N2 Absorption Research Articles

Facile synthesis of ZSM-5 nanosheet arrays by preferential growth over MFI zeolite [100] face for methanol conversion

Abstract In pertrochemical and biomass processes, HZSM-5 crystals with short straight channels are always preferred for easier diffusion reason and less coke formation. In this study, ZSM-5 nanosheets arrays with 50 nm straight channels are synthesized through their preferential growth over [100] faces of parent HZSM-5. The composite HZSM-5 was characterized by XRD, SEM, TEM, XPS, N2 absorption and NH3-TPD and its anit-coking capability was evaluated with methanol conversion as a probe reaction. The short straight channels of HZSM-5 nanosheets facilitate the diffusion of molecules and showed extended lifetime than the corresponding parent HZSM-5. It is suggested that the [100] face of parent HZSM-5 crystal is more vulnerable than the [010] face, and produced much more defects in the alkaline recrystallization environment, and thus enabled the preferential growth of nanosheets. The mechanisms of nanosheets formation can be applied to the synthesis of ZSM-5 with shorter straight channels.

Unique thiophilic affinity MOFs as specific sorbent for disulfide bond-containing compounds capture

Stationary sorbents play a key role in the separation process. We present here a kind of unique separative material, called thiophilic affinity MOFs, as specific sorbent for the capture of compounds containing disulfide-bond. The sorbent was obtained through epoxide ring-opening reaction among MOF-5-NH2, tris(2,3-epoxypropyl) isocyanurate, and thiophilic reagents under mild reaction condition. The synthesized sorbent was characterized with X-ray diffraction, scanning electron microscope, transmission electron microscope, Fourier transform infrared, thermogravimetric analysis and N2 absorption. The capillary electrophoresis experiments verified their high specific recognization and separation for disulfide bond-containing compounds.

Plasmon Sensitized Heterojunction 2D Ultrathin Ag/AgI-δ-Bi2O3 for Enhanced Photocatalytic Nitrogen Fixation.

A novel 2D ultrathin Ag/AgI-δ-Bi2O3 photocatalyst was constructed by a facile hydrothermal and in situ photodeposition method, which presented a uniform nanosheet structure with an average height of 6 nm. Its composition, morphology and light-harvesting properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectrophotometer (UV–vis) and photoluminescence (PL) measurements in detail. The Ag/AgI-δ-Bi2O3 nanocomposites showed an excellent photocatalytic nitrogen fixation performance of 420 μmol L−1 g−1 h−1 in water without any sacrificial agent. The introduction of Ag/AgI nanoparticles caused the morphology modification of δ-Bi2O3, a higher concentration of oxygen vacancy, and the construction of a plasmon sensitized heterojunction, resulting in enhanced light absorption, improved separation efficiency of charge carriers and strong N2 absorption and activation ability, which are responsible for the superior photocatalytic performance of Ag/AgI-δ-Bi2O3.

Synthesis of Rosin Methyl Ester Using PTSA/ZrO2/Mo-MCM-41 Mesoporous Molecular Sieves

In this work, Mo-MCM-41, Zr-MCM-41, Sn-MCM-41 and Ti-MCM-41 mesoporous molecular sieves were successfully synthesized via hydrothermal synthesis. An acidic group (SO42−, PTSA etc.) was introduced into the mesoporous molecular sieves to obtain modified mesoporous molecular sieve catalysts. The XRD, N2 absorption–desorption isotherms, FT-IR and Py-IR results reveal that PTSA/ZrO2/Mo-MCM-41 had a mesoporous molecular sieve structure containing a large number of acidic centers. The PTSA/ZrO2/Mo-MCM-41 catalyst illustrated superior catalytic performance for synthesis of rosin methyl ester and the esterification rate was 88.2% under the optimized conditions. At the same time, the PTSA/ZrO2/Mo-MCM-41 catalyst has excellent stability and can be recycled and reused with negligible loss in activity over six cycles.

Linear and nonlinear optical properties of chlorophyll-a extracted from Andrographis paniculata leaves

This paper reports the linear and third-order nonlinear optical (NLO) properties of chlorophyll-a, a natural pigment extracted from the medicinal plant Andrographis paniculata. Silica column chromatography technique was used to extract the chlorophyll-a from the plant leaves. The functional groups present in the extracted sample were recognized by Fourier transform infrared (FT-IR) spectra. The sample was also characterized by UV–Vis, fluorescent spectra and Z–scan techniques. Z–scan study reveals that the extracted natural pigment chlorophyll-a evinces a large negative nonlinear refractive index n2 and nonlinear absorption coefficient β respectively owing to self-defocusing and saturable absorption behaviors. Third-order NLO susceptibility χ(3) of chlorophyll-a was measured to be of the order of 10–6 esu. The sample fulfilled the conditions for figure of merit and we believe that the natural pigments extracted from the Andrographis paniculata leaves may be suitable for all-optical switching applications.

Photocatalytic Fixation of Nitrogen to Ammonia by Single Ru Atom Decorated TiO2 Nanosheets

Photocatalysis shows a great potential for N2 fixation to NH3 under mild conditions, which intrigues increasing research attention in recent decades. To this end, the design of efficient photocatalysts is the key. Herein, we report the synthesis of single atom Ru decorated TiO2 nanosheets rich in oxygen vacancies. Single Ru sites greatly promoted photoreduction of aqueous N2 to NH3, affording an NH3 formation rate of 56.3 μg/h/gcat. We found that isolated Ru atoms likely weakened the hydrogen evolution, promoted absorption of N2, and also improved the charge carrier separation, which led to enhanced N2 photofixation.

Neural network aided fast pointing information determination approach for occultation payloads from in-flight measurements: Algorithm design and assessment

Pointing information is decisive to solving precise profile retrieval issues from occultation measurements. Research regarding stratospheric O3 hole in Antarctic and surface O3 pollution would significantly benefit from massive occultation measurements. A neural network aided pointing information determination approach, in terms of tangent heights, is proposed to address issues requiring fast and easy-to-use determined tangent heights. The geometrical triangular iteration (GTI) algorithm in this work is based on N2 absorption microwindows, and several treatments (e.g., tangential stride generator and triangular-net optimization) are adopted. In addition, LSTM is employed to reduce time consumption and increase accuracy. Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) in-flight measurements are used to assess this approach. The comparison between the proposed algorithm and eight official products indicates a promising performance. Correlation coefficient for each orbit is greater than 0.99. The processing time is about 16.6 min per orbit with an average cost of ∼0.06. The introduction of LSTM technique demonstrates an approximate 28.49% better result, with less computation time. It costed less than 30 s to determine eight orbit tangent heights. In general, although minor issues remain, this LSTM-aided GTI algorithm is applicable in industry.

Confined growth of multiple gold nanorices in dual-mesoporous silica nanospheres for improved computed tomography imaging and photothermal therapy.

IntroductionIn this work, we have developed a novel “confined-growth” strategy to synthesize PEGylated multiple gold nanorices-encapsulated dual-mesoporous silica nanospheres (designated as PEGylated MGNRs@DMSSs) containing both small mesopores (2.5 nm) in the shell and large mesopores (21.7 nm) in the core based on a well-established, seed-mediated growth method. The photothermal effect and CT imaging ability were also studied.MethodsThe nanoparticles were characterized by Fourier transform infrared (FT-IR) spectra, N2 absorption isotherms, Field-emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Confocal microscopy.ResultsThe longitudinally-localized surface (LSPR) absorption properties of MGNRs@DMSSs can be easily tuned by altering the amount of HAuCl4 in the gold growth solution. Additionally, the resultant PEGylated MGNRs@DMSSs have monodispersed, spherical morphology and good colloidal stability in an aqueous solution. More importantly, when exposed to NIR irradiation, the PEGylated MGNRs@DMSSs exhibit both higher temperature increments and better photothermal effects than that of single PEGylated gold nanorods at nearly an equivalent LSPR absorption. In addition, as CT contrast agents, the PEGylated MGNRs@DMSSs display a better CT imaging performance, in comparison with single PEGylated gold nanorods at the same Au concentration.ConclusionTaken together, results indicate the potential for MGNRs@DMSSs used in CT imaging-guided photothermal therapy. Such a simple “confined-growth” strategy within a porous matrix offers a promising platform to design and prepare novel metal(s) oxide@silica nanocomposites for use in further cancer bio-imaging and therapy.

Collision-induced absorption and electric quadrupole transitions of N2 by OF-CEAS near 4.0 µm and CRDS near 2.1 µm

Highly sensitive cavity enhanced laser techniques are used for accurate measurements of the absorption of dinitrogen (N2) at two spectral points of the fundamental and first overtone bands. Spectra of pure N2 and of a N2/O2 mixture were recorded near 2491 and 4720 cm−1 by Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) and Cavity Ring Down Spectroscopy (CRDS), respectively. The noise level of the OF-CEAS and CRDS spectra corresponds to a minimum detectable absorption, αmin, of about 10-9 and 10-11 cm−1, respectively. Measurements involve both the N2 collision-induced absorption (CIA) bands and the very weak 2–0 S(10) and S(11) electric quadrupolar transitions. Accurate CIA binary coefficients, BN2−N2 and BN2−O2, are derived from the pressure-squared dependence of the baseline level of the spectra recorded at pressures below 1 atm. These CIA values are compared to previous determinations from high pressure spectra (up to 90 atm) and to recent classical molecular dynamics simulations (CMDS). An overall good agreement is obtained although a significant deviation is observed for the first overtone CIA near 4720 cm−1. The line position and intensity (on the order of a few 10−30 cm/molecule) of the 2–0 S(10) and S(11) electric quadrupolar transitions are determined experimentally for the first time and compared to theoretical values provided in the HITRAN2016 database.

The trinuclear platinum(ii) complex in Vèzes' red salt as a building block of coordination polymers.

One-dimensional (1D) and three-dimensional (3D) coordination polymers comprising triangular [Pt3(NO2)6(μ3-O)]2- ([Pt3]2-) units were prepared from K2[Pt3]·3H2O (1), also known as Vèzes' red salt. The reaction between 1 and excess 18-crown-6 ether afforded the 1D coordination polymer [K(18-crown-6)]2[Pt3] (2), whereas the reaction between 1, excess 18-crown-6 ether, and AgPF6 afforded the 1D coordination polymer [Ag(18-crown-6)]2[Pt3]·(CH3)2CO (3). However, the reaction between 1 and equimolar amounts of 18-crown-6 and AgPF6 afforded the 3D coordination polymer [Ag2(18-crown-6)][Pt3]·(CH3)2CO (4). Furthermore, the 3D coordination polymer [Ag2Pt3(μ3-O)(NO2)6((CH3)2CO)2]·(CH3)2CO (5) containing three Pt2+ → Ag+ dative bonds was obtained by the reaction of 1, Bu4NPF6, and AgPF6. The N2, O2, and CO2 gas absorption isotherms of 1-5 were obtained, revealing that the dry crystals of 4 exhibit a selective CO2 absorption ability.

Preparation of Ag@zeolitic imidazolate framework-67 at room temperature for electrochemical sensing of hydrogen peroxide.

In this work, a novel non-enzymatic hydrogen peroxide sensor, Ag@zeolitic imidazolate framework-67 (Ag@ZIF-67)/glassy carbon electrode (GCE), was fabricated by a simple method at room temperature. The morphology and structure of Ag@ZIF-67 were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, atomic absorption spectrophotometry, and N2 absorption isotherms, which indicated that core-shell Ag@ZIF-67 was successfully synthesized with a porous rhombic dodecahedron structure. Electrochemical investigations demonstrated that the Ag@ZIF-67/GCE had strong electrocatalytic activity towards hydrogen peroxide reduction with a low detection limit of 1.5 μM (S/N = 3), a fast response time of 3 s, and three different linear relationships in the ranges of 5.0 μM-275 μM, 775 μM-2775 μM, and 4775 μM-16 775 μM with sensitivities of 27 μA mM-1 cm-2, 13 μA mM-1 cm-2, and 5.3 μA mM-1 cm-2, respectively. Moreover, the fabricated sensor exhibited an excellent recovery rate in real sample analysis of medical hydrogen peroxide disinfectant. These results proved that Ag@ZIF-67/GCE is an effective electrochemical sensor for detecting hydrogen peroxide.

Analysis of Mechanical Performance and Microstructure of Steel Slag Processed with Accelerated Carbonation

The accelerated carbonation with different pressure steaming conditions was used to process the steel slag, so the slag could turn into a primary cementitious product with carbonation activity. XRD, FTIR, TG, N2 absorption BET surface area analyzer and SEM were used to characterize the mineral and chemical compositions and microstructure of each sample before and after the carbonation. The results show that: the carbonation products with different morphologies are formed under different temperature conditions. The optimum temperature for the accelerated carbonation for processing the steel slag is selected to be 90 °C, which results in the compressive strength of 32.8 MPa. The BET specific surface area of the steel slag reduces after carbonation, the sample density increased after carbonation.

Fabrication of Ag@AgCl with Enhanced Plasmonic Photocatalysis Performance via a Deep Eutectic Solvent

The plasmonic photocatalyst Ag@AgCl was successfully prepared through a facile solvothermal method via a deep eutectic solvent (DES), which is composed of choline chloride and urea. X-Ray diffraction, scanning electron microscopy, energy-dispersive X-ray, element-mapping, X-ray photoelectron spectroscopy, N2 absorption–desorption, and UV-vis diffuse reflectance techniques were adopted to analyse the performance of the plasmonic photocatalyst. Characterisation results indicated that the DES not only served as a solvent and Cl source, but also as a reductant. Meanwhile, the probable mechanism for the formation of Ag@AgCl is discussed, which revealed a visible light enhanced photocatalytic property for the degradation of benzidine. Furthermore, the photocatalyst showed no decrease in its catalytic activity even after five cycles of operation. Finally, a possible photocatalytic oxidation mechanism of Ag@AgCl is proposed.

Study on Cogasification of Food Waste Char with Biomass/Coal Char and Their Interaction Mechanisms

In this paper, the effects of gasification temperature and blending ratios on cogasification reactivity of food waste char with sawdust/Shenfu coal char were studied via a thermogravimetric analyzer. Moreover, the relationship between synergy and char physical–chemical structure evolution was further studied using scanning electron microscopy equipped with energy-dispersive X-ray analysis (SEM–EDS), N2 absorption, and Fourier transform (FT) Raman techniques. The results revealed a significant synergetic effect between food waste and Shenfu coal. The synergetic effect always occurred at the mid-later reaction stage and was enhanced with the increase in carbon conversion. However, no synergy was found between food waste and sawdust. In the food waste–Shenfu cogasification process, ash present in food waste (rich in Ca) transferred to the surface of Shenfu char without blocking the pore structure of Shenfu char. Moreover, the FT-Raman analysis revealed that the food waste ash reacted with Shenfu char to form...

Toxicological Evaluation of Luminescent Silica Nanoparticles as New Drug Nanocarriers in Different Cancer Cell Lines.

Luminescent mesoporous silica nanoparticles, CdTeQDs@MNs@PEG1, SiQDs@Isoc@MNs and SiQDs@Isoc@MNs@PEG2, were successfully synthetized and characterized by SEM, TEM, XRD, N2 nitrogen isotherms, 1H NMR, IR, absorption, and emission spectroscopy. Cytotoxic evaluation of these nanoparticles was performed in relevant in vitro cell models, such as human hepatoma HepG2, human brain endothelial (hCMEC/D3), and human epithelial colorectal adenocarcinoma (Caco-2) cell lines. None of the tested nanoparticles showed significant cytotoxicity in any of the three performed assays (MTT/NR/ LDH) compared with the respective solvent and/or coating controls, excepting for CdTeQDs@MNs@PEG1 nanoparticles, where significant toxicity was noticed in hCMEC/D3 cells. The results presented reveal that SiQDs-based mesoporous silica nanoparticles are promising nanoplatforms for cancer treatment, with a pH-responsive drug release profile and the ability to load 80% of doxorubicin.

Enabling Nitrogen Fixation on Bi2WO6 Photocatalyst by c-PAN Surface Decoration

It remains a challenge to obtain active sites on semiconductor-based photocatalysts for nitrogen fixation. Herein, we decorate Bi2WO6 by cyclized polyacrylonitrile (c-PAN) to craft a hybrid photocatalyst with superior nitrogen fixation performance (160 μmol·h–1·g–1). The unsaturated N in c-PAN can serve as active sites to achieve strong N2 absorption and activation. This facile approach provides new insight into the reasonable design of elegant photocatalysts with abundant active sites.

Transmission Electron Microscopic Observation of Both Ionomer and Pt Distribution and Their Effects on Cathode Performance for Polymer Electrolyte Fuel Cells

In the electrode of a polymer electrolyte fuel cell (PEFC), the distribution of perfluorosulfonic ionomer on the Pt catalyst supported on carbon black (CB) significantly affects the fuel cell performance. The observation of the distribution of the ionomer and Pt catalyst on the carbon support are important for the improvement of PEFC performance. Recently, the direct observation of the ionomer with transmission electron microscopy (TEM) without damage by the electron beam has become possible due to technological improvements.In this study, four types of cathode catalyst inks were prepared in which the added amount of the perfluorosulfonic ionomer, prepared by AGC, was varied with respect to the CB (I/C ratio; I, weight of fluoro-ionomer; C, weight of graphitized CB (GCB)). The membrane electrode assemblies (MEAs) were made from catalyst layers (CLs), which were decals printed with these inks by the hot-press method. The catalyst powders collected from the cathodes were placed on a TEM grid without pretreatment. The ionomer distribution on GCB-supported Pt catalysts was observed with a high resolution TEM (Hitachi HT7700) with a low acceleration voltage (80 kV).1 The pore distribution of each sample was measured by use of N2 absorption analysis. The current-voltage (I-V) performances of the MEAs were also evaluated, and the effects of the ionomer distribution on the cell performance were investigated. A TEM image of the catalyst collected from the cathode (I/C = 0.8) is shown in Fig. 1a. The amorphous structure of the ionomer is able to be clearly observed on the surfaces of both the GCB and the Pt nanoparticles with the low acceleration voltage, high resolution TEM. A TEM image of the electrode catalyst of I/C = 1.6 sample is shown in Fig. 1b. The amorphous areas increased with increasing ionomer content and were observed more frequently. Agglomerations of Pt particles were also observed in some areas. In a previous study, Pt agglomeration and re-deposition due to sulfonate groups included in the high IEC ionomer were reported.2 These results suggested that the increased acid concentration of the ionomer around the Pt nanoparticles can cause severe Pt agglomeration. The mobilities of both ionomer and Pt particles might be influenced by the surface of the CB, and those on GCB would be expected to be larger than those on CB due to the smooth surface of graphite. The I-V performance of the MEAs is shown in Fig. 2. The performance increased with increasing I/C from 0.4 to 0.8 and 1.2 and then decreased for 1.6. Improvements in current density were considered to be due to increases in the number of proton-conductive pathways due to the ionomer in the CLs. The pore distribution of various the I/C samples were measured by use of N2 absorption analysis. The pore volumes of both nanopores of 2-5 nm and primary pores of 5-10 nm for the I/C = 1.6 cathode were decreased. The performance decrease for I/C = 1.6 is considered to be due to a decrease in the number of oxygen transport paths due to occupation of the pores of the carbon support with the ionomer. References (1) Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources, 315, 179 (2016). (2) R. Shimizu, Y.-C. Park, K. Kakinuma, A. Iiyama, M. Uchida, J. Electrochem. Soc., 165 (6) F3063-F3071 (2018) Figure 1

Optical nonlinearities in LiKB4O7-Ag2O and LiKB4O7-Ag2O-Gd2O3 glasses containing Ag nanoparticles.

The results on optical studies of LiKB4O7-Ag2O and LiKB4O7-Ag2O-Gd2O3 glasses containing Ag nanoparticles formed during annealing in vacuum and air are presented. Strong bands that appear in optical transmission spectra of the samples correspond to plasmon excitations associated with Ag nanoparticles. The average radius of Ag nanoparticles was retrieved from FWHM of the plasmon bands and found to be 1.8-3.8nm. Nonlinear optical properties of the glasses were studied by the single-beam Z-scan technique. In particular, influence of Ag nanoparticles on nonlinear refraction n2 and nonlinear absorption β coefficients was investigated.

Synthesis of mesoporous silicon from industrial waste sodium-based slag

An increasing amount of waste sodium-based slag was generated during the purification process of metallurgical silicon that causes a posed problem to the environment. Here, a simple but effective approach was developed for the synthesis of mesoporous silicon from waste sodium-based slag. The as-received slag was leached and then calcined to fabricate silica as a precursor. Subsequently, the nanostructured silicon was produced through the reduction of the silica in a magnesium (Mg) vapor. The mechanism suggested that the Mg-containing phases (Mg2Si, MgSiO3, and MgO) were performed as an intermediary agent and facilitated the formation of nano-scale silicon. Nitrogen (N2) adsorption study of the final silicon product showed a BET surface area of 75.5 m2/g and a distributional BJH pore size of 3.7 nm. Significantly, the N2 absorption capacity of the mesoporous silicon reached 200 m3/g. The aim of this study is to recycle the waste sodium-based slag and provide an alternative for the synthesis of mesoporous silicon materials.

Structural, Optical, and Magnetic Properties of Gd-Doped TiO2 Nanoparticles

Polycrystalline pure and (1, 3 and 5%) Gd-doped TiO2 nanoparticles were synthesised by simple sol-gel method. The structure, morphology and physico-chemical properties of samples were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, transmission electron microscopy and N2 absorption and desorption isotherms. Photoluminescence (PL) measurements revealed that the samples exhibit extended light absorption frequencies in visible light region. The visible emission of TiO2 is found to be largely dependent on the defects and which were found to be tailored by varying Gd doping concentration. Room temperature magnetic studies reveal the transition from ferromagnetic to paramagnetic nature which occurs due to the high magnetic moment of Gd ions and its interaction with host lattice.