.5MgLu(PO4)7 host matrix was demonstrated to be of a resonant type via a dipole- dipole mechanism with the critical distance of ∼16.7 A. By the Sr substitution for Ca and properly tuning by the relative composition change of Eu2+/Mn2+, chromaticity coordinates of (0.329, 0.326) can be reached at near UV light excitation. The combination of host composition design and energy transfer may provide a novel strategy to obtain white light and tunable luminescence.

This work demonstrates the combined effect of nano-TiO2 decoration and UV radiation on the ethanol sensing of ZnSnO3 hollow microcubes. TiO2-decorated ZnSnO3 samples were synthesized by a facile co-precipitation method, followed by the calcination treatment of precursor–dehydration. The morphology and structure of the as-prepared samples were further characterized by XRD, EDS, SEM and TG analysis. Obtained samples were fabricated to thick film gas sensors for ethanol detection. Sensing tests showed a strong influence of TiO2 decoration on the sensing properties. Light excitation by means of a low-powered UV source (365 nm) has been used to reinforce the sensor performance especially at lower operating temperature. The optimal sensor based on TiO2-decorated ZnSnO3 showed promising performance towards ethanol, ensuring high response and fast dynamics at operating temperature as low as 80 °C.

The Eu2+ /Eu3+ mixed valence phosphor Ca2 SiO2 F2 :Eu2+ /Eu3+ was prepared using a solid-state reaction synthesis method in a CO atmosphere, and the optical properties were investigated. The spectroscopic properties revealed that Ca2+ ions were occupied by both Eu2+ and Eu3+ ions in Ca2 SiO2 F2 , and both ions were able to generate their characteristic emissions. A broad 5d → 4f Eu2+ band at ~470 nm and narrow 4f → 4f Eu3+ peaks upon excitation with n-UV light were observed. The ratio between Eu2+ and Eu3+ emissions changed regularly, and the relative intensity of the red component from Eu3+ became systematically stronger with increasing overall Eu content. As a result, the emission color of these phosphors can be tunable from blue to pink under n-UV light excitation.