The Characteristics of the Metal-Free and Non-Conjugated Polymer Film with Self-Assembled Nanoparticles.

It is shown in this paper that a polymer, MA-PEG 1000-DGEBA (MP1D), exhibits antireflection, substrate-dependent photoluminescence (SDP), wide band-gap, and photoconduction characterization. MP1D was synthesized from maleic anhydride, polyethylene glycol 1000, and bisphenol-A diglycidyl ether. Self-assembled nanoparticles embedded in MP1D film and ranging from 2.5 to 31.6 nm are observed, which could be expected as scatterers to enhance light trapping and extraction. The size of the nanoparticle increases with the concentration of the MP1D solution. Besides solution concentration, the nanoparticle dimension could be modified by the chain length of polyethylene glycol in the polymer synthesis. The effects of solution concentration, annealing temperature, annealing period, and substrate on the photoluminescence (PL) of MP1D films are examined. Increasing solution concentration increases PL intensity. However, aggregation-caused quenching is explicit as the solution concentration exceeds 100 mM. PL intensity increases with annealing temperature, which could be attributed to crystallinity improvement. PL intensity increases with increasing the annealing period from 0.5 to 2 h. Nonetheless, as the annealing period exceeds 2 h, PL quenching is emerging, which could be due to aggregation. It is expected that MP1D could be a promising candidate for host materials and MP1D film could play a multifunctional role (antireflective and light-trapping functions) in optoelectronics.

The Optical Properties of Metal-Free Polymer Films with Self-Assembled Nanoparticles.

In this paper, it is reported that a metal-free and non-conjugated polymer, MA-PEG 8000-BADGE (MP8B), exhibits an antireflective property and substrate-dependent photoluminescence (SDP). MP8B was constructed from maleic anhydride, poly(ethylene glycol) and bisphenol-A diglycidyl ether. Self-assembled nanoparticles are found in MP8B and can prospectively act as scattering centers to improve light trapping and extraction. MP8B films prepared from MP8B solutions have been characterized by photoluminescence (PL), atomic force microscopy (AFM), tunnelling electron microscope (TEM), reflectance, transmittance, and UV-Vis absorption spectrum. MP8B films can suppress light reflection and enhance light transmission. The PL spectrum of MP8B film on ITO peaks at approximately 538 nm, spanning from 450 to 660 nm at a concentration of 25 mM. Meanwhile, the effects of concentration and substrate on the PL of MP8B films are also investigated in this study. Surface roughness becomes larger with concentration. A red shift of the PL spectrum is observed as solution concentration increases. Meanwhile, aggregation-caused quenching (ACQ) is insignificant. Moreover, the PL spectra of MP8B films show a substrate-dependent phenomenon due to dielectric screening. The optical band-gap energy of MP8B is approximately 4.05 eV. It is concluded that MP8B is a promising candidate for a host material, and its film can be utilized as a multifunctional layer (i.e., antireflective and light-scattering functions) for optoelectronic applications.

One-Pot CuI/DBU-Catalyzed Carboxylative Cyclization toward Oxazolidinones Using Recyclable Molecular Sieves as Efficient Promoters for Fixation of CO2 in Water Medium.

An efficient one-pot synthesis of oxazolidinones was developed through CuI/DBU/MS joint system-catalyzed carboxylative cyclization of arylacetylene, arylaldehyde, and arylamine in water medium under a 1 atm carbon dioxide (CO2) atmosphere. The 4 Šmolecular sieves (MSs) were added to improve CO2 capture and facilitate carboxylation to give the products in high yields. The CuI/DBU/MS system is robust and highly effective for the reactions with different substrates, and some target products were obtained in an excellent yield of ∼96%, with no side products in the final step.

Microwave-Assisted One-Pot Synthesis of Indole-Based Fluorescent Probe for Sensitive Detection of Copper (II).

In this study, a rapid, inexpensive and convenient microwave assisted synthesis of indole-3-propionic acid-bisphenol A diglycidyl ether (IPA-SR3) fluorescent probe was developed. This fluorescent probe has the dual illumination characteristics of photoinduced electron transfer and aggregation-induced emission for the specific detection of Cu2+ ion in water. The wavelength-dependent photoluminescence behavior of the aggregated IPA-SR3 was highly selective (Ksv = 1.5 × 104 M-1) and sensitive in Cu2+ ion detection, with a low limit of detection (2.9 µM). Therefore, it can be used to detect low-concentration Cu2+ in water samples. Details of the synthesis procedure and fluorescence characteristics are presented herein. Graphical Abstract.

Tetranuclear silver(I) clusters showing high ionic conductivity in a bicontinuous cubic mesophase.

The synthesis and characterization of tetranuclear silver triazole metallomesogens, [Ag4(L(4)-C(n))6][BF4]4 (L(4)-C(n) = 4-alkyl-1,2,4-triazoles where C(n) stands for C(n)H(2n+1) with n = 12, 14, 16, and 18), are reported. Upon heating, a phase transition sequence of Cr → SmC → Cub → SmA → isotropic liquid is observed for all of these compounds. Depending on the alkyl chain length, two types of cubic phases are found in this series of compounds. Those with shorter alkyl chains (n = 12 and 14) exhibit a micellar cubic phase, whereas long alkyl chains (n =16 and 18) show a bicontinuous cubic phase. Superior ionic conductivity at the bicontinuous cubic mesophase for [Ag4(L4-C16)6][BF4]4 is observed because of the presence of a three-dimensional ion-transporting channel. Doping a small amount of AgBF4 enhances the ionic conduction dramatically, presumably via promotion of the migration of Ag(I) ions in the channels.

Conformational dynamics and excitation wavelength dependent photoluminescence of decameric organic nanoparticles.

We report a new type of fluorescent organic nanoparticles (16-EDFONP) which are composed of ten bis(3,4,5-tris(16-alkyloxy) monobenzoylglyceride) bisphenol A molecules. The nanoparticles are only found in high concentration solution and exhibit the excitation-dependent fluorescence (EDF). The 16-EDFONP shows clear spectral relaxation on the nanosecond time scale. We have observed similar spectral shifts in cyclohexane, and thus attribute the time-dependent Stokes shift to the emission from multiple conformations of 16-EDFONP. With the employment of steady state and time-resolved fluorescence anisotropy measurements, the hydrodynamic radius of 16-EDFONP is estimated to be 3.13 nm, which is consistent with the size measured using the dynamic light scattering and high-resolution transmission electron microscopy techniques. The time-resolved anisotropy reveals the change in fundamental anisotropy upon different excitation wavelengths, arising from the structural heterogeneity of hydrogen-bonded monoacylglycerol clusters of the 16-EDFONP. Our findings indicate that incomplete spectral relaxation and the size distribution of nanoparticles are not the source of the observed EDF. The EDF comes from the selective excitation of the 16-EDFONP with different monoacylglycerol hydrogen-bond conformations.

Excitation-dependent visible fluorescence in decameric nanoparticles with monoacylglycerol cluster chromophores.

Organic fluorescent nanoparticles, excitation-dependent photoluminescence, hydrogen-bonded clusters and lysobisphosphatidic acid are four interesting individual topics in materials and biological sciences. They have attracted much attention not only because of their unique properties and important applications, but also because the nature of their intriguing phenomena remained unclear. Here we report a new type of organic fluorescent nanoparticles with intense blue and excitation-dependent visible fluorescence in the range of 410-620 nm. The nanoparticles are composed of ten bis(monoacylglycerol)bisphenol-A molecules and the self-assembly occurs only in elevated concentrations of 2-monoacylglycerol via radical-catalysed 3,2-acyl migration from 3-monoacylglycerol in neat conditions. The excitation-dependent fluorescence behaviour is caused by chromophores composed of hydrogen-bonded monoacylglycerol clusters, which are linked by an extensive hydrogen-bonding network between the ester carbonyl groups and the protons of the alcohols with collective proton motion and HO···C=O (n→π) interactions.

A triple helical structure supported solely by C-H···O hydrogen bonding.

A novel triple helical structure that is self-assembled by cationic molecules, 1-acetamido-3-(2-pyrazinyl)-imidazolium, is reported. The computational analysis underpins that the formation of the triple helix is driven by C-H···O hydrogen bonding.

Design criteria for ionic liquid crystalline phases of phosphonium salts with three equivalent long n-alkyl chains.

The factors influencing the formation, organizations, and temperature ranges of the smectic phases of a structurally diverse family of phosphonium salts have been examined. The salts consist of one short group and three long n-alkyl chains attached to a positively charged phosphorus atom and either a free or covalently attached counterion, the latter resulting in zwitterionic salts. Of the 61 salts investigated, of which 37 have not been synthesized previously, most pack in lamellae within their solid phases. Single-crystal X-ray structures of two of amidomethyl-tri-n-tetradecylphosphonium bromide (1P14CONH(2)Br) and carboxymethyl-tri-n-tetradecylphosphonium bromide (1P14CO(2)HBr) have been solved. In each, the constituent molecules are packed in stacks of bilayers in which the directors of molecules on opposite sides of the ionic planes (where the phosphonium cationic centers and anions are located) that separate the layers are antiparallel. In each molecule, two of the long n-alkyl chains are paired while the third is antiparallel to the other two and paired with an n-alkyl chain of a molecule in a neighboring bilayer. The tri-n-alkylmethylphosphonium salts (1PnX) with small anions X (where n = 6-18 is the number of carbon atoms in the three long chain and 1 is the methyl group) do not form liquid-crystalline phases as a consequence of strong alternating intra- and intermolecular P(+)-X(-) interactions within the ionic planes that separate the bilayers of long chains. Thermotropic and enantiotropic liquid-crystalline phase formation of 1PnX salts is favored by larger anions and longer n-alkyl chains, which reduce order within ionic planes while promoting order within the lipophilic layers. We conjecture that covalent attachment of a hydroxymethylene, carboxy, or amido functional group Y to the alpha-methyl group of a 1PnX salt (resulting in mPnYX salts, where m is the number of methylene units separating the phosphorus atom from the Y group on the short chain) moves the anion X farther from the P(+) ion as a result of intramolecular X(-)...H(Y) H-bonding interactions and, therefore, substantially weakens intramolecular P(+)-X(-) ionic interactions within the ionic planes. In contrast to the trends mentioned for the 1PnX salts, liquid-crystalline phases of mPnYX are found more frequently when n is shorter and X is smaller. The observation that the liquid-crystalline phases of mPnYX salts have lower clearing and onset temperatures than the corresponding 1PnX may be attributed to the greater freedom of motion at and near the ionic planes of the former as a result of their more dispersed ionic interactions. Overall, a detailed study of the dependence of phase type and phase transition temperatures on several key structural factors of phosphonium salts has been made. The correlations found provide insights into how new mesmorphic phosphonium salts can be designed and exploited for a wide range of potential applications.

Probing C-H...X hydrogen bonds in amide-functionalized imidazolium salts under high pressure.

We have probed under high pressure the C-H hydrogen bonds formed by N,N(')-disubstituted imidazolium ions having PF(6) (-) and Br(-) counterions. High-pressure infrared spectral profiles, x-ray crystallographic analysis, and ab initio calculations allow us to make a vibrational assignment of these compounds. The appearance of a signal for the free-NH unit (or weakly bonded N-H...F unit) in the infrared spectrum of the PF(6) (-) salt indicates that conventional N-H...O and N-H...N hydrogen bonds do not fully dominate the packing. It is likely that the charge-enhanced C(2)-H...F interactions, combined with other weak hydrogen bonds, disturb the formation of N-H hydrogen bonds in the PF(6) (-) salt. This finding is consistent with the pressure-dependent results, which reveal that the C(2)-H...F interaction is enhanced upon increasing the pressure. In contrast to the PF(6) (-) salt, the imidazolium C-H bonds of the Br(-) salt have low sensitivity to high pressure. This finding suggests that the hydrogen bonding patterns are determined by the relative hydrogen bond acceptor strengths of the Br(-) and PF(6) (-) ions.

C[bond]H- - -O hydrogen bonds in beta-sheetlike networks: combined X-ray crystallography and high-pressure infrared study.

Close interactions of the C(alpha)[bond]H- - -O type have been analyzed via X-ray crystallography and high-pressure infrared spectroscopy. The results demonstrate that the C(alpha)[bond]H- - -O interactions can offer an additional stability to the beta-sheet formation. X-ray structural data suggest that while 1-acetamido-3-(2-pyrimidinyl)-imidazolium bromide exhibits a bilayer stacking, the PF(6)(-) salt reveals a beta-sheetlike pattern. The appearance of the free-NH infrared absorption indicates that the conventional N[bond]H- - -O or N[bond]H- - -N hydrogen bonds do not fully dominate the packing for the PF(6)(-) salt. The high-pressure infrared study suggests that the C(alpha)[bond]H- - -O hydrogen bonds are the important determinants for the stability of the PF(6)(-) salt. This study also verifies that the imidazolium C[bond]H stretching frequency shifts to a longer wavelength upon the formation of the C[bond]H- - -O hydrogen bonds.