Narrow Carbon Research Articles

Solvent mediated synthesis of multicolor narrow bandwidth emissive carbon quantum dots and their potential in white light emitting diodes

The development of efficient and environmentally sustainable materials for white light-emitting diodes (WLEDs) is of paramount importance in the field of lighting technology. In this study, we present a solvent-modulated synthesis approach for the fabrication of multicolor narrow-bandwidth emissive carbon quantum dots (CQDs) as a promising solution for constructing WLEDs. The synthesis method involves the controlled reaction of organic precursors in different solvent environments, leading to the formation of CQDs with distinct emission wavelengths with a relatively small full width at half maximum, ranging from 28 to 42 nm. Moreover, these synthesized multicolor CQDs demonstrate a remarkably high fluorescence quantum yield of up to 65%, indicating their potential for constructing efficient WLED when incorporated in polymer matrix and coated on the surface of blue light-emitting diode (LED).

Surface matters: Decarburising wootz crucible steel ingots

Wootz, the Indian crucible steel, is a hypereutectoid iron–carbon alloy and famous for its outstanding qualities. Due to the paucity of archaeological and historical ingot finds and conservative sampling strategies, discussions of the homogeneity of such ingots and the microstructural representativeness of samples have remained generic and assumptive. Thus two major shortcomings in the study of crucible steel ingots include the determination of their absolute carbon content and its relative distribution across the ingots. The recent discovery of a large hoard of wootz ingots from Telangana (Jaikishan et al. 2021) offered a unique opportunity to study their microstructure and determine their carbon content.Reports based on traditional metallography suggest a wide carbon range, from 1 to 2 wt% carbon, for similar ingots (Scott 2013). Recent work based on image analysis (Desai and Rehren 2023) offered narrower carbon estimates (about 1.8 wt%) for several of the recently discovered ingots, with some variation in concentration towards the edge of the samples. As a collaborative effort to determine absolute carbon values and potential uneven distribution of the carbon in the Telangana ingots, traditional metallography was coupled with laser-induced breakdown spectroscopy (LIBS). Beyond documenting the microstructure across several ingots, the study provides macrostructural evidence of rim decarburisation, which we believe to be intentional. This study presents the micro- and macrostructure of two of the hypereutectoid Telangana ingots, highlighting the skill of the craftsmen in decarburising the outer surfaces of their ingots, potentially for ease of subsequent forging.

Fractional distillation of waste plastic pyrolysis oil for isolating narrow hydrocarbons cuts

Pyrolysis of polyolefins generates a large amount of olefins, which can serve as a valuable feedstock for the synthesis of chemicals. Nevertheless, their effective utilization requires refining owing to their diverse carbon distribution. This study performed a comprehensive GC×GC analysis of pyrolysis oils derived from waste polypropylene (PP) and waste high-density polyethylene (HDPE). The chemical composition of PP pyrolysis oil exhibited a high content of iso-olefins, whereas HDPE pyrolysis oil contained mainly alpha-olefins. Experimental batch distillation of PP pyrolysis oil yielded narrow hydrocarbon cuts with iso-olefins content exceeding 70 wt%. In contrast, distillation of HDPE resulted in cuts with more than 25 wt% alpha-olefins content. To perform ASPEN simulations, the physical properties (density, viscosity) of the oil were determined, two ways for obtaining boiling curves (ASTM D2887 and ASTM D86) were compared and two property methods (Peng-Robinson and Soave-Redlich-Kwong) were compared. It was concluded that the ASTM D2887 boiling curve and the Peng-Robinson property method present better experimental agreement for pyrolysis oils using the Theil’s Inequality Coefficients test. Based on the validated batch simulation, continuous distillation process schemes for isolating narrow carbon cuts in the refinery atmospheric tower indicate that a side draw configuration provides a better yield of (19.1 wt%) compared to a dedicated separate distillation column of (11.9 wt%) for the same number of trays, while the dedicated column allows the possibility to achieve higher purity.

Long-term pure- and mixed-gas performance of carbon molecular sieve membranes derived from a tetraphenylethylene-based ladder polymer of intrinsic microporosity (TPE-PIM) for propylene/propane separation

Continuous long-term evaluation of propylene and propane permeation through narrow slit carbon molecular sieve (CMS) membranes is essential for an in-depth study of their steady-state separation performance. CMS membranes are characterized by finely tuned ultramicroporous structures, exceptional thermal and chemical stability, and hold great promise for the energy-intensive separation of propylene and propane. However, the gradual changes in their performance over time due to penetrant-induced structural chain rearrangements have often been overlooked. In this study, we prepared CMS membranes using a polymer of intrinsic microporosity (PIM) with a highly aromatic tetraphenylethylene (TPE) based building block. The presence of bulky and sterically hindered TPE repeat units renders this polymer an excellent precursor for the fabrication of high-performance CMS membranes. The TPE-PIM-based precursor underwent pyrolysis at temperatures ranging from 550 to 700 °C for 1 h. Pure- and mixed-gas permeation tests were accompanied by various characterization techniques to assess the carbonization state of the CMS materials. The CMS pyrolyzed at 700 °C exhibited a decline in pure-gas C3H6/C3H8 selectivity from an initial value of 300 to 161 at steady state over a 20-day period. Even more notable, under equimolar mixed-gas feed conditions, the isotropic CMS film displayed a substantial C3H6/C3H8 selectivity reduction from 214 to 62 over a 24-day period. This performance decline can be attributed to competitive sorption and very slow dilation kinetics, which led to moderately reduced propylene permeability while significantly enhancing propane permeability. Our study suggests that long-term, continuously performed mixed-gas permeation experiments are essential to assess the ‘steady-state’ performance of CMS membranes for mixtures containing highly sorbing feed components, as observed for propylene/propane separation.

Ionic Coulomb blockade controls the current in a short narrow carbon nanotube.

We use all-atom molecular dynamics simulations to investigate ionic conduction in a short, charged, single-wall carbon nanotube. They reveal ionic Coulomb blockade (ICB) oscillations in the current as a function of the fixed charge on the wall, and an associated occupancy staircase. Current peaks related to fluctuations around the 2 → 1 and 1 → 0 steps in occupancy are clearly resolved, in agreement with ICB theory. Current peaks were also observed at constant occupancy. These unpredicted secondary peaks are attributed to edge effects involving a remote knock-on mechanism; they are attenuated, or absent, for certain choices of model parameters. The key parameters of the system that underlie the current oscillations are estimated using ICB theory and the potential of the mean force. Future perspectives opened up by these observations are discussed.

Structural model of oxidatively unzipped narrow single-walled carbon nanotubes

In this study, we present a synthetic method for the preparation of oxo-graphene nanoribbons (oxo-GNRs) by oxidative cleavage of C–C bonds of enriched (6,5)-single-walled carbon nanotubes (SWCNTs). We applied a mild oxidation protocol to oxidize SWCNTs involving sulfuric acid as dispersion medium and potassium permanganate as oxidant. The obtained oxo-GNRs exhibit stunning fluorescence properties with emission maxima of about 300 nm and 400 nm, respectively, depending on oxidation time. The analyses reveal that functional oxo-groups are predominantly located at the rims of oxo-GNRs. Next to lactones, 1,3-ketones are identified, which can be further reacted with hydrazine, most likely forming pyrazoline groups. Based on our data, we propose a chemical structure model for the oxo-GNRs. The model is based on an intact inner π-system, responsible for photoluminescence properties and oxo-functionalized rims of GNRs.

Do new-type urbanisation pilots narrow urban household carbon emission differences between cities? A temporal-spatial within-between decomposition analysis

The relationship between urbanisation and carbon emissions has been widely discussed. However, whether new-type urbanisation, which aims to achieve green development, helps reduce urban household carbon emissions (UHC), remains unclear. By expanding the temporal-spatial within-between refined Laspeyres index decomposition model with data from 236 Chinese cities from 2015 to 2021, this study investigated the differences in UHC between pilot and non-pilot cities under the new-type urbanisation pilot policy and further explored the drivers of these differences. The temporal decomposition results highlighted the changes and their drivers in UHC between pilot and non-pilot cities. UHC have increased in both types of cities, with the increase linked to higher urbanisation rates, greater carbon intensity, and rising incomes. However, the energy intensity and the urban-rural income gap effects helped curb the extent of the increase. Although a higher level of UHC existed in the pilot cities, the new-type urbanisation pilot policy helped narrow the gap in UHC between pilot and non-pilot cities, thus curbing UHC. The spatial decomposition results further explored the causes of the UHC gap between pilot and non-pilot cities. The within-between decomposition results suggested that, for pilot cities, those with higher UHC than the pilot-group average should close the gap with the group average, whereas those with lower UHC than the national average should close the gap with the national average. The findings present a useful reference for balancing urbanisation with a low-carbon household sector.

Ion Coupling, Bonding, and Transfer in Narrow Carbon Nanotubes.

Narrow carbon nanotubes (nCNT) are unique mimics of biological channels with water-ion selectivity attractive for applications such as water purification and osmotic energy harvesting, yet their understanding is still incomplete. Here, an ab initio computation is employed to develop the full picture of ion transfer in nCNT including specificity and coupling between ions. The thermodynamic costs of ion transfer are computed for single ions and ion pairs and used to evaluate different local coupling scenarios including strong (pairing) and weak (free-ion) coupling as well as "electroneutrality breakdown" (EB), possible for cations only due to their chemisorption-like interaction with nCNT. The results also indicate that nCNT behaves as a highly polarizable metal-like shell, which eliminates the dielectric energy when CNT accommodates coupled cation and anion. This allows facile computation and comparison of the full transfer costs, including translation entropy, for different ions in different coupling modes to identify the dominant regime. EB transfer appears most favorable for K+, while anions strongly favor transfer as pairs, except for chloride which favors weak coupling and, at neutral pH, transfers as a trace ion coupled to both cation and OH-. The results demonstrate that, in general, observed ion permeation and conduction in nCNT, especially for anions, reflect a complex ion-specific and composition-dependent interplay between different ions.

Analysis of yellow mealworm (Tenebrio molitor) frass as a resource for a sustainable agriculture in the current context of insect farming industry growth

With the ongoing rapid growth of the human population, the industrial development of mass insect rearing for feed and food is gaining momentum. This approach has proved to be a more efficient and effective alternative to traditional livestock to produce animal protein. In this context, the Tenebrio molitor production sector emerges as highly promising in the edible insect market, being among the most commonly bred species in the large-scale insect rearing industry. A recent modification of the European regulatory framework in this matter has authorized insect-produced feed for pigs and poultry, which will boost the creation of new insect industries, resulting in huge quantities of frass, the insect excrement, that could be valorized. This by-product holds substantial amounts of nutrients and advantageous microorganisms that have enormous potential for organic farming. It typically exhibits high organic content and an abundance of essential nutrients like nitrogen (N), phosphorus (P), and potassium (K), alongside a narrow carbon (C) to nitrogen (N) ratio. In addition to providing plants with essential macronutrients, frass has been discovered to boost soil microbial biomass and introduce biomolecules and microbes that foster plant growth. The study of utilizing frass in sustainable agriculture is a relatively new and actively researched field in recent years. By conducting a comprehensive review of peer reviewed works, this article highlights the advantages associated with the effects of its use as organic fertilizer. Among these, the effect of frass as (1) a plant growth promoter and productivity enhancer and as (2) phytofortifyer against biotic and abiotic stresses, has been underlined in recent studies. With regard to its promoting effect, it has been observed that the effects of frass depend very much on its dose and the type of crop, with remarkably favorable results in many of the tests carried out. Hence, frass derived from the mass rearing of yellow mealworm for feed and food, could serve as an important and potent source of organic fertilizer in intensive horticultural crops or in high-value woody crops, contributing to a more sustainable agriculture, which can decrease the use of conventional synthetic agrochemicals.

The Central South Atlantic: The origin of its waters, its evolution and effects beyond

The primitive sea that occupied the Central South Atlantic (CSA), part of the intra-Gondwana rift during the Early Cretaceous, allowed precipitation of an extensive and thick layer of evaporites, the Ibura Salt, followed by the deposition of a prominent Albian carbonate package. Although the shallow platform facies do not contain classical benthic Tethys markers, the pelagic open sea carbonates are essentially dominated by planktonic elements coming from the Tethys Realm. This condition led some researchers to think that Tethys waters also contributed to salt formation, an idea that clashes with the geotectonic model of northward separation of Africa and South America and ingression of predominantly Austral marine waters. Now, a new controversy arises as to the age of this salt layer when trying to position bio-events and lithological and chemostratigraphic markers from these rocks with respect to established data for the Global Boundary Stratotype Section and Point for the Aptian/Albian boundary (GSSP-Alb). Biochronostratigraphic information on planktonic foraminifera points to an Aptian age as opposed to the earliest Albian traditionally accepted for the carbonate section that overlies the giant salt layer. On the other hand, stratigraphic and geochronological data suggest an age of 113 Ma for the base of the salt, very near to the 113.2 ± 0.1 Ma arbitrated for the GSSP-Alb. In this study, we adopt the base of the evaporite bed as the Aptian/Albian boundary in the CSA, Equatorial South Atlantic (ESA), and northeastern Brazilian interior basins (BNE) as well. Based on these criteria, a broad review and the integration of available information have led to new interpretations regarding the earliest phase of these segments of the South Atlantic and adjacent areas. Initially, during the Aptian-Albian transition, an ephemeral interior sea within Brazil, drawing its waters from the north, would have contributed to salt deposition in the intra-Gondwana rift (evaporitic stage of the CSA). Afterward, but still within the earliest Albian, the evaporitic system evolved into a carbonate gulf when the northern barrier, the Exception Zone (EZ), disappeared. The lagoonal circulation pattern that then formed in the CSA created a hypersaline and warm outflow plume that swept across the marine bottom of the ESA and part of the Tethys Sea. Paleoceanographic events registered at Site 545, Mazagan Plateau, support this new hypothesis and illustrate the potential complexity of correlation of organic-rich deposits in which local influences have been greater than global ones. This long, narrow, and continuous carbonate gulf disappeared at the end of the Albian with the arrival of southern waters from the Meridional South Atlantic (MSA), and the South Atlantic became consolidated as a proto-ocean.

Superfluidity Meets the Solid State: Frictionless Mass Transport through a (5,5) Carbon Nanotube.

Superfluidity is a well-characterized quantum phenomenon which entails frictionless motion of mesoscopic particles through a superfluid, such as ^{4}He or dilute atomic gases at very low temperatures. As shown by Landau, the incompatibility between energy and momentum conservation, which ultimately stems from the spectrum of the elementary excitations of the superfluid, forbids quantum scattering between the superfluid and the moving mesoscopic particle, below a critical speed threshold. Here, we predict that frictionless motion can also occur in the absence of a standard superfluid, i.e., when a He atom travels through a narrow (5,5) carbon nanotube (CNT). Because of the quasilinear dispersion of the plasmon and phonon modes that could interact with He, the (5,5) CNT embodies a solid-state analog of the superfluid, thereby enabling straightforward transfer of Landau's criterion of superfluidity. As a result, Landau's equations acquire broader generality and may be applicable to other nanoscale friction phenomena, whose description has been so far purely classical.

Fundamental aspects of phase formation in WC-based cemented carbides containing FeMn-based binders

The hardmetal industry is continuously seeking for (Co, Ni)-free binder alternatives. Several attempts have been made to use FeMn binders, Mn being a very effective austenite stabilizer. Substitution of Co binders for FeMn based binders comes along with many challenges such as: narrow carbon windows, evaporation of Mn during sintering or the formation of stable Mn-oxides. This work presents an overview on the phase formation in hardmetals with different carbon contents prepared from FeMn, FeMnSi and FeMnNi binders. Due to the efficient role of Mn as cementite stabilizer, it was not possible to avoid the presence of eta-carbides and cementite under the conditions studied, and samples with intermediate carbon contents presented both eta-carbides and cementite in the microstructure. Only after the addition of 25 wt% of Ni to the binder it was possible to observe materials with two phase microstructures. The challenges related to Mn evaporation and formation of stable oxides can be overcome by a proper selection of the starting materials and the sintering conditions. It is thus proved that the main challenge posed by these materials is the difficulty to obtain microstructures without detrimental phases.

Expansion of carbon source utilization range of Shewanella oneidensis for efficient azo dye wastewater treatment through co-culture with Lactobacillus plantarum.

Shewanella oneidensis has demonstrated excellent potential for azo dye decolorization and degradation. However, in anaerobic environments, S. oneidensis has a narrow carbon source spectrum, which requires additional electron donors, such as sodium lactate. This increases the practical application costs for wastewater treatment. Here, we aimed to expand the carbon source utilization range of S. oneidensis FJAT-2478 by co-culturing it with Lactobacillus plantarum FJAT-7926, leveraging their commensalism relationship to develop a metabolic chain. Results showed that a 1:2 initial ratio of L. plantarum FJAT-7926 to S. oneidensis FJAT-2478 achieved a 97.16% decolorization rate of methyl orange when glucose served as the sole carbon source. This co-culture system achieved a decolorization rate comparable to that obtained using sodium lactate as an electron donor and was significantly higher than that achieved by L. plantarum FJAT-7926 (7.88%) or S. oneidensis FJAT-2478 (6.89%) alone. After undergoing five cycles, the co-culture system continued to exhibit effective decolorization. It was demonstrated that the co-culture system could use common and inexpensive carbon sources, such as starch, molasses, sucrose, and maltose, to decolorize azo dyes. For instance, 100mg/L methyl orange could be degraded by over 98.05% within 24h. The results indicated that the degradation rates of methyl orange were higher when L. plantarum was inoculated first, followed by a subsequent inoculation of S. oneidensis after 2h. The co-culturing of L. plantarum FJAT-7926 and S. oneidensis FJAT-2478 proved to be an effective strategy in treating azo dye wastewater, expanding the potential practical applications of S. oneidensis.

A blessing or a curse? Can digital economy development narrow carbon inequality in China?

The importance of carbon emissions reduction notwithstanding, the issue of its inequality should also elicit the urgent attention of scholars. This paper first evaluates the carbon inequality between urban and rural areas based on a panel dataset of 30 provinces in China from 2006 to 2019. Then we quantitively investigate the role of digital economy development in reducing carbon inequality. We further explore the possible moderating role of residential disposable income in the rural areas and the impact channels in the nexus between digital economy development and carbon inequality. We find that (1) the relationship between digital economy development and carbon inequality is negative, and digital economy development exerts a significant mitigating impact on carbon inequality. (2) The nexus between digital economy development and carbon inequality is heterogeneous in terms of capital: provinces endowed with lower levels of social and human capital tend to exhibit a stronger connection between digital economy development and carbon inequality. (3) Rural residential disposable income can not only reduce carbon inequality, but can also show a synergistic effect with digital economy development, which means the interaction between rural residential disposable income and digital economy development also restricts carbon inequality significantly. (4) Digital economy development works on carbon inequality by increasing environmental regulation and technology innovation, and these two channels show a mitigating impact on carbon inequality. We propose several policy implications to accelerate the reduction of carbon inequality and the improvement of digital economy development.

SN 2022ann: a Type Icn supernova from a dwarf galaxy that reveals helium in its circumstellar environment

ABSTRACT We present optical and near-infrared (NIR) observations of the Type Icn supernova (SN Icn) 2022ann, the fifth member of its newly identified class of SNe. Its early optical spectra are dominated by narrow carbon and oxygen P-Cygni features with absorption velocities of ∼800 km s−1; slower than other SNe Icn and indicative of interaction with a dense, H/He-poor circumstellar medium (CSM) that is outflowing slower than typical Wolf–Rayet wind velocities of >1000 km s−1. We identify helium in NIR spectra 2 weeks after maximum and in optical spectra at 3 weeks, demonstrating that the CSM is not fully devoid of helium. Unlike other SNe Icn, the spectra of SN 2022ann never develop broad features from SN ejecta, including in the nebular phase. Compared to other SNe Icn, SN 2022ann has a low luminosity (o-band absolute magnitude of ∼−17.7), and evolves slowly. The bolometric light curve is well-modelled by 4.8 M⊙ of SN ejecta interacting with 1.3 M⊙ of CSM. We place an upper limit of 0.04 M⊙ of 56Ni synthesized in the explosion. The host galaxy is a dwarf galaxy with a stellar mass of 107.34 M⊙ (implied metallicity of log(Z/Z⊙) ≈ 0.10) and integrated star-formation rate of log (SFR) = −2.20 M⊙ yr−1; both lower than 97 per cent of galaxies observed to produce core-collapse supernovae, although consistent with star-forming galaxies on the galaxy Main Sequence. The low CSM velocity, nickel and ejecta masses, and likely low-metallicity environment disfavour a single Wolf–Rayet progenitor star. Instead, a binary companion is likely required to adequately strip the progenitor and produce a low-velocity outflow.

Observation and Isochoric Thermodynamic Analysis of Partially Water-Filled 1.32 and 1.45 nm Diameter Carbon Nanotubes

Recent measurements of fluids under extreme confinement, including water within narrow carbon nanotubes, exhibit marked deviations from continuum theoretical descriptions. In this work, we generate precise carbon nanotube replicates that are filled with water, closed from external mass transfer, and studied over a wide temperature range by Raman spectroscopy. We study segments that are empty, partially filled, and completely filled with condensed water from -80 to 120 °C. Partially filled, nanodroplet states contain submicron vapor-like and liquid-like domains and are analyzed using a Clausius-Clapeyron-type model, yielding heats of condensation of water inside closed 1.32 nm diameter carbon nanotubes (3.32 ± 0.10 kJ/mol and 3.72 ± 0.11 kJ/mol) and 1.45 nm diameter carbon nanotubes (3.50 ± 0.07 kJ/mol) that are lower than the bulk enthalpy of vaporization and closer to the bulk enthalpy of fusion. Favored partial filling fractions are calculated, highlighting the effect of subnanometer changes in confining diameter on fluid properties and suggesting the promise of molecular engineering of nanoconfined liquid/vapor interfaces for water treatment or membrane distillation.

Misalignment of magnetic field in DIII-D assessed by post-mortem analysis of divertor targets

We assess the toroidal magnetic field B t asymmetry in DIII-D due to a misalignment of the toroidal field coils with respect to the poloidal magnetic field coils and vacuum vessel. The peak-to-peak variation of the divertor strike point (SP) radius is measured to be 1 cm, with an n = 1 toroidal pattern. We use the centre of a narrow carbon deposition band on tungsten-coated divertor tiles just inside the outer strike point (OSP) as a proxy for the divertor SP location. The band occurred in a series of reverse B t discharges with the OSP positioned on the divertor inserts due to strong E × B drift transport of C from the inner to the outer SP through the private flux region. The variation in band radius (and hence the magnetic SP) is a (4.89 ± 0.31) mm shift toward (310 ± 4)° toroidal direction. These measurements agree well with previous measurements of the 3D magnetic field distribution (Luxon 2003 Nucl. Fusion 43 1813), simulations performed by the mafot field line integration code, and recent Langmuir probe measurements in the small-angle-slot (SAS) divertor (Watkins et al 2019 Nucl. Mater. Energy 18 46). Comparison of these measurements in the SAS divertor also indicates that there is the possibility of a tilt (in conjunction with the shift) of the B t coil field of (0.04 ± 0.07)° towards the toroidal angle of (215 ± 25)°. Previous measurements suggested a field misalignment of (4.6 ± 0.3) mm in the 270° toroidal direction, and a tilt of (0.06 ± 0.02)° toward the 114° toroidal direction, which is similar to the results reported here. These studies will be important for better understanding the radial variation of the toroidal strike line in DIII-D, for designing the new generation of SAS divertor, and for developing an understanding of the impact of error fields on tokamaks with tightly baffled slot divertors.

Solvent-free and dispersant-free synthesis of narrow full width at half maximum carbon dots via sole precursor of p-phenylenediamine

Narrow band gap emissive carbon dots (CDs), especially those with full width at half maximum (FWHM) below 40 nm, is extremely important for biological imaging application due to higher color purity and better resolution. The synthesis of narrow FWHM emissive CDs usually requires the use of specific-structured molecular precursors with a large π conjugated domain. In comparison, the most common precursors for CDs, for instance p-phenylenediamine, are usually believed unsuitable for preparing CDs with FWHM emission below 40 nm. In this work, we challenged this stereotype by using p-phenylenediamine precursor to synthesize CDs with a small FWHM of only 29 nm. Instead of using traditional solvothermal method, a facile solvent-free method was developed to synthesize CDs with the powder of p-phenylenediamine in the autoclave under a reaction temperature of 200 °C. After dispersed in solution, CDs show a red emission around 615 nm with FWHM of 29 nm and a photoluminescence quantum yield (PLQY) of 12.8%. Through experiments and theoretical calculation, we found that the FWHM emission is positive correlated to the content of amino groups on the surface of CDs. In comparison to traditional solvothermal method, the current solvent-free method can promote the synthesis of CDs with less amino groups on the surface, reducing fluorescence center types, and hence realizing smaller FWHM emission. In addition, as-prepared CDs were used for biological imaging, and realized a rapid no-wash cell imaging.

From normal to anomalous diffusion of water molecules in narrow carbon nanotubes with defects, gases, and salts

In this letter, we study the diffusion of water molecules inside narrow carbon nanotubes in the presence of nanotube defects, gas molecules and salt ions by using molecular dynamics simulations. Mean square displacement (MSD) with a power-law fitting parameter , and the probability distribution function (PDF) with an distribution parameter a, of water molecules are calculated. It is found that within the diffusion time scale, water molecules exhibit a superdiffusion behavior with inside a perfect nanotube and the superdiffusion is weakened in the presence of gas molecules and salt ions. Meanwhile, a normal diffusion behavior with is observed inside a defective nanotube, and it is replaced by a subdiffusion behavior with when gas molecules and salt ions are involved. PDF of water molecules is found to be Gaussian-like with subject to superdiffusion and normal diffusion, while it becomes a center-peaked and long-tailed Lévy distribution with a < 2 subject to subdiffusion. Furthermore, it is found that the diffusion behavior of water molecules approaches normal diffusion as the radius size of the nanotube increases. Our result implies anomalous transport behavior of water in nanochannels due to the common presence of defects, gases and salts in nanochannels.

Efficient upgrading of polyolefin plastics into C5–C12 gasoline alkanes over a Pt/W/Beta catalyst

A Pt/W/Beta catalyst allows for an excellent yield (63.6 wt%) of C5–C12 gasoline alkanes along with a narrow carbon number distribution and abundant mono-branched isomers under mild conditions.