Nonpolar Organic Solvents Research Articles

Preparation and characterization of ZrO2 nanoparticles capped by trioctylphosphine oxide (TOPO)

Monodisperse ZrO2 nanoparticles capped by trioctylphosphine oxide (TOPO) were prepared in non-aqueous solvent using in-situ synthesis method. Transmission electron microscopy(TEM), X-ray diffraction(XRD), X-ray photoelectron spectrometer(XPS), Fourier transformation infrared spectroscopy (FTIR), and thermogravimetric analysis(TGA) were adopted to characterize and investigate the size, structure, composition, and the binding manners between organic capping agent TOPO and inorganic ZrO2 nanocores of the as-prepared nanoparticles. In addition, the nanoparticles were also studied to determine their solubility and relative stability. The experimental results show that the prepared nanoparticles contain about 25% organic capping shell TOPO, 75% inorganic ZrO2 nanocores, and can be easily dissolved and be stably disersed in nonpolar organic solvents.

Organocatalysis with cysteine derivatives: recoverable and cheap chiral catalyst for direct aldol reactions

Highly enantioselective, recoverable and cheap cysteine derivatives have been developed with improved solubility properties in common, nonpolar organic solvents. The reactions were catalyzed using 5 mol% 1e, and the aldol products could be obtained with up to 99:1 syn/anti ratio and >99% ee. The catalyst could be easily recovered and reused, with only a slight decrease of enantioselectivity observed for five cycles. Catalyst 1e can be efficiently used in large-scale reactions with enantioselectivity being maintained at the same level, which offers great possibility for application in industry. (i) Direct aldol reactions proceeded in 1,2-dichloroethane using simple procedures. (ii) Direct S-acylation of cysteine to give organocatalysts 1a–f can be economically carried out easily in a single step from commercially available sources, with both enantiomers being readily available. (iii) 5 mol% catalyst 1e was sufficient to furnish the aldol products in excellent yields (up to 93%) and enantioselectivities (up to 99%). (iv) Catalyst 1e could be easily recovered and reused, and also can be efficiently used in large-scale reactions with enantioselectivity being maintained at the same level, which offers great possibility for applications in industry.

Ion transfer coupled discrete charging of immobilised gold nanoclusters in polar organic solvents

We herein investigated the counterion-dependent redox charging properties of gold nanocluster films in polar organic solvents. They were found to be in between those demonstrated in polar aqueous and weakly polar/nonpolar organic media, typically characteristic of a significant voltage separation between the first oxidation and reduction dependent on the lipophilicity of electrolyte counterions. The overall process was proposed to be an ion transfer coupled electron transfer reaction, which was thermodynamically limited by the counterion migration at the film/solution interface and kinetically by the diffusion-like electron hopping among MPCs within the film. These data are helpful in understanding why in previous works the counterion-dependent redox charging is evident only in highly polar aqueous media but not in weakly polar or nonpolar organic solvents.

Carboxylic Acid-Directed Clustering and Dispersion of ZrO2 Nanoparticles in Organic Solvents: A Study by Small-Angle X-ray/Neutron Scattering and NMR

The stable dispersion of nanoparticles in organic solvents, essential for their practical application, is often achieved by the grafting of organic dispersants. Good dispersion is usually assumed when a transparent colloidal sol is formed. However, even in such a case, the dispersion may not be in the form of distinct nanoparticles. In this study, zirconia nanoparticles have been modified with a series of carboxylic acids so that they can be dispersed in polar protic/aprotic solvents or nonpolar organic solvents as transparent colloidal sols. The dispersed state in these solvents was characterized by SAXS and SANS. In most cases, the transparent sol consists of “soft” secondary clusters generated from the ZrO2 nanoparticles. The size and fractal structure of the dispersed clusters varied with the acid modifier. Only in the linoleic acid-modified case and with chloroform as the solvent was the ZrO2 dispersed as primary particles. However, the same modification leads to secondary clusters in other solvents,...

Synthesis, electrochemical and spectroelectrochemical properties of highly soluble tetra substituted phthalocyanines with [4-(thiophen-3-yl)-phenoxy

Zinc, oxo-titanium, cobalt, and manganese phthalocyanine derivatives substituted with nonperipheral 3-( tetra[4-(thiophen-3-yl)-phenoxy] moieties have been synthesized and characterized by elemental analysis, IR, 1H NMR spectroscopy, electronic spectroscopy, and mass spectra. The compounds have good solubility in various polar and nonpolar organic solvents and not aggregated (in the same solvents) within a wide concentration range. Electrochemical and spectroelectrochemical measurements exhibit that incorporation redox active metal centers, Co II, Ti IVO and Mn IIIOAc into the phthalocyanine core extend the redox richness of the Pc ring with the reversible metal-based reduction and oxidation couples of the metal centers in addition to the common Pc ring-based electron transfer processes.

Synthesis, characterization, and controlled aggregation of biotemplated polystyrene nanodisks

Cross-linked polystyrene nanodisks were prepared by controlled polymerization of styrene and divinylbenzene in the interior of bicelles, discoidal lipid aggregates. Aggregation behavior of polymer nanodisks was studied in water, organic solvents, and solid phase. Nanodisks form stable dispersions in aqueous solutions of surfactants, such as sodium dodecyl sulfate (SDS). Varying SDS/nanodisk ratio allowed us to control the size of nanodisk aggregates. Nanodisks are readily solubilized in nonpolar organic solvents, such as toluene and carbon tetrachloride, to yield stable monodisperse suspensions. These findings open opportunities for creating nanodisk-based nanocomposite materials. Stable nanodisk suspension in toluene enabled small angle neutron scattering (SANS) measurements. SANS data confirmed the nanodisk diameter and allowed accurate measurement of nanodisk thickness (19.5 ± 1.0 A). In solid phase, nanodisks aggregate in sub-micron platelets.

Multidentate-Protected Colloidal Gold Nanocrystals: pH Control of Cooperative Precipitation and Surface Layer Shedding

Colloidal gold nanocrystals (AuNCs) with broad size tunability and unusual pH-sensitive properties have been synthesized using multidentate polymer ligands. Because they contain both carboxylic functional groups and sterically hindered aliphatic chains, the multidentate ligands can not only reduce gold precursors but also stabilize gold nanoclusters during nucleation and growth. The "as-synthesized" AuNCs are protected by an inner coordinating layer and an outer polymer layer and are soluble in water and polar solvents. When the solution pH is lowered by just 0.6 units (from 4.85 to 4.25), the particles undergo a dramatic cooperative transition from being soluble to insoluble, allowing rapid isolation, purification, and redispersion of the multidentate-protected AuNCs. A surprising finding is that when a portion of the surface carboxylate groups are neutralized by protonation, the particles irreversibly shed their outer polymer layer and become soluble in nonpolar organic solvents. Furthermore, the multidentate polymer coatings are permeable to small organic molecules, in contrast to the tightly packed self-assembled monolayers of alkanethiols on gold. These insights are important in regard to the design of "smart" imaging and therapeutic nanoparticles that are activated by small pH changes in the tumor interstitial space or endocytic organelles.

Formation of self-organized graphene honeycomb films on substrates

Mixing graphene oxide (GO) aqueous solution with tridodecylmethylammonium chloride (TDMAC) aqueous solution has gradually produced a precipitate of a complex of GO and TDMAC. The complex is soluble in many polar and nonpolar organic solvents, including low dielectric nonpolar organic solvents such as toluene and hexane. In addition, thin films cast the complex specified organic solutions under high humidity conditions have honeycomb-like structures with ordered self-organized macropores. Such insulating honeycomb films have become well conductive, when they were treated by the p-toluenesulfonicacid and then reduced by chemicals such as hydrazine or HI acid.

Improving the filtration performance of ZrO 2 membrane in non-polar organic solvents by surface hydrophobic modification

Recently, ceramic membranes have been used increasingly in the treatment of non-polar organic solvents, such as oil purifying. The presence of water in organic solvents leads to membrane fouling, because of the hydrophilic property of ceramic membranes. To improve the filtration performance, surface hydrophobic modification was conducted in this study. ZrO 2 membranes with a mean pore size of 0.2 μm were modified with a self-assembled monolayer of hexadecyltrimethoxysilane (HDTMS). The modified membranes were characterized with FTIR, TGA, SEM, contact angle measurements, and gas permeation tests. The filtration performance of the modified membranes was experimentally studied in the treatment of water-in-oil (W/O) emulsions. All of the characterizations showed that HDTMS was successfully grafted onto the membrane surface and surface modification had little influence on the membrane morphology and pore structure. The filtration results showed that a higher permeate flux and water rejection was obtained with the modified membranes. As a result, surface hydrophobic modification was effective to mitigate membrane fouling. The presented method is important for developing robust membranes with a low level of membrane fouling in the filtration of non-polar organic solvents.

The synthesis and characterization of a side-by-side iron phthalocyanine dimer

The QCA paradigm is one of the approaches to decrease the size scale of computing devices. When molecules are used as QCA cells, they may be able to perform computing at room temperature. This paper describes a novel molecular QCA cell candidate which is a side-by-side iron phthalocyanine dimer, and an investigation of its optical and redox properties. The new dodeca(pentyloxy) substituted side-by-side iron phthalocyanine dimer, along with the octa(pentyloxy) iron phthalocyanine monomer, are soluble in non-polar organic solvents. These compounds were isolated by gel permeation chromatography (GPC) and high-performance liquid chromatography (HPLC) to final purities of 98% and 99%, respectively. The NMR spectra of both compounds in CDCl3 are broad due to aggregation, but become well resolved after the addition of the coordinating solvent pyridine-d5. Addition of pyridine also gives changes in the UV-vis spectra and electrochemical peaks of both monomer and dimer in dichloromethane indicative of axial iron coordination. The electrochemical data indicates the loss of pyridine ligands from the oxidized products of both monomer and dimer. The comproportionation constant of side-by-side phthalocyanine dimer shows that its oxidized and reduced mixed-valence complexes are fairly stable. The dimer is thus a candidate for molecular QCA systems.

Preparation of protein nanoparticles using AOT reverse micelles

Biopolymeric nanoparticles made of protein via cross-linking reaction was prepared using sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle system as a nanoreactor. The prepared ribonuclease A nanoparticles were stably dispersed in aqueous solutions and the size of the nanoparticles was controlled in the range of 6–100 nm with water content in the system. Solvent species formulating the reverse micellar organic phase also can control the nanoparticle size. These effects on the nanoparticle size would be attributed to the dynamic behavior of reverse micelles. In contrast, cytochrome c nanoparticles were stably dispersed in ethanol while completely precipitated in both aqueous solutions and non-polar organic solvents. These findings indicate that a specific interaction of protein with AOT, which depends on the solubilization site of each protein in reverse micelles, is a significant factor to affect the surface properties of protein nanoparticles.

High-quality reduced graphene oxide-nanocrystalline platinum hybrid materials prepared by simultaneous co-reduction of graphene oxide and chloroplatinic acid

Reduced graphene oxide-nanocrystalline platinum (RGO-Pt) hybrid materials were synthesized by simultaneous co-reduction of graphene oxide (GO) and chloroplatinic acid with sodium citrate in water at 80°C, of pH 7 and 10. The resultant RGO-Pt hybrid materials were characterized using transmission electron microscopy (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Platinum (Pt) nanoparticles were anchored randomly onto the reduced GO (RGO) sheets with average mean diameters of 1.76 (pH 7) and 1.93 nm (pH 10). The significant Pt diffraction peaks and the decreased intensity of (002) peak in the XRD patterns of RGO-Pt hybrid materials confirmed that the Pt nanoparticles were anchored onto the RGO sheets and intercalated into the stacked RGO layers at these two pH values. The Pt loadings for the hybrid materials were determined as 36.83 (pH 7) and 49.18% (pH 10) by mass using XPS analysis. With the assistance of oleylamine, the resultant RGO-Pt hybrid materials were soluble in the nonpolar organic solvents, and the dispersion could remain stable for several months.

Relation between the Solution-State Behavior of Self-Assembled Monolayers on Nanoparticles and Dispersion of Nanoparticles in Organic Solvents

The solution-state property of three-dimensional self-assembled monolayers (3D SAMs) on CeO2 nanoparticles (NPs) has been found to seriously affect dispersion of the NPs. The chain length and solvent-dependent changes in the properties of SAMs were investigated by using various n-alkanoic acid SAMs on CeO2 NPs and various nonpolar organic solvents. NMR and DSC were employed to analyze solution-state behavior of the 3D SAMs. A scaling approach on the chain length and the grafting density of the SAMs could characterize the behavior of SAMs in solution: whether the SAMs were swelling or not. The solvent quality (good or poor) for SAMs was also important for the swelling of the SAMs. In addition, the volume of the solvent molecule was also a critical parameter. The swollen SAMs could provide effective repulsion to overcome van der Waals attraction between NPs. Combining our scaling analysis on solution-state behavior of the 3D SAMs and the experimental results of dispersion of the CeO2 NPs, a criterion for the 3D SAMs to obtain well-dispersed surface-modified NPs was proposed.

Simple chiral urea gelators, (R)- and (S)-2-heptylurea: Their gelling ability enhanced by chirality

We present the first report on the synthesis of chiral ureas, (R)- and (S)-2-heptylurea, and their gelling behaviors. The ureas were prepared by the reactions of chiral amines and phenyl carbamate in the presence of triethylamine. On cooling from homogeneous solutions, the chiral ureas form gels in water and various nonpolar organic solvents, such as cyclohexane, toluene, and tetrachloromethane, while the racemate gelatinize only toluene and tetrachloromethane among the solvents we examined. The gelling ability of the enantiomeric urea is higher than the racemate, as the critical gelling concentrations in toluene, for example, were 0.2% and 0.7% (wt/wt), respectively. The enhanced gelling ability of the enantiomeric ureas is due to the 1D supramolecular structure formed during gelation. In contrast, the racemate crystallizes into two-dimensional lamellae, where the (R)- and (S)-2-heptylurea exist alternatingly in a plane (P21/c space group). Powder X-ray diffraction pattern of the enantiomeric urea showed that it has a different crystal lattice from that of the racemate, implying that the steric effect by the methyl group at the chiral center prevents the pure enantiomers from having 2D hydrogen bonding networks, which lead to sheet-like structures for the racemate and the achiral analog. Thus the pure enantiomers self-organize into one-dimensional fibrous structures. The simplicity and the ambidextrous gelling behaviors of the chiral ureas in forming both hydrogels and organogels present numerous possibilities for future applications.

Preparation of cross-linked lipase-coated micro-crystals for biodiesel production from waste cooking oil

A dual modification procedure composed of cross-linking and protein coating with K2SO4 was employed to modify Geotrichum sp. lipase for catalyzing biodiesel production from waste cooking oil. Compared to single modification of protein coating with K2SO4, the dual modification of cross-linking and lipase coating improved catalytic properties in terms of thermostable stability, organic solvent tolerance, pH stability and operational stability in biodiesel production process, although biodiesel yield and initial reaction rate for CLPCMCs were not improved. After five successive batch reactions, CLPCMCs could still maintain 80% of relative biodiesel yield. CLPCMCs retained 64% of relative biodiesel yield after incubation in a pH range of 4–6 for 4h, and 85% of relative biodiesel yield after incubation in a range of 45–50°C for 4h. CLPCMCs still maintained 83% of relative biodiesel yield after both treated in polar organic solvent and non-polar organic solvent for 4h.

Dual-mode of assembly of anthracene-based imidazolium salts both in non-polar organic solvents and in aqueous solution

Amphiphilic anthracene derivatives showed solvent-polarity-dependent fluorescence. Monomer emission and aggregation-induced emission (AIE) were observed in polar and non-polar organic solvents, respectively. AIE became predominant in aqueous solution in the case of hexafluorophosphate as a counter anion.

Synthesis of charged particles in an ultra-low dielectric solvent

A novel method for creating charged polymer particles in non-polar organic solvents is demonstrated. A small amount of an oleophilic tetraalkylammonium tetraphenylborate group is incorporated into a poly(methyl methacrylate) particle to provide ionic groups which dissociate in low permittivity solvents.

Preparation of a self-supporting cell architecture mimic by water channel confined photocrosslinking within a lamellar structured hydrogel

A self-supporting biomimetic chemical hydrogel that can be reversibly swollen in water is described. An aqueous dispersion of a diacrylate end-derivatized PEO-PPO-PEO macromer, a saturated phospholipid, and a zwitterionic co-surfactant self-assembles into a multilamellar-structured physical gel at room temperature as determined by SAXS. The addition of a water soluble PEGDA co-monomer and photoinitiator within the water layers does not alter the self-assembled structure. ATR/FT-IR spectroscopy reveals that photoirradiation initiates the crosslinking between the acrylate end groups on the macromer with the PEGDA, forming a polymeric network within the aqueous domains. The primitive cytoskeleton mimic serves to stabilize the amphiphile bilayer, converting the physical gel into an elastic self-supporting chemical gel. Storage under ambient conditions causes dehydration of the hydrogel to 5 wt % water which can be reversed by swelling in water. The fully water swollen gel (85 wt % water) remains self-supporting but converts to a non-lamellar structure. As water is lost the chemical gel regains its lamellar structure. Incubation of the hydrogel in nonpolar organic solvents that do not dissolve the uncrosslinked lipid component (hexane) allow for swelling without loss of structural integrity. Chloroform, which readily solubilizes the lipid, causes irreversible loss of the lamellar structure.

Resorcinarene amine stabilized nanodiamond dispersions in organic solvents: applications in diamond film growth

Nanodiamonds of widely differing sizes (4 to >100 nm), shapes, and origin could be extracted from aqueous dispersions into toluene by a multidentate resorcinarene amine surfactant, in the absence of any elaborate covalent functionalization or extreme conditions. Resorcinarene amine encapsulated nanodiamonds displayed excellent dispersion stability in non-polar organic solvents for several months. The IR spectral analysis of these extracted and further precipitated nanodiamonds suggests that the carboxylic acid groups present on the nanodiamond surfaces are electrostatically stabilized by the resorcinarene amine surfactant. Such nanodiamond dispersions can also act as nucleation sources for the fabrication of continuous diamond films by CVD growth. Notably, this process resulted in diamond films with better uniformity, smaller grain size and reduced surface roughness when compared to the films prepared with unmodified nanodiamonds as nucleating agents.

Regioisomeric Control Induced by DABCO Coordination to Rotatable Self‐Assembled Bis‐ and Tetraporphyrin α,γ‐Cyclic Octapeptide Dimers

The design and synthesis of two α,γ-cyclic octapeptides decorated with one and two Zn-porphyrin units in their periphery is described. In nonpolar organic solvents the α,γ-cyclic octapeptides quantitatively self-assemble into Zn-bis- or -tetraporphyrin architectures that could act as molecular tweezers. The self-assembly process, however, is not regioselective and affords a mixture of different regioisomers that are involved in chemical exchange processes. The regioisomers with the Zn-porphyrin units positioned in register with respect to each other are proposed to be the less abundant species in the solution mixture. It has been demonstrated that the coordination of 1,4-diazabicyclo[2.2.2]octane (DABCO) to the supramolecular bis- or tetraporphyrin tweezers is an effective way to achieve regioisomeric control of the self-assembled mixture of dimers. Thus, DABCO functions as an external molecular trigger and, when used under strict stoichiometric control with respect to the Zn-porphyrin units, provokes the exclusive formation of self-assembled dimers with a cofacial arrangement of Zn-porphyrin units through the formation of sandwich-type complexes. The use of excess DABCO fragments the sandwich complexes and affords open dimers of high stoichiometry with DABCO molecules axially monocoordinated to the Zn-porphyrin units, probably as a regioisomeric mixture. In the case of Zn-tetraporphyrin tweezers, the ditopic coordination of DABCO at the two binding sites shows a moderate positive cooperativity factor, αP=5. These assemblies have potential applications as light-induced energy and electron-transfer switches regulated by DABCO coordination; such applications would require the introduction of additional chromophores in the cyclic peptide scaffold.