NIR-II fluorescence imaging in liver tumor surgery: A narrative review

In liver tumor surgery,the recognition of tumor margin and radical resection of microcancer focis have always been the crucial points to reduce postoperative recurrence of tumor.However,naked-eye inspection and palpation have limited effectiveness in identifying tumor boundaries,and traditional imaging techniques cannot consistently locate tumors in real time.As an intraoperative real-time navigation imaging method,NIRfluorescence imaging has been extensively studied for its simplicity,reliable safety,and superior sensitivity,and is expected to improve the accuracy of liver tumor surgery.In recent years,the research focus of NIRfluorescence has gradually shifted from the-rst near-infrared window(NIR-I,700–900 nm)to the second near-infrared window(NIR-II,1000–1700 nm).Fluorescence imaging in NIR-II reduces the scattering effect of deep tissue,providing a preferable detection depth and spatial resolution while signi-cantly eliminating liver autofluorescence background to clarify tumor margin.Developingfluorophores combined with tumor antibodies will further improve the precision offluorescence-guided surgical navigation.With the development of a bunch offluorophores with phototherapy ability,NIR-II can integrate tumor detection and treatment to explore a new therapeutic strategy for liver cancer.Here,we review the recent progress of NIR-IIfluorescence technology in liver tumor surgery and discuss its challenges and potential development direction.

Self-confocal NIR-II fluorescence microscopy for multifunctional in vivo imaging

Fluorescence imaging in the second near-infrared window(NIR-II,900–1880 nm)with less scattering background in biological tissues has been combined with the confocal microscopic system for achieving deep in vivo imaging with high spatial resolution.However,the traditional NIR-IIfluorescence confocal microscope with separate excitation focus and detection pinhole makes it possess low confocal e±ciency,as well as di±cultly to adjust.Two types of upgraded NIR-IIfluorescence confocal microscopes,sharing the same pinhole by excitation and emission focus,leading to higher confocal e±ciency,are built in this work.One type is-ber-pinhole-based confocal microscope applicable to CW laser excitation.It is constructed forfluorescence intensity imaging with large depth,high stabilization and low cost,which could replace multiphotonfluorescence microscopy in some applications(e.g.,cerebrovascular and hepatocellular imaging).The other type is air-pinhole-based confocal microscope applicable to femtosecond(fs)laser excitation.It can be employed not only for NIR-IIfluorescence intensity imaging,but also for multi-channelfluorescence lifetime imaging to recognize different structures with similarfluorescence spectrum.Moreover,it can be facilely combined with multiphotonfluorescence microscopy.A single fs pulsed laser is utilized to achieve up-conversion(visible multiphotonfluorescence)and down-conversion(NIR-II one-photonfluorescence)excitation simultaneously,extending imaging spectral channels,and thus facilitates multi-structure and multi-functional observation.

Isomeric fluorescence sensors for wide range detection of ionizing radiations

In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.

Near-Infrared Fluorescence Imaging Contrast Agents for Clinical Research: Limitations and Alternatives

Introduction: Near-infrared fluorescence imaging is a technique that will establish itself in the short term at the international level because it is recognized for its potential to improve the performance of surgical interventions, its moderate investment and operating costs and its portability. Although the technology is now mature, there is currently the problem of the availability of contrast agents to be injected IV. The aim of this methodology article is to propose an alternative solution to the need for contrast agents for clinical research, particularly in oncology. Methodology: They consist of coupling a fluorescent marker in the form of an NHS derivative, such as IR DYE manufactured in compliance with GMP, with therapeutic monoclonal antibodies having marketing authorization for molecular imaging. For a given antibody, the marking procedure must be the subject of a validation file on the final preparation filtered on a sterilizing membrane at 0.22 μm. Once the procedure has been validated, it would be unnecessary to repeat the tests before each clinical research examination. A check of the marking by thin-layer chromatography (TLC) and place it in a sample bank at +4˚C for 1 month of each injected formulation would be sufficient for additional tests if necessary. Conclusion: Molecular near-infrared fluorescence imaging is experiencing development, the process of which could be accelerated by greater availability of clinical contrast agents. Alternative solutions are therefore necessary to promote clinical research in this area. These methods must be shared to make it easier for researchers.

A ratiometric fluorescent probe for hypoxanthine detection in aquatic products based on the enzyme mimics and fluorescence of cobalt-doped carbon nitride

A ratiometric fluorescent probe for hypoxanthine(Hx)detection was established based on the mimic enzyme and fluorescence characteristics of cobalt-doped graphite-phase carbon nitride(Co doped g-C_(3)N_(4)).In addition to emitting strong fluorescence,the peroxidase activity of Co doped g-C_(3)N_(4)can catalyze the reaction of O-phenylenediamine and H_(2)O_(2)to produce diallyl phthalate which can emit yellow fluorescence at 570 nm.Through the decomposition of Hx by xanthine oxidase,Hx can be indirectly detected by the generating hydrogen peroxide based on the measurement of fluorescent ratio I(F_(570)/F_(370)).The linear range was 1.7-272.2 mg/kg(R^(2)=0.997),and the detection limit was 1.52 mg/kg(3σ/K,n=9).The established method was applied to Hx detection in bass,grass carp,and shrimp,and the data were verified by HPLC.The result shows that the established probe is sensitive,accurate,and reliable,and can be used for Hx detection in aquatic products.

Indocyanine green fluorescence in gastrointestinal surgery:Appraisal of current evidence

Applying indocyanine green(ICG)fluorescence in surgery has created a new dimension of navigation surgery to advance in various disciplines.The research in this field is nascent and fragmented,necessitating academic efforts to gain a comprehensive understanding.The present review aims to integrate diverse perspectives and recent advances in its application in gastrointestinal surgery.The relevant articles were selected by using the appropriate keyword search in PubMed.The angiography and cholangiography property of ICG fluorescence is helpful in various hepatobiliary disorders.In gastroesophageal and colorectal surgery,the lymphangiography and angiography property of ICG is applied to evaluate bowel vascularity and guide lymphadenectomy.The lack of objective parameters to assess ICG fluorescence has been the primary limitation when ICG is used to evaluate bowel perfusion.The optimum dose and timing of ICG administration need to be standardized in some new application areas in gastrointestinal surgery.Binding tumor-specific ligands with fluorophores can potentially widen the fluorescence application to detect primary and metastatic gastrointestinal tumors.The narrative review outlines prior contributions,limitations,and research opportunities for future studies across gastrointestinal sub-specialty.The findings of the present review would be helpful for scholars and practitioners to explore and progress in this exciting domain of gastrointestinal surgery.

Monitoring the in vivo siRNA release from lipid nanoparticles based on the fluorescence resonance energy transfer principle

The siRNA-loaded lipid nanoparticles have attracted much attention due to its significant gene silencing effect and successful marketization.However,the in vivo distribution and release of siRNA still cannot be effectively monitored.In this study,based on the fluorescence resonance energy transfer(FRET)principle,a fluorescence dye Cy5-modified survivin siRNA was conjugated to nanogolds(Au-DR-siRNA),which were then wrapped with lipid nanoparticles(LNPs)for monitoring the release behaviour of siRNA in vivo.The results showed that once Au-DR-siRNA was released from the LNPs and cleaved by the Dicer enzyme to produce free siRNA in cells,the fluorescence of Cy5 would change from quenched state to activated state,showing the location and time of siRNA release.Besides,the LNPs showed a significant antitumor effect by silencing the survivin gene and a CT imaging function superior to iohexol by nanogolds.Therefore,this work provided not only an effective method for monitoring the pharmacokinetic behaviour of LNP-based siRNA,but also a siRNA delivery system for treating and diagnosing tumors.

From static to dynamic:live observation of the support system after ischemic stroke by two photon-excited fluorescence laser-scanning microscopy

Ischemic stroke is one of the most common causes of mortality and disability worldwide.However,treatment efficacy and the progress of research remain unsatisfactory.As the critical support system and essential components in neurovascular units,glial cells and blood vessels(including the bloodbrain barrier)together maintain an optimal microenvironment for neuronal function.They provide nutrients,regulate neuronal excitability,and prevent harmful substances from entering brain tissue.The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis,supporting neuronal function,and reacting to injuries.However,most studies have focused on postmortem animals,which inevitably lack critical information about the dynamic changes that occur after ischemic stroke.Therefore,a high-precision technique for research in living animals is urgently needed.Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions.Twophoton fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure,information on multicellular component interactions,and provide images of structure and function in the cranial window.This technique shifts the existing research paradigm from static to dynamic,from flat to stereoscopic,and from single-cell function to multicellular intercommunication,thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain.In this review,we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy,highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain’s support systems.We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.

Molecular fluorescence significantly enhanced by gold nanoparticles@zeolitic imidazolate framework-8

Noble metal nanoparticles exhibit unique surface plasmon resonance dependent optical properties.On this basis,gold nanoparticles(AuNPs)encapsulated in metal–organic frameworks(MOFs)can form AuNPs@MOFs composites to modulate the optical properties of fluorescent molecules,which is less reported.In this paper,based on the fluorescence enhancement effect of AuNPs on 2-(2-hydroxyphenyl)-1H-benzimidazole(HPBI)molecules,zeolitic imidazolate framework-8(ZIF-8)crystals with structural stability were introduced.AuNPs@ZIF-8 exhibited a significantly pronounced fluorescence enhancement of the HPBI molecules.In addition,by comparing the fluorescence characteristics of the HPBI molecules adsorbed on AuNPs@ZIF-8 and those captured in AuNPs@ZIF-8,we found that the ZIF-8 can act as a spacer layer with highly effective near-field enhancement.All our preliminary results shed light on future research on the composite structures of noble metal particles and MOFs for fluorescent probes and sensing applications.

Experimental Study on Ultrasonic Cavitation Intensity Based on Fluorescence Analysis

The Ultrasonic cavitation effect has been widely used in mechanical engineering,chemical engineering,biomedicine,and many other fields.The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty.Based on this,a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper.In the experiment of fluorescence intensity measurement,terephthalic acid(TA)was used as the fluorescent probe,ultrasonic power,ultrasonic frequency,and irradiation time were independent variables,and fluorescence intensity and fluorescence peak area were used as experimental results.The collapse of cavitation bubble will cause molecular bond breakage and release·OH,and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with·OH.The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer.The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment,and then increased slowly with the increase of ultrasonic power,which gradually increased with the increase of irradiation time.They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz.The irradiation time was the most influential factor,and the cavitation intensity of low frequency was higher overall.The fluorescence intensity and fluorescence peak area of the samples increased by 2-20 times after ultrasonic treatment,which could increase from 69 and 5238 to 1387 and 95451,respectively.After the irradiation time exceeded 25 min,the growth rate of fluorescence intensity slowed down,which was caused by the decrease of gas content and TA concentration in the solution.The study quantitatively characterized the cavitation intensity,reflecting the advantages of fluorescence analysis,and provided a basis for the further study of ultra-sonic cavitation.

Construction of Fluorescence Sensing Platform on the Basis of Carbon Nitride Nanosheet for the Detection of Interferon-γ

Purpose: Interferon-γ (INF-γ) is a cytokine that participates in the immune reaction of the body. Its level of secretion can reflect the immune response condition after the body is infected by pathogens, which is a significant indication of clinically-related diseases. Therefore, it is of great significance in application to develop a fluorescence biosensor to inspect INF-γ with rapidness, high sensitivity and high practicability. Method: The fluorescence sensor is made on the basis of the two-dimensional nano-material namely Carbon Nitride Nanosheet (CNNS) and the Aptamer probe to identify INF-γ (Apt®INF-γ). CNNS can quickly quench the Cy5 fluorescent dye modified on the Apt®INF-γ probe due to the Photoinduced Electron Transfer (PET), but when the INF-γ exists, Apt®INF-γ specifically identifies and combines it. The complex of Apt®INF-γ and INF-γ is away from CNNS, which can effectively block the fluorescent signal of Apt?INF-γ being quenched by CNNS. Result: The sensitive detection of IFN-γ protein can be achieved through the application of CNNS/Apt®INF-γ fluorescence sensing platform. In this method, the intensity of the fluorescent signal is positively correlated with the concentration of IFN-γ, of which the liner response range is 0.5 - 100 ng/mL and the limit of detection is 0.303 ng/mL. In addition, this fluorescence sensing platform has the advantages of high specificity, simple operation and low costs. It can inspect the content of IFN-γ in clinical serum samples without interference. The actual recovery rate of serum samples is 97.11% - 106.96%. Conclusion: Therefore, the CNNS/Apt®INF-γ sensing platform is expected to be implemented in the actual clinical detection, also conducive to developing a universal fluorescence biosensor to inspect other target materials.

Adaptive Design of Fluorescence Imaging Systems for Custom Resolution, Fields of View, and Geometries

Objective and Impact Statement:We developed a generalized computational approach to design uniform,high-intensity excitation light for low-cost,quantitative fluorescence imaging of in vitro,ex vivo,and in vivo samples with a single device.Introduction:Fluorescence imaging is a ubiquitous tool for biomedical applications.Researchers extensively modify existing systems for tissue imaging,increasing the time and effort needed for translational research and thick tissue imaging.These modifications are applicationspecific,requiring new designs to scale across sample types.Methods:We implemented a computational model to simulate light propagation from multiple sources.Using a global optimization algorithm and a custom cost function,we determined the spatial positioning of optical fibers to generate 2 illumination profiles.These results were implemented to image core needle biopsies,preclinical mammary tumors,or tumor-derived organoids.Samples were stained with molecular probes and imaged with uniform and nonuniform illumination.Results:Simulation results were faithfully translated to benchtop systems.We demonstrated that uniform illumination increased the reliability of intraimage analysis compared to nonuniform illumination and was concordant with traditional histological findings.The computational approach was used to optimize the illumination geometry for the purposes of imaging 3 different fluorophores through a mammary window chamber model.Illumination specifically designed for intravital tumor imaging generated higher image contrast compared to the case in which illumination originally optimized for biopsy images was used.Conclusion:We demonstrate the significance of using a computationally designed illumination for in vitro,ex vivo,and in vivo fluorescence imaging.Applicationspecific illumination increased the reliability of intraimage analysis and enhanced the local contrast of biological features.This approach is generalizable across light sources,biological applications,and detectors.

Automated apoptosis identification in fluorescence imaging of nucleus based on histogram of oriented gradients of high-frequency wavelet coefficients

The automatic and accurate identification of apoptosis facilitates large-scale cell analysis.Most identification approaches using nucleus fluorescence imaging are based on specific morphological parameters.However,these parameters cannot completely describe nuclear morphology,thus limiting the identification accuracy of models.This paper proposes a new feature extraction method to improve the performance of the model for apoptosis identification.The proposed method uses a histogram of oriented gradient(HOG)of high-frequency wavelet coefficients to extract internal and edge texture information.The HOG vectors are classified using support vector machine.The experimental results demonstrate that the proposed feature extraction method well performs apoptosis identification,attaining 95:7% accuracy with low cost in terms of time.We confirmed that our method has potential applications to cell biology research.

Polymeric assembled nanoparticles through kinetic stabilization by confined impingement jets dilution mixer for fluorescence switching imaging

Traditional fluorescence switching molecules achieving the state change between on and off states commonly based on UV irradiation. However, it is worth noting that UV irradiation is harmful to both the cancer cells and the normal cells. To achieve fluorescence switching under visible wavelength and avoid complicate molecular design, a fluorophore of 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene(4Cz IPN) and a quencher of diarylethene(DAE) were physically incorporated within the biocompatible block copolymer poly(lactic-co-glycolic acid)-b-poly(ethylene glycol)(PLGA-b-PEG) to form 4Cz IPNDAE nanoparticles(NPs) through flash nanoprecipitation(FNP). By using the FNP method, the NPs were prepared within milliseconds in a confined impingement jets dilution(CIJ-D) mixer. Quenching and recovery of fluorescence could achieve in the presence of DAE under 475 nm and 560 nm irradiation.Appropriate structure and fluorescent properties of the nanoparticles can be tuned by external conditions for their efficient fluorescence resonance energy transfer(FRET) in a kinetic stabilization process. This NPs formation process was further optimized by varying the dilution ratio, Reynolds number(Re) and polymer concentration to modulate the mixing and particle nucleation and growth process. The size and fluorescence switching properties of the NPs were systematically investigated in solution and in cellular uptake experiments. This work is anticipated to provide a simple and highly effective engineering strategy for the modulation of fluorescence switching nanoparticles and beneficial to its engineering application.

Application and development of fluorescence probes in MINFLUX nanoscopy(invited paper)

The MINimal emission FLUXes(MINFLUX)technique in optical microscopy,widely recognized as the next innovative fluorescence microscopy method,claims a spatial resolution of 1-3 nm in both dead and living cells.To make use of the full resolution of the MINFLUX microscope,it is important to select appropriate fluorescence probes and labeling strategies,especially in living-cell imaging.This paper mainly focuses on recent applications and developments of fluorescence probes and the relevant labeling strategy for MINFLUX microscopy.Moreover,we discuss the deficiencies that need to be addressed in the future and a plan for the possible progression of MINFLUX to help investigators who have been involved in or are just starting in the field of super-resolution imaging microscopy with theoretical support.

Water Stress Early Detection of Eggplant Plants by Hyperspectral Fluorescence Spectroscopy

Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlorophyll fluorescence technology as a rapid, non-destructive approach to detect the water deficiency of eggplant plants using their spectral footprint. So, an experiment was made on 54 eggplant plants subjected to three water treatments: normal irrigation (T100), intermediate irrigation (T50) and no irrigation (T0). The fluorescence spectra were acquired in vivo and in situ using a USB4000 spectrometer from Ocean optics. For the classification of the plants subjected to three water treatments, we used three pretreatments of the raw hyperspectral data in order to suppress the non-informative variability present in these spectra and to obtain robust models. These are the Savitzky-Golay smoothing (SG), the standard normal variable (SNV) and the first derivative of Savitzky-Golay (SG-D1). The preprocessed data were then subjected to two partial least squares discriminant analyses (PLS-DA): Hard PLS-DA and Soft PLS-DA. These statistical approaches are suitable for large samples as it reduces the dimensionality of the data but improves the accuracy of the prediction. The SG-D1 combined with the Soft PLS-DA gave the best discrimination of plants with scores of sensitivity, specificity and total efficiency respectively of 97.33%, 94% and 95% for calibration, 6 days after hydric stress induction. For the plants used for the prediction, the scores are 86%, 91% and 90% respectively. This study shows that hyperspectral chlorophyll fluorescence spectroscopy is a fast and non-destructive technology allowing early detection of water stress in eggplant plants.

Fluorescence Properties and Chemical Composition of Fine Particles in the Background Atmosphere of North China

To understand the aerosol characteristics in a regional background environment,fine-particle(PM_(2.5),n=228)samples were collected over a one-year period at the Shangdianzi(SDZ)station,which is a Global Atmospheric Watch regional background station in North China.The chemical and optical characteristics of PM_(2.5)were analyzed,including organic carbon,elemental carbon,water-soluble organic carbon,water-soluble inorganic ions,and fluorescent components of watersoluble organic matter.The source factors of major aerosol components are apportioned,and the sources of the fluorescent chromophores are further analyzed.The major chemical components of PM_(2.5)at SDZ were NO_(3)^(-),organic matter,SO_(4)^(2-),and NH_(4)^(+).Annually,water-soluble organic carbon contributed 48%±15%to the total organic carbon.Secondary formation(52%)and fossil fuel combustion(63%)are the largest sources of water-soluble organic matter and water-insoluble organic matter,respectively.In addition,three humic-like and one protein-like matter were identified via parallel factor analysis for excitation–emission matrices.The fluorescence intensities of the components were highest in winter and lowest in summer,indicating the main impact of burning sources.This study contributes to understanding the chemical and optical characteristics of ambient aerosols in the background atmosphere.

Construction of Fluorescence Sensing Platform on the Basis of Molybdenum Disulfide Nanosheet for the Detection of AFB1

Purpose: Aflatoxin B1 is the most common mycotoxin in cereal crops;it is of stronger toxicity and has a carcinogenic effect. In recent years, a series of fluorescence sensors constructed on the basis of MoS2NS fluorescence quenching property have become a research hotspot. Therefore, we can construct a fast and simple analysis method with high specificity to detect AFB1 by utilizing MoS2NS, which can be effectively applied to food safety monitoring and clinical diagnosis. Method: In the current research, a fluorescence biosensor is developed on the basis of a new type of two-dimensional nano-material namely MoS2NS applied for the detection of AFB1. The fluorescence of Apt@AFB1 can be quickly quenched by MoS2NS through the fluorescence resonance energy transfer (FRET). When the target molecule AFB1 exists, after the specificity binding between AFB1 and aptamer, the Apt@AFB1 loses its single stranded structure and is away from MoS2NS, and the fluorescence of Apt®AFB1 cannot be quenched effectively. Such sensing signals can be used to achieve the sensitive detection of AFB1. Result: With this new method, under the optimized conditions, the AFB1 is analyzed in the MoS2NS/Apt®AFB1 sensing platform. Within the dynamic range of 0.2 - 25 ng/mL, the sensing platform expresses a good linear response to the level of AFB1 with the R2 = 0.9964 and LOD as 90 pg/mL. This method is applied to detect the actual serum samples and soybean milk with the recovery rate of 93.10% - 107.23% and 95.15% - 102.60% separately, and it can be used in the quantitative detection under the interference of other mycotoxins in a relatively accurate way. Conclusion: It is proved that this new detection method can be used as a potential biosensor platform for the detection of AFB1. This detection method features several advantages such as specificity, rapidness and low costs, which can meet the requirement of trace detection in clinical detection and food safety.

L-shell x-ray fluorescence relative intensities for elements with 62≤Z≤83 at 18 keV and 23 keV by synchrotron radiation

The relative intensities of L-subshell x-ray fluorescence(XRF)for elements with atomic numbers 62≤Z≤83 were measured at two excitation energies,18 keV and 23 keV,using a synchrotron radiation source at a beamline of the Synchrotron Light Center for Experimental Science and Applications in the Middle East(SESAME),Jordan.The experimentally measured results of the relative intensities were compared with the calculated results using the subshell fluorescence yield and the Coster-Kronig transition probabilities recommended by Campbell and the values based on the Dirac-Hartree-Slater model by Puri.The experimental and theoretical results are in agreement.In this work,L XRF relative intensities for the elements Sm,Gd,Tb,Er,Ta,W,Re,Hg,Pb and Bi at energies of 18 keV and 23 keV were measured.

Simple synthesis of silver nanocluster composites AgNCs@PE-g-PAA by irradiation method and fluorescence detection of Cr^(3+)

Silver nanoclusters(AgNCs)are a new type of nanomaterials with similar properties to molecules and unique applications.The applications of AgNCs can be significantly expanded by combining them with different matrix materials to obtain AgNC composites.Using irradiation techniques,we developed a simple two-step method for preparing silver nanocluster composites.First,polyacrylic acid(PAA)chains were grafted onto the surface of a PE film as templates(PE-g-PAA).Subsequently,silver ions were reduced in situ on the surface of the template material to obtain the AgNC composites(AgNCs@PE-g-PAA).The degree of AgNC loading on the composite film was easily controlled by adjusting the reaction conditions.The loaded AgNCs were anchored to the carboxyl groups of the PAA and wrapped in the graft chain.The particle size of the AgNCs was only 4.38±0.85 nm,with a very uniform particle size distribution.The AgNCs@PE-g-PAA exhibited fluorescence characteristics derived from the AgNCs.The fluorescence of the AgNCs@PE-g-PAA was easily quenched by Cr^(3+)ions.The composite can be used as a fluorescence test paper to realize visual detection of Cr^(3+).