Xiangli Chen

An Ultrasensitive Fluorescent Sensing Nanofilm for Organic Amines Based on Cholesterol‐Modified Perylene Bisimide

A stable, ultrasensitive, and fully reversible fluorescent sensing film for organic amines has been fabricated by assembling cholesterol (Chol)-derived perylene bisimide on a glass plate surface. The compound exhibits excellent film formation properties and forms well-defined nanofibers, as evidenced by SEM and AFM measurements. It has been revealed that besides the molecular structure of the specially designed perylene derivative, the existence of nanofibers in the film is another key factor to endow the film with superior sensing ability for organic amines, including aniline. The detection limit of the amine is ca. 150.0 ppt in the vapor phase and at room temperature. Furthermore, the sensing process is free of interference from common organic solvents, nitroaromatics, and particularly phenols, which makes the film a potential candidate to be used in lung cancer diagnoses and related applications.

Ternary System Based on Fluorophore−Surfactant Assemblies—Cu2+ for Highly Sensitive and Selective Detection of Arginine in Aqueous Solution

A new cationic dansyl derivative-based (DIlSD) fluorescence probe was designed and synthesized. Its combination with anionic surfactant SDS assemblies shows enhanced fluorescence intensity and blue-shifted maximum wavelength. Its fluorescence can be slightly quenched by Cu(2+); however, the fluorescence quenching efficiency by Cu(2+) is highly increased upon titration of arginine (Arg). As a result, the ternary system containing the cationic fluorophore, anionic surfactant, and Cu(2+) functions as a highly sensitive and selective sensor to Arg. The optimized sensor system displays a detection limit of 170 nM, representing the highest sensitivity to Arg in total aqueous solution by a fluorescent sensor. Control experiments reveal that the imidazolium groups in the fluorophore, the anionic surfactant, and Cu(2+) all play important roles in the process of sensing Arg. The electrostatic interaction between the cationic fluorophore and anionic surfactants facilitates the binding of imidazolium rings with Cu(2+), the surfactant surface-anchored Cu(2+) is responsible for further binding of Arg, and the electrostatic interaction between anionic surfactants and positively charged amino acids accounts for the selective responses to Arg.

Fluorescent films based on molecular-gel networks and their sensing performances.

A pyrene-capped terthiophene of cholesteryl derivative (CholG-3T-Py) was designed, synthesized, and utilized for the fabrication of a fluorescent film. Unlike the commonly adopted direct-coating method, the film was fabricated by the physical immobilization of the fluorophore, CholG-3T-Py, onto a glass plate surface via preformed low-molecular-mass gelator (LMMGs)-based molecular-gel networks. The photophysical behavior of the film as prepared and its sensing performances to nitrobenzene (NB) were conducted after activation with toluene. It was found that the film as prepared and activated is sensitive to the presence of NB, and the sensing process is fully reversible. Furthermore, the effects of commonly found interferents, including structural analogues, raw materials, which are commonly used for the production of NB, and other nitroaromatics (NACs), on the sensing process were also tested. It was shown that only aniline and phenol possess slight interference. The present work not only extends the applications of LMMGs-based molecular gels but also provids a new approach for preparation of micro- and nano-structure-based fluorescent sensing films.

Facile preparation of porous polymeric composite monoliths with superior performances in oil-water separation - a low-molecular mass gelators-based gel emulsion approach†

A series of water in oil (W/O) gel emulsions was prepared by using a low-molecular mass gelator (LMMG), a ferrocene derivative of cholesterol, as a stabilizer and tertiary butylmethacrylate (t-BMA) as the continuous phase. Via polymerization of the emulsions as created, a series of porous polymeric monoliths with different internal structures was prepared. SEM observation reveals that the internal structures of the monoliths could be largely adjusted via simple variation of the compositions of the gel emulsions. Importantly, introduction of hydrolysable silanes into the continuous phase of the gel emulsion before polymerization significantly alters the mechanical strengths of the porous materials, and remarkably promotes the sorption of the porous materials to some water-immiscible and -miscible liquids, such as benzene, kerosene, already-used transformer oil, ethanol, tetrahydrofuran, etc., of which kerosene is a representative of oils of lower viscosities and the transformer oil a representative of oils of higher viscosities. Furthermore, the oil absorbed by the monoliths could be recovered by centrifugation or squeezing, and the monoliths could be reused by washing them with alcohol or some other suitable volatile organic liquids. The sorption and desorption process could be repeated at least 13 times. More importantly, the LMMGs-based gel emulsion approach established in the present study for preparing porous polymeric or composite monoliths is facile, versatile and environmentally benign, showing a bright future for real-life uses.

A novel calix[4]arene-based dimeric-cholesteryl derivative: synthesis, gelation and unusual properties

A calix[4]arene-based dimeric-cholesteryl derivative with naphthalene in the linkers (C2N2C) was designed and synthesized. The gelation behaviors of the compound in 36 liquids were evaluated. It was demonstrated that C2N2C could gel 16 of the liquids tested, which include both polar and apolar liquids. SEM and AFM studies revealed that the morphologies of the gel networks are dependent on the concentrations of C2N2C and the nature of the liquids under study. Importantly, rheological studies revealed that the gel of the compound in benzene possesses sensitive, fast and fully reversible thixotropic property. More importantly, the Tgel of the C2N2C/benzene gel could be at least more than 60 degrees higher than the boiling point of benzene when the gelator concentration is greater than 6% (w/v), a result never reported before. CD measurements revealed the chiral nature of the assemblies of the gel networks. Further investigation by AFM measurements confirmed the right-hand helical structures of the gel networks of C2N2C/benzene gel. As anticipated, hydrogen bonding and π–π stacking are the two main driving forces for the formation of the gels.

Formation of An Ionic PTCA-β-CDNH2 Complex and Its Application for Phenol Sensing in Aqueous Phase

On the basis of proton transfer in aqueous phase, we prepared a water-soluble and highly fluorescent ionic complex of 3,4,9,10-perylene tetracarboxylic acid (PTCA) and 6-deoxy-6-amino-β-CD (β-CDNH2) and studied its fluorescence behavior. It was found that the fluorescence emission of the complex is sensitive and selective to the presence of trace amount of toxic phenolic compounds, in particular phenol, which is crucial for water quality control. The detection limit (DL) of the method to the analyte is ~0.03 μM, a lowest value reported in literatures for similar techniques. Interestingly, the detection at an unprecedented subnanogram (DL, ~0.12 ng/cm(2)) level can also be conducted in a visualized manner, which may provide a simple and low-cost protocol for on-site and real-time detection of the analyte. Moreover, the complex is humidity sensitive in dry state, and its color changes from bright yellow to bright green when exposed to wet vapor. Unlike other PTCA bisimide derivatives, preparation of the ionic complex of PTCA/β-CDNH2 is simple and avoids complicated synthetic burden. Furthermore, introduction of methanol into the aqueous solution of the complex resulted in aggregation as indicated by solution color change and proved by transmission electron microscopy and dynamic light scattering studies, which explains why the compound in dry state is sensitive to the presence of water and water vapor. X-ray diffraction, UV-vis, and fluorescence studies uncovered the H-packing nature of the structure of the aggregate.

Synthesis and sensing applications of a new fluorescent derivative of cholesterol

A fluorescent 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD) derivative of cholesterol (CTN) was designed and synthesized. The compound forms a 1 : 1 non-fluorescent complex with Hg2+ in a solvent mixture of water and ethanol. Based on this discovery, a detection method with a detection limit (DL) of ∼0.08 μM for Hg2+ was developed. The presence of other commonly found metal ions has little effect on the detection. Though Fe2+ and Cu2+ have some interference, it could be avoided by a simple oxidation or reduction procedure. Further studies revealed that the complex can be used for the turn-on detection of some organophosphorus pesticides (OPs), such as DDVP, glyphosate, chlorpyrifos, diazinon and phoxim, either in solution or film state. The DLs for the five OPs are 0.015, 0.018, 0.087, 0.098 and 0.113 μg mL−1 in solution, respectively. In addition, the compound as developed is interesting and attractive because it can sense the heavy metal ion and the OPs in a fast and sensitive manner. It is therefore believed that the developed method possesses the potential to be used for rapid on-site detection of hazardous chemicals.

Specially Treated Aramid Fiber Stabilized Gel‐Emulsions: Preparation of Porous Polymeric Monoliths and Highly Efficient Removing of Airborne HCHO

Porous polymeric monoliths with densities as low as ≈0.060 g cm-3 are prepared in a gel-emulsion template way, of which the stabilizer employed is a newly discovered acidified aramid fiber that is so efficient that 0.05% (w/v, accounts for continuous phase) is enough to gel the system. The porous monoliths as obtained can be dried at ambient conditions, avoiding energy-consuming processes. Importantly, the monoliths show selective adsorption to HCHO, and the corresponding adsorption capacity (M6) is ≈2700 mg g-1 , the best result that is reported until now. More importantly, the monoliths can be reused after drying.