Excitation Light Source Research Articles

Tunable diode laser absorption spectroscopy for open-path monitoring gas markers in fire combustion products

This paper presents an open-path gas sensing technique based on tunable diode laser absorption spectroscopy (TDLAS) for simultaneously detecting multiple gas markers in fire combustion products for the purpose of early warning of fires. To demonstrate this detection method, a dual-gas sensing system was developed by combing calibration-free direct absorption spectroscopy (DAS) and a homemade three-mirror multi-pass optical system. A near-infrared (NIR) distributed feedback (DFB) diode laser emitting near 1579 nm was used as an excitation light source for simultaneously measuring dual-gas fingerprint absorption spectra of CO and CO2 in combustion products. Details of laser tuning characteristics, the cross-talk effect of CO and CO2 absorption spectra, and concentration response characteristics are initially investigated both theoretically and experimentally. Finally, various coal samples (anthracites) are used for evaluating the developed dual-gas sensor’s real-time response and combustion characteristics. The experimental results are in good agreement with the theoretical expectation, which proves its great potential for early diagnosis and warning research of fires and practical engineering applications.

Development of visible-light driven photo-switching copolymers with pH indicating performance

Visible-light-driven azobenzene had been reported by theoretical calculation, but could not be detected by any characterization method due to unstable cis structure. Herein, copolymerization was applied to solve the problem based on a time-dependent characteristic of macromolecular motion. Therefore, two copolymers, namely, MRAA-PEG20 copolymer and MRAA-NIPAM copolymer, were synthesized with a definite segment ratio. Both copolymers had photosensitive groups, which were confirmed by UV-vis spectra. Furthermore, copolymer concentration had a linear relationship with absorbance value at 425 nm. Firstly, blue light as an excitation source to induce the isomerization of copolymers. At the same time, repeated interval irradiation was used to evaluate the fatigue performance of the copolymer. Consequently, both copolymers could quickly transform to their cis isomers upon irradiation, which could be reversible recovered to their trans isomers in operable recovery time after removing irradiation. However, the MRAA-PEG20 copolymer had an obvious photobleaching phenomenon along with the circle index, which did not exist in the MRAA-NIPAM copolymer. Secondly, the effects of excitation light source on isomerization were investigated. It was found that blue light was the most efficient excitation source for both copolymers though other light could also induce trans-to-cis transition. Thirdly, the influence of light intensity and temperature was respectively studied. With increasing of light intensity, the absorbance ratio before and after irradiation monotonously decreased, the irradiation response time shortened and the recovery response time prolonged. Moreover, higher temperature resulted in a higher absorbance ratio, shorter irradiation response time, and shorter recovery response time. Finally, synthesized copolymers had characteristic of pH indicator with a critical point of pH 5.0.

Defect elimination to enhance photoluminescence and optical transparency of Pr-doped ceramics for self-calibrated temperature feedback windows

Pr-doped metal oxide polycrystalline transparent ceramics are highly desirable for photothermal window systems served in extreme environments, however, obtaining efficient photoluminescence together with high transparency in these ceramics is still posing serious challenges, which undoubtedly limits their applications. Here, Pr-doped Y₂Zr₂O₇ (YZO) transparent ceramics, as an illustrative example, are prepared by a solid-state reaction and vacuum sintering method. Owing to the elimination of defect clusters [ Pr_Y⁴⁺-O^2- - Pr_Y⁴⁺] and [Pr_Y⁴⁺ - e'] without introduction of impurities and additional defects, the fabricated YZO:Pr ceramics exhibit high transparency (74 %) and efficient photoluminescence (39-fold enhanced) after air annealing plus vacuum re-annealing treatment. Moreover, upon 295/450 nm excitation, the emission bands (blue, green, red, and dark red) from YZO:Pr ceramic present different temperature-dependent properties due to the thermal quenching channel generated by the intervalence charge transfer state (IVCT) between Pr³⁺ and Zr⁴⁺ ions. Furthermore, a self-calibrated temperature feedback window with same FIR model (I₆₁₃/I₅₀₃) under different excitation light sources (295 nm and 450 nm) is designed. The developed photothermal window operated in a wide temperature range (303 - 663 K) shows relatively high sensitivities (<em>S</em>_a and <em>S</em>_r reach 0.008 K^-1 at 663 K and 0.47 % K^-1 at 363 K, respectively), high repeatability (&gt; 98 %), and low temperature uncertainty (&lt; 3 K). This work presents a paradigm for achieving enhanced photoluminescence along with elevated transparency of lanthanides doped ceramics through vacuum re-annealing treatment engineering and demonstrates their promising potential for photothermal window systems.

Smartphone-based photoelectrochemical immunoassay of prostate-specific antigen based on Co-doped Bi2O2S nanosheets

Portable and on-site detection of target biomarker is of great significance in early diagnosis of diseases. Herein, we designed a portable smartphone-based PEC immunoassay platform to detect prostate specific antigen (PSA) adopting Co-doped Bi2O2S nanosheets as photoactive materials. The fast photocurrent response under visible light and excellent electrical transport rate invest Co-doped Bi2O2S with the property of being effectively excited even under a weak light source. Therefore, with the incorporation of a carriable flashlight that act as the excitation light source, disposable screen-printed electrodes, a microelectrochemical workstation and a smartphone that served as control center, point-of-care analytical detection of low-abundance small molecule analytes was successfully realized. Specifically, a sandwich-type immunoreaction was performed using alkaline phosphatase labeled secondary antibody as signal indicator. In the presence of PSA, ascorbic acid as generated through a catalytic reaction, resulting in the enhancement of photocurrent intensity. The photocurrent intensity increased linearly with the logarithm of PSA concentrations ranging from 0.2 to 50 ng mL−1 with a detection limit of 71.2 pg mL−1 (S/N = 3). This system provided an effective method for the construction of portable and miniaturized PEC sensing platform for the application of point-of-care health monitoring.

Light Conversion Nanomaterials for Wireless Phototherapy.

ConspectusPhototherapy including optogenetics, photodynamic therapy (PDT), photothermal therapy (PTT), and photoimmunotherapy (PIT) has been proven to be effective against different diseases. However, as the name suggests, phototherapy requires light irradiation, thus its therapeutic efficiency is often restricted by limited depth of light penetration within biological tissue. This light penetration limitation is significantly adverse to PDT and optogenetics because both therapies are usually activated with UV and visible light of very poor tissue penetration efficiency. Current light delivery methods usually involve cumbersome setups and require optical fiber or catheter insertion, which not only restrict the movement of patients but also impose incompatibility issues with chronic implantation. To address the existing challenges, wireless phototherapy was developed through various approaches over recent years, which usually relies on implantable wireless electronic devices. However, the application of wireless electronic devices is limited by invasion during implantation, unwanted heat generation, and adverse immunogenicity of these devices.Over the recent years, applying light conversion nanomaterials as light transducers for wireless phototherapy has garnered much interest. Compared with implantable electronic devices and optical fiber, nanomaterials can be easily injected into the body with minimal invasiveness and can also be surface functionalized to increase their biocompatibility and cell accumulation efficiency. Commonly applied light conversion nanomaterials include upconversion nanoparticles (UCNPs), X-ray nanoscintillators, and persistent luminescence nanoparticles (PLNPs). UCNPs and X-ray nanoscintillators can respectively convert near-infrared (NIR) light and X-ray, which have good tissue penetration efficiency, to UV or visible light, which is suitable for activating phototherapy. PLNPs can be excited by external light such as X-rays and NIR light and retain long afterglow luminescence after the removal of the excitation light source. As a result, applying PLNPs in phototherapy can potentially reduce irradiation time from external light sources, thus minimizing tissue photodamage. This Account aims to briefly discuss (i) the mechanisms of different phototherapies, (ii) the development and mechanisms of light conversion nanomaterials, (iii) the application of light conversion nanomaterials in wireless phototherapy, highlighting how they relieve current challenges in phototherapy, and (iv) perspectives for future development of light conversion nanomaterials for wireless phototherapy.

Ratiometric optical oxygen sensor based on perovskite quantum dots and Rh110 embedded in an ethyl cellulose matrix

Ratiometric optical sensor gas sensing continues to develop optical sensing techniques and materials used in various industrial and environmental applications. This research focuses on a new ratiometric optical sensor using the development of new material of FAPbI3 perovskite QDs and a simple method to detect oxygen (O2) gas. FAPbI3 perovskite QDs are used as an indicator of oxygen gas, and rhodamine 110 (Rh 110) is a reference material in a ratiometric optical sensor. All of the sensing and reference materials are embedded in an ethyl cellulose (EC) matrix and coated on the surface of the filter paper. Using a UV LED with a central wavelength of 380 nm as the excitation light source, the emission spectra results show that the emission wavelengths of the oxygen-sensitive dye (O2) FAPbI3 perovskite QDs do not overlap with the Rh 110 reference signal. Thus, oxygen concentration can be measured using a ratiometric fluorescence reference-based approach. The sensing signal will be obtained in the presence of analyte gas in the ratiometric sensitivity of R0/R100, where R0 and R100 represent the luminescence intensity detected in 100% nitrogen and 100% oxygen concentrations, respectively. The experimental results show the optical oxygen sensor's sensitivity as R0/R100 = 12.7. In addition, the response time and recovery of the oxygen gas sensor produced are 75 s and 93 s, respectively. The use of a new type of FAPbI3 perovskite QDs material has been successfully developed in the optical ratiometric sensor for oxygen gas. The sensor proposed in this study has a low cost and easy fabrication process. The effect of spurious fluctuations in the excitation source intensity can be suppressed by the ratiometric optical sensing method.

Classification of Fluorescently Labelled Maize Kernels Using Convolutional Neural Networks.

Accurate real-time classification of fluorescently labelled maize kernels is important for the industrial application of its advanced breeding techniques. Therefore, it is necessary to develop a real-time classification device and recognition algorithm for fluorescently labelled maize kernels. In this study, a machine vision (MV) system capable of identifying fluorescent maize kernels in real time was designed using a fluorescent protein excitation light source and a filter to achieve optimal detection. A high-precision method for identifying fluorescent maize kernels based on a YOLOv5s convolutional neural network (CNN) was developed. The kernel sorting effects of the improved YOLOv5s model, as well as other YOLO models, were analysed and compared. The results show that using a yellow LED light as an excitation light source combined with an industrial camera filter with a central wavelength of 645 nm achieves the best recognition effect for fluorescent maize kernels. Using the improved YOLOv5s algorithm can increase the recognition accuracy of fluorescent maize kernels to 96%. This study provides a feasible technical solution for the high-precision, real-time classification of fluorescent maize kernels and has universal technical value for the efficient identification and classification of various fluorescently labelled plant seeds.

A Low-Cost, Portable Device for Detecting and Sorting Aflatoxin-Contaminated Maize Kernels.

Aflatoxin contamination of maize is a major food safety issue worldwide. The problem is of special significance in African countries because maize is a staple food. This manuscript describes a low-cost, portable, non-invasive device for detecting and sorting aflatoxin-contaminated maize kernels. We developed a prototype employing a modified, normalized difference fluorescence index (NDFI) detection method to identify potentially aflatoxin-contaminated maize kernels. Once identified, these contaminated kernels can be manually removed by the user. The device consists of a fluorescence excitation light source, a tablet for image acquisition, and detection/visualization software. Two experiments using maize kernels artificially infected with toxigenic Aspergillus flavus were implemented to evaluate the performance and efficiency of the device. The first experiment utilized highly contaminated kernels (71.18 ppb), while mildly contaminated kernels (1.22 ppb) were used for the second experiment. Evidently, the combined approach of detection and sorting was effective in reducing aflatoxin levels in maize kernels. With a maize rejection rate of 1.02% and 1.34% in the two experiments, aflatoxin reduction was achieved at 99.3% and 40.7%, respectively. This study demonstrated the potential of using this low-cost and non-invasive fluorescence detection technology, followed by manual sorting, to significantly reduce aflatoxin levels in maize samples. This technology would be beneficial to village farmers and consumers in developing countries by enabling safer foods that are free of potentially lethal levels of aflatoxins.

White light and long persistent luminescence from metal cluster-based metal-organic frameworks

Metal-organic frameworks (MOFs) with long persistent luminescence (LPL) have raised particular attention among researchers for their potential applications in optical recording devices, biological imaging, security systems, and so on. Compared with traditional MOFs materials constructed by the single metal as a node, MOFs materials with multinuclear cluster substructure units can effectually facilitate the fixation of molecular conformations through multiple coordination bonds, which would form a dense stacking and rigid environment to suppress the non-radiation transition of triplet excitons. At the same time, metal clusters can act as heavy atoms to increase the spin–orbit coupling to a certain extent, promote Sn-Tn energy conversion to effectively improve the ISC efficiency and enhance the LPL performance. However, MOFs-based LPL materials centred on multinuclear clusters are rarely studied. In this paper, two LPL MOFs (SUST-WJ-12 and SUST-WJ-13) based on the polydentate ligand 2-hydroxyniotinic acid (H2L) with multinuclear cluster are reported and their formulas are [CdL]n and [Zn3(L)2(HCOO)(OH)]n, respectively. In the solid state, they both exhibit excitation-dependent emission color-tuning from blue to green, in which SUST-WJ-12 obtains a white light emission under 280 nm excitation. Importantly, two MOFs both give the long-lived phosphorescence with the lifetimes of 69.92 and 63.22 ms, respectively, and emit the bright and visible LPL for 2–3 s after the removal of the excitation light source. Single-crystal X-ray diffraction analysis and theoretical calculations reveal that LPL of two MOFs arise from the ligand center which is enhanced by metal cluster. The thus obtained LPL provides potentials in lighting and security systems and so on.

Highly stable multi-encapsulated red-emitting cesium lead halide nanocrystals for efficient copper ion detection and imaging in live cells

Recently, cesium lead halide (CsPbX3: X = Cl, Br, I) perovskite nanocrystals (NCs) have shown potentiality in the detection of different heavy metal ions and bioimaging applications for their smaller particle size, tunable emission spectra, high luminescent intensity, narrow emission spectra, multiphoton absorption property, etc. CsPbBr3 NCs are explored extensively in bioimaging applications for their comparatively higher stability in water. A longer wavelength excitation light source is recommended due to less scattering of light results in deeper penetration in living cells. However, imaging in live cells with red-emitting perovskite NCs is not suitable because of their poor structural stability, low emission intensity, and complex synthesis process. To tackle these issues, we introduce a specific halide exchange to the NCs and then multi-encapsulation shelling techniques that eventually improve the structural and environmental stability of the red-emitting NCs. Here, we synthesized Zn-doped CsPbBr3 NCs via the ligand-assisted reprecipitation (LARP) synthesis method in an open atmosphere. Then the highly luminescent red emitting CsPbBrxI3−x NCs with Zn doping were grown via the exchange of halide ions from pre-synthesized Zn-doped CsPbBr3 NCs to maintain the stable perovskite crystal structure in the nanoscale regime. Such NCs were further encapsulated with different shelling materials and then compared their photophysical properties. Among them, n-isopropyl acrylamide passivated Zn-doped CsPbBrxI3−x/SiO2/polyvinylpyrrolidone core/shell/shell NCs showed the highest stability against water and UV-irradiation. These NCs efficiently detect Cu2+-ions in water and achieved a detection limit of around 9.68 µM. The NCs were also tested for their compatibility as a fluorescent probe for live cell imaging using mammalian Chinese Hamster Ovary cells. As a proof-of-principle, we demonstrate both the efficient uptake and biocompatibility of the perovskite NCs. This work provides insight for expanding research activities on red-emitting perovskite NCs by developing a new strategy to improve the stability of the NCs, which is beneficial for both cost-effective bioimaging applications and heavy metal ion detection in water.

Photochromism and Long Persistent Luminescence in Pr3+‐Doped Garnet Transparent Ceramic via UV or Blue Light Up‐Conversion Charging

AbstractMultifunctional phosphors with photochromism and persistent luminescent (PersL) properties have attracted increasing interest owing to the capability of absorbing the photon energy and trapping the generated carriers via defects. However, the opacity of materials compromises the enhancement of photochromism and PersL properties; besides, the need of high energy excitation light source limits their applicability. To bridge these obstacles, Pr3+‐doped Y3Al2Ga3O12 transparent ceramic with in‐line transmittance over 80% at 1,800 nm is reported, which exhibits strong red PersL after several minutes UV light or blue light up‐conversion charging. The luminance duration time can reach &gt;7 h at 0.32 mcd m−2 threshold value after UV light charging. Interestingly, the phosphor also displays photochromic properties with robust fatigue resistance, i.e., the color changes from light green to red by UV/blue light illumination and is bleached at 300 °C. The nature of trap centers, trapping and detrapping processes is explored based on thermoluminescence and electron spin resonance. Finally, the mechanism of photochromism and PersL is discussed by using vacuum referred binding energy diagram. This work opens new avenues for future research on multifunctional materials and brings potential applications in optical information encryption media and optical sensors.

Highly Stable and Photoluminescent CsPbBr3/Cs4PbBr6 Composites for White-Light-Emitting Diodes and Visible Light Communication

Inorganic lead halide perovskite is one of the most excellent fluorescent materials, and it plays an essential role in high-definition display and visible light communication (VLC). Its photochromic properties and stability determine the final performance of light-emitting devices. However, efficiently synthesizing perovskite with high quality and stability remains a significant challenge. Here, we develop a facile and environmentally friendly method for preparing high-stability and strong-emission CsPbBr3/Cs4PbBr6 composites using ultrasonication and liquid paraffin. Tuning the contents of liquid paraffin, bright-emission CsPbBr3/Cs4PbBr6 composite powders with a maximum PLQY of 74% were achieved. Thanks to the protection of the Cs4PbBr6 matrix and liquid paraffin, the photostability, thermostability, and polar solvent stability of CsPbBr3/Cs4PbBr6-LP are significantly improved compared to CsPbBr3 quantum dots and CsPbBr3/Cs4PbBr6 composites that were prepared without liquid paraffin. Moreover, the fabricated CsPbBr3/Cs4PbBr6-LP-based WLEDs show excellent luminescent performance with a power efficiency of 129.5 lm/W and a wide color gamut, with 121% of the NTSC and 94% of the Rec. 2020, demonstrating a promising candidate for displays. In addition, the CsPbBr3/Cs4PbBr6-LP-based WLEDs were also demonstrated in a VLC system. The results suggested the great potential of these high-performance WLEDs as an excitation light source to achieve VLC.

Multi-Mode Lanthanide-Doped Ratiometric Luminescent Nanothermometer for Near-Infrared Imaging within Biological Windows

Owing to its high reliability and accuracy, the ratiometric luminescent thermometer can provide non-contact and fast temperature measurements. In particular, the nanomaterials doped with lanthanide ions can achieve multi-mode luminescence and temperature measurement by modifying the type of doped ions and excitation light source. The better penetration of the near-infrared (NIR) photons can assist bio-imaging and replace thermal vision cameras for photothermal imaging. In this work, we prepared core-shell cubic phase nanomaterials doped with lanthanide ions, with Ba2LuF7 doped with Er3+/Yb3+/Nd3+ as the core and Ba2LaF7 as the coating shell. The nanoparticles were designed according to the passivation layer to reduce the surface energy loss and enhance the emission intensity. Green upconversion luminescence can be observed under both 980 nm and 808 nm excitation. A single and strong emission band can be obtained under 980 nm excitation, while abundant and weak emission bands appear under 808 nm excitation. Meanwhile, multi-mode ratiometric optical thermometers were achieved by selecting different emission peaks in the NIR window under 808 nm excitation for non-contact temperature measurement at different tissue depths. The results suggest that our core-shell NIR nanoparticles can be used to assist bio-imaging and record temperature for biomedicine.

Single-shot multi-channel plasmonic real-time polymerase chain reaction for multi-target point-of-care testing.

Plasmonic nucleic acid amplification tests demand high-throughput and multi-target detection of infectious diseases as well as short turnaround time and small size for point-of-care molecular diagnostics. Here, we report a multi-channel plasmonic real-time reverse-transcription polymerase chain reaction (mpRT-qPCR) assay for ultrafast and on-chip multi-target detection. The mpRT-qPCR system features two pairs of plasmonic thermocyclers for rapid nanostructure-driven amplification and microlens array fluorescence microscopes for in situ multi-color fluorescence quantification. Each channel shows a physical dimension of 32 mm, 75 mm, and 25 mm in width, length, and thickness. The ultrathin microscopes simultaneously capture four different fluorescence images from two PCR chambers of a single cartridge at a single shot exposure per PCR cycle of four different excitation light sources. The experimental results demonstrate a single assay result of high-throughput amplification and multi-target quantification for RNA-dependent RNA polymerase, nucleocapsid, and human ribonuclease P genes in SARS-CoV-2 RNA detection. The mpRT-PCR increases the number of tests four times over the single RT-PCR and exhibits a short detection time of 15 min for the four RT-PCR reactions. This point-of-care molecular diagnostic platform can reduce false negative results in clinical applications of virus detection and decentralize healthcare facilities with limited infrastructure.

A digital multimeter-based portable photoelectrochemical immunoassay for the detection of cardiac troponin I with enzymatic biocatalytic precipitation.

Early diagnosis of acute myocardial infarction (AMI) can significantly reduce mortality, which can be achieved by the highly sensitive detection of AMI-specific cardiac troponin I (cTnI) biomarkers. Herein a highly sensitive and portable photoelectrochemical (PEC) immunoassay for the detection of cTnI was innovatively fabricated based on an efficient photocurrent response of Cu2O coupling with a split-type enzymatic biocatalytic precipitation reaction with a digital multimeter readout. Initially, Cu2O cubic nanomaterials with a good photocurrent response were obtained by facile green room temperature synthesis and dropped on fluorine-doped tin oxide (FTO) plates as photoactive materials (Cu2O/FTO). In the presence of target cTnI, horseradish peroxidase (HRP) on the detection antibody catalyzes the substrate 4-chloro1-naphthol (4-CN) to produce insoluble precipitates of benzo-4-chlorohexadienone (4-CD) on Cu2O/FTO with the assistance of H2O2, resulting in a decrease in the photocurrent of the Cu2O/FTO electrode. To make the whole inspection process more concise and efficient, we used a flashlight and a digital multimeter as the excitation light source and reading device for the PEC sensing system, respectively. Under the optimal conditions of immunoreaction time, pH, and loading, the photocurrent of Cu2O/FTO decreased with increasing target cTnI concentration with a limit of detection (LOD) of 4.7 pg mL-1 in the operating range of 0.01-10 ng mL-1. It is of interest that the developed portable PEC immunoassay is also capable of detecting cTnI in human serum samples with acceptable accuracy compared to the reference cTnI enzyme-linked immunosorbent assay (ELISA) method while maintaining portability and sensitivity.

Making multi-twisted luminophores produce persistent room-temperature phosphorescence.

Multi-twisted molecules, especially those with more than four branched rotation axes, have served as superior prototypes in diverse fields like molecular machines, optical materials, sensors, and so forth. However, due to excessive non-radiative relaxation of these molecules, it remains challenging to address their persistent room-temperature phosphorescence (pRTP), which limits their further development. Herein, we develop a host-guest energy-transfer relay strategy to improve the phosphorescence lifetime of multi-twisted luminophores by over thousand-fold to realize pRTP, which can be witnessed by the naked eye after removing the excitation light source. Moreover, we employ photoexcitation-induced molecular rearrangement to further prolong the phosphorescence lifetime, which, to the best of our knowledge, is the first example of photoactivation in ordered host-guest systems. Our systems show superior humidity and oxygen resistance, enabling long-term (at least over 9-12 months) stability of the pRTP properties. By achieving pRTP of multi-twisted luminophores, this work can advance the understanding of molecular photophysical mechanisms and guide the study of more molecular systems that are difficult to achieve pRTP.

Design and optimization of a blue fluorescent microcavity-organic light-emitting diode (MOLED) on AZO anode for an algae excitation light source application

In this work, we present simultaneous organic light-emitting diode (OLED) stack optimization and optical modelling for a blue microcavity-OLED (MOLED) based on AZO anode to be used as algae excitation light in optical biosensor. Fluorescent materials (MADN and DPAVBi) were chosen as host:guest for the doped emissive layer due their known stability compared to phosphorescent and thermally activated delayed fluorescence (TADF) materials. The MOLED modelling was performed by targeting 470 nm as the maximal excitation wavelength and suppressing the emission in the algae fluorescence bandwidth (600–800 nm) in order to fulfil the sensor requirements. By using a bilayer hole transport layer/electron blocking layer (HTL/EBL) instead of a single HTL, the total thickness was adjusted to meet the resonance wavelength condition without loss of efficiency, while at the same time preserving a maximum electric field intensity in the emissive layer (antinode position). MOLED devices were fabricated by organic semiconductor evaporation on three dielectric distributed Bragg reflectors (DBRs) with 3 different numbers of TiO2/SiO2 (high-index/low-index) pairs and aluminum-doped zinc oxide (AZO) transparent electrode. Devices with 1.5 pairs as DBR showed not only an improved external quantum efficiency (+33%) compared to a standard OLED but also an increase of about 3 times the intensity of the peak at 470 nm combined to a lower emission in the 600–800 nm bandwidth, as aimed. This increase in the peak intensity should lead to a longer device lifetime, as the current density necessary to excite algae at 470 nm is significantly lower owing to the microcavity effect.

Upconversion fluorescence-based PDT nanocomposites with self-oxygenation for malignant tumor therapy

Upconversion fluorescence-based-PDT nanocomposites with self-oxygenation have excellent anti-tumor properties, including deep penetration of the excitation light source and the ability to remodel the anoxic microenvironment, and has feasibility in clinical application.

"Glow ELISA": sensitive immunoassay with minimal equipment and stable reagents.

Glow enzyme-linked immunosorbent assay (glow ELISA) uses inexpensive and shelf-stable glow stick reagents to chemically excite fluorescent reporters, obviating the need for excitation light sources, filters, and complex optics. It achieves excellent limits of detection while offering portability and equipment cost comparable to lateral flow immunoassays.

Multi-color luminescence and anticounterfeiting application of upconversion nanoparticle.

Multi-color luminescence materials are important in the illumination, solid-state three-dimensional display, information storage, biological labelling and anticounterfeiting fields. Herein, we designed a novel core-shell structure upconversion nanoparticle (UCNP) material (NaYF4) with lanthanide ion doping to achieve multi-color luminescence under a single NIR excitation laser. Different from the typical single-sensitizer materials, the core-shell structure utilizes Nd3+, Yb3+, Tm3+ and Er3+ ions to obtain tuning of the color and brightness. The doping of Nd3+ ions enhances the weak color (red) light source to maintain the light color balance. Benefiting from the color adjustment of the sensitizers and the change of the core-shell coating, bright-white emission and flexible color emission from red to green, cyan and blue can be achieved via the diverse doped rare earth ions in a single UCNP under continuous-wave laser excitation (980 nm). Simultaneously, the emission color of the UCNPs can change with the intensity of the excitation light source and the wavelength. The bright-white emission can be used for lighting displays, and the flexible full-color emission can be applied in the anticounterfeiting and information storage fields.