Click Reaction Functionalization of Hydroxylated Nanoparticles by Cyclic Azasilanes for Colloidal Stability in Oilfield Applications

The growing interest in functionalized nanoparticles and their implementation in oilfield applications (e.g., drilling fluids and enhanced oil recovery (EOR)) facilitate the ongoing efforts to improve their chemical functionalization performance in stabilization of water based or hydrocarbon based nanofluids. Cyclic azasilanes (CAS), substituted 1-aza-2-silacyclopentanes, possess a strained 5-member ring structure. Adjacent Si and N atoms in the ring provide opportunity for highly efficient covalent surface functionalization of hydroxylated nanoparticles through a catalyst-free and byproduct-free click reaction. In this work, hydroxylated silica, alumina, diamond, and carbon coated iron core-shell nanoparticles have been studied for monolayer CAS functionalization. Two cyclic azasilanes with different R groups at N atom, such as methyl (CAS-1) and aminoethyl (CAS-2), have been utilized to functionalize nanoparticles. All reactions were found to readily proceed under mild conditions (room temperature, ambient pressure) during 1 - 2 hours of sonication. CAS functionalized adducts of hydroxylated nanoparticles have been isolated and their microstructure, composition, solubility and thermal stability have been characterized. As a result, it has been demonstrated, for the first time, that covalent surface modification with cyclic azasilanes can be extended beyond the previously known porous silicon structures to hydroxylated silica, alumina and carbon nanoparticles. The developed methodology was also shown to provide access to the nanoparticles with the hydrophilic or hydrophobic surface functional groups needed to enable oilfield applications (e.g., EOR, tracers, drilling fluids) that require stable water based or hydrocarbon based colloidal systems.

Bio-inspired Hydroxyapatite/Gelatin Transparent Nanocomposites

Hydroxyapatite(HA)nanoparticles impart outstanding mechanical properties to organicinorganic nanocomposites in bone.Inspired by the composite structure of HA nanoparticles and collagen in bone,a high performance HA/gelatin nanocomposite was first developed.The nanocomposites have much better mechanical properties(elongation at break 29.9%,tensile strength 90.7 MPa,Young’s modulus 5.24 GPa)than pure gelatin films(elongation at break 9.3%,tensile strength 90.8 MPa,Young’s modulus 2.5 GPa).In addition,the composite films keep a high transmittance in visible wavelength range from 0%to 60%of the HA solid content.These differences in properties are attributed to the homogeneous distribution of HA nanoparticles in the gelatin polymer matrix and the strong interaction between the particle surfaces and the gelatin molecules.This protocol should be promising for HA-based nanocomposites with enhanced mechanical properties for biomedical applications.

Tumor-targeting intravenous lipid emulsion of paclitaxel:Characteristics,stability,toxicity,and toxicokinetics

Lipid nanoemulsions are promising nanodrug delivery carriers that can improve the efficacy and safety of paclitaxel(PTX).However,no intravenous lipid emulsion of PTX has been approved for clinical treatment,and systemic safety profiles have not yet been reported.Here we outline the development of a PTXloaded tumor-targeting intravenous lipid emulsion(PTX Emul)and describe its characteristics,colloidal stability,and systemic safety profiles in terms of acute toxicity,long-term toxicity,and toxicokinetics.We also compare PTX Emul with conventional PTX injection.Results showed that PTX Emul exhibited an ideal average particle size(approximately 160 nm)with narrow size distribution and robust colloidal stability under different conditions.Hypersensitivity reaction and hemolysis tests revealed that PTX Emul did not induce hypersensitivity reactions and had no hemolytic potential.In addition,where the alleviated systemic toxicity of PTX Emul may be attributed to the altered toxicokinetic characteristics in beagle dogs,including the decreased AUC and increased plasma clearance and volume of distribution,PTX Emul alleviated acute and long-term toxicity as evidenced by the enhanced the median lethal dose and approximate lethal dose,moderate body weight change,decreased bone marrow suppression and organ toxicity compared with those under PTX injection at the same dose.A fundamental understanding of the systemic safety profiles,high tumor-targeting efficiency,and superior antitumor activity in vivo of PTX Emul can provide powerful evidence of its therapeutic potential as a future treatment for breast cancer.

Aqueous Preparation of Highly Dispersed Hydroxyapatite Nanorods for Colloidal Liquid Crystals

Hydroxyapatite(HA)nanorods were synthesized using a citrate-assisted hydrothermal method.NaH2PO4,Na2HPO4,and Na3PO4 were used as the phosphate sources and the influences of pH value were investigated.The XRD results show that pure hexagonal HA can be synthesized using Na3PO4·12H2O as the phosphate source with the citrate solution pH ranging from 5.0 to 7.6.The zeta potential evaluation demonstrates that as-synthesized HA nanorods are colloidally stable and the aqueous dispersion can be maintained homogenous without any sediment or creaming for more than at least a month.The Ca/P molar ratio of the HA nanorods is about 1.60,indicating that the HA nanorods are calcium-deficient hydroxyapatite.Besides,owing to the excellent colloidal stability and rod-like morphology with a high aspect ratio(>6),the HA aqueous dispersion undergoes a phase transition from an isotropic state to a liquid crystalline state upon increasing the particle concentration to 17wt%.The completely liquid crystalline phase forms when the particle concentration reaches above 30wt%.

Preparation and cellular uptake behaviors of uniform fiber-like micelles with length controllability and high colloidal stability in aqueous media

Fragmentation/disassembly of fiber-like micelles generated by living crystalline-driven self-assembly(CDSA)is usually encountered in aqueous media,which hinders the applications of micelles.Herein,we report the generation of uniform fiber-like micelles consisting of a𝜋Л-conjugated oligo(p-phenylenevinylene)core and a crosslinking silica shell with grafted poly(ethylene glycol)(PEG)chains by the combination of living CDSA,silica chemistry and surface grafting-onto strategy.Owing to the presence of crosslinking silica shell and the outmost PEG chains,the resulting micelles exhibit excellent dispersity and colloidal stability in PBS buffer,BSA aqueous solution and upon heating at 80℃ for 2 h without micellar fragmentation/disassembly.The micelles also show negligible cytotoxicity toward both HeLa cervical cancer and HEK239T human embryonic kidney cell lines.Interestingly,micelles with Ln of 156 nm show the“stealth”property with no significant uptake by HeLa cells,whereas some certain amounts of micelles with Ln of 535 nm can penetrate into HeLa cells,showing length-dependent cellular uptake behaviors.These results provide a route to prepare uniform,colloidally stable fiber-like nanostructures with tunable length and functions derived for biomedical applications.

Stable PbS colloidal quantum dot inks enable blade‑coating infrared solar cells

Infrared solar cells are more efective than normal bandgap solar cells at reducing the spectral loss in the near-infrared region,thus also at broadening the absorption spectra and improving power conversion efciency.PbS colloidal quantum dots(QDs)with tunable bandgap are ideal infrared photovoltaic materials.However,QD solar cell production sufers from small-areabased spin-coating fabrication methods and unstable QD ink.Herein,the QD ink stability mechanism was fully investigated according to Lewis acid–base theory and colloid stability theory.We further studied a mixed solvent system using dimethylformamide and butylamine,compatible with the scalable manufacture of method-blade coating.Based on the ink system,100 cm2 of uniform and dense near-infrared PbS QDs(~0.96 eV)flm was successfully prepared by blade coating.The average efciencies of above absorber-based devices reached 11.14%under AM1.5G illumination,and the 800 nm-fltered efciency achieved 4.28%.Both were the top values among blade coating method based devices.The newly developed ink showed excellent stability,and the device performance based on the ink stored for 7 h was similar to that of fresh ink.The matched solvent system for stable PbS QD ink represents a crucial step toward large area blade coating photoelectric devices.

Preparation of Sr-substituted Hydroxyapatite Nanorods for Liquid Crystal Phase Transition

A citrate-assisted hydrothermal method was utilized for the preparation of Sr-substituted hydroxyapatite (HA) nanoparticles.The influences of Sr-substituting degree on the phase identifications,microstructures and colloidal stability of the resultant products were studied.The experimental results show that the crystalline structures and morphologies of final resultants are significantly changed by controlling the Sr-substituting degree.As the Sr-substituting degree increases,the colloidal stability of samples first increases and then decreases rapidly;the morphology of the product first changes from nanorods to short nanorods rod and then becomes nanowires.Uniform HA hexagonal nanorods with high aspect ratio (>4.0) and excellent aqueous colloidal stability were prepared by 6 h hydrothermal reaction at 180℃ without Sr substitution.The dispersion underwent the phase transition from isotropic to liquid-crystalline state upon the increasing concentration of25wt% and the complete liquid-crystalline phase was achieved when at the concentration above 31wt%.These novel findings provide new insights into the role of Sr substitution on both the citrate-assisted hydroxyapatite crystallization and tailoring of colloidal stability.Moreover,HA liquid crystal behavior was successfully observed,which lays a foundation for the fabrication of macroscopically assembled hydroxyapatite-based biomimetic materials for biomedical applications.

Evaluation of Influence of Multiple Scattering Effect in Light-Scattering-Based Applications

The extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The necessity of the correction of the refractive indices of water and polystyrene for different incident wavelengths is particularly addressed in the calculation. By this means, the volume fractions allowed for certain accuracy requirements of single-scattering approximation in the light scattering experiment can be evaluated. The volume fractions calculated with corrected refractive indices are compared with those obtained with fixed refractive indices which have been rather commonly used, showing that fixed refractive indices may cause significant error in evaluating multiple scattering effect. The results also give a simple criterion for selecting the incident wavelength and particle size to avoid the ＇blind zone＇ in the turbidity measurement, where the turbidity change is insensitive to aggregation of two particles.

Improving the colloidal stability of Cellulose nano-crystals by surface chemical grafting with polyacrylic acid

Cellulose nano-crystals(CNC)can be tailored for various value-added applications.However,its use in aqueous systems is hampered by its limited dispersability,especially at a high CNC concentration.In this study,the improvement of CNC colloidal stability by surface chemical grafting with polyacrylic acid(PAA)was investigated,and the zeta potential and the charge density of the chemically modified CNC were analyzed.The results showed that an acrylic dosage of 1%(based on the dry weight of CNC)was sufficient to significantly enhance the colloidal stability.CNC,after chemical grafting with PAA,showed better stability against the increase in storage time or solid content of the aqueous medium,compared with the un-modified CNC.

Efficient flexible perovskite solar cells and modules using a stable SnO_(2)-nanocrystal isopropanol dispersion

The outstanding advantages of lightweight and flexibility enable flexible perovskite solar cells(PSCs)to have great application potential in mobile energy devices.Due to the low cost,low-temperature processibility,and high electron mobility,SnO_(2) nanocrystals have been widely employed as the electron transport layer in flexible PSCs.To prepare high-quality SnO_(2) layers,a monodispersed nanocrystal solution is normally used.However,the SnO_(2) nanocrystals can easily aggregate,especially after long periods of storage.Herein,we develop a green and cost-effective strategy for the synthesis of high-quality SnO_(2) nanocrystals at low temperatures by introducing small molecules of glycerol,obtaining a stable and well-dispersed SnO_(2)-nanocrystal isopropanol dispersion successfully.Due to the enhanced dispersity and super wettability of this alcohol-based SnO_(2)-nanocrystal solution,large-area smooth and dense SnO_(2) films are easily deposited on the plastic conductive substrate.Furthermore,this contributes to effective charge transfer and suppressed non-radiative recombination at the interface between the SnO_(2) and perovskite layers.As a result,a greatly enhanced power conversion efficiency(PCE)of 21.8%from 19.2%is achieved for small-area flexible PSCs.A large-area 5 cm×5 cm flexible perovskite solar mini-module with a champion PCE of 16.5%and good stability is also demonstrated via this glycerol-modified SnO_(2)-nanocrystal isopropanol dispersion approach.

Nanofluids:Stability,phase diagram,rheology and applications

There is no doubt about the potential technological significance of nanofluids. The promising application areas have been identified as effective heat transfer fluids, contrast agents in magnetic resonance imaging, magnetohyperthermia treatment, precursors to high performance nanocomposites and ordered nanostructures. However, commercial applications are rare, in part due to the limited understanding of the nanofluid fundamentals such as colloid stability, phase diagrams and rheology. This paper intends to provide a brief overview of the scientific disciplines that are important to nanofluids, and the interconnection among different disciplines in order to gain a perspective on the future development of this intriguing area.

Study of asphaltene reaggregation in toluene/heptane mixture by dynamic and static light scattering

This paper presents the study of the effect of multiple ultrasonic impacts on submicron asphaltene aggregates in a toluene/heptane solution,conducted with dynamic light scattering technique.The objects of the study were four samples of asphaltenes obtained from four different oils.For all samples,the change in the average size of the asphaltene submicron aggregates with time was measured after the addition of a precipitant(heptane)to a solution of asphaltenes in toluene at an amount above the threshold concentration.Asphaltene aggregates formed in solution after the addition of the precipitant and were subjected to ultrasonic treatment,which led to the destruction of the asphaltene aggregates.Aggregation of destroyed asphaltenes was observed.The kinetics of this aggregation were similar to the kinetics of aggregation of asphaltenes after the addition of a precipitant.Multiple iterations of asphaltene aggregate destruction in the sample led to a significant change in the kinetics of aggregation:the growth of aggregates slowed and stabilized at a size of approximately 200 nm and 30 nm for the different studied samples.

Colloidal lead-free Cs_(2)AgBiBr_(6)double perovskite nanocrystals:Synthesis,uniform thin-film fabrication,and application in solution-processed solar cells

Recently developed lead-free double perovskite nanocrystals(NCs)have been proposed for the possible application in solutionprocessed optoelectronic devices.However,the optoelectronic applications of double perovskite NCs have been hampered due to the structural and chemical instability in the presence of polar molecules.Here,we report a facile strategy for the synthesis and purification of Cs_(2)AgBiBr_(6)double perovskite NCs that remained stable even after washing with polar solvent.This is realized with our efficient colloidal route to synthesize Cs_(2)AgBiBr_(6)NCs that involve stable and strongly coordinated precursor such as silvertrioctyl phosphine complex together with bismuth neodecanoate,which leads to a significantly improved chemical and colloidal stability.Using layer-by-layer solid-state ligand exchange technique,a compact and crack-free thin film of Cs_(2)AgBiBr_(6)NCs were fabricated.Finally,perovskite solar cells consisting of Cs_(2)AgBiBr_(6)as an absorber layer were fabricated and tested.

Preparation of stable colloidal suspensions of superdisintegrants via wet stirred media milling

Superdisintegrants are cross-linked polymers that can be used as dispersants for fast release of drug nanoparticles from nanocomposite microparticles during in vitro and in vivo dissolution. Currently avail- able superdisintegrant particles have average sizes of approximately 5-130 μm, which are too big for drug nanocomposite applications. Hence, production of stable superdisintegrant suspensions with less than 5 μm particles is desirable. Here, we explore the preparation of colloidal suspensions of anionic and nonionic superdisintegrants using a wet stirred media mill and assess their physical stability. Sodium starch glycolate （SSG） and crospovidone （CP） were selected as representative anionic and nonionic superdisintegrants, and hydroxypropyl cellulose （HPC） and sodium dodecyl sulfate （SDS） were used as a steric stabilizer and a wetting agent/stabilizer, respectively. Particle sizing, scanning electron microscopy, and zeta potential measurements were used to characterize the suspensions. Colloidal superdisintegrant suspensions were prepared reproducibly. The extensive particle breakage was attributed to the swelling-induced softening in water. SSG suspensions were stable even in the absence of stabilizers, whereas CP suspensions required HPC-SDS for minimizing particle aggregation. These findings were explained by the higher absolute （negative） zeta potential of the suspensions of the anionic superdisintegrant （SSG） as compared with those of the nonionic superdisintegrant （CP）.

Flexible synthesis of high-purity plasmonic assemblies

The self-assembly of nanoparticles has attracted a vast amount of attention due to the ability of the nanostructure to control light at the sub-wavelength scale,along with consequent strong electromagnetic field enhancement.However,most approaches developed for the formation of discrete assemblies are limited to a single and homogeneous system,and incorporation of larger or asymmetrical nanoparticles into assemblies with high purity remains a key challenge.Here,a simple and versatile approach to assemble nanoparticles of different sizes,shapes,and materials into various discrete homo-or hetero-structures using only two complementary deoxyribonucleic acid(DNA)strands is presented.First,surface functionalisation using DNA and alkyl-polyethylene glycol(PEG)enables transformation of as-synthesised nanoparticles into readily usable plasmonic building blocks for self-assembly.Optimisation of the DNA coverage enables the production of different assembly types,such as homo-and hetero-dimers,trimers and tetramers and core-satellite structures,which are produced in high purity using electrophoresis purification.The approach is extended from purely plasmonic structures to incorporate(luminescent)semiconductor nanoparticles for formation of hybrid assemblies.The deposited assemblies form a high yield of specific geometrical arrangements,attributed to the van der Waals attraction between particles.This method will enable the development of new complex colloidal nanoassemblies for biological and optical applications.

Interaction between Cu^(2+) and different types of surface-modified nanoscale zero-valent iron during their transport in porous media

This study investigated the interaction between Cu^2＋and nano zero-valent iron（NZVI）coated with three types of stabilizers（i.e., polyacrylic acid [PAA], Tween-20 and starch） by examining the Cu^2＋ uptake, colloidal stability and mobility of surface-modified NZVI（SM-NZVI） in the presence of Cu^2＋. The uptake of Cu^2＋ by SM-NZVI and the colloidal stability of the Cu-bearing SM-NZVI were examined in batch tests. The results showed that NZVI coated with different modifiers exhibited different affinities for Cu^2＋, which resulted in varying colloidal stability of different SM-NZVI in the presence of Cu^2＋. The presence of Cu^2＋ exerted a slight influence on the aggregation and settling of NZVI modified with PAA or Tween-20. However, the presence of Cu^2＋caused significant aggregation and sedimentation of starch-modified NZVI, which is due to Cu^2＋complexation with the starch molecules coated on the surface of the particles. Column experiments were conducted to investigate the co-transport of Cu^2＋ in association with SM-NZVI in water-saturated quartz sand. It was presumed that a physical straining mechanism accounted for the retention of Cu-bearing SM-NZVI in the porous media. Moreover, the enhanced aggregation of SM-NZVI in the presence of Cu^2＋ may be contributing to this straining effect.

Adsorption of Ca2+on single layer graphene oxide

Graphene oxide（GO） holds great promise for a broad array of applications in many fields,but also poses serious potential risks to human health and the environment.In this study,the adsorptive properties of GO toward Ca^（2＋） and Na＋were investigated using batch adsorption experiments,zeta potential measurements,and spectroscopic analysis.When pH increased from 4 to 9,Ca^（2＋）adsorption by GO and the zeta potential of GO increased significantly.Raman spectra suggest that Ca^（2＋）was strongly adsorbed on the GO via –COO Ca~＋ formation.On the other hand,Na＋was adsorbed into the electrical diffuse layer as an inert counterion to increase the diffuse layer zeta potential.While the GO suspension became unstable with increasing pH from 4 to 10 in the presence of Ca^（2＋）,it was more stable at higher pH in the NaC l solution.The findings of this research provide insights in the adsorption of Ca^（2＋）on GO and fundamental basis for prediction of its effect on the colloidal stability of GO in the environment.