Colloidal Carbon Research Articles

Efficient preparation of monodisperse CaCO3 nanoparticles as overbased nanodetergents in a high-gravity rotating packed bed reactor

The preparation of oil-soluble metal carbonate colloids is of interest in the area of lubricant additives. This study presents a novel mass-transfer intensified approach for efficient preparation of monodisperse CaCO3 nanoparticles as overbased nanodetergents based on W/O microemulsion using a high-gravity rotating packed bed (RPB) reactor. The effects of high gravity level, gas-liquid ratio, gas and liquid flow rates were systematically investigated. The as-prepared products had good transparency, an average particle size of about 6nm, a high storage stability of over 18months, a solid content of 38.5wt% and a highest total base number (TBN) of 417 mgKOH/g. As compared to conventional stirring tank reactor (STR), the product prepared in the RPB reactor had better monodispersity and stability, smaller average particle size, narrower size distribution and higher TBN. Furthermore, the RPB reactor had a greatly shortened carbonation reaction time from 120min of STR to 53min, increasing the production efficiency by about 56%.

Impacts of coagulation-flocculation treatment on the size distribution and bioavailability of trace metals (Cu, Pb, Ni, Zn) in municipal wastewater

This study investigated the impact of coagulation-flocculation treatment on metal form and bioavailability in municipal wastewater. Real humus effluent samples were separated into particulate, colloidal and truly dissolved fractions before and after treatment with either ferric chloride (FeCl3) or the biopolymer Floculan. Results revealed that both reagents effectively (≥48%) eliminated Cu, Pb and Zn from the particulate fraction and removed Cu and Zn from the colloidal fraction in conjunction with colloidal organic carbon (COC). Although organics in the truly dissolved fraction were resistant to removal, Floculan reduced Cu in this fraction by 72% owing to the complexation of free Cu ions to phenol and amino groups along the polymeric chains, revealing an additional removal pathway. In fact, COC removed in the CF process by Floculan was replaced with truly dissolved compounds, input as a result of this reagents organic composition. Floculan, therefore, reduced the soluble concentration of Cu and Zn without changing the DOC concentration, thus reducing the bioavailability of these metals in treated effluent. FeCl3 did not reduce the bioavailability of target metals, thus did not deliver any environmental benefit. This work provides important information for the selection and development of high performance coagulants to improve metal removal.

Flexible, Three-Dimensional Ordered Macroporous TiO2 Electrode with Enhanced Electrode–Electrolyte Interaction in High-Power Li-Ion Batteries

A simple methodology is developed for the in-situ preparation of flexible, three-dimensional ordered macroporous (3DOM) TiO₂ electrodes with greatly enhanced mass transfer. The 3DOM electrode is fabricated using a polystyrene colloidal crystal templated carbon cloth, and provides significant improvements over conventional nanoparticle electrodes without the use of binder or other additive. When evaluated as an anode in a Li-ion battery, the 3DOM electrode provides outstanding high rate performance. The electrode provides a specific capacity of 174 mAh g-1 at a current density of 2 A g-1, which is 2.6 times greater than that achieved with a nanoparticle electrode (68 mAh g-1). The 3DOM electrode also achieves excellent cycling stability, with a capacity retention of 94.8% (181 mAh g-1) over 1000 cycles at 10C (1.7 A g-1) compared to 93.7% (67 mAh g-1) for the nanoparticle electrode. To the best of our knowledge, the performance of our 3DOM electrode is among the highest of binder-free, flexible TiO₂ electrodes. We believe that this methodology is highly useful and is easily transferable to other materials and applications.

Preparation of carbon nanospheres/Fe3O4 composites and their supercapacitor performances

Colloidal carbon spheres were synthesized with hydrothermal method by taking glucose as raw material. By using colloidal carbon spheres as carbon precursor and ferrocene as iron source, a series of carbon nanospheres/Fe3O4 composites with different Fe3O4 contents were prepared under high temperature condition. The structure of composites was analyzed by X-ray diffraction and scanning electron microscope. The electrochemical performances of composites were analyzed by cyclic voltammetry, galvanostatic charge–discharge, alternating current impedance and cycle-life testing. The study results showed that Fe3O4 nanoparticles are successfully attached to the carbon nanospheres. The composites have excellent energy storage capacity, high charge–discharge efficiency and well cycle stability.

Fluorescence Characterization of Fractionated Colloids in Wastewaters Received by Huangpu River

The spectral characteristics of fractionated colloids in wastewaters from Huangpu River were isolated and investigated via cross flow ultrafiltration systems with different molecular mass of membranes and three-dimensional excitation-emission matrix fluorescence spectroscopy. The results showed that the colloidal concentration (CC) and colloidal organic carbon content (COC) of all size fractions in all samples were in the ranges 9.60-32.50 mg·L-1 and 0.03-6.25 mg·L-1, respectively. Moreover, both CC and COC values increased as the colloidal size increased. The protein- (i.e., peaks D and T) and humic-like (peaks C and A) materials were present in all the size fractions (except for the Mr 300×103-1 μm size fraction of the influent sample), of which protein- and humic-like materials were mainly in the Mr 1×103-5×103 and Mr 10×103-300×103 size fractions, respectively. In addition, fluorescence indices (including the fluorescence index (FI), humification index (HIX), and the index of recent autochthonous contribution (BIX)) were introduced to determine the source and spectral characteristic of the selected colloids. These indices indicated that the relatively small colloids with high aromaticity and hydrophobicity mainly originated from terrestrial sources, whereas the relatively large colloids were predominantly from the recent autochthonous organic matter and the protein-like components.

Removal of Cationic Neutral Red Dye from Aqueous Solutions using Natural and Modified Rice Straw

Modified colloidal carbons were prepared by reacting colloidal carbon obtained from rice straw with thermal oxidation, nitric acid and urea treatment. The textural and chemistry characteristics of the surface of non-modified and modified carbons were obtained from nitrogen adsorption at -196oC, elemental analysis and fourier transform infrared (FTIR) techniques. The uptake of cationic neutral red (NR) dye from aqueous solutions by these carbons was determined by kinetic and equilibrium experiments. The surface area and the total pore volume decreased, whereas the pore radius increased after the treatment with nitric acid.The surface pH of un–modified carbon was basic while those of modified carbons were acidic. Urea treated carbons with the lowest acidic character and high nitrogen content presented the lowest NR dye uptake capacity. The maximum removal of NR dye was obtained at a pH of 4. The amount of adsorption by the investigated carbons was found to depend on the amount of surface acidity. The adsorption results were analyzed considering Langmuir, Freundlich and Dubinin-Radushkevich(D-R) models. The adsorption of NR dye onto the assessed adsorbents is of the physical sorption type following pseudo – first – order kinetic.Nitric acid modification brought about a significant rise in NR dye adsorption which was ascribed to the formation of oxygen containing acidic groups on the surface of adsorbent.The equilibrium adsorption data of NR dye were well fitted with Langmuir and D-R models.

Efficient synthesis of hollow silica microspheres useful for porous silica ceramics

Abstract Hollow silica microspheres (HSMs) have been successfully synthesized in large quantities using colloidal carbon spheres (CCSs) as template, cetyltrimethylammonium bromide (CTAB) as modifying agent and tetraethylorthosilicate (TEOS) as silicon source. The CCSs are fabricated by a simple hydrothermal treatment of D -glucose, which exhibit well monodisperse and homogeneous in dimension. The CTAB effectively modifies the surface charge characteristics of CCSs, which provides a favorable circumstance for the deposition of TEOS hydrolysis products. The HSMs can be eventually obtained after CCSs and CTAB being removed by sintering. The as-prepared HSMs are nearly uniform in dimension with particle size of about 500 nm. Porous silica ceramics with a three-dimensional network structure is prepared using these HSMs as raw material. Such ceramics possesses low density and dielectric constant, which make it very potential in the application of lightweight or low dielectric materials.

Light-Driven Au-WO3@C Janus Micromotors for Rapid Photodegradation of Dye Pollutants

A novel light-driven Au-WO3@C Janus micromotor based on colloidal carbon WO3 nanoparticle composite spheres (WO3@C) prepared by one-step hydrothermal treatment is described. The Janus micromotors can move in aqueous media at a speed of 16 μm/s under 40 mW/cm2 UV light due to diffusiophoretic effects. The propulsion of such Au-WO3@C Janus micromotors (diameter ∼ 1.0 μm) can be generated by UV light in pure water without any external chemical fuels and readily modulated by light intensity. After depositing a paramagnetic Ni layer between the Au layer and WO3, the motion direction of the micromotor can be precisely controlled by an external magnetic field. Such magnetic micromotors not only facilitate recycling of motors but also promise more possibility of practical applications in the future. Moreover, the Au-WO3@C Janus micromotors show high sensitivity toward extremely low concentrations of sodium-2,6-dichloroindophenol (DCIP) and Rhodamine B (RhB). The moving speed of motors can be significantly accelerated to 26 and 29 μm/s in 5 × 10-4 wt % DCIP and 5 × 10-7 wt % RhB aqueous solutions, respectively, due to the enhanced diffusiophoretic effect, which results from the rapid photocatalytic degradation of DCIP and RhB by WO3. This photocatalytic acceleration of the Au-WO3@C Janus micromotors confirms the self-diffusiophoretic mechanism and opens an opportunity to tune the motility of the motors. This work also offers the light-driven micromotors a considerable potential for detection and rapid photodegradation of dye pollutants in water.

Nanomaterial Based Biosensors for Detection of Biomarkers of Exposure to OP Pesticides and Nerve Agents: A Review

AbstractOrganophosphorus (OP) pesticides are primarily used as insecticides and chemical warfare agents worldwide. Due to their impact on the environment and health, it is important to develop prompt and accurate pesticide analysis method. This review addresses recent advances and new trends in nanotechnology‐based biosensors for biological monitoring of exposures to OP pesticides and nerve agents. In order to determine them, we have to find the corresponding biomarkers. In 1989, the national academy of sciences (NAS)divided biomarkers into the following three categories: biomarker of exposure, biomarker of effect and biomarker of susceptibility (Figure 1A). The unique chemical and physical properties of nanomaterial have paved the way to new and improved sensing devices, in general, and electrochemical/optical biosensors, in particular. In this paper, background information and a general overview of electrochemical/immunoassay detection techniques are provided. Various nanomaterial labels are discussed. Usually nanomaterials can be roughly divided into nanometer powder, nanometer fiber, nanometer film, nanometer block and so on four classes, such as colloidal gold, semiconductor nanoparticles and carbon nanomaterial (Figure 1B). In addition, we discuss some future considerations and opportunities for advancing the use of biosensors for environmental and health studies.

Design and construction of a new optical solid-state mercury(ii) sensor based on PVC membrane sensitized with colloidal carbon dots

A new Hg2+ ion solid-state double layer sensor impregnated with colloidal carbon dots and N′-(3-(4-(dimethylamino)phenyl)allylidene)isonicotinohydrazide (NDPAI, as a second layer) was inserted in plasticized polyvinyl chloride (PVC) as the first layer.

Nonlinear Optical Characteristics of Colloidal Carbon Nanoparticles According to their Concentration

Nonlinear Optical Characteristics of Colloidal Carbon Nanoparticles According to their Concentration

Effects of a controlled freeze-thaw event on dissolved and colloidal soil organic matter.

This study investigated the effects of the freezing and thawing that accompany the warming process on the composition of the soil organic matter in the dissolved and colloidal fractions. Temperate soil samples were incubated in a refrigerator at 2°C for 4weeks and compared with those frozen at -20°C in the second week followed by thawing at 2°C to study a freeze-thaw effect with minimal effect from the thawing temperature. The freeze-thaw group was compared with those incubated at 25°C in the last week to investigate a warming effect after thawing. Thawing at 2°C after freezing at -20°C increased the dissolved organic carbon (DOC), but decreased colloidal Ca. The subsequent warming condition greatly increased both DOC and colloidal Ca. The colloidal organic carbon (COC) and dissolved Ca showed rather subtle changes in response to the freeze-thaw and warming treatments compared to the changes in DOC and colloidal Ca. The fluorescence excitation-emission matrix (EEM) and Fourier transformation-infrared spectrometry (FT-IR) results showed that the freeze-thaw and warming treatments gave the opposite effects on the compositions of dissolved humic-like substances, polysaccharides or silicates, and aliphatic alcohols. A principal component analysis (PCA) with the DOC, fluorescence EEM, and FT-IR spectra produced two principal components that successfully distinguished the effects of the freeze-thaw and warming treatments. Due to the contrasting effects of the freeze-thaw and warming treatments, the overall effects of freeze-thaw events in nature on the dissolved and colloidal soil organic matter could vary depending on the thawing temperature.

Flexible, Three-Dimensional Ordered Macroporous TiO2 Electrode with Enhanced Electrode-Electrolyte Interaction in High-Power Li-Ionbatteries

A simple methodology is developed for the in-situ preparation of flexible, three-dimensional ordered macroporous (3DOM) TiO₂ electrodes with greatly enhanced mass transfer. The 3DOM electrode is fabricated using a polystyrene colloidal crystal templated carbon cloth, and provides significant improvements over conventional nanoparticle electrodes without the use of binder or other additive. When evaluated as an anode in a Li-ion battery, the 3DOM electrode provides outstanding high rate performance. The electrode provides a specific capacity of 174 mAh g-1 at a current density of 2 A g-1, which is 2.6 times greater than that achieved with a nanoparticle electrode (68 mAh g-1). The 3DOM electrode also achieves excellent cycling stability, with a capacity retention of 94.8% (181 mAh g-1) over 1000 cycles at 10C (1.7 A g-1) compared to 93.7% (67 mAh g-1) for the nanoparticle electrode. To the best of our knowledge, the performance of our 3DOM electrode is among the highest of binder-free, flexible TiO₂ electrodes. We believe that this methodology is highly useful and is easily transferable to other materials and applications.

SnO2/polypyrrole hollow spheres with improved cycle stability as lithium-ion battery anodes

SnO2/polypyrrole (SnO2/PPy) hollow spheres were fabricated by a liquid-phase deposition method using colloidal carbon spheres as templates followed by an in-situ chemical-polymerization route. The obtained SnO2/PPy composite particles had a size of 610–730 nm. The thickness of inner shell (SnO2) and outer shell (PPy) for composites was about 35 and 90 nm, respectively. As an anode for lithium ion batteries, the SnO2/PPy composites electrode showed superior rate capability and excellent long-term cycling performance. After a long-term cycling of 600 cycles at different current densities, a capacity of 899 mAh g−1 was achieved at the current density of 100 mA g−1 for SnO2/PPy composites. The excellent electrochemical performance was attributed to the synergistic effect between the PPy coating layer and the hollow SnO2 spheres, which guaranteed vast lithium storage sites, good electronic conductivity, fast lithium ion diffusion, and sufficient void space to buffer the volume expansion.

Nonlinear optical effects in colloidal carbon nanohorns—a new optical limiting material

Many carbon based nanomaterials exhibit nonlinear optical response over a large wavelength range when irradiated with intense laser light what makes them promising candidates for optical limiting purposes. Besides nonlinear absorption some of these well studied nanostructures like carbon nanotubes or carbon black owe their prominent limiting efficiency particularly to induced nonlinear scattering. In this paper, our investigations on carbon nanohorns are presented—a new and very promising nonlinear optical material. It offers excellent properties like a low optical limiting threshold and a high nonlinear attenuation when tested with nanosecond laser pulses at wavelengths of 532 nm or 1064 nm. At moderate irradiation levels near the nonlinear threshold our measurements performed on colloidal carbon nanohorns reveal broadband nonlinear absorption as the dominant optical limiting effect. Towards higher irradiation levels significant nonlinear scattering takes place as a secondary process. In contrast to 532 nm, at 1064 nm nonlinear scattering is less strong even at high irradiation levels and the nonlinear response is dominated by nonlinear absorption.

Point-of-care detection of extracellular vesicles: Sensitivity optimization and multiple-target detection

Extracellular vesicles (EVs) are membrane-bound nanovesicles delivered by different cellular lineages under physiological and pathological conditions. Although these vesicles have shown relevance as biomarkers for a number of diseases, their isolation and detection still has several technical drawbacks, mainly related with problems of sensitivity and time-consumed. Here, we reported a rapid and multiple-targeted lateral flow immunoassay (LFIA) system for the detection of EVs isolated from human plasma. A range of different labels (colloidal gold, carbon black and magnetic nanoparticles) was compared as detection probe in LFIA, being gold nanoparticles that showed better results. Using this platform, we demonstrated that improvements may be carried out by incorporating additional capture lines with different antibodies. The device exhibited a limit of detection (LOD) of 3.4×106EVs/µL when anti-CD81 and anti-CD9 were selected as capture antibodies in a multiple-targeted format, and anti-CD63 labeled with gold nanoparticles was used as detection probe. This LFIA, coupled to EVs isolation kits, could become a rapid and useful tool for the point-of-care detection of EVs, with a total analysis time of two hours.

The electric conductivity of composites based on various carbonaceous fillers and estimation of their percolation model parameters

We have studied the electric conductivity of composites with various carbonaceous fillers (multiwalled carbon nanotubes, colloidal graphite, and amorphous carbon) as a function of the filler content. The widths of critical regions of the percolation transition to the conducting state are determined and the percolation critical exponents are estimated. It is established that there is a tendency to increase in the width of transition region and values of critical exponents when the filler is varied in the following order: carbon nanotubes–colloidal graphite–amorphous carbon.

Multi-functionality Redefined with Colloidal Carotene Carbon Nanoparticles for Synchronized Chemical Imaging, Enriched Cellular Uptake and Therapy.

Typically, multiplexing high nanoparticle uptake, imaging, and therapy requires careful integration of three different functions of a multiscale molecular-particle assembly. Here, we present a simpler approach to multiplexing by utilizing one component of the system for multiple functions. Specifically, we successfully synthesized and characterized colloidal carotene carbon nanoparticle (C3-NP), in which a single functional molecule served a threefold purpose. First, the presence of carotene moieties promoted the passage of the particle through the cell membrane and into the cells. Second, the ligand acted as a potent detrimental moiety for cancer cells and, finally, the ligands produced optical contrast for robust microscopic detection in complex cellular environments. In comparative tests, C3-NP were found to provide effective intracellular delivery that enables both robust detection at cellular and tissue level and presents significant therapeutic potential without altering the mechanism of intracellular action of β-carotene. Surface coating of C3 with phospholipid was used to generate C3-Lipocoat nanoparticles with further improved function and biocompatibility, paving the path to eventual in vivo studies.

Multiphase partitioning and risk assessment of endocrine-disrupting chemicals in the Pearl River, China.

Multiphase partitioning of endocrine-disrupting chemicals (EDCs) in the Pearl River (China) were investigated. The colloidal concentrations for 4-tert-octylphenol, 4-nonylphenol, bisphenol A (BPA), and estrone (E1) were in the ranges of 0.2 ng/L to 0.8 ng/L, 23.2 ng/L to 108 ng/L, 2.3 ng/L to 97.6 ng/L, and not detectable (nd) to 0.32 ng/L, respectively; for truly dissolved concentrations, the ranges were 0.5 ng/L to 5.4 ng/L, 39 ng/L to 319 ng/L, 13.7 ng/L to 91.2 ng/L, and nd to 1.2 ng/L, respectively. Positive correlations of EDCs with colloidal organic carbon (COC) were observed. The in situ COC normalized partitioning coefficients (log KCOC ) for 4-tert-octylphenol (5.35 ± 0.42), 4-nonylphenol (5.69 ± 0.50), and BPA (5.51 ± 0.77) were within the ranges reported by other studies, whereas they were 1 to 2 orders of magnitude higher than their particulate/truly dissolved phase partition coefficients (log KOCint), revealing much strong sorption of EDCs by aquatic colloids. Moreover, colloid-bound percentages of 4-tert-octylphenol, 4-nonylphenol, and BPA ranged, respectively, from 6.9% to 36.4%, from 16.7% to 63.1%, and from 3.6% to 52.4%; their estimated mass fractions were 0.29 ± 0.21, 0.38 ± 0.26, and 0.39 ± 0.33, respectively. Obviously the colloid-bound fractions are significant. Furthermore, a medium risk of estrogenic effects was estimated from the truly dissolved concentrations of EDCs in the Pearl River, which was lower than the estimated high risk according to the conventionally dissolved concentrations. It is suggested that the presence of colloids be incorporated into future water quality prediction and ecological risk assessment. Environ Toxicol Chem 2016;35:2474-2482. © 2016 SETAC.

Poly(vinylpylrrolidone) as Surfactant in the Sol–Gel Preparation of Lithium Iron Phospate/Carbon Cathodes for Lithium‐Ion Batteries

AbstractLithium iron phosphate/carbon (LiFePO4/C) is synthesized by a modified sol–gel method, in which the nonionic surfactant poly(vinylpyrrolidone) (PVP) is used. PVP plays a dual roles in the preparation of LiFePO4/C: it is used as surfactant to prevent the colloid particles and carbon source from aggregating, and is a carbon source. The carbon contents and conductivities of LiFePO4/C increase with increasing of PVP. When the ratio of PVP to LiFePO4 reaches 1 ‰, the conductivity of LiFePO4/C reaches its optimal value of 2.67×10−2 S cm−1 and its discharge capacity at 1 C is 131.0 mAh g−1. This is because the use of PVP leads particles that are small and have a homogeneous size distribution, which is due to dispersion by PVP. Titanium (Ti4+)‐doped samples, obtained from a sol–gel method, possess even better performances. The discharge capacities of this sample is 111.1 mAh g−1at 5 C and 87.3 mAh g−1 at 8 C. The gap in potential between the oxidative and reductive peaks is as low as 0.2053 V, which shows its reversibility is excellent.