An acid-chromic luminescent lanthanide metallogel for time-dependent information encryption and anti-counterfeiting.

Luminescent materials with dynamic color transformation demonstrate significant potential in advanced information encryption and anti-counterfeiting. In this study, we designed multi-color luminescent lanthanide metallogels featuring time-dependent color transformation. These materials are based on Förster resonance energy transfer (FRET) platforms, facilitating cascade energy transfer from the ligand 4,4',4''-[1,3,5-benzenetriyltris (carbonylimino)]trisbenzoic acid (H3L) to Tb3+ ions and subsequently to Sulforhodamine 101. The emission color of the gels can be readily adjusted by the introduction of HCl, transitioning from initial green, yellow, light red, and red hues to blue, violet, pink, and deep red, respectively. Importantly, the color change in these gels is time-dependent, controlled by the hydrolysis time of glucono-δ-lactone, which modulates the luminescence intensity of H3L, Tb3+, and Sulforhodamine 101. Exploiting these characteristics, we developed methods for information encryption utilizing 3D color codes and anti-counterfeiting flower patterns. These patterns undergo time-dependent transformations, generating a series of 3D codes and flower patterns that can only be recognized in a predetermined manner. These findings highlight the promising application of lanthanide metallogels in advanced information protection strategies.

Reaction of KHP with excess NaOH or TRIS as standard reactions for calibration of titration calorimeters from 0 to 60 °C.

Calibration of titration calorimeters is an ongoing problem, particularly with calorimeters with reaction vessel volumes < 10 mL in which an electrical calibration heater is positioned outside the calorimetric vessel. Consequently, a chemical reaction with a known enthalpy change must be used to accurately calibrate these calorimeters. This work proposes the use of standard solutions of potassium acid phthalate (KHP) titrated into solutions of excess sodium hydroxide (NaOH) or excess tris(hydroxymethyl)aminomethane (TRIS) as standard reactions to determine the collective accuracy of the relevant variables in a determination of the molar enthalpy change for a reaction. KHP is readily available in high purity, weighable for easy preparation of solutions with accurately known concentrations, stable in solution, not compromised by side reactions with common contaminants such as atmospheric CO2, and non-corrosive to materials used in calorimeter construction. Molar enthalpy changes for these reactions were calculated from 0 to 60 °C from reliable literature data for the pKa of KHP, the molar enthalpy change for protonation of TRIS, and the molar enthalpy change for ionization of water. The feasibility of using these reactions as enthalpic standards was tested in several calorimeters; a 50 mL CSC 4300, a 185 µL NanoITC, a 1.4 mL VP-ITC, and a TAM III with 1 mL reaction vessels. The results from the 50 mL CSC 4300, which was accurately calibrated with an electric heater, verified the accuracy of the calculated standard values for the molar enthalpy changes of the proposed reactions.

A sodium carboxymethyl cellulose-induced emission and gelation system for time-dependent information encryption and anti-counterfeiting.

Many lanthanide complexes do not form gel or even exhibit characteristic luminescence of lanthanide ions, which limits their applications in many fields. Therefore, there is an urgent need for a third component that can not only promote emission but also gel the lanthanide complex system to construct new smart materials such as time-dependent information encryption and anti-counterfeiting materials. Herein, a luminescent lanthanide metallogel was successfully prepared by using the third component sodium carboxymethyl cellulose (NaCMC) to induce the gelation and luminescence of the complex (H3L/Tb3+) of 4,4',4″-((benzene-1,3,5-tricarbonyl)tris(azanediyl)) tris(2-hydroxybenzoic acid) (H3L) and Tb3+. The H3L/Tb3+ complex itself does not form gel and has no characteristic luminescence of Tb3+. Moreover, the multicolor emission of H3L/Tb3+/NaCMC gels was prepared based on Förster resonance energy transfer (FRET) platforms to obtain a high-security level information encryption and anti-counterfeiting materials. These multicolor emission gels exhibit emission color tunability with time dependence due to the different energy transfer efficiencies at each pH node controlled by glucono-δ-lactone hydrolysis time. Based on the time response characteristics, the time-dependent information encryption and anti-counterfeiting materials are developed.

Activation and Inhibition of Isomerization of a Cationic Azobenzene Surfactant in the Large Void Space of Polyglycerol Dendron Micelles.

Owing to the unique geometric structure of dendritic amphiphiles with voluminous dendrons, their micelles can harbor a large void space, which provides a new research focus and approach for micellar functionalization. In this work, we used the void space to construct a UV responsive micelle system of the mixed dendritic amphiphile (C12-(G3)2) and cationic azobenzene surfactant (C4AzoTAB). The synthesized C12-(G3)2 that possesses double third generation polyglycerol (PG) dendrons and a single alkyl chain is expected to highlight the large void space within the inside of the micelles. Thus, the aims of this work are to achieve the isomerization of C4AzoTAB in situ and to deeply understand the intermolecular interaction in the mixed micelles. The effect of the large void room with a wall decorated with the ether oxygen atoms on the isomerization of C4AzoTAB was studied by isomerization kinetics, conductivity measurements, isothermal titration calorimetry (ITC), and 1H NMR and 2D NOESY spectroscopies. The isomerization behavior of C4AzoTAB in C12-(G3)2 micelles was presented in terms of its kinetic constant, counterionic association, interaction enthalpy, and position and orientation of C4AzoTAB. The results of NMR and conductivity show that the quaternary ammonium group of C4AzoTAB situates on the surface of the mixed micelles with C12-(G3)2 both before and after UV-irradiation, while the position of azobenzene group in C12-(G3)2 micelles depends on its conformation. The C12-(G3)2 micelles can inhibit the UV response of the trans-isomer and activate the thermal relaxation of the cis-isomer, which has a potential application in the field of light-controlled smart nanocarriers.

Ionic Liquid Mixture Electrolyte Matching Porous Carbon Electrodes for Supercapacitors.

Ionic liquids (ILs), with their wide electrochemical stable potential window, are promising electrolytes for supercapacitors (SCs). The suitable matching of the ion size and shape of the ILs to the pore size and structure of porous carbon (PC) electrode materials can realize the enhanced capacitive performance of the SCs. Here we report an interesting result: The capacitance of PC-based SCs shows a quasi-sinusoidal relationship with the composition (mass fraction) of the binary IL mixture as the electrolyte. This relationship is also interpreted based on the matching between the pore sizes of the PC materials and the size/shape of various ions of the IL mixture electrolyte. This can provide a new strategy to improve the performance of SCs by formulating a suitable mixture of different ILs to match the carbon-based electrode materials with a special pore size distribution.

Supramolecular Vector/Drug Coassemblies of Polyglycerol Dendrons and Rutin Enhance the pH Response.

A coassembly strategy for a supramolecular vector/drug was proposed with a biocompatible ternary dodecyl-bi(third-generation polyglycerol (PG) dendrons) (C12-(G3)2) amphiphile, dodecyl sulfobetaine (SB3-12) surfactant, and poorly water-soluble drug rutin. C12-(G3)2 and rutin will mutually enhance their pH response by protonation and deprotonation of dendritic PG and rutin's ionization as the pH changes from the acidic gastric lumen to the weakly alkaline intestine. SB3-12 may increase the payload and bring about sustained release for rutin by intermolecular interactions. Self-assembling behaviors of C12-(G3)2, SB3-12, sodium dodecyl sulfate (SDS), and dodecyl trimethylammonium bromide (DTAB) and their hybrids with rutin were characterized by UV-vis spectroscopy, a fluorescence probe, and 1H NMR. UV-vis and 1H NMR were used to identify the position and orientation of rutin in the vectors. The functions of the vector/drug were confirmed by measuring the solubility and in vitro release of rutin. The ternary coassembling vector/drug easily imparted functions of pH-responsive and sustained release without complex synthetic processes. The nanocaves framed by PG dendrons in the micelles provide pH-responsive compartments for rutin and SB3-12 in the supramolecular vector/drug anchors that accommodate rutin by weak interactions. The finely matched supramolecular vector/drug coassemblies exhibit the pH-responsive function for a potential application in the treatment of inflammatory bowel disease.

Green and Simple Synthesis of Photoluminescence-Tunable Carbon Dots for Sensing and Cell Imaging Applications.

Innovative nitrogen and boron co-doped carbon dots are hydrothermally produced using fructose, urea, and boric acid as precursors. The synthesized carbon dots possess a uniform morphology, and exhibit excellent fluorescence stability, tunable luminescence property, strong resistance to photobleaching, low-toxicity, and excellent biocompatibility. It is also found more dopant urea is conducive to the formation of the carbon dots with more B-N bonds, and shorter wavelength of fluorescence emission. Meanwhile, the synthesized carbon dots are well utilized as a photoluminescent probe for facile Hg2+ determination and fluorescent imaging reagent in cells.

Controllable enzymatic superactivity of α-chymotrypsin activated by the electrostatic interaction with cationic gemini surfactants.

Surfactant plays a critical role in enzymatic multi-functionalization processes. However, a deep understanding of surfactant-enzyme interactions has been lacking up until now due to the extreme complexity of the mixed system. This work reported the effect of cationic gemini surfactants, alkanediyl-α,ω-bis(dimethyldodecylammonium bromide) (C12C S C12Br2, S = 2, 6, and 10) on the enzymatic activity and conformation of α-chymotrypsin (α-CT) in phosphate buffer solution (PBS, pH 7.3). The enzymatic activity was assessed by the rate of 2-naphthyl acetate (2-NA) hydrolysis measured by UV-vis absorption. The superactivity of α-CT in the presence of C12C S C12Br2 appears in the concentration region below the critical micelle concentration (cmc) of the surfactant, and its maximum superactivity is correlated to the spacer length of C12C S C12Br2. Subtle regulation of the charge density of headgroups of the cationic surfactant can be achieved through partial charge neutralization of cationic headgroups by introducing inorganic counterions or oppositely charged surfactant, demonstrating that the electrostatic interaction plays the crucial role for emergence of the superactivity. The interaction between C12C S C12Br2 (S = 2,6, and 10) and α-CT was characterized by isothermal titration calorimetry (ITC), and the obtained endothermic enthalpy change indicates that the interaction induces the change in conformation and enzymatic superactivity. The methodologies of fluorescence spectroscopy, circular dichroism (CD), and differential scanning calorimetry (DSC) show that the gemini surfactants with different spacer lengths induct and regulate the secondary, tertiary and even fourth structures of the protein. The present work is significant to get deeper insight into the mechanism of the activation and denaturation of enzymes.

Construction of Rich Conductive Pathways from Bottom to Top: A Highly Efficient Charge-Transfer System Used in Durable Li/Na-Ion Batteries at -20 °C.

The construction of potential electrode materials with wide temperature property for high-energy-density secondary batteries has attracted great interest in recent years. Herein, a hybrid electrode, consisting of a nitrogen-doped carbon/α-MnS/flake graphite composite (α-MnS@N-C/FG), is prepared through a post-sulfurization route. In the α-MnS@N-C/FG composite, α-MnS nanoparticles wrapped by the N-C layer are uniformly embedded onto FG, forming a novel nanofoam structure. The as-obtained α-MnS@N-C/FG shows excellent lithium/sodium storage performance, with a specific capacity of 712 mA h g-1 in the 700th cycle at 1.0 A g-1 or 186.4 mA h g-1 in the 100th cycle at 100 mA g-1 using lithium or sodium foil as the counter electrode, respectively. Moreover, even operated at -20 °C, the α-MnS@N-C/FG can still attain a high specific capacity of 350 mA h g-1 after 50 cycles at 100mA g-1 for LIBs. This exceptional electrochemical response is attributed to the synergetic effect of the smart design of a hybrid nanofoam structure, in which the FG skeleton and N-C coating layer can significantly enhance the conductivity of the whole electrode from bottom to top. Accordingly, the enhanced redox kinetics endow the electrode with pseudocapacitive-dominated electrochemical behavior, leading to fast electrode reactions and robust structural stability in the whole electrode.

Silanized carbon dot-based thermo-sensitive molecularly imprinted fluorescent sensor for bovine hemoglobin detection.

Using the surface molecular imprinting technique, a thermo-sensitive molecularly imprinted fluorescent sensor was constructed for bovine hemoglobin (BHb) detection with the silanized carbon dots (CD@SiO2) as fluorescent signal, N-isopropylacrylamide as monomer sensitive to temperature, and BHb as template. The silanized carbon dots coated by the molecularly imprinted polymer (CD@SiO2@MIP) were characterized by high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy. Owing to the combination of the strong fluorescence sensitivity of CDs and the high selectivity of the molecular imprinting shell, the prepared sensor showed good recognition and detection performance to the target protein BHb, with a linear range of 0.31-1.55 µM and a detection limit of 1.55 µM. Furthermore, the sensor was utilized to detect the content of BHb in real urine with a recovery of 98.6-100.5%. The CD@SiO2@MIP sensors present a high potential for applications in the detection of BHb in biological systems. Graphical abstract.

Fluorescent probe based on carbon dots/silica/molecularly imprinted polymer for lysozyme detection and cell imaging.

The abnormal concentration of lysozyme in body fluids and tissues is a potential indicator for diseases such as leukemia and meningitis. In this work, by combining the excellent optical properties of carbon dots (CDs) with the favorable selectivity of molecularly imprinted polymer (MIP), a novel fluorescent probe for lysozyme detection and cell imaging was constructed, where silanized CDs with low cytotoxicity (CDs/SiO2) were used as the fluorescence signal reporter and N-isopropylacrylamide (NIPAM) was used as the temperature-sensitive monomer. The as-prepared CDs/SiO2/MIP showed a thermo-sensitive property for the response to lysozyme. Moreover, this probe could be used for quantitative detection of lysozyme, with a wider detection range (0.001~0.01 mg/mL), a low detection limit (0.55 µg/mL), and a high selectivity. Importantly, the MTT assay testified that the fluorescent CDs/SiO2/MIP probe had low cytotoxicity. In addition, human hepatoma carcinoma cells (HepG-2 cells) could be stained by the CDs/SiO2/MIP, and showed a bright intracellular green fluorescence, indicating that the imaging of live cells was possible. This study provides a new way to detect lysozyme in vitro and an attractive perspective to probe intracellular lysozyme in vivo.

A hybrid shell material with mixed ion/electron conductivity used for high-performance Li-S batteries.

A hybrid shell material of hollow Nb2O5 microspheres has been engineered as an effective sulfur host for use in Li-S batteries. Of particular note is that the selected Nb2O5 not only exhibits ultrafast Li+ motion properties due to its unique room-and-pillar NbO6/NbO7 framework structure, but also demonstrates moderate polar affinities to the lithium polysulfides based on theoretical calculations.

DNA-functionalized gold nanoparticle-based fluorescence polarization for the sensitive detection of silver ions.

Despite their practical applications, Ag+ ions are environmental pollutants and affect human health. So the effective detection methods of Ag+ ions are imperative. Herein, we developed a simple, sensitive, selective, and cost-effective fluorescence polarization sensor for Ag+ detection in aqueous solution using thiol-DNA-functionalized gold nanoparticles (AuNPs). In this sensing strategy, Ag+ ions can specifically interact with a cytosine-cytosine (CC) mismatch in DNA duplexes and form stable metal-mediated cytosine-Ag+-cytosine (C-Ag+-C) base pairs. The formation of the C-Ag+-C complex results in evident changes in the molecular volume and fluorescence polarization signal. To achieve our aims, we prepared two complementary DNA strands containing C-base mismatches (probe A: 5'-SH-A10-TACCACTCCTCAC-3' and probe B: 5'-TCCTCACCAGTCCTA-FAM-3'). The stable hybridization between probe A and probe B occurs with the formation of the C-Ag+-C complex in the presence of Ag+ ions, leading to obvious fluorescence quenching in comparison to the system without AuNP enhancement. The assay can be used to identify nanomolar levels of Ag+ within 6 min at room temperature, and has extremely high specificity for Ag+, even in the presence of higher concentrations of interfering metal ions. Furthermore, the sensor was successfully applied to the detection of Ag+ ions in environmental water samples and showed excellent selectivity and high sensitivity, implying its promising application in the future.

Cationic gemini surfactant as a dual linker for a cholic acid-modified polysaccharide in aqueous solution: thermodynamics of interaction and phase behavior.

Understanding the thermodynamics of formation of biocompatible aggregates is a key factor in the bottom up approach to the development of novel types of drug carriers and their structural tuning using small amphiphilic molecules. We chose an anionic amphiphilic and biocompatible polymer that consists of a dextran and grafted cholic acid pendants, randomly distributed along the dextran backbone, with a degree of substitution (DS) of 15 mol% (designated Dex-15CACOONa). The thermodynamics of interaction and phase behavior of mixtures of this polyelectrolyte and a cationic gemini surfactant hexanediyl-α,ω-bis(dodecyldimethylammonium bromide) (C12C6C12Br2) or its monomer surfactant dodecyltrimethylammonium bromide (DTAB) in aqueous solution were characterized by isothermal titration calorimetry (ITC) and turbidity, together with cryogenic transmission electron microscopy (Cryo-TEM). The various critical concentrations and the enthalpy changes of the corresponding phase transitions for the oppositely charged system were obtained from the plots of the observed enthalpy change (ΔHobs) and turbidity measurements as a function of gemini concentration. The morphologies of the aggregates in various phases were observed by Cryo-TEM. Altogether these results suggest the critical role of gemini as a dual linker. At the concentrations where the crosslink between the pendant aggregates happens, the free gemini concentration is proximately zero and the aggregate retains its negative charge. The analysis of various factors involved in the interaction allowed a rationalization of the driving forces for mixed aggregate formation, which will contribute to a subsequent rational design of drug delivery systems based on this polymer/surfactant system.

Probing the binding of trypsin to glutathione-stabilized gold nanoparticles in aqueous solution.

We investigate the interaction of trypsin with glutathione-stabilized Au nanoparticles (NPs) using fluorescence, synchronous fluorescence and ultraviolet (UV) absorption spectroscopy. We find that trypsin binds strongly to the Au NPs with a static quenching mechanism, and that the interaction is characteristic of positive cooperative binding. Furthermore, we determine the binding constants and the thermodynamic parameters, which suggest that the main binding forces between the glutathione-stabilized Au NPs and trypsin are electrostatic interactions and hydrogen bonding. Analysis of UV-vis absorption spectra suggests that aggregation of the Au NPs occurs in the trypsin/Au NPs system, which significantly alters the conformation of the protein.

Self-Aggregation of Amphiphilic Dendrimer in Aqueous Solution: The Effect of Headgroup and Hydrocarbon Chain Length.

The self-aggregation of amphiphilic dendrimers G1QPAMCm based on poly(amidoamine) PAMAM possessing the same hydrophilic group but differing in alkyl chain length in aqueous solution was investigated. Differences in the chemical structures lead to significant specificities in the aggregate building process. A variety of physicochemical parameters presented monotonous regularity with the increase in alkyl chain length in multibranched structure, as traditional amphiphilic molecules. A significant difference, however, existed in the morphology and the microenvironment of the microdomain of the aggregates, with G1QPAMCm with an alkyl chain length of 16 intending to form vesicles. To obtain supporting information about the aggregation mechanism, the thermodynamic parameters of micellization, the free Gibbs energy ΔGmic, and the entropy ΔSmic were derived subsequently, of which the relationship between the hydrophobic chain length and the thermodynamic properties indicated that the self-assembly process was jointly driven by enthalpy and entropy. Other than traditional surfactants, the contribution of enthalpy has not increased identically to the increase in hydrophobic interactions, which depends on the ratio of the alkyl chain length to the radius in the headgroup. Continuous increases in the hydrophobic chain length from 12 to 16 lead to the intracohesion of the alkyl chain involved in the process of self-assembly, weakening the hydrophobic interactions, and the increase in -ΔHmic, which offers an explanation of the formation of vesicular structures.

Hydrolysis of cellulose catalyzed by novel acidic ionic liquids.

The conversion of cellulosic biomass directly into valuable chemicals becomes a hot subject. Six novel acidic ionic liquids (ILs) based on 2-phenyl-2-imidazoline were synthesized and characterized by UV-VIS, TGA, and NMR. The novel acidic ionic liquids were investigated as catalysts for the hydrolysis of cellulose in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The acidic ionic liquids with anions HSO4(-) and Cl(-) showed better catalytic performance for the hydrolysis of cellulose than those with H2PO4(-). The temperature and dosage of water affect significantly the yield of total reducing sugar (TRS). When the hydrolysis of cellulose was catalyzed by 1-propyl sulfonic acid-2-phenyl imidazoline hydrogensulfate (IL-1) and the dosage of water was 0.2g, the TRS yield was up to 85.1% within 60 min at 100°C. These new acidic ionic liquids catalysts are expected to have a wide application in the conversion of cellulose into valuable chemicals.

Critical role of the degree of substitution in the interaction of biocompatible cholic acid-modified dextrans with phosphatidylcholine liposomes.

The interaction between biocompatible cholic acid-modified dextrans with different pendent cholic acid groups' content and phosphatidylcholine liposomes was studied by a variety of techniques including isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), turbidity measurements, microscopy imaging (transmission electron microscopy (TEM), and cryo-scanning electron microscopy (cryo-SEM)). The variation of the interaction enthalpy with polymer concentration, as obtained by ITC, highlighted the formation of different aggregates. Complete phase modification, from vesicles covered with a few polymer chains to vesicle disintegration, was observed by turbidity measurements. DSC showed the effect of polymer addition to the liposome gel to liquid-crystalline phase transition, and microscopy images gave information about the size and morphology of the aggregates. The composition, structure, and morphology of polymer/liposome aggregates were found to be strongly influenced by the cholic acid content in the polymer (degree of substitution, DS). Along with a rather monotonous change in the polymer/liposome system's properties with increasing DS, a discontinuity in behavior could also be observed at DS = 4 mol %. For DS ≤ 4 mol %, the polymer/liposome interaction takes place mainly between individual components, and liposome disintegration occurs in a narrow concentration range, whereas for DS > 4 mol % extended physical networks are formed, which last over a wide concentration range. A mechanism of interaction, as a function of DS, is proposed and discussed in detail.

Calorimetric and theoretical study of the interaction between some saccharides and sodium halide in water.

Dilution enthalpies and mixing enthalpies of sodium halide and some saccharides (glucose, galactose, xylose, arabinose, fructose, and sucrose) in aqueous solution were determined by calorimetric measurements at 298.15 K. The values were used to determine enthalpic pair interaction parameters. Combined with Gibbs energy pair parameters, entropic pair interaction parameters were also obtained. Theoretical calculations at the B3LYP/6-311++G(d,p) level were carried out to provide the information of structures and thermodynamic functions. The information reveals the thermodynamic essence of the interactions between sodium halide and saccharides in aqueous solutions. The experimental results and theoretical calculations show that the sign of enthalpic pair interaction parameter 2υh(ES) is determined by the direct interaction between saccharides and ions, whereas the difference in value of 2υh(ES) for different saccharides or electrolytes depends on the partial dehydration of saccharides or anions in aqueous solution. The difference in value of entropic pair interaction parameters depends partly on the different dominant interactions in the process of partial dehydration of saccharides or ions. An enthalpy-entropy compensation relationship was observed for the sodium bromide-aldopyranose-water systems. Remarkably, it can be conjectured that the hydration entropy of glucose is lower than for other monosaccharides. Perhaps it is one of the reasons why glucose plays an important role in living organisms rather than other monosaccharides.

Does cation dehydration drive the binding of metal ions to polyelectrolytes in water? What we can learn from the behaviour of aluminium(III) and chromium(III).

Much stronger binding is seen in aqueous solutions between the anionic polyelectrolyte potassium poly(vinyl sulfate) and the substitution labile aluminium(III) than with the kinetically inert chromium(III). This strongly supports the idea that entropy driven water loss from the hydration sphere of the metal ion plays a major role in driving binding of the trivalent metal ion to the polyelectrolyte.