Excited Up-conversion Fluorescence Research Articles

Highly hydrostable and flexible opal photonic crystal film for enhanced up-conversion fluorescence sensor of COVID-19 antibody

Efficient detection of related markers is significant for the early screening of COVID-19. Near infrared (NIR) light excited up-conversion fluorescence probes are ideal for biosensing but limited by the low luminescence efficiency. In this work, a novel highly stable opal photonic crystal (OPC) structure was designed to provide an OPC effect for up-conversion fluorescence enhancement, and sensitive Novel Coronavirus IgG up-conversion FRET-based sensor was further constructed. For the problems of water stability and mechanical stability of polymer OPC which cannot be solved for a long time, polymer spray combined with a flipped OPC film strategy is presented. Fragmented size OPC film was firmly fixed by polymer modification layer, which gave large size OPC film great water stability, mechanical stability and bending performance without affecting the fluorescence enhancement property. On this basis, the up-conversion emission intensity was enhanced significantly, and fluorescence resonant energy transfer (FRET) based Novel Coronavirus IgG antibody sensor was constructed. Monolayer up-conversion nanoparticles (UCNPs) on the surface of the polydopamine (PDA)/OPC film can make the fluorescent signal more sensitive, and effectively reduce the detection limit. The test device integrating NIR excitation and mobile phone realized the visual fast detection, showing remarkable sensing performance for COVID-19 antibodies with the limit of detection (LOD) of 0.1 ng mL−1. This detection platform will provide a more effective tool for early detection of the novel coronavirus.

Synthesis and two-photon properties of phenothiazine-based dendrimers with tetraphenylmethane cores

We have synthesized two new two-photon active dendritic molecules with tetraphenylmethane core with four phenothiazine-based arms. They show good solubility in organic solvents, including dichloromethane, chloroform, toluene and tetrahydrofuran. It is found that the two dendrimers display strong two-photon absorption and two-photon excited up-conversion fluorescence at 800 nm. • Two new phenothiazine-based dendrimers with tetraphenylmethane cores have been synthesized. • The dendritic molecules display two-photon absorption activity. • The two-photon absorption cross section increased with the increasing of the conjugation degree.

UV-Vis-NIR Full-Range Responsive Carbon Dots with Large Multiphoton Absorption Cross Sections and Deep-Red Fluorescence at Nucleoli and In Vivo.

Carbon dots (CDs), with excellent optical property and cytocompatibility, are an ideal class of nanomaterials applied in the field of biomedicine. However, the weak response of CDs in the near-infrared (NIR) region impedes their practical applications. Here, UV-vis-NIR full-range responsive fluorine and nitrogen doped CDs (N-CDs-F) are designed and synthesized that own a favorable donor-π-acceptor (D-π-A) configuration and exhibit excellent two-photon (λex = 1060 nm), three-photon (λex = 1600 nm), and four-photon (λex = 2000 nm) excitation upconversion fluorescence. D-π-A-conjugated CDs prepared by solvothermal synthesis under the assistance of ammonia fluoride are reported and are endowed with larger multiphoton absorption (MPA) cross sections (3PA: 9.55 × 10-80 cm6 s2 photon-2 , 4PA: 6.32 × 10-80 cm8 s3 photon-3 ) than conventional organic compounds. Furthermore, the N-CDs-F show bright deep-red to NIR fluorescence both in vitro and in vivo, and can even stain the nucleoli of tumor cells. A plausible mechanism is proposed on the basis of the strong inter-dot and intra-dot hydrogen bonds through NH···F that can facilitate the expanding of conjugated sp2 domains, and thus not only result in lower highest occupied molecular orbital-lowest unoccupied molecular orbital energy level but also larger MPA cross sections than those of undoped CDs.

Efficient Red/Near-Infrared-Emissive Carbon Nanodots with Multiphoton Excited Upconversion Fluorescence.

Red/near‐infrared (NIR) emissive carbon nanodots (CNDs) with photoluminescence (PL) quantum yield (QY) of 57% are prepared via an in situ solvent‐free carbonization strategy for the first time. 1‐Photon and 2‐photon cellular imaging is demonstrated by using the CNDs as red/NIR fluorescence agent due to the high PL QY and low biotoxicity. Further study shows that the red/NIR CNDs exhibit multiphoton excited (MPE) upconversion fluorescence under excitation of 800–2000 nm, which involves three NIR windows (NIR‐I, 650–950 nm; NIR‐II, 1100–1350; NIR‐III, 1600–1870 nm). 2‐Photon, 3‐photon, and 4‐photon excited fluorescence of the CNDs under excitation of different wavelengths is achieved. This study develops an in situ solvent‐free carbonization method for efficient red/NIR emissive CNDs with MPE upconversion fluorescence, which may push forward the application of the CNDs in bioimaging.

Enhanced three-photon absorption and excited up-conversion fluorescence of phenanthroimidazole derivatives

Two novel phenanthroimidazole derivatives were synthesized for efficient three-photon excited fluorescence and absorption. By introducing spirobi [9H-fluorene] to replace fluorene, the three-photon-excited fluorescence and cross-section are significantly enhanced to 3.56 ± 0.15 × 10−78 cm6 s2 photon−2, which is among the highest reported values for organic molecules. Our results supply a useful method to develop novel materials for applications of three-photon excited fluorescence and absorption.

Dipicolinate as acceptor in D–π–A chromophores: synthesis, characterization and fluorescence following single- and two-photon excitation

Three novel donor–π–acceptor type compounds with dipicolinate as acceptor have been synthesized. Their absorption, photoluminescence as well as their two-photon absorption properties have been investigated. Two of them show strong two-photon absorption and two-photon excited up-conversion fluorescence.

Upconversion Fluorescence Enables Homogeneous Immunoassay in Whole Blood

Many medical conditions are related to alterations in protein or hormone concentrations in blood. These changes are commonly detected with heterogeneous immunoassays that require a separation step before signal measurement. A simple homogeneous assay performable directly in whole blood would be useful in clinical diagnostics, but the performance of homogeneous fluorescence-based immunoassays has been severely limited by autofluorescence and strong absorption of ultraviolet and visible light in whole blood. These problems might be avoided by the use of near-infrared excited upconversion fluorescence. We recently described a novel homogeneous assay method based on upconversion fluorescence resonance energy transfer (FRET). In this method an upconverting phosphor (UCP) is used as a donor and a fluorescent protein or a small-molecular fluorescent dye is used as an acceptor (1)(2). We report here the use of a competitive homogeneous immunoassay for 17β-estradiol (E2) in whole blood as a model to demonstrate the application of upconversion FRET using a near-infrared fluorescent acceptor dye (Fig. 1A⇓ ; and see Fig. 1 in the Data Supplement that accompanies the online version of this Letter at http://www.clinchem.org/content/vol53/issue1). Figure 1. Principle ( A ) and standard curves ( B ) of the upconversion FRET-based competitive homogeneous E2 immunoassay. ( A ), the anti-E2-Fab-coated FCD-546–1 UCP (donor) can bind E2 (analyte) and E2-AF680 conjugate (acceptor). Phosphor emission at …

Ho 3+:TeO 2 glass, a probe for temperature measurements

Considerable effort has recently been devoted to the development of optical fiber based temperature monitoring device owing to their advantage over conventional thermometric techniques. Optical thermometry based upon near infrared excited upconversion fluorescence emission in Ho 3+ activited tellurite glasses excited at 890 nm is presented. Temperature sensing in the range 265–440 K within 2 K accuracy using excitation powers readily obtainable from commercially available Ti–sapphire laser have been achieved. This temperature sensing approach is independent of fluctuations in excitation intensity, environment, transmission and requires a simple and low cost signal detection and processing system. Our results also indicate that the glassy host material also plays a major role in the process of the temperature sensing capacity.

Metal-Enhanced Up-Conversion Fluorescence: Effective Triplet−Triplet Annihilation near Silver Surface

Up-conversion phenomena are traditionally related to two- or multiphoton processes occurring under relatively high excitation intensities. Here we present the first results of ultralow excitation intensity (in order of Wcm(-2)) continuous-wave (CW) excited up-conversion fluorescence in Kretschmann surface plasmon geometry. The active system is a blue-emitting polymer matrix blended with metalated porphyrine macrocycles. The up-conversion fluorescence is a consequence of a two-particle triplet-triplet annihilation process (TTA).

Trivalent boron as acceptor in D-pi-A chromophores: synthesis, structure and fluorescence following single- and two-photon excitation.

A series of new donor-pi-acceptor type compounds with trivalent boron as acceptor which show strong two-photon excited up-conversion fluorescence have been synthesized and one crystal structure described.

Thermal effect on multiphonon-assisted anti-Stokes excited upconversion fluorescence emission in Yb 3+ -sensitized Er 3+ -doped optical fiber

The temperature effect upon infrared-to-visible frequency upconversion fluorescence emission in Yb3+-sensitized Er3+-doped germanosilicate optical fibers excited with cw radiation at 1.064 μm is investigated. The experimental results revealed an eightfold enhancement in the visible upconversion emission intensity as the fiber temperature was increased from 17 °C to 180 °C. The fluorescence emission enhancement is attributed to the temperature-dependent multiphonon-assisted anti-Stokes excitation process of the ytterbium sensitizer. A theoretical approach that takes into account a sensitizer absorption cross-section, which depends on the phonon occupation number, has proven to agree very well with the experimental data

Optical thermometry through infrared excited upconversion fluorescence emission in Er/sup 3+/- and Er/sup 3+/-Yb/sup 3+/-doped chalcogenide glasses

Optical thermometry based upon infrared excited upconversion fluorescence emission in Er/sup 3+/- and Er/sup 3+/-Yb/sup 3+/- doped Ga/sub 2/S/sub 3/-La/sub 2/O/sub 3/ chalcogenide glasses excited at 1.54 and 1.06 /spl mu/m, respectively, is presented. Temperature sensing in the region of 20/spl deg/C-220/spl deg/C with 0.3/spl deg/C accuracy using excitation powers readily obtainable from commercially available semiconductor lasers was achieved. The temperature sensing approach is independent of fluctuations in excitation intensity and transmission and requires a simple and low-cost signal detection and processing system. The results also indicate that the glassy host material plays a major role in the performance of the sensing system.

Investigating up-conversion fluorescence of Phloxine B.

The steady-state and time-resolved emission of Phloxine B was examined when excited with 90 fs pulses from a mode-locked Ti:sapphire laser. Above the excitation wavelength (775 nm), Phloxine B was found to display two-photon excitation fluorescence with estimated cross-section for excitation of 0.87/spl times/10/sup -49/ cm/sup 4/ s/photon, and fluorescence spectrum consistent with one-photon excitation. Over the excitation wavelength range from 590 to 650 nm, Phloxine B was found to display one-photon excitation up-conversion fluorescence. The up-conversion fluorescence of Phloxine B was confirmed by frequency-domain measurements. The intensity decays revealed different double-exponential intensity decays for one-photon excitation at 390 nm and 633 nm. The longer fluorescence lifetimes were observed with 633 nm excitation. Hence, anti-Stokes excitation of Phloxine B causes delay emission at shorter wavelengths. Time-resolved anisotropy decay measurements revealed similar correlation times, but different amplitudes, as has been observed previously for two- versus one-photon excitation.