The structure-activity relationship of hydrophilic carbon dots regulated by the nature of precursor ionic liquids

A highly water-soluble hydrogen-bond-induced emission carbon dots for ratiometric fluorescent detection of water content in organic solvents

Water in organic solvents is a prevalent impurity that significantly influences chemical reactions and industrial processes. Carbon dots (CDs) gained attention as promising tools for chemosensing due to their advantageous characteristics, including easy synthesis, cost-effectiveness, and excellent adjustability and stability. However, limited solubility in water and turn off fluorescence response mode hinder the practical utilization of CDs for water sensing. To tackle such dilemma, a highly water-soluble CDs with distinctive hydrogen-bond-induced emission (HBIE) was rationally designed through introducing sulfone group into the widely employed p-phenylenediamine precursor. The inclusion of sulfone group imparts the CDs with notable water solubility, as well as distinctive ratiometric fluorescent response towards water content, exhibiting high sensitivity and selectivity. Upon exposure to water, the emission color of CDs undergoes a real-time transition from blue to yellow-green, which can be readily discerned by naked eyes. The CDs have been successfully applied in detecting water in commercially available alcohol. This study presents a straightforward yet efficacious approach for rationally design of CDs with unique HBIE characteristics and ratiometric fluorescent response, offering great potential for practical chemosensing applications.

Modulation of the binding ability to biomacromolecule, cytotoxicity and cellular imaging property for ionic liquid mediated carbon dots

For the preparation of carbon dots (CDs), a variety of carbon sources and synthetic protocols are available which endow CDs with variable and unpredictable properties. In the present study, three CDs were developed with ionic liquid 1-butyl-3-methylimidazolium dicyanamide as the precursor through ethanol-thermal and hydrothermal strategies, termed as E-CDs and H-CDs, respectively. The features of these carbon dots, i.e., their physicochemical and optical properties, their interactions with bovine serum albumin (BSA) as well as their imaging capability were investigated with respect to the CDs prepared with microwave assisted approach (W-CDs). E-CDs and H-CDs were demonstrated to exhibit similar framework structures and optical properties, and they exhibited larger particle-sizes than that of W-CDs. In addition, the increase of ethanol-thermal and hydrothermal reaction time strengthened the quantum yields of the CDs and promoted their binding capability with BSA. E-CDs and H-CDs showed similar cytotoxicity on normal (LX-2) and cancer (SK-Hep-1) cells. We further found that these CDs may readily enter the cells within 5 min, while the fluorescence of hydrophilic E-CDs and H-CDs was very weak with respect to that of hydrophobic W-CDs in cell imaging. On the other hand, all the CDs exhibited little impact on the level of intracellular reactive oxygen species. The present study is conducive to guide the preparation of suitable carbon dots for different application scenarios.

Precise regulation of the properties of hydrophobic carbon dots by manipulating the structural features of precursor ionic liquids

To prepare carbon dots (CDs), there are numerous protocols that use a wide variety of carbon sources, which results in properties of CDs that are unpredictable and highly variable. Therefore, the development of reliable approaches for precisely regulating the nature of CDs is urgently required. Herein, a series of organophilic/hydrophobic CDs (OCDs) were prepared under microwave agitation with ionic liquid 1-alkyl-3-methylimidazolium dicyanamide as the precursor, by varying the alkyl chain linked in the cationic imidazolium moiety. The physicochemical, optical and biological properties, and imaging performance of OCDs were exploited to elucidate the structure-activity relationship, and it was discovered that the alkyl chain plays key roles in governing the properties of OCDs. The increase in the alkyl chain length, from ethyl, butyl, hexyl, and octyl to decyl, led to a remarkable variation in the properties of the OCDs, i.e., a reduction in nitrogen doping from 40.71 to 20.75%, a decrease in binding affinity with bovine serum albumin (BSA), and an increase in cytotoxicity. The interaction of OCDs with BSA and the formation of a 'protein corona' substantially increased the biocompatibility of the OCDs. The OCDs penetrated into MCF-7 human breast cancer cells in 10 min and demonstrated bright fluorescence imaging.

Enhanced Drug Loading in the Drug-in-Adhesive Transdermal Patch Utilizing a Drug-Ionic Liquid Strategy: Insight into the Role of Ionic Hydrogen Bonding

Though pharmaceutical polymers were widely used in inhibiting drug recrystallization via strong intermolecular hydrogen and ionic bonds, the improved drug stability was achieved at the cost of the drug release rate or amount in the drug-in-adhesive transdermal patch. To overcame the difficulty, this study aimed to increase drug loading utilizing a novel drug-ionic liquid (drug-IL) strategy and illustrate the underlying molecular mechanism. Here, naproxen (NPX) and triamylamine (TAA) were chosen as the model drug and corresponding counterion, respectively. In addiiton, carboxylic pressure-sensitive adhesive (PSA) was chosen as the model polymer. The drug-IL (NPX-TAA) was synthesized and characterized by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and proton nuclear magnetic resonance. The miscibility between NPX-TAA and PSA was assessed using microscopy study, X-ray diffraction, fluorescence spectroscopy, and solubility parameter calculation. In addition, molecular mechanisms of crystallization inhibition were revealed by FT-IR, Raman spectroscopy, DSC, X-ray photoelectron spectroscopy (XPS), and molecular docking. Finally, the release pattern of the high load patch of NPX-TAA was evaluated using in vitro drug release and verified by a skin permeation experiment. The results showed that drug loading in PSA was increased by 5.0 times, which was caused by the synergistic effect of strong ionic hydrogen bonding (the decreased intensity and blue shift of the O-H peak of COOH in PSA) formed between NPX-TAA and PSA-COO^- and normal hydrogen bonding (red shift of the C═O peak in PSA) formed between NPX-TAA and the carbonyl group of PSA. In addition, -NH⁺ of TAA was confirmed as the molecular basis of ionic hydrogen bonding through new peak appearance (binding energy: 400.0 eV) in XPS spectra. Moreover, high drug release percent (80.8 ± 1.8%) was achieved even at high drug loading compared with the control group (72.4 ± 2.2%). Thus, this study introduced an effective drug-IL method to enhance drug loading capacity and illustrated the brand-new action mechanism, which provided a powerful instrument for the development of a high drug loading-high release patch.

Imidazolium-type ionic liquid-based carbon quantum dot doped gels for information encryption

Here, a strategy for the preparation of adjustable imidazolium-type ionic liquid (IL)-based carbon quantum dots (CQDs) was reported. The effect of chemical structure, including carbon chain length of the N-substitution and the type of anion, on the amphiphilicity of CQDs was systematically investigated. It was found that the hydrophobicity of CQDs can be increased with the increase of carbon chain length for substitution at the N3 position. Moreover, the amphiphilicity of CQDs was also switched by changing the hydrophilic anions to hydrophobic anions. Due to adjustable amphiphilicity, the hydrophilic and hydrophobic CQDs were used for the preparation of fluorescent hydrogels and organogels, respectively. The fluorescent CQD-doped gels showed light- and force-dual stimuli responsiveness, which provides more secure information encryption than traditional single encryption inks.

Ionic liquid-aided hydrothermal treatment of lignocellulose for the synergistic outputs of carbon dots and enhanced enzymatic hydrolysis

How to propel an efficient exploitation of waste streams is a pivotal tache for the long-range augment of hydrothermal biomass valorization. A facile approach was proposed to simultaneously produce carbon dots (CDs), fermentable sugar, and cellulose enzymatic lignin from agricultural straw with the aid of ionic liquid (IL, 1-aminoethyl-3-methylimidazolium nitrate, [C2NH2MIm][NO3]) catalyzed hydrothermal treatment. The graphite N-doped CDs with bright-blue fluorescence, which was mainly derived from the incorporation of hemicellulose (e.g. xylooligosaccharides), lignin and [C2NH2MIm][NO3], exhibited an average-diameter of 8.14 nm. The exfoliation of amorphous parts and robust fibers was formed to improve cellulose digestibility from 14.7 to 81.6%. The efficient recovery and checkup of lignin pave a way for its potential depolymerization into arenes. This protocol offers a significant benefit for large-scale hydrothermal biorefinery where reduction of process waste is a prime concern, and leads to high-value products (i.e., CDs and lignin) that also fosters the feasibility of bioethanol.