High Yield Carbon Research Articles

A high-yield and versatile method for the synthesis of carbon dots for bioimaging applications.

A facile and versatile molten-salt method was developed to prepare hydrosoluble carbon dots (CDs) from various precursors, in high yields and on a large scale. Citric acid-based CDs (CA-CDs) were obtained in a maximum yield of 39.6% and exhibited a high fluorescence quantum yield of 20.8% without any passivation. The CA-CDs showed little cytotoxicity even at a concentration as high as 800 μg mL-1. In addition, CA-CDs could be used as multicolour fluorescence imaging agents in vitro with blue, green, and red fluorescence emissions at excitation wavelengths of 405, 488, and 543 nm, respectively. Moreover, the CA-CDs could be chelated with gadolinium ions (Gd3+) to construct Gd-CA-CDs for dual-mode magnetic resonance and fluorescence imaging. The Gd-CA-CDs showed good water dispersibility, excellent biocompatibility, a strong fluorescence quantum yield of 13.1%, and a high magnetic resonance relaxivity of 22.45 mM-1 s-1. The molten-salt method was demonstrated to be applicable to other precursors, such as sodium lignosulphonate, sucrose, glucose, and p-phenylenediamine, and the maximum yield of the four as-prepared CDs was as high as 66.7%, which is much higher than the value reported in previous studies. This study proves that the molten-salt synthesis is a versatile method to obtain CDs in high yields, which will promote the application of CDs in the field of bioimaging.

CVD nano-coating of carbon composites for space materials atomic oxygen shielding

Abstract: The present work analyzes the possibility to employ carbon nanostructures as a basic material to prevent the erosion effects of atomic oxygen suffered by the carbon fiber reinforced polymeric material used in low earth orbit space environment. The application of thin protecting coatings to base materials is a widely used method for preventing the atomic oxygen induced erosion, and thus degradation. The generic purpose is to integrate carbon nanostructures onto carbon composites surface in order to develop the basic substrate of advanced nanocomposite for atomic oxygen protection. The final goal is the characterization of carbon nanostructures-reinforced carbon composites by means of on-ground atomic oxygen simulation facility, with the future objective to assess and optimize the process of carbon-multiscale advanced composites production. With such an aim, a wide investigation on the methane chemical vapor deposition (CVD) over catalyzed carbon fiber-based substrates has been carried out. The as grown nanostructures have been analyzed in terms of morphology, as well as regarding the main features of the resulting growth (yield, purity, homogeneity, coating uniformity, etc.) and the influence of the deposition route operating parameters (catalyst typology, gas flowing rate, growth time/temperature, etc.). A high degree of reproducibility in terms of the relationship between the carbon deposit type/yield and the main process variables (catalyst and protocol) has been thus obtained. Finally, atomic oxygen ground tests have been conducted in order to evaluate the coating process effectiveness. The on-ground test in atomic oxygen environment, with respect to the performances of the reference carbon composites (in terms of total mass loss and atomic oxygen rate of erosion), showed a worsening for the disordered carbon deposit, while an intriguing improvement was achieved by the high-yield carbon nano-filaments deposition.

Development of carbon dot based microplate and microfluidic chip immunoassay for rapid and sensitive detection of HIV-1 p24 antigen

A highly sensitive, precisely specific, environmentally friendly, high-throughput, microwell-plate and microchip-based sandwich assay was developed to detect HIV-1 p24 antigen, a protein biomarker using fluorescent carbon dots. High quantum yield carbon dots were synthesized using citric acid and ethylenediamine as carbon and nitrogen sources by a single-step hydrothermal reaction. The desired amine groups confirmed by FTIR on the carbon dots were coupled to streptavidin by amine–amine coupling reaction using glutaraldehyde. The detection range of the carbon dot based immunoassay (CDIA) was found to be between 20 and 1000 pg/mL in a linear dose-dependent manner. CDIA tested for HIV negative plasma samples showed no false positive results in the detection of HIV-1 p24 antigen. The CDIA was extended to develop a microfluidic carbon dot immunoassay (μCDIA) which exhibited analytical sensitivity in the range of 30–1000 pg/mL. The CDIA and μCDIA can easily be adapted to a lab-on-a-chip platform for use in resource limited settings and can also be multiplexed for the detection of other pathogens like TB and Hepatitis.

The influence of different parameters on biomass gasification in circulating fluidized bed gasifiers

The mechanism of biomass gasification has been studied for decades. However, for circulating fluidized bed (CFB) gasifiers, the impacts of different parameters on the gas quality and gasifiers performance have still not been fully investigated. In this paper, different CFB gasifiers have been analyzed by multivariate analysis statistical tools to identify the hidden interrelation between operating parameters and product gas quality, the most influencing input parameters and the optimum points for operation. The results show that equivalence ratio (ER), bed material, temperature, particle size and carbon content of the biomass are the input parameters influencing the output of the gasifier the most. Investigating among the input parameters with opposite impact on product gas quality, cases with optimal gas quality can result in high tar yield and low carbon conversion while low tar yield and high carbon conversion can result in product gas with low quality. However using Olivine as the bed material and setting ER value around 0.3, steam to biomass ratio to 0.7 and using biomass with 3mm particle size and 9wt% moisture content can result in optimal product gas with low tar yield.

A New Technology for Efficient, High Yield Carbon Dioxide and Water Transformation to Methane by Electrolysis in Molten Salts

This study presents a new green technology for the sustainable utilization of carbon dioxide. Synthetic methane, if produced efficiently and with low carbon footprint, provides a ready replacement for natural gas in the existing energy, manufacturing, and transportation industries. The first technology for the production of methane from CO2 and water by molten electrolysis is demonstrated. The technology is more efficient than alternative renewable methane production by microbial, aqueous, or solid oxide electrolysis, or than various photocatalytic processes. Methane is produced at 1000‐fold the rate observed in photoelectrochemical systems, and without noble metals or an external hydrogen source. Added steam and CO2 continuously renew the electrolyte. CO2 and H2O are directly transformed by electrolysis at 97.4% current efficiency at a constant current of 250 mA through 20 cm2 iron and nickel electrodes in a 600 °C alkali carbonate/LiOH electrolyte at low (<2 V) energy. The electrolysis product is comprised of 64.9% methane, 34.8% H2, and 0.3% longer (than C1) hydrocarbons.

ChemInform Abstract: Silica‐Grafted Basic Amino Acids as Environmentally Benign Catalysts for the Solventless Synthesis of Cyclic Carbonates from Epoxides and CO2 under Metal‐Free and Halide‐Free Conditions.

AbstractSilica‐supported L‐histidine efficiently catalyzes the solvent‐free reaction of epoxides from styrene and terminal alkenes with carbon dioxide to the cyclic carbonates in high yields.

Economic trade-offs in acrylic acid reactor design

Abstract The acrylic acid process using air oxidation of propylene presents many interesting design trade-offs, particularly in the design of the reactor. The desired and undesired reactions are highly exothermic and very temperature dependent (large activation energies), so a large flowrate of inert water is also fed to the reactor to act as a thermal sink. Propylene conversion increases with temperature and reactor size, but acrylic acid yield decreases with increasing temperature. The heat of reaction is removed by generaing steam, and the steam pressure is an important design optimization variable since it sets low limits on reactor temperature. Using low-pressure steam gives high acrylic acid yield and lower carbon dioxide generation but requires large reactors. Larger air flowrates increase reactor oxygen concentrations, which reduce reactor volume but increase air compression costs. This paper explores the effects of the many design trade-offs on capital investment, energy cost and product selectivity.

Anaerobic digestion of wastewater from the production of bleached chemical thermo‐mechanical pulp – higher methane production for hardwood than softwood

ABSTRACTBACKGROUNDChemical thermo‐mechanical pulp (CTMP) mills holds a large biomethane potential in their wastewater. Their broadened market has involved increased bleaching and utilization of different raw materials. Therefore, the main aim of this study was to obtain and maintain a well‐functioning anaerobic digestion (AD) process, with a high methane yield and total organic carbon (TOC) reduction, when digesting CTMP wastewater, from different production protocols including shifts in raw material and bleaching. A lab‐scale upflow anaerobic sludge bed (UASB) reactor was used for the tests.RESULTSThe variations in raw material (spruce, birch and aspen) and consequently in TOC‐loading (3.6–6.6 kg TOC m−3 and day−1) did not affect the UASB process negatively. Methane production values from 360 to 500 NmL g−1 TOC were obtained, with the highest yield for wastewater from the production of birch‐ followed by aspen‐ and spruce pulp. The acetic acid and filtered‐TOC (fTOC) reduction ranged from 90 to 95% and 61 to 73%, respectively.CONCLUSIONSA well‐functioning process maintained during shifts in raw material for pulp production which shows that AD is feasible for CTMP mills with a diversified product portfolio. Furthermore, the increased use of hardwood and bleaching will most likely increase their potential as a biomethane producer. © 2016 Society of Chemical Industry

Hydrogensulphate ionic liquids as an efficient catalyst for the synthesis of cyclic carbonates from carbon dioxide and epoxides

BACKGROUND The use of CO2 as a raw material to synthesize cyclic carbonates has attracted much attention in recent years. Ionic liquids (ILs) due to their unique properties are often used as effective catalysts for the reaction between CO2 and epoxide to afford cyclic carbonates. This report describes an efficient method for the synthesis of cyclic carbonates in the presence of IL with HSO4− anion as a catalyst which could be easily separated and reused. RESULTS The synthesis of cyclic carbonates from CO2 and epoxides using the two-component catalytic system consisting of the ionic liquid based on the imidazolium cation and the hydrogensulphate anion and an aqueous solution of zinc iodide is described. The cyclic carbonates were obtained with high yields (69–99%) and selectivities (>99%) under the optimized conditions: 120 °C, 2 MPa of CO2, without utilization of any organic solvents. CONCLUSION The new and effective catalytic system allows one to obtain cyclic carbonates in high yields and can be reused several times without significant loss of activity. Therefore, the proposed method seems to be useful for practical applications. © 2016 Society of Chemical Industry

Optimization of Parameters to Achieve High Yield and Purity Single-Walled Carbon Nanotube by Thermal and Chemical Oxidation and Its Effect on Conductivity.

Single wall carbon nanotubes due to their unique structural and electronic characteristics have revolutionized the field of nanotechnology and are widely used the field of transistors, drug delivery, and nanocomposities. For improved efficiency of these applications, the utilized tubes must of preeminent purity. Here, we report key parameters that are optimized to achieve their highest purity upto 98 wt%, and yield as high as 50 wt% by thermal and chemical oxidation. The as-produced SWCNT were heated in air at 470 °C, for 90 min, and later subjected to chemical oxidation. The chemical oxidation involved the treatment of thermally treated SWCNT with different concentrations of HCl (4N, 6N, 8N) and 30% H₂O₂, for different time periods (4 hr, 6 hr). This method does not cause damage to the walls of the tubes, observing no loss of nanotubes. The sheet resistance of as-produced and purified tubes was measured and the conductivity was calculated.

Trade-offs between water yield and carbon sequestration for sub-alpine catchments in western Sichuan, China

Aims: There is increasing concern on the trade-off between carbon sequestration and water yield of forest ecosystems. Our objective was to explore the effects of vegetation composition on water and carbon trade-off in the sub-alpine watersheds of western Sichuan during 1982-2006. Methods: The WaSSI-C, which is an eco-hydrological model with coupled water and carbon cycles, was employed to calculate the key components in water balance and carbon sequestration for the 22 sub-catchments in the upper reaches of Zagunao River. Spearman's Rho trend analysis was used to examine the trends in runoff and net ecosystem productivity. Important findings: Compared with either subalpine meadow or mixed forest dominated catchments, the conifer-dominated catchments had much higher water loss due to high evapotranspiration, and the loss was not offset by its higher soil water infiltration during the growing season. The change in soil water storage for subalpine meadow, mixed forest and coniferous forest are -44 mm, -18 mm and -5 mm, respectively, which indicated significant decline in soil water storage and thus water yield particularly in alpine meadow catchments. Significant negative relationship was found between runoff and net ecosystem productivity, the alpine meadow as the dominant vegetation type showed high water yield and low carbon sequestration, and the conifer-dominant and mixed forest vegetation showed low water yield and high carbon sequestration, moreover, the higher the forest coverage, the lower the water yield. Upward trends in net ecosystem productivity were observed in the three vegetation types during the study period and the alpine meadow type was significant.

The effects of catalyst pretreatment, growth atmosphere and temperature on carbon nanotube synthesis using Co–Mo/MgO catalyst

The growth of high quality and high yield carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of CH4 over Co–Mo/MgO catalyst was investigated for different growth temperatures and H2 flow rates. It was observed that CNT yield decreased with the H2 flow rate, however, quality increased with increasing H2 flow rate. CNT yield increased for the temperatures 850–950°C but dropped significantly above 950°C. In this study, the highest yield of 1526% was obtained at the growth temperature of 950°C. The optimum H2 flow rate was 200sccm; this rate gave both high graphitization and high yield of product. Various CNT growth atmospheres including Ar, H2 and the mixture of both gases were also analyzed and it was observed that the highest quality CNTs were obtained for both pretreatment and growth carried out with H2. This gave a high yield of 292%. On the other hand, CNT growth carried out under Ar atmosphere gave higher CNT yield of 368%, however, the CNTs grown with Ar were more defective and had larger diameters. Prime novelty statementWe demonstrate a sorbitol added catalysis synthesis method and importance of the ideal growth conditions to improve high quality single walled carbon nanotube yield up to 1500%.

Synthesis of highly photoluminescent carbon dots via citric acid and Tris for iron(III) ions sensors and bioimaging

In this work, high quantum yield and strong photoluminescent carbon quantum dots (C-QDs) are successfully synthesized via a facile and green hydrothermal method using citric acid and Tris as precursors. The as-synthesized C-QDs with a quantum yield (QY) as high as 52% were characterized by UV, FT-IR, TEM, XPS and fluorescence spectroscope. TEM results show that C-QDs are mono-dispersed spherical particles and the diameter distribution of C-QDs is 2.8±1.1nm. The extraordinary photoluminescent properties and low cytotoxicity of C-QDs were obtained through optical property characterization and cytotoxicity assay. In addition, we found that the as-prepared C-QDs had a high affinity for Fe3+ ions and the response toward Fe3+ ions was highly linear (R2=0.997) over the concentration range from 2 to 50μM, which could provide an effective platform for portable detection of Fe3+ ions. Also, it is demonstrated that the photoluminescent C-QDs display hypotoxicity and are biocompatible for use as biosensors in living cells.

One-pot atom-efficient synthesis of bio-renewable polyesters and cyclic carbonates through tandem catalysis.

One-pot synthesis of well-defined bio-renewable polyesters and cyclic carbonates in high yields was successfully realized for the first time by way of a tandem reaction using metal salen complexes as catalysts. This tandem process offered unprecedented opportunities for the atom-efficient production of two relevant compounds.

OCCURRENCE AND ENRICHMENT OF TRACE ELEMENTS IN MARINE OIL SHALE (CHINA) AND THEIR BEHAVIOUR DURING COMBUSTION

The Shengli River-Changshe Mountain oil shale zone represents the potentially largest marine oil shale resource in China. With the aim to have better knowledge of the distribution of trace elements in oil shale, and their behaviour during oil shale combustion and gasification, 28 raw Changliang Mountain oil shale and marl samples, 19 oil shale combustion residue samples and 23 samples of minerals isolated from Changliang Mountain oil shale are studied for trace element content. The oil shale samples from the Changshe Mountain area are characterized by high ash yield (54.69-86.75%) and total organic carbon (TOC) content (2.20- 13.44%). The contents of Se, Mo, Cd, As, B, and Ni in raw oil shale samples are 3.78 to 28.44 times their upper continental crust values. The enrichment of an element in oil shale seams may be a function of that association and the origin of oil shale fractions. Some trace elements in the Changshe Mountain oil shale show susceptibility to release into the atmosphere, including about 93% Hg and 20-30% As, Ba, Be, Co, Cr, Nb, and Sc. The behaviour and migration of trace elements during oil shale combustion strongly depend on their mode of occurrence in the rock. Based on Pearson's coefficients of correlation between elements, as well as cluster and isolated mineral analyses, the main modes of occurrence of trace elements in marine oil shale are distinguished: 1) clay mineral affined - B, Ba, Be, Cr, Cs, Ga, Hf, Li, Nb, Rb, Sc, Sn, Ta, Th, V, W, Zr, REEs; 2) organic affined - As, Mo, Se; 3) Fe-bearing mineral affined - Bi, Co, Cu, Ni, Pb, U; 4) calcite affined - Cd, Sr and 5) fossil affined - Cd, Zn.

Hydroxyl‐Functionalized Imidazoles: Highly Active Additives for the Potassium Iodide‐Catalyzed Synthesis of 1,3‐Dioxolan‐2‐one Derivatives from Epoxides and Carbon Dioxide

Abstract4(5)‐(Hydroxymethyl)imidazole and potassium iodide were identified as an efficient catalyst system for the cycloaddition of epoxides and carbon dioxide producing 1,3‐dioxolan‐2‐one derivatives under solvent‐free conditions. The high activity of the catalyst system even at 60 °C was probably due to synergistic effects between potassium iodide and the substituted imidazole. Various functionalized and nonfunctionalized terminal epoxides as well as internal epoxides were converted into the corresponding cyclic carbonates in high yields (up to 99 %) under mild reaction conditions within a short reaction time. Compared with the previously reported amino alcohols e.g. triethanolamine based catalyzed synthesis of cyclic carbonates, the catalyst system described herein demonstrates a higher activity toward a broad substrate scope

Organic carbonate synthesis from CO2 and alcohol over CeO2 with 2-cyanopyridine: Scope and mechanistic studies

The combination system of CeO2-catalyzed carboxylation and 2-cyanopyridine hydration (CeO2+2-cyanopyridine system) is effective for the direct synthesis of organic carbonates from CO2 and alcohols. This catalyst system can be applied to various alcohols to afford the corresponding carbonates in high alcohol-based yields. The hydration of 2-cyanopyridine over CeO2 rapidly proceeds under the low concentration of water, which can remove the water from the reaction media. Since the reaction is limited by the chemical equilibrium, the removal of water remarkably shifts the chemical equilibrium to the carbonate side, leading to high carbonate yields. In addition, 2-picolinamide that is produced by hydration of 2-cyanopyridine forms an intramolecular hydrogen bonding between H atom of the amide group and N atom of the pyridine ring, which weakens the adsorption of 2-picolinamide on CeO2 by reduction of the acidity. The reaction mechanism of DMC formation in CeO2+2-cyanopyridine system is also proposed.

ChemInform Abstract: Effective Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides by Phosphonium Iodides as Catalysts in Alcoholic Solvents.

AbstractThe optimized reaction conditions allow the synthesis of five‐membered cyclic carbonates in high yields under mild reaction conditions.

One-step green synthesized fluorescent carbon nanodots from bamboo leaves for copper(II) ion detection

High quantum yield carbon quantum dots (CQDs) are successfully synthesized via a simple, low cost, and green hydrothermal method using bamboo leaves as carbon source for the first time. Branched polyethylenimine (BPEI)-capped CQDs (BPEI-CQDs) are prepared by coating the CQDs with BPEI via electrostatic adsorption. The BPEI-CQDs are then employed as fluorescent probes for sensitive and selective Cu2+ detection. Experimental results show that the synthesized CQDs have average size of 3.6nm in diameter with narrow size distribution. The biomass-based CQDs offer high quantum yield of 7.1%. The BPEI-CQDs-based sensing system renders a simple, reliable and sensitive Cu2+detection with limit of detection (LOD) as low as 115nM and a dynamic range from 0.333 to 66.6μM. In addition, the BPEI-CQDs are successfully used to detect Cu2+ in river water, demonstrating its good selectivity and great potential for analysis of environmental water samples.

Novel functionalized guanidinium ionic liquids: Efficient acid–base bifunctional catalysts for CO2 fixation with epoxides

A series of functional guanidinium-based ionic liquids (FGBILs) that contain both Lewis acid and basic sites was prepared by a simple method, and used as catalysts for the synthesis of cyclic carbonates through the cycloaddition of CO2 to epoxides in the absence of co-catalyst and solvent. Propylene oxide conversion was near completion at 130°C and 2.5MPa in 2h when [TMGC2H4NH2]Br was used as catalyst. The effects of functional groups and counter anions on catalytic performance were investigated. The synergistic effect of polarization by hydrogen bonding and the nucleophilic attack by bromide anion account for the facile ring-opening of epoxide. Furthermore, the protocol is applicable to a variety of terminal epoxides, producing the corresponding cyclic carbonates in high yield and selectivity. It is envisaged that the metal- and solvent-free process using a single catalyst has high potential for large-scale fixation of CO2.