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Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals
摘要： The main aim of this work is to provide a method to retrieve the intrinsic spatial resolution of a gamma-ray detector block based on monolithic crystals within an assembled scanner. This method consists on a discrimination of the data using a software collimation process. The results are compared with an alternative method of separating two detector blocks far enough to produce a "virtual" source collimation due to the geometric constraints on the allowed coincidence event angles. A theoretical model has been deduced to fit the measured light distribution profiles, allowing estimating the detector intrinsic spatial resolution. The detector intrinsic spatial resolution is expected to follow a Gaussian distribution and the positron-emitter source shape, given the small size of a 22Na source with 0.25 mm in diameter, can be assumed to follow a Lorentzian profile. However, the collimation of the data modifies the source shape that is no longer a pure Lorentzian distribution. Therefore, the model is based on the convolution of a Gaussian shaped distribution (contribution of the detector) and a modified Lorentzian distribution (contribution of the collimated source profile) that takes into account the collimation effect. Three LYSO crystals geometries have been studied in the present work, namely a 10 mm thick trapezoidal monolithic block, and two rectangular monolithic blocks with thicknesses of 15 mm and 20 mm, respectively. All the blocks have size dimensions of 50 mm × 50 mm. The experimental results yielded an intrinsic detector spatial resolution of 0.64 ± 0.02 mm, 0.82 ± 0.02 and 1.07 ± 0.03 mm, for the 10 mm, 15 mm and 20 mm thick blocks, respectively, when the source was placed at the center of the detector. The detector intrinsic spatial resolution was moreover evaluated across one of the axis of each crystal. These values worsen to an average value of 0.68 ± 0.04 mm, 0.90 ± 0.14 and 1.29 ± 0.19 mm, respectively, when the whole crystal size is considered, as expected. These tests show an accurate method to determine the intrinsic spatial resolution of monolithic-based detector blocks, once assembled in the PET system.
关键词： Intrinsic spatial resolution,SiPM array,Monolithic blocks,Positron Emission Tomography,Gamma ray detectors
更新于2025-09-23 15:23:52
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Dual-emission color-controllable nanoparticle based molecular imprinting ratiometric fluorescence sensor for the visual detection of Brilliant Blue
摘要： Single-component dual-emission nanoparticles were synthesized by chelating the organic ligand 8-hydroxyquinoline (HQ) to the surface of CdTe/ZnS quantum dots, namely CdTe/ZnQ2, and were used to construct a novel mesoporous structured molecular imprinting ratiometric fluorescence sensor by facile one-pot sol-gel polymerization for the visual detection of Brilliant Blue. The CdTe/ZnQ2 had bimodal fluorescence belonging to CdTe and ZnQ2 segments, respectively; significantly, the emission wavelength of CdTe was optimized to be 630 nm for the largest overlap with the absorption spectrum of Brilliant Blue. Consequently, fluorescence resonance energy transfer (FRET) efficiency was greatly enhanced, resulting in ideal determination. A favorable linearity toward Brilliant Blue was obtained within 0–1.0 μmol?L-1 along with profuse color evolution from orange to yellowish orange to yellowish green to green, and a high detectability of 8.8 nmol?L-1 was offered. Excellent recognition selectivity for Brilliant Blue over possibly coexistent food colorants was demonstrated, with a high imprinting factor of 7.1. Furthermore, endogenous Brilliant Blue was detected ranging from 0.21–41.03 mg/kg in six typical food samples with relative standard deviations lower than 3.5%, and the results agreed well with that afforded by conventional methods. Using Brilliant Blue as a model, this dual-emission color-controllable nanoparticle based imprinting ratiometric fluorescence sensor provided promising perspectives for the highly selective and sensitive, rapid, visual detection of colored substances in complicated matrices.
关键词： Molecular imprinting,Brilliant Blue,Dual-emission nanoparticles,Ratiometric fluorescence,Visual detection
更新于2025-09-23 15:23:52
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An AIEgen-based fluorescent probe for highly selective and specific imaging of lipid droplets in L02 and HepG2 cells
摘要： Lipid droplets (LDs), as dynamic organelles, are associated with physiologically and pathologically metabolic processes. Especially, in human liver cancer cells (HepG2 cells) the lipid metabolism shows significant difference by comparing with the human normal liver cell (L02 cells). In this work, a new highly selective and specific fluorescent probe TPA-SD for the detection of LDs has been rationally designed and easily prepared from triphenylamine and salicylaldehyde, which possesses aggregation-induced emission (AIE) and excited state intramolecular proton transfer characteristics (ESIPT). Ideal probes for LDs imaging require high concentration accumulation of fluorophores in LDs and lack of self-quenching in the aggregated state, so the AIE property is necessary. TPA-SD can successfully and specifically accumulate in LDs, thus facilitating clearly distinguishing L02 cells from HepG2 cells according to obvious difference in the number of dot-shaped LDs marked by TPA-SD. The dot-shaped LDs in the HepG2 cells is found to be obviously more than that in the L02 cells. Moreover, the spatial distribution of LDs could be identified by TPA-SD. The results indicate TPA-SD possesses great potential in imaging and diagnosis of LDs-related diseases.
关键词： fluorescent probe,aggregation-induced emission,dot-shaped LDs number,lipid droplets (LDs) imaging
更新于2025-09-23 15:23:52
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SwissKnife-Inspired Multifunctional Fluorescence Probes for Cellular Organelle Targeting Based on Simple AIEgens
摘要： Facile, efficient and mass production of aggregation-induced emission (AIE) luminogens (AIEgens) with excited-state intramolecular proton transfer (ESIPT) characteristics was achieved by one-step condensation reaction of 2-(hydrazonomethyl)phenol with benzaldehydes. The function of as-prepared AIEgens could be tuned easily by varying the functional group carrying on the phenyl ring of benzaldehyde just like Swiss knife handle. The suitable distance and angle of intramolecular hydrogen bond in these AIEgens endowed them with ESIPT properties, intense solid-state luminescence and large Stokes shifts (155?169 nm). These AIEgens could not only serve as biological probes showing specific targeting to lipid droplets, endoplasmic reticulum and lysosomes, respectively, but also generate reactive oxygen species upon visible light irradiation to make them promise for photodynamic therapy.
关键词： Fluorescence probes,Aggregation-induced emission,Excited-state intramolecular proton transfer,Photodynamic therapy,Organelle-targeting
更新于2025-09-23 15:23:52
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Hierarchical MoS2-Based Onion-Flower-like Nanostructures with and without Seedpods via Hydrothermal Route Exhibiting Low Turn-on Field Emission
摘要： Herein, we report facile hydrothermal synthesis of hierarchical MoS2 -based nanomorphs (displaying onion-flower-like features) with the primary focus on field-emitter applications. The synthesized nanostructures were characterized physicochemically to understand their basic structural and morphological features. Interesting nanoscale morphological evolution of onion-flower-like MoS2—from plain nanoflowers to those containing seedpods—is observed with the change in hydrothermal reaction time from 9 h to 21 h. Peculiarly, MoS2 nanomorphs with only onion-flower-like morphology displayed lower turn-on field value of 3.7 V/μm as compared to 4.2 V/μm for the nanoflowers containing seedpod-like particles. This might be attributed to the possibility of an easy electron conduction path available for the petals in plain nanoflowers, which may be impeded by the seedpod-like particles in the latter case.
关键词： Molybdenum disulfide,hierarchical nanostructures,field emission,hydrothermal
更新于2025-09-23 15:23:52
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Effect of Electron Irradiation on the Transport and Field Emission Properties of Few-Layer MoS <sub/>2</sub> Field-Effect Transistors
摘要： Electrical characterization of few-layer MoS2 based field effect transistors with Ti/Au electrodes is performed in the vacuum chamber of a scanning electron microscope in order to study the effects of electron beam irradiation on the transport properties of the device. A negative threshold voltage shift and a carrier mobility enhancement is observed and explained in terms of positive charges trapped in the SiO2 gate oxide, during the irradiation. The transistor channel current is increased up to three order of magnitudes after the exposure to an irradiation dose of 100e-/nm2. Finally, a complete field emission characterization of the MoS2 flake, achieving emission stability for several hours and a minimum turn-on field of ≈ 20 V/μm with a field enhancement factor of about 500 at anode-cathode distance of ~1.5 μm, demonstrates the suitability of few-layer MoS2 as two-dimensional emitting surface for cold-cathode applications.
关键词： electron beam irradiation,2D materials,field emission,molybdenum disulfide,field effect transistors
更新于2025-09-23 15:23:52
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Blue Electrogenerated Chemiluminescence from Halide Perovskite Nanocrystals
摘要： Electrogenerated chemiluminescence (ECL) has been extensively used in ultrasensitive electroanalysis because it can be generated electrochemically without using expensive optics and light sources. Visible ECL emission can be obtained with a reasonable quantum yield and stability. Blue ECL is rare and often suffers from stability and poor quantum efficiency. Blue ECL emission at 473 nm from organometallic halide perovskite nanocrystals (PNCs), CH3NH3PbCl1.08Br1.92, is reported here for the first time using tripropylamine (TPrA) as co-reactant. The blue ECL emission peak resembles its photoluminescence peak position. In addition to this blue emission peak, the ECL spectra of CH3NH3PbCl1.08Br1.92 PNCs also showed a broad ECL peak at 745 nm. Generation of the second ECL peak at 745 nm from CH3NH3PbCl1.08Br1.92 PNCs was can be explained by the existence of surface trap states on as-synthesized PNC due to incomplete surface passivation. Halide anion tunability of ECL emission from CH3NH3PbX3 (X: Cl, Br, I) PNCs is also demonstrated. The fluorescence microscopy image of single PNC and stability of selected single PNCs are presented in this with simultaneous acquisition of fluorescence spectra using 405-nm laser excitation. The photoluminescence (PL) decay was described by PL lifetime (τ) of 1.2 ns. The effect of the addition of surfactants (oleic acid and n-octylamine) on the fluorescence intensity and stability of CH3NH3PbCl1.08Br1.92 PNCs is also discussed.
关键词： Surfactants,Blue light emission,ECL (electrogenerated chemiluminescence),Photoluminescence (PL),Perovskite nanocrystals (PNCs),Photoluminescence quantum yield (PLQY)
更新于2025-09-23 15:23:52
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Highly Efficient Luminescent Liquid Crystal with Aggregation-Induced Energy Transfer
摘要： A luminescent liquid crystal molecule (TPEMes) with efficient solid-state emission is rationally constructed via the chemically conjugation of blue-emitting tetraphenylethene cores and luminescent mesogenic tolane moieties, which are both featured with aggregation-induced emission properties. As for this fluorophore, aggregation induced energy transfer from the emissive tolane mesogens to the lighting-up tetraphenylethene units endows the molecule pure blue emission in the suspension and bulk state. Combining DSC, POM and 1D XRD experiments, TPEMes is deduced to adapt thermodynamically more stable layered crystalline phase, and can be 'frozen' into a monotropic smectic mesophase due to kinetic reasons. As a result of more densely packing of TPEMes in the crystalline phase indicated by 1D XRD, the luminescence of TPEMes in crystalline phase has blue-shifted with 17 nm relative to the metastable mesophase.
关键词： tolane,tetraphenylethene,aggregation induced emission,aggregation induced energy transfer,hexagonal columnar phase,luminescent liquid crystals
更新于2025-09-23 15:23:52
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Non-Invasive Optical Guided Tumor Metastasis/Vessel Imaging by Using Lanthanide Nanoprobe with Enhanced Down-Shifting Emission beyond 1500 nm
摘要： Visualization of tumor vessels/metastasis and cerebrovascular architecture is vital important for analyzing pathological states of brain diseases and tumor's abnormal blood vessel to improve cancer diagnosis. In vivo fluorescence imaging using second near infrared emission beyond 1500 nm (NIR-IIb) is emerged as a next generation optical imaging method with significant improvement in imaging sensitivity and spatial resolution. Unfortunately, highly biocompatible probe capable of generating NIR-IIb emission with sufficient brightness and uniformed size is still scarce. Here, we have proposed the polyacrylic acid (PAA)-modified NaLnF4:40Gd/20Yb/2Er nanorods (Ln=Y, Yb, Lu, PAA-Ln-NRs) with enhanced downshifting NIR-IIb emission, high quantum yield (QY), relative narrow bandwidth (~160 nm) and high bio-compatibility via Ce3+ doping for high performance NIR-IIb bioimaging. The downshifting emission beyond 1500 nm is improved by 1.75~2.2 times with simultaneously suppressing the upconversion (UC) path in Y, Yb, and Lu hosts via Ce3+ doping. Moreover, compared with the traditionally used Y-based host, the QY of NIR-IIb emission in Lu-based probe in water is improved from 2.2% to 3.6%. The explored bright NIR-IIb emitted PAA-Lu-NRs were used for high sensitivity small tumor (~ 4 mm)/metastatic tiny tumor detection (~ 3 mm), tumor vessel visualization with high spatial resolution (41 μm) and brain vessel imaging. Therefore, our findings open up the opportunity of utilizing lanthanide based NIR-IIb probe with bright 1525 nm emission for in vivo optical-guided tumor vessel/metastasis and non-invasive brain vascular imaging.
关键词： enhancement of downshifting emission,tiny metastatic tumor detection,tumor vascular imaging,rare-earth nanoprobes,brain vascular imaging
更新于2025-09-23 15:23:52
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Broadband Emission in Hybrid Organic–Inorganic Halides of Group 12 Metals
摘要： We report syntheses, crystal and electronic structures, and characterization of three new hybrid organic?inorganic halides (R)ZnBr3(DMSO), (R)2CdBr4·DMSO, and (R)CdI3(DMSO) (where (R) = C6(CH3)5CH2N(CH3)3, and DMSO = dimethyl sulfoxide). The compounds can be conveniently prepared as single crystals and bulk polycrystalline powders using a DMSO?methanol solvent system. On the basis of the single-crystal X-ray diffraction results carried out at room temperature and 100 K, all compounds have zero-dimensional (0D) crystal structures featuring alternating layers of bulky organic cations and molecular inorganic anions based on a tetrahedral coordination around group 12 metal cations. The presence of discrete molecular building blocks in the 0D structures results in localized charges and tunable room-temperature light emission, including white light for (R)ZnBr3(DMSO), bluish-white light for (R)2CdBr4·DMSO, and green for (R)CdI3(DMSO). The highest photoluminescence quantum yield (PLQY) value of 3.07% was measured for (R)ZnBr3(DMSO), which emits cold white light based on the calculated correlated color temperature (CCT) of 11,044 K. All compounds exhibit fast photoluminescence lifetimes on the timescale of tens of nanoseconds, consistent with the fast luminescence decay observed in π-conjugated organic molecules. Temperature dependence photoluminescence study showed the appearance of additional peaks around 550 nm, resulting from the organic salt emission. Density functional theory calculations show that the incorporation of both the low-gap aromatic molecule R and the relatively electropositive Zn and Cd metals can lead to exciton localization at the aromatic molecular cations, which act as luminescence centers.
关键词： zero-dimensional structures,broadband emission,group 12 metals,exciton localization,photoluminescence quantum yield,hybrid organic?inorganic halides
更新于2025-09-23 15:23:52