Fluorescence In Near-infrared Region Research Articles

N-quaternization of heterocyclic compound extended the emission to NIR with large Stokes shift and its application in constructing fluorescent probe

This is great significant to establish a method that extends the small molecules fluorescence emission wavelength to the near-infrared region (NIR) for in vivo imaging. Hence, we firstly reported a novel fluorogenic scaffold QOH that could extend its fluorescence wavelength from (λem = 555 nm) to NIR (λem = 720 nm) with a large Stokes shift (120 nm) by forming its N-quaternization product (QMOH). In addition, the effect of the introduction of substituent at different modification sites and the properties of substituent on the optical properties of QOH were fully discussed by theoretical calculation. To investigate the possibility of QOH as probe construction, the compound Q-SH and QM-R were synthesized and applied to detect H2S and H2O2 in vitro and in vivo, respectively. This study provided an efficient strategy to extend fluorescence emission to NIR and design fluorescence probes with large ratio variation for accurately imaging biomarkers in biological system.

A novel ratiometric near-infrared fluorescent probe for monitoring cyanide in food samples

Cyanide is a highly toxic anion. Nonetheless, many food plants could produce endogenous cyanide, which causes great danger to human health. Thus, monitoring cyanide in food samples is critically significant. Herein, we rationally developed the first ratiometric near-infrared fluorescent probe for sensing cyanide in food samples. The probe displayed noticeable fluorescence in near-infrared region. Moreover, upon treatment with cyanide, the probe exhibited highly selective and sensitive ratiometric fluorescence response, with limit of detection determined to be 0.075μM and limit of quantification determined to be 0.25μM. The ratios of fluorescent intensities at 519 and 688nm (I519/I688) was linear with added cyanide concentrations from 0 to 80μM. The relative standard deviations for repeatability and reproducibility varied from 0.55 to 8.94 and from 1.17 to 9.46, respectively. Significantly, probe Hy has been successfully applied for monitoring cyanide in various food samples, such as almonds, sprouting potatoes, and bamboo shoots.

Graphene oxide-based NIR fluorescence probe with aggregation-induced emission property for lectins detection and liver cells targeting

Probing lectin–sugar interactions is crucial to understand important biological process as well as develop clinical diagnostics and drug for the disease. Effective tools that target these interactions are thus in great demand. In this paper, two new aggregation-induced emission (AIE)-based glycosyl probes (PT-Man and PT-Gal) have been developed for the detection of lectin–sugar interactions in the near-infrared region (NIR). PT-Man and PT-Gal show significant fluorescence enhancement upon addition of a selective lectin with a relatively low detection limit. The fluorescence increment mechanism is ascribed to the aggregation of the AIE-based glycosyl probes after complexation with the selective lectin, which has been confirmed by the scanning electron microscope (SEM) measurement. Also, in order to further improve the sensitivity and selectivity of the probes, graphene oxide (GO) has been used as a platform to assemble with the two glycosyl probes. To our delight, the PT-Man@GO and PT-Gal@GO composites exhibit better sensitivity and selectivity for probing lectin–sugar interactions. In addition, due to the specific sugar-receptor interactions, the liver cancer cell line that over express the glycoprotein receptor can be specifically targeted by PT-Gal@GO.

3-Aminophenyl boronic acid-functionalized CuInS2 quantum dots as a near-infrared fluorescence probe for the determination of dopamine

Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid were directly synthesized in aqueous solution. Consequently, the CuInS2 QDs were covalently linked to 3-aminophenyl boronic acid molecules to form the 3-aminophenyl boronic acid-functionalized CuInS2 QDs (F-CuInS2 QDs). The F-CuInS2 QDs had a fairly symmetric fluorescence emission centered at 736nm that was in the near-infrared region (NIR). The F-CuInS2 QDs containing boronic acid functional groups were reactive toward vicinal diols to form five- or six-member cyclic esters in an alkaline aqueous solution. The reaction would cause the fluorescence quenching, which could be used as a fluorescence probe for the determination of dopamine (DA). This assay could also probe other vicinal diols such as catechol, pyrogallol, and gallate, based on the fluorescence quenching of the F-CuInS2 QDs, and this assay was nearly unaffected by other phenol compounds such as phenol, resorcinol, and hydroquinone without the vicinal diol structures. The developed F-CuInS2 QDs were applied to the detection of DA in human serum samples with satisfactory results. Therefore, this experment provided a simple and sensitve NIR fluorescence probe for the detection of DA, catechol, pyrogallol, and gallate.

Solid-state fluorescence of squarylium dyes

An N-butyl indolenine squarylium dye could include toluene and p-xylene and exhibited the solid-state fluorescence in near-infrared region (Fmax=761nm) in crystalline form due to inhibition of π/π-interactions between the fluorophores.