A solvatochromic AIE tetrahydro[5]helicene derivative as fluorescent probes for water in organic solvents and highly sensitive sensors for glyceryl monostearate

Water bridges as the trigger in an amino functionalized Zn-MOF for highly selective and sensitive fluorescent sensing of water

Water is a fundamental element for life. The highly selective and sensitive sensing of water is always attractive for mankind in activities such as physiological processes study and extraterrestrial life exploration. Fluorescent MOFs with precise channels and functional groups might specifically recognize water molecules with hydrogen-bond interaction or coordination effects and work as water sensors. As a proof of concept, herein, an amino functionalized Zn-MOF (named as complex 1) with pores that just right for water molecules to form hydrogen bond bridges is revealed for highly selective and sensitive fluorescent sensing of water. The single-crystal X-ray diffraction analysis indicates that the 3D framework of complex 1 is functionalized with free amino groups in the channels. Hydrogen bonds formed in the channel along b-axis as water bridges to connect two adjacent NH2bdc ligands and result in the restriction of intramolecular motions (RIM) which could responsible for the selective turn-on fluorescence response to water. Complex 1 exhibits high sensitive to trace amount of water in organic solvents and could be used for water detection in a wide range water contents. Take advantages of complex 1, portable sensors (complex 1@PMMA) were prepared and used in the highly sensitive water sensing.

Water detection in organic solvents using a copolymer membrane immobilised with a fluorescent intramolecular charge transfer-type dye: effects of intramolecular hydrogen bonds

Numerous fluorescent dye-based optical sensors have been developed to detect water in organic solvents. However, only a few such sensors can detect water in polar solvents such as methanol or dimethyl sulfoxide, and their detection range is generally narrow. Therefore, in this study, a copolymer membrane incorporated with a pyridinium betaine dye (denoted PB1), which exhibited intramolecular charge transfer (ICT) characteristics, was developed to realise simple water detection in organic solvents. The pyridinium betaine structure, comprising intramolecular hydrogen bonds between the oxygen in the maleimide moiety and the hydrogen in the pyridinium, was vital for achieving efficient fluorescence emission. The membrane was prepared by copolymerising PB1 with the N,N-dimethyl acrylamide/acrylamide monomer on a glass plate, and the fluorescence in water-mixed organic solvents was investigated (λabs = 490 nm, λfl = 630 nm). The fluorescence intensity of the dye-immobilised membrane decreased with increasing water content of the organic solvents. The detection ranges in tetrahydrofuran, ethanol, methanol, and dimethyl sulfoxide were approximately <40, <40, <40, and <60 vol% water, respectively. In contrast, membranes based on a quaternary pyridinium dye (without intramolecular hydrogen bonds) did not detect water in methanol and dimethyl sulfoxide, although it was more sensitive than PB1 in the narrow region of low water concentration in THF. Theoretical calculations corroborated the importance of the pyridinium betaine structure in detecting water in organic solvents, with the increase in polarity and the formation of intermolecular hydrogen bonds between PB1 and water found to induce molecular rotation and fluorescence quenching.

Luminescent Properties of β-(hydroxyaryl)-butenolides and Fluorescence Quenching in Water

This work describes the luminescent properties of the new compound β-(hydroxyaryl)-butenolides recently discovered. The compounds were subjected to UV-Vis absorption and fluorescence analyzes when diluted in different solvents. Through the results, it was possible to observe that the β-hydroxyarylutenolides have two absorption bands, one at 289-291 nm and the other with higher intensity at 328-354 nm. The emission band between 385-422 nm is observed under excitation at 324-327 nm. The compounds showed solvatochromism as a function of the analyzed solvent. In water, fluorescence quenching of all compounds occurs. Therefore, studies with compound containing the methylenedioxy group attached in phenyl ring were carried at different concentrations of water in DMSO. The decrease in the fluorescence intensity of this compound is linearly proportional to the increase in the amount of water in the DMSO, with a minimum detection volume of 0.028%. Quantum yields of three compounds were evaluated in different solvents, showing that the relationship between the structure of the compound and the solvent is essential for a high value. The fluorescence quantum yield was also measured by Thermal Lens Spectroscopy (TLS) using DMSO as the solvent, confirming the high value for the analyzed samples. Despite being preliminary, the studies revealed that these compounds have luminescent properties that could be applied in the development of chemical sensors for detecting water in DMSO.

An "ON-OFF" fluorescent sensor based on a novel zinc-based flower-like structured metal-organic framework for sequential detection of deferasirox and tigecycline

Deferasirox (DEF) is essential for patients with thalassemia requiring long-term transfusion therapy. Tigecycline (TIGE) is a first-line drug for the clinical treatment of complex, severe bacterial infections. The two drugs can be coordinated to treat Pseudomonas aeruginosa infections. Easy and efficient techniques for monitoring these two drugs in biological samples are few. Metal-organic framework (Zn-MOF) prepared from zinc nitrate hexahydrate and dithioglycolic acid has a flower structure. Interestingly, Zn-MOF can cause DEF to aggregate on it and induce DEF luminescence. The principle may be that Zn-MOF limits the vibration and rotation of DEF to avoid its nonradiative jump, which triggers aggregation-induced emission (AIE) and exhibits intense fluorescence. Further investigation revealed that TIGE could decompose Zn-MOF, thus alleviating the inhibitory effect of Zn-MOF on DEF and reducing the fluorescence intensity of DEF@Zn-MOF. A DEF/TIGE detection biosensor was created based on the fluorescence "turn-on" effect of Zn-MOF on DEF and the fluorescence "turn-off" effect of TIGE on DEF@Zn-MOF. The proposed technique was subsequently used to identify DEF/TIGE levels in pharmaceuticals and human plasma. The mean values for the percentage of the labeled amount of DEF/TIGE in DEF dispersible tablets/TIGE injection were 104.5 and 104.9%, respectively. The detection limits for the fluorescence detection of DEF and TIGE were 3.6 and 1.2 nM, respectively. This fluorescence assay is the first application of MOF to the simultaneous detection of DEF and TIGE and has the advantages of rapid sensitivity and high selectivity, providing a new strategy for drug detection.

Investigating the AIE and water sensing properties of a concise naphthalimide fluorophore

A simple naphthalimide fluorophore NAP-H₂O was designed and synthesized. Basic photophysical properties were investigated, especially found that the probe showed robust green fluorescence in water compared with that in various organic solvents, and the specific mechanism was conformed to be the aggregation induced emission (AIE) through dynamic light scattering (DLS) analysis, solid-state luminescence and fluorescence imaging. Accordingly, the capability of NAP-H₂O for water sensing was examined, and good linear relationships between fluorescence intensities at the green emission band and the water content were obtained, enabling quantitative detection of water in organic solvents. The detection limits were calculated to be 0.004 % (v/v) in ACN, 0.117 % (v/v) in 1,4-dioxane, 0.028 % (v/v) in THF, 0.022 % (v/v) in DMF and 0.146 % (v/v) in DMSO, respectively. In addition, the probe presented fast response time within 5 s to water and good photostability. Furthermore, the probe was successfully applied for fast and naked-eye detection of water in organic solvents via test papers. This work provides a rapid, sensitive and naked-eye method for trace amount detection of water in organic solvents and has potential for practical applications.

Determination of water content in dimethyl sulfoxide/N,N-dimethyl formamide and methanol content in ethanol by solvatochromism of azo dye, 2-(tert-butyl)-4-methoxy-6-(naphthalen-1-yldiazenyl) phenol

A novel 2-(tert-butyl)-4-methoxy-6-(naphthalen-1-yldiazenyl)phenol (NAP) was synthesized by coupling reaction of 2-tert-butyl-4-methoxyphenol with diazotized naphthylamine as diazo component. The azo dye was characterized by NMR, FT-IR and UV-vis spectroscopic techniques. The visible spectrum of NAP was recorded in different solvents and at different pHs. NAP exhibited a large wavelength shift with increasing solvent polarity, showing significant color change over a wide range in different solvents. The determination of water content in organic solvents miscible with water such as dimethyl sulfoxide (DMSO)/N,N-dimethyl formamide (DMF) and methanol content in ethanol, which is also a common mixture were investigated with NAP which is azo dye. The present reported solvatochromic compound for the determination of water content in DMSO/DMF and methanol content in ethanol showed a fairly wide linear range compared to some previously reported solvatochromic compounds in the literature. In addition, the solvatochromism of NAP allows the determination of methanol content in ethanol, which has caused many deaths, with a fast, cheap and easy method.

Insights into AIE materials: A focus on biomedical applications of fluorescence

Aggregation-induced emission (AIE) molecules have garnered considerable interest since its first appearance in 2001. Recent studies on AIE materials in biological and medical areas have demonstrated that they show their promise as biomaterials for bioimaging and other biomedical applications. Benefiting from significant advantages of their high sensitivity, excellent photostability, and good biocompatibility, AIE-based materials provide dramatically improved analytical capacities for in vivo detection and demonstration of vital biological processes. Herein, we introduce the development history of AIE molecules and recent progress in areas of biotesting and bioimaging. Additionally, this review also offers an outlook for the potential applications of versatile AIE materials for tracing and treating pathological tissues, including overcoming challenges and feasible solutions.

A dipodal bimane-ditriazole-diCu(II) complex serves as an ultrasensitive water sensor

An ultrasensitive fluorescent water sensor based on a dipodal bimane-Cu(II) complex is reported here. This complex, which is non-fluorescent in the absence of water, demonstrates a remarkable turn-on fluorescence in the presence of extremely low (0.000786% v/v) concentrations of water, via highly selective water-induced displacement of copper and restoration of the innate bimane fluorescence.

A novel ratiometric fluorescent probe for water content in ethanol and temperature sensing

In this paper, two tetrahydo[5]helicene-based dyes (THH1 and THH2) were studied on their twist intramolecular charge transfer. And the water-soluble blue carbon dots (N-CDs) were synthesized. Considering that their different optical propeties, the ratiometric fluorescence probes N-CDs/THH1 and N-CDs/THH2 were constructed by mixing N-CDs and dyes simply. It was found that N-CDs/THH1 and N-CDs/THH2 could quickly and sensitively detect water content in ethanol, with linear range of 0.500-25.0 vol% and 0.500-30.0 vol%, respectively. What's more, through the actual sample test, it showed that the detection had good accuracy and precision. At the same time, it was found that two ratiometric probes could also be applied to the thermometry with good reversibility based on optical temperature sensors.

Mechanochemical synthesis of an AIE-TICT-ESIPT active orange-emissive chemodosimeter for selective detection of hydrogen peroxide in aqueous media and living cells, and solid-phase quantitation using a smartphone

We report herein the design and mechanochemical synthesis of a chemodosimeter, benzothiazole-derived unsymmetrical azine protected by 4-bromomethylphenylboronic acid (BTPAB), an orange aggregation-induced emission (AIE), for the selective detection of H2O2 in a turn-on manner.

Design and Structural Regulation of AIE photosensitizers for imaging-guided photodynamic anti-tumor application

In recent years, photodynamic therapy (PDT) has become one of the important therapeutic methods for treating cancer. Aggregation-induced emission (AIE) photosensitizers (PSs) overcome the aggregation-caused quenching (ACQ) effects of conventional...

An AIE material with time-dependent luminescence conversion obtained by 2D coordination polymer modification via covalent post-synthetic modification

In this study, we reported the covalent post-synthetic modification (PSM) of a luminescent complex to achieve aggregation-induced emission (AIE), prepared using the Schiff base reaction of TPE-CHO and HLC-NH2, denoted by HLC-NH2-TPE. HLC-NH2 formed a 2D luminescent complex which was constructed using 4,4'-diamino-[1,1'-biphenyl]-2,2'-dicarboxylic acid and zinc ions via a solvothermal reaction. HLC-NH2-TPE inherited the luminescence properties of HLC-NH2 and exhibited noticeable AIE properties in response to environmental viscosities and temperature changes. Interestingly, HLC-NH2-TPE displayed a time-dependent luminescence conversion phenomenon in a mixed solution of DMF/H₂O (v : v/1 : 9).

Seeking Aggregation-Induced Emission Materials in Food: Oat β-Glucan and Its Diverse Applications

With the basic understanding and broad application prospects of luminescent materials, the emission mechanism of unconventional luminescent agents has been revealed gradually. Here, we report a non-conjugated biomass material, oat β-glucan (oat-β-Glu), which actually does not emit light in a dilute solution but emits significantly when forming aggregates. Inherently visible emission of oat-β-Glu from the concentrated solutions and solid state could be observed. In addition, we have observed room temperature phosphorescence in oat-β-Glu powders, which is also unusual in pure organic materials. It can be proposed that the luminescence property of oat-β-Glu originates from the spatial conjugation of the oxygen atoms of oat-β-Glu. This clustering-triggered emission mechanism may well be expanded to other unconventional biomacromolecules, inspiring the rational design of luminescent agents. Due to its good biocompatibility and intrinsic emission characteristics, oat-β-Glu has shown great potential application prospects in bioimaging and biosensors.