► The adsorption capacity of PAC and chitosan was greater than that of CNTs. ► The adsorption of Cr(VI) was found to be favored at low pH. ► The anions resulted in negative effects on Cr(VI) ...adsorption.
The adsorption behavior of ppb-level aqueous solutions of hexavalent chromium Cr(VI) on four different adsorbents was investigated as a function of pH, contact time, initial Cr(VI) concentration, adsorbent dose, and the copresence of competing anions. The adsorbents selected were powered activated carbon (PAC), chitosan, single-walled carbon nanotubes (SWNTs), and multi-walled carbon nanotubes (MWNTs). Each adsorbent was characterized by Fourier transform infrared spectroscopy and measurements of zeta potential to determine its suitability for Cr(VI) adsorption. The adsorption of Cr(VI) was found to be favored at low pH because all adsorbents were positively charged under acidic conditions (pH 4), while a dosage of 100mg/L resulted in efficient adsorption behavior. PAC and chitosan provided the best removal performance. The highly functionalized and porous PAC and the protonated amines on chitosan enabled a better performance and resulted in high Cr(VI) removal efficiencies of 99.4% and 94.7%, respectively, while the removal efficiencies of SWNTs and MWNTs were 72.9% and 51.9%, respectively. Isotherm and kinetic studies were undertaken to evaluate the characteristics of the Cr(VI) adsorption process. A well-fitted Langmuir isotherm model suggested that monolayer adsorption was the main process operating with an adsorption capacity (qm) of 46.9, 35.6, 20.3, and 2.48mg/g for PAC, chitosan, SWNTs, and MWNTs, respectively. Pseudo second-order fitted models revealed the importance of kinetic parameters (apart from adsorption capacity) in understanding the transport of Cr(VI) in the solution, while an intra-particle diffusion model fitted well for μg/L levels of Cr(VI) adsorption. This indicated that both physisorption and chemisorption were dominant, particularly for SWNTs. Anions such as Cl− and SO42- in the solution competed with HCrO4- and this phenomenon resulted in negative effects on Cr(VI) adsorption.
Large‐area flexible transparent conductive films (TCFs) are highly desired for future electronic devices. Nanocarbon TCFs are one of the most promising candidates, but some of their properties are ...mutually restricted. Here, a novel carbon nanotube network reorganization (CNNR) strategy, that is, the facet‐driven CNNR (FD‐CNNR) technique, is presented to overcome this intractable contradiction. The FD‐CNNR technique introduces an interaction between single‐walled carbon nanotube (SWNT) and Cu─‐O. Based on the unique FD‐CNNR mechanism, large‐area flexible reorganized carbon nanofilms (RNC‐TCFs) are designed and fabricated with A3‐size and even meter‐length, including reorganized SWNT (RSWNT) films and graphene and RSWNT (G‐RSWNT) hybrid films. Synergistic improvement in strength, transmittance, and conductivity of flexible RNC‐TCFs is achieved. The G‐RSWNT TCF shows sheet resistance as low as 69 Ω sq−1 at 86% transmittance, FOM value of 35, and Young's modulus of ≈45 MPa. The high strength enables RNC‐TCFs to be freestanding on water and easily transferred to any target substrate without contamination. A4‐size flexible smart window is fabricated, which manifests controllable dimming and fog removal. The FD‐CNNR technique can be extended to large‐area or even large‐scale fabrication of TCFs and can provide new insights into the design of TCFs and other functional films.
A novel facet‐driven carbon nanotube network reorganization method is developed to prepare large‐area flexible freestanding transparent and conductive carbon nanofilms with synergistic enhancement of multiple properties, such as mechanical strength, transmittance and conductivity, and the area up to A3 size and even meter‐length. Based on the film, a new smart window is fabricated.
The large‐scale fabrication of efficient and inexpensive bifunctional catalysts is highly desirable but very challenging for oxygen reduction reaction and oxygen evolution reaction (ORR–OER) in ...metal–air batteries. Here, a facile and scalable approach for the fabrication of hierarchically porous air electrode consisting of cobalt nanoparticles embedded in bamboo‐like nitrogen‐rich carbon nanotubes (Co/N@CNTs), which are in situ grown onto the surface of carbon nanotube macrofilm (CNMF) through a catalytic growth of crosslinked carbon nanotubes is reported. The resulting hybrid macrofilm (Co/N@CNTs@CNMF) can be directly used as a freestanding air electrode without adding any binder or addivities. More importantly, when incorporated in a zinc–air battery (ZAB), the Co/N@CNTs@CNMF electrode demonstrates drastically enhanced ORR and OER activity while maintaining excellent durability during cycling. Further, when it is used to assemble an all‐solid‐state ZAB, the cell also displays excellent mechanical flexibility, implying promising perspectives as power sources for wearable electronics.
An integrated, freestanding, and flexible air electrode, consisting of bamboo‐like cobalt nanoparticles encapsulated in N‐doped carbon nanotubes (Co/N@CNTs) achieved via in situ growth on the surface of the carbon nanotube macrofilm is prepared based on structural engineering, which exhibits an outstanding performance in flexible, rechargeable solid‐state zinc‐air batteries.
Photothermal ablation of primary tumors with single‐walled carbon nanotubes is demonstrated to be able to trigger significant adaptive immune responses, which are not observed if tumors are removed ...by surgical resection. Such a treatment in combination with anti‐CTLA‐4 antibody therapy is able to prevent the development of tumor metastasis, which is a major cause of cancer death.
Nanotechnology is an advanced field of science having the ability to solve the variety of environmental challenges by controlling the size and shape of the materials at a nanoscale. Carbon ...nanomaterials are unique because of their nontoxic nature, high surface area, easier biodegradation, and particularly useful environmental remediation. Heavy metal contamination in water is a major problem and poses a great risk to human health. Carbon nanomaterials are getting more and more attention due to their superior physicochemical properties that can be exploited for advanced treatment of heavy metal-contaminated water. Carbon nanomaterials namely carbon nanotubes, fullerenes, graphene, graphene oxide, and activated carbon have great potential for removal of heavy metals from water because of their large surface area, nanoscale size, and availability of different functionalities and they are easier to be chemically modified and recycled. In this article, we have reviewed the recent advancements in the applications of these carbon nanomaterials in the treatment of heavy metal-contaminated water and have also highlighted their application in environmental remediation. Toxicological aspects of carbon-based nanomaterials have also been discussed.
The synthesis of gold nanoparticles reinforced functionalized single‐walled/multi‐walled carbon nanotubes nanohybrid based polyaniline nanocomposites were carried out using in situ polymerization. ...The chemical interaction and nanostructured morphology of the synthesized nanocomposites are studied using ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, x‐ray diffraction analysis, x‐ray photoelectron spectroscopy, and field emission scanning electron microscopy. Thermal stability of synthesized PANI/Au@f‐SWNTs is boosted by a magnitude of 30°C as compared with the pristine PANI matrix, which is attributed to a strong barrier effect because of the development of tortuous path that resulted from a uniform distribution of Au@f‐CNTs throughout the PANI matrix. For PANI/Au@f‐SWNTs, the AC conductivity and dielectric permittivity are improved by a value of 83.58 S/cm and 1.35 × 10−5 as well as the dielectric loss is reduced by a factor of 0.11 in comparison with the pure PANI matrix at an applied frequency of 106 Hz. PANI/Au@f‐SWNTs and PANI/Au@f‐MWNTs ternary nanocomposites exhibited excellent selectivity toward the hazardous Cr(VI) heavy metal ions in an aqueous medium with a limit of detection of 0.74 and 0.89 μM with a binding constant of 1.028 × 105 and 3.46 × 104 M−1, respectively, that can be selective and sensitive for the detection of Cr(VI) metal ions in water at trace level.
Synthesis of PANI/Au@f‐CNTs ternary nanocomposites using an in situ polymerization approach: Evaluation of thermal, dielectric, and sensing properties.
Developing active, robust, and nonprecious electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is highly crucial and ...challenging. In this work, a facile strategy is developed for scalable fabrication of dicobalt phosphide (Co2P)–cobalt nitride (CoN) core–shell nanoparticles with double active sites encapsulated in nitrogen‐doped carbon nanotubes (Co2P/CoN‐in‐NCNTs) by straight forward pyrolysis method. Both density functional theory calculation and experimental results reveal that pyrrole nitrogen coupled with Co2P is the most active one for HER, while Co–N–C active sites existing on the interfaces between CoN and N‐doped carbon shells are responsible for the ORR and OER activity in this catalyst. Furthermore, liquid‐state and all‐solid‐state Zn–air batteries are equipped. Co2P/CoN‐in‐NCNTs show high power density as high as 194.6 mW cm−2, high gravimetric energy density of 844.5 W h kg−1, very low charge–discharge polarization, and excellent reversibility of 96 h at 5 mA cm−2 in liquid system. Moreover, the Co2P/CoN‐in‐NCNTs profiles confirm excellent activity for water splitting.
Dicobalt phosphide–cobalt nitride core–shell particles act as double active centers and are encapsulated into the channel of N‐doped carbon nanotubes by an in situ one‐step self‐assembly and confined pyrolysis approach, which is demonstrated to afford trifunctional performance in catalyzing hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction for Zn–air batteries and water splitting.
Carbon nanotubes (CNT) have numerous industrial applications and may be released to the environment. In the aquatic environment, pristine or functionalized CNT have different dispersion behavior, ...potentially leading to different risks of exposure along the water column. Data included in this review indicate that CNT do not cross biological barriers readily. When internalized, only a minimal fraction of CNT translocate into organism body compartments. The reported CNT toxicity depends on exposure conditions, model organism, CNT-type, dispersion state and concentration. In the ecotoxicological tests, the aquatic organisms were generally found to be more sensitive than terrestrial organisms. Invertebrates were more sensitive than vertebrates. Single-walled CNT were found to be more toxic than double-/multi-walled CNT. Generally, the effect concentrations documented in literature were above current modeled average environmental concentrations. Measurement data are needed for estimation of environmental no-effect concentrations. Future studies with benchmark materials are needed to generate comparable results. Studies have to include better characterization of the starting materials, of the dispersions and of the biological fate, to obtain better knowledge of the exposure/effect relationships.
A Copper (Cu) matrix composites reinforced with 0.2, 5 and 10vol% single walled carbon nanotubes (SWCNT) and 5 and 10vol% multi-wall carbon nanotubes (MWCNT) was processed by high energy attritor ...milling of pure copper powder with carbon nanotubes (CNT) and subsequently consolidated by spark plasma sintering (SPS). Microstructural characterization shows a network of CNT along the grain boundaries and the presence of porosities at grain boundaries as well as triple junctions. By covering the particle boundaries, the higher volume fraction of CNT makes the sintering difficult as compared to single phase copper or low volume fraction CNT composites. Raman spectroscopy indicates that there is an increase in number of defects in the nanotube after milling and sintering of the composite. Mechanical properties evaluation shows that SWCNT composites results in higher strength and deformability compared to MWCNT. The failure strain decreases with increase in volume percent of CNT due to clustering of CNTs.
ZnCo2O4 quantum dots anchored on nitrogen‐doped carbon nanotubes (N‐CNT) retain the high catalytic activity of ZnCo2O4 to oxidize water while enabling an efficient oxygen reduction performance ...thereby combining these desirable features. These advantages realize a bifunctional catalytic activity for ZnCo2O4/N‐CNT that can be used in rechargeable zinc–air batteries.
PDF
