Low Molecular Mass Organogelator Research Articles

Hydrazone‐Based Supramolecular Organogel for Selective Chromogenic Detection of Organophosphorus Nerve Agent Mimic

AbstractSynthesis and spectroscopic characterization of a low molecular mass organogelator based on alkyl chain‐substituted tricyanofuran hydrazone (TCFH) dyes are described for detecting organophosphorus based nerve agent mimic. The reactivity of the prepared TCFH‐based organogel towards diethylchlorophosphonate (DCP) has been examined in organic phases. TCFH chromophore showed a successful gelation ability of different organic solvents. In addition, responsiveness of TCFH to nerve agent mimic with a gel‐sol reversible switching was monitored associated with colorimetric shifting from yellow to blue. The supramolecular self‐assembly of TCFH occurs via van der Waals interactions as well as cooperative π‐π stacking leading to gel formation in organic solvents. Moreover, the existence of nerve agents‐based gases results in a remarkable variation in the rheological behavior of the tricyanofuran hydrazone‐based gel. Scanning electron microscopy (SEM) images demonstrated that the xerogel generated from n‐propanol (n‐PrOH) is able to create fibrous supramolecular architecture with the ability for naked‐eye detection of a nerve agent mimic. The development of TCFH‐based supramolecular organogel in organic solvents was disturbed by the nerve agent mimic presenting a novel detection technique for organophosphorus warfare agents.

A low molecular mass organogelator electrolyte with TiO2 nanoparticles for stable and efficient quasi-solid-state dye sensitized solar cells

We report stable and efficient quasi-solid-state dye-sensitized solar cells (QS-DSSCs) fabricated using a combination of TiO2 nanoparticles and a low-molecular-mass organogelator (LMOG) as a nanoparticle–gel composite electrolyte.

Quasi-Solid-State Dye-Sensitized Solar Cell with Ionic Gel Electrolytes By Semifluorinated Alkoxy Benzene Derivative

Quasi-solid-state dye-sensitized solar cells (QS-DSSCs) have rapidly become an important research orientation in electronic vehicles. Especially, ionic liquid gel electrolytes (ILGEs) solidified by low molecular mass organogelators (LMOGs) can effectively possess higher ionic conductivity and good pore filling.1 Based on the advantage of ILGEs, we present here a kind of LMOGs (compounds 1(n)) by semifluorinated benzene derivatives. ILGEs formed by compounds 1(n) with different ionic liquids can divide two parts. One is with the representative [BMIM] posion-based ionic liquids (ILs), such as [BMIM] [I], [BMIM] [BF4], [BMIM] [FSA] and [BMIM] [TFSA]. Another one is with the representative [TFSA] anion-based ILs, such as [DEME] [TFSA], [EMIM] [TFSA], [TMPA] [TFSA], [AAIM] [TFSA] and [P13] [TFSA]. The minimum gelation concentrations in weight percent were determined at concentrations ranging from 5% to 1% in a heating-cooling cycle by the “stable to inversion in a test tube” method. The thermal properties of ILGEs which exactly is the effect of the concentration on the gel-sol phase transition temperatures (T gel) upon heating were examined. The ionic conductivity (σ) of ILGEs which is an important property for ILGEs was also examined. Compared with the data of ionic conductivities which has been reported in literature, it was found that the ionic conductivities in gel state were similar with ionic conductivities in liquid state. The conductivities of ILGEs with different concentrations of LMOGs were also analyzed. The diffusion of redox couple (I3 - and I-) ions in the ILGEs is an important factor for DSSCs property.2 In order to analyze the behavior of in I3 - and I- the ILGEs, linear sweep voltammetry studies were performed at a scan rate of 1.0 mVs-1 at room temperature. The performance of [BMIM] [I] was different with others. It maybe that ionic liquid of [BMIM] [I] contains anion of I- by itself. Reference 1. (a) Wang, P.; Zakeeruddin, S. M.; Comte, P.; Exnar, I.; Grätzel, M. Gelation of ionic liquid-based electrolytes with silica nanoparticles for quasi-solid-state dye-sensitized solar cells. Journal of the American Chemical Society 2003, 125 (5), 1166-1167; (b) Tao, L.; Huo, Z.; Ding, Y.; Li, Y.; Dai, S.; Wang, L.; Zhu, J.; Pan, X.; Zhang, B.; Yao, J. High-efficiency and stable quasi-solid-state dye-sensitized solar cell based on low molecular mass organogelator electrolyte. Journal of Materials Chemistry A 2015, 3 (5), 2344-2352. 2. Yoon, J.; ki Kang, D.; Won, J.; Park, J.-Y.; Kang, Y. S. Dye-sensitized solar cells using ion-gel electrolytes for long-term stability. Journal of Power Sources 2012, 201, 395-401.

Effect of the self-assembled gel network formed from a low molecular mass organogelator on the electron kinetics in quasi-solid-state dye-sensitized solar cells

A low molecular mass organogelator (LMOG), N , N ¢ -1,5-pentanediylbis-dodecanamide, was applied to quasi-solid-state dye-sensitized solar cells (QS-DSSCs). The crosslinked gel network was self-assemblied by the LOMG in the liquid electrolyte, and the in situ assembly process of gelator can be obtained by the polarized optical microscopy (POM). On one hand, the network hinders the diffusion of redox species and accelerates the electron recombination at the interface of the TiO2 photoanode/electrolyte. On the other hand, Li+ can interact with the amide carbonyl groups of the gelators and the adsorption of Li+ onto the TiO2 surface decreases, leading to a negative shift of the TiO2 conduction band edge, accelerated electron transport and decreased electron injection efficiency ( η inj) of QS-DSSC. As a result, the incidental photon-to-electron conversion efficiency (IPCE), the short circuit photocurrent density ( J sc) and the open circuit voltage ( V oc) of the QS-DSSC are decreased compared with those of the liquid electrolyte based DSSC (L-DSSC), which indicates that the electron recombination plays a great role in the photovoltaic performances of DSSC. Remarkably, the QS-DSSC exhibits excellent thermal and light-soaking stabilities during accelerated aging tests for 1000 h, which is attributed to a great intrinsic stability of the gel electrolyte with a high gel to solution transition temperature ( T gel = 108°C).

Quasi-solid-state dye-sensitized solar cell based on gel electrolyte with high gel to solution transition temperature using low molecular mass organogelator

Quasi-solid-state dye-sensitized solar cell (QS-DSSC) were fabricated using N,N'-1,4-butylenediylbis-dodecanamide as low molecular mass organogelator (LMOG). The gel to solution transition temperature (Tgel) of this gel electrolyte is 115.8 °C which ensures a good intrinsic stability of the gel electrolyte at the QS-DSSC operating temperature. The kinetic processes of electron transport and recombination of DSSCs influenced by the gel electrolyte are investigated in detail. Due to the diffusion of redox species in the gel electrolyte is hindered by the crosslinked network and the electron recombination at the interface of the TiO2 photoanode/electrolyte is accelerated, the incidental photon-to-electron conversion efficiency (IPCE) and the short circuit photocurrent density (Jsc) of the QS-DSSC are slightly decreased compared with those of liquid electrolyte based DSSC (L-DSSC). Remarkably, the QS-DSSC exhibits excellent thermal and light-soaking stabilities during accelerated aging tests for 1000 h. The QS-DSSC retains 90% of its initial photoelectric conversion efficiency, whereas that of L-DSSC only retains 83% under successive one sun light soaking with UV cut-off filter at 50 °C for 1000 h.

Quasi‐Solid‐State Dye‐Sensitized Solar Cells Based on Ru(II) Polypyridine Sensitizers

AbstractThe Ru(II) polypyridine complexes SA22 and SA25 consisting of anchoring and light harvesting moieties and possessing broad light absorption spectra were used to fabricate and optimize dye‐sensitized solar cells (DSSCs). The highly efficient Z960 electrolyte was used as redox‐mediator, and the J–V characteristics and incident photon‐to‐current conversion efficiency (IPCE) data were measured. The solar cells based on these dyes and electrolyte yielded power conversion efficiencies (PCE) of 7 % using SA22 and 5 % with SA25. The higher‐performance sensitizer SA22 was selected to build solar‐cell devices, using either the high‐thermal‐stability Z946 electrolyte or a gel‐electrolyte composed of Z946 electrolyte and 2 wt % low‐molecular‐mass organogelator (LMOG) NME‐5. The quasi‐solid‐state electrolyte produced a DSSC with a PCE of 4.7 %, whereas that made using Z946 showed 5 % efficiency. The quasi‐solid‐state DSSC was sealed and a stability study was performed using accelerated thermal aging conditions at 70 °C for 7 days, by which the cell parameters (including PCE, Jsc, Voc, and FF) retained more than 90 % of their original values.

Dicyclohexylammonium bromoacetate: a low molecular mass organogelator with a one-dimensional secondary ammonium monocarboxylate (SAM) synthon.

The asymmetric unit of the title salt, C12H24N(+)·C2H2BrO2(-), contains a dicyclohexylammonium cation connected to a bromoacetate anion by means of an N-H...O hydrogen bond. In the crystal, the ion pairs assemble via N-H...O interactions, forming zigzag infinite chains parallel to the c axis with the (...H-N-H...O-C-O...)n motif that is considered to be a prerequisite for ensuring gelation properties of secondary ammonium monocarboxylate salts. The title salt was characterized by FT-IR, X-ray powder diffraction (XRPD), TG-DTA and (1)H NMR spectroscopy in solution. Gelation experiments revealed that dicyclohexylammonium bromoacetate forms molecular gels with dimethylformamide and dimethyl sulfoxide. Scanning electron microscopy (SEM) was used to reveal morphological features of dried gels.

Effect of alkyl chain length of imidazolium cations on the electron transport and recombination kinetics in ionic gel electrolytes based quasi-solid-state dye-sensitized solar cells

A series of stable quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are prepared by the 12-hydroxystearicacid as low molecular mass organogelator (LMOG) to gelate the ionic liquid with different alkyl chain lengths (3, 4, and 7). The influence of alkyl chain length of imidazolium cations (Im+) on the kinetic processes of electron transport and recombination are investigated by Electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy (IMPS/IMVS). It is found that the ionic gel electrolytes (IGEs) with different alkyl chain lengths of Im+ can influence the competitive adsorption effects of imidazolium cations (Im+) and Li+, and further affect the charge diffusion, the electron recombination/transport processes, the shift of TiO2 conduction band edge and surface states distribution. The IGE with longer alkyl chain length of Im+ can prolong the electron recombination lifetime, promote the incidental photon-to-electron conversion efficiency (IPCE) and the short circuit photocurrent density (Jsc). An excellent QS-DSSC based on the IGE with the longer alkyl chain of Im+ gives the highest photoelectric conversion efficiency. Moreover, all the QS-DSSCs based on IGEs exhibit excellent durability without losing their photovoltaic performances during the accelerated thermal and light–soaking test. These results are very important to the researches on the electrochemical mechanism and application of QS-DSSCs based on IGEs.

A novel polysulfide hydrogel electrolyte based on low molecular mass organogelator for quasi-solid-state quantum dot-sensitized solar cells

A quasi-solid-state quantum dot-sensitized solar cell (QDSSC) is fabricated by using 12-hydroxystearic acid as a low molecular mass organogelator to gelate the polysulfide electrolyte. Noticeably, the gel to liquid transition temperature of this polysulfide hydrogel electrolyte is 96 °C, which contributes to the long-term stability of the quasi-solid-state QDSSC (QS-QDSSC). The influences of gelation on the charge transport, electron recombination and photovoltaic performance of the QS-QDSSC are investigated by electrochemical impedance spectroscopy. Moreover, the network of the hydrogel is investigated by the Field emission scanning electron microscopy and polarized optical light microscopy. It is found that the charge transport is influenced by the network in the hydrogel electrolyte, and the accelerated electron recombination at the photoanode/electrolyte interface leads to the decreased open-circuit voltage. The QS-QDSSC exhibits an energy conversion efficiency of 2.40% at AM 1.5 (100 mW cm−2) which is slightly lower than that of liquid electrolyte based cell (2.88%). However, the QS-QDSSC exhibits significantly improved stability during the accelerated thermal test. Especially, during the accelerated aging test, the short-circuit current density (Jsc) of the liquid electrolyte based QDSSC sharply decreased to nearly 35% of its initial value, while there is relatively less change in the Jsc for the QS-QDSSC.

High-efficiency and stable quasi-solid-state dye-sensitized solar cell based on low molecular mass organogelator electrolyte

A quasi-solid-state dye-sensitized solar cell with high photoelectric conversion efficiency (9.61%) and long-term stability is fabricated with a low molecular mass organogelator based gel electrolyte.

1,3:2,4-di-(3,4-dimethyl)benzylidene sorbitol organogels used as phase change materials: solvent effects on structure, leakage and thermal performance

Organogels used as shape-stable phase change materials were prepared by impregnating a low molecular mass organogelator into organic phase change materials.

Stable quasi-solid-state dye-sensitized solar cell using ionic gel electrolyte with low molecular mass organogelator

Long-term stability is essential for the application and commercialization of dye-sensitized solar cells (DSCs). A quasi-solid-state DSC (QS-DSC) with excellent long-term stability is fabricated using ionic gel electrolyte (IGE) with N,N′-methylenebisdodecanamide as low molecular mass organogelator (LMOG). The gel to solution transition temperature (Tgel) of this IGE is 127 °C, well above the working temperature of the device, which contributes to the thermal properties of the IGE and the device. The electrochemical properties of the IGE and the kinetic processes of electron transport and recombination of the QS-DSC are investigated by means of electrochemical impedance spectroscopy (EIS) and controlled intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS). Due to the obstructed diffusion of redox species caused by the network of IGE, the electron recombination at the TiO2 photoelectrode/electrolyte interface in the QS-DSC is accelerated. More importantly, compared with the ionic liquid electrolyte (ILE) based DSC, the QS-DSC based on the IGE exhibits excellent thermal and light-soaking stabilities during the accelerated aging tests for 1000 h. Especially, there is almost no degradation in the short-circuit current density (Jsc) in the IGE based QS-DSC, while the Jsc of the ILE based DSC decreased to 85–94% of their initial values.

Stable quasi-solid-state dye-sensitized solar cell using a diamide derivative as low molecular mass organogelator

High stability is a significant target for practical applications of dye-sensitized solar cells. 2-(1-oxododecyl)hydrazide, a diamide derivative, is synthesized and applied in quasi-solid-state dye-sensitized solar cells (QS-DSSCs) as a low molecular mass organogelator (LMOG). It is noteworthy that the transition temperature from gel state to liquid state (Tgel) of this gel electrolyte is 125.2 °C, which ensures the gel state of the electrolyte at the DSSC operating temperature. The influences of the gel electrolyte on the kinetic processes of electron transport and recombination are investigated. The diffusion of redox species in the gel electrolyte is hindered by the crosslinked network, and the decreased electron recombination lifetime indicates an increased electron recombination in QS-DSSC. Significantly, the QS-DSSC exhibits excellent thermal and light-soaking stabilities during accelerated aging tests for 1000 h. Especially, there is almost no change in the short-circuit current density (Jsc) in the QS-DSSC, while the Jsc of the liquid electrolyte based DSSC decreases to 79–90% of their initial values. These results are very important for the application and commercialization of DSSCs.

Influence of solvent on the thermal stability and organization of self-assembling fibrillar networks in methyl-4,6- O-( p-nitrobenzylidene)-α- d-glucopyranoside gels

Sugar based low-molecular-mass organogelator (LMOG) methyl-4,6- O-( p-nitrobenzylidene)-α- d-glucopyranoside, is a unique gelator because its small and weakly-interacting molecules can form large supramolecular structures in nonpolar, but also in polar, solvents and cause their gelation. The self-assembling properties of the gelator were studied in selected nonpolar and polar solvents. It was shown that the driving forces for both types of solvent are the intermolecular hydrogen bond interaction. The effect of the nature of the solvent on the thermal stability of the gels and on the three-dimensional network organization was determined. Different solvent parameters, such as dielectric constant, one-component solubility parameter, the polarity parameter and the Kamlet–Taft parameters were considered to quantify solvent effects on the gelation. Some correlation between these parameters and the gel stability, microstructure and the enthalpy of the phase transition were established. The effort to correlate the Kamlet–Taft parameters to the thermal stability and gelation ability is also possible but applies only to the studied gelator.

Low molecular mass organogelator based gel electrolyte gelated by a quaternary ammonium halide salt for quasi-solid-state dye-sensitized solar cells

Quasi-solid-state dye-sensitized solar cells (DSC) are fabricated using tetradodecylammonium bromide as a low molecular mass organogelator (LMOG) to form gel electrolyte with a high solution-to-gel transition temperature ( T SG) of 75 °C to hinder flow and volatilization of the liquid. The steady-state voltammograms reveal that the diffusion of the I 3 − and I − in the gel electrolyte is hindered by the self-assembled network of the gel. An increased interfacial exchange current density ( j 0) of 4.95 × 10 −8 A cm −2 and a decreased electron recombination lifetime ( τ) of 117 ms reveal an increased electron recombination at the dyed TiO 2 photoelectrode/electrolyte interface in the DSC after gelation. The results of the accelerated aging tests show that the gel electrolyte based dye-sensitized solar cell can retain over 93% of its initial photoelectric conversion efficiency value after successive heating at 60 °C for 1000 h, and device degradation is negligible after one sun light soaking with UV cutoff filter for 1000 h.

Synthesis of reversible fluorescent organogel containing 2-(2′-hydroxyphenyl)benzoxazole: fluorescence enhancement upon gelation and detecting property for nerve gas simulant

A new low molecular mass organogelator 1 containing 2-(2′-hydroxyphenyl)benzoxazole (HPB) group with long alkyl chain was synthesized by the reaction with 5-amino-2-(2′-hydroxy-4′-methylphenyl)benzoxazole and dodecyl isocyanate in THF at room temperature. The reversible gelation ability of 1 was investigated using a heating-cooling method in various organic solvents. The stable organogel was formed from carbon tetrachloride or from cyclohexane at the concentration as low as 0.9%. The self-assembled supramolecular gel structure formed by non-covalent bonding was confirmed with field emission-scanning electron microscope (FE-SEM) exhibiting fibril- or ribbon-shaped structure depending on the solvent used. Regarding the aggregation-induced emission enhancement (AIEE) phenomenon, the optical properties were investigated in its solution and gelled state. The detecting properties of resulting organogel toward nerve gas simulant were monitored by UV–vis and fluorescence spectroscopy. Both color change from colorless to greenish yellow and disruption of gel structure resulting from alteration in intermolecular forces were observed upon the exposure to nerve gas simulant.

Low Molecular Mass Organogelator Based Gel Electrolyte with Effective Charge Transport Property for Long-Term Stable Quasi-Solid-State Dye-Sensitized Solar Cells

Stable quasi-solid-state dye-sensitized solar cells (DSC) were fabricated using 12-hydroxystearic acid as a low molecular mass organogelator (LMOG) to form gel electrolyte. TEM image of the gel exhibited the self-assembled network constructed by the LMOG, which hindered flow and volatilization of the liquid. The formation of less-mobile polyiodide ions such as I 3 (-) and I 5 (-) confirmed by Raman spectroscopy increased the conductivity of the gel electrolytes by electronic conduction process, which should be rationalized by the Grotthuss-type electron exchange mechanism caused by rather packed polyiodide species in the electrolytes. The results of the accelerated aging tests showed that the gel electrolyte based dye-sensitized solar cell could retain over 97% of its initial photoelectric conversion efficiency value after successive heating at 60 degrees C for 1000 h and device degradation was also negligible after one sun light soaking with UV cutoff filter for 1000 h.

1,2- O-(1-Ethylpropylidene)-α- d-glucofuranose, a low molecular mass organogelator: benzene gel formation and their thermal stabilities

Fourier transform infrared spectroscopy has demonstrated that hydrogen bonds are responsible for the aggregation of 1,2- O-(1-ethylpropylidene)-α- d-glucofuranose molecules in solid and benzene gels. The thermal stability of the studied gel is described by its melting temperature T GS and thermal parameters. The deduced value of the gel–sol transition enthalpy is 50 kJ/mol. Viscosity is the major factor which influences the dynamics of the benzene molecules in the gels, as proved by the relaxation measurements.

Synthesis and properties of novel nanocomposites made of single-walled carbon nanotubes and low molecular mass organogels and their thermo-responsive behavior triggered by near IR radiation

For the preparation of novel organogel–carbon nanotube nanocomposites, pristine single-walled carbon nanotubes (SWNT) were incorporated into physical gels formed by an L-alanine based low molecular mass organogelator (LMOG). The gelation process and the properties of the resulting nanocomposites were found to depend on the kind of SWNTs incorporated in the gels. With pristine SWNTs, only a limited amount could be dispersed in the organogels. Attempted incorporation of higher amounts of pristine SWNTs led to precipitation from the gel. To improve their solubility in the gel matrix, a variety of SWNTs functionalized with different aliphatic and aromatic chains were synthesized. Scanning electron microscope images of the nanocomposites showed that the texture and organization of the gel aggregates were altered upon the incorporation of SWNTs. The microstructures of the nanocomposites were found to depend on the kind of SWNTs used. Incorporation of functionalized SWNTs into the organogels depressed the sol to gel transition temperature, with the n-hexadecyl chain functionalized SWNTs being more effective than the n-dodecyl chain functionalized counterpart. Rheological investigations of pristine SWNT containing gels indicated that the flow of nanocomposites became resistant to applied stress at a very low wt% of SWNT incorporation. Again more effective control of flow behavior was achieved with functionalized SWNTs possessing longer hydrocarbon chains. This happens presumably via effective interdigitation of the pendant chains with the fatty acid amides of L-alanine in the gel assembly. Remarkably, using near IR laser irradiation at 1064 nm for a short duration (1 min) at room temperature, it was possible to selectively induce a gel-to-sol phase transition of the nanocomposites, while prolonged irradiation (30 min) of the organogel under identical conditions did not cause gel melting.

Molecular organogels of the sodium salt of ( R)-12-hydroxystearic acid and their templated syntheses of inorganic oxides

( R)-12-Hydroxystearic acid (HSA), a natural product from castor oil, is a well-known low-molecular mass organogelator (LMOG). Here, we demonstrate that the sodium salt of HSA, HSA-S, is an extremely versatile and efficient LMOG. Furthermore, its self-assembled fibrillar networks (SAFINs) in gels with ethanol, benzene, tetrahydrofuran, and dimethyl sulfoxide, as well as the gel of HSA with benzene, are shown to act as templates during the sol–gel polymerization of tetraethyl orthosilicate (TEOS) in the absence or presence of an external catalyst. The templated, fiber-like objects obtained after calcinations have been characterized. The shape of the templated silica is strongly influenced by the catalyst applied. In addition, it has been possible to effect the formation of assemblies of nanoscale objects of Fe 2O 3 and CuO by polymerization of appropriate precursors in HSA-S based gels and in suspensions, respectively, followed by drying and calcination. The procedures employed are efficient and inexpensive protocols to make porous nanomaterials using organogels. Typically, templated syntheses of such materials in organogels have employed less accessible and more structurally complex LMOGs than HSA-S or HSA. Electrostatic interactions via Na + bridges or H-bonding between silicate intermediates and gelator strands are proposed to be a primary driving force for templating.