煤化程度对煤基固体酸结构及其水解纤维素性能的影响

利用煤具有缩合芳环、脂肪侧链及含氧官能团的结构特点，采用不同煤化程度的煤为碳源，在不同炭化温度下制备了煤基固体酸催化剂（CSA）。通过XRD、FT-IR、¹³C NMR对催化剂结构进行了表征。以还原糖和葡萄糖的产率为考察指标，探讨了煤化程度和炭化温度对煤基固体酸非均相催化水解纤维素的影响。结果表明，煤作为碳源具有传统碳源所不具备的结构优势，煤基固体酸碳层片上除含有磺酸基、酚羟基和羧基外，还含有传统碳基固体酸不具备的桥键（-O-、-CH₂-）和侧链（-CH₃、-OCH₃、-CH₂CH₃）。除磺酸基外，其余均由煤的结构演化而来。随着炭化温度的升高，催化剂的芳香度增大、活性基团的种类和数量减少、磺酸基密度逐渐下降，且随着煤化程度增加，煤基固体酸结构可调性降低，所需要的最佳炭化温度也逐渐降低。不同种类的煤基固体酸在水解纤维素过程中表现出了较高的活性，其中，霍林河煤基固体酸的活性最高。水解活性受催化剂芳香片层大小及堆叠高度、片层之间桥键和磺酸基密度等因素的影响，是众多活性基团协同作用的结果。     

Electrochemical Synthesis of Carbon Nanodots Directly from Alcohols

Carbon nanodots (C‐dots) show great potential as an important material for biochemical sensing, energy conversion, photocatalysis, and optoelectronics because of their water solubility, chemical inertness, low toxicity, and photo‐ and electronic properties. Numerous methods have been proposed for the preparation of C‐dots. However, complex procedures and strong acid treatments are often required, and the as‐prepared C‐dots tend to be of low quality, and in particular, have a low efficiency for photoluminescence. Herein, a facile and general strategy involving the electrochemical carbonization of low‐molecular‐weight alcohols is proposed. As precursors, the alcohols transited into carbon‐containing particles after electrochemical carbonization under basic conditions. The resultant C‐dots exhibit excellent excitation‐ and size‐dependent fluorescence without the need for complicated purification and passivation procedures. The sizes of the as‐prepared C‐dots can be adjusted by varying the applied potential. High‐quality C‐dots are prepared successfully from different small molecular alcohols, suggesting that this research provides a new, highly universal method for the preparation of fluorescent C‐dots. In addition, luminescence microscopy of the C‐dots is demonstrated in human cancer cells. The results indicate that the as‐prepared C‐dots have low toxicity and can be used in imaging applications.     

Biomass‐Derived Carbon Quantum Dot Sensitizers for Solid‐State Nanostructured Solar Cells

New hybrid materials consisting of ZnO nanorods sensitized with three different biomass‐derived carbon quantum dots (CQDs) were synthesized, characterized, and used for the first time to build solid‐state nanostructured solar cells. The performance of the devices was dependent on the functional groups found on the CQDs. The highest efficiency was obtained using a layer‐by‐layer coating of two different types of CQDs.     

Supplementary research of clinoptilolite-rich tuff composites after adsorption trials using the XPS technique

The paper deals with fabrication of carbonized and hydrophobized clinoptilolite-rich tuff using organic carbon rich substances, here particularly starch and waste vegetable residues, which were pyrolytically combusted and covered the external zeolite surface. Hydrophobization of the zeolite external surface was accomplished by octadecylammonium surfactant. Both surface modified clinoptilolite-rich tuffs were tested and compared with each other with regard to removal of organic (phenol) and inorganic (chromate, arsenate) pollutants from aqueous solutions. These elaborated composites with surface adsorbed pollutant species were analysed by X-ray photoelectron spectroscopy (XPS).     

Carbonization of electrospun poly(acrylonitrile) nanofibers containing multiwalled carbon nanotubes observed by transmission electron microscope with in situ heating

Composite nanofibers with 5% w/w multiwalled carbon nanotubes (MWCNTs) in polyacrylonitrile (PAN) were fabricated using the electrospinning technique. Morphological development during the carbonization process was characterized by transmission electron microscopy (TEM) with in situ heating. It was found that the orientation of graphitic layers increases with temperature and does not change significantly with time during our TEM measurement, except the 750 °C. In the heating stage at 750 °C noticeable enhancement of orientation with time was observed. The presence of embedded CNTs enhances the order of the formed graphitic structures even when the CNTs are irregular or entangled. The results indicate that embedded MWCNTs in the PAN nanofibers nucleate the growth of carbon crystals during PAN carbonization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

One-step synthesis of novel biacidic carbon via hydrothermal carbonization

The novel biacidic carbon has been synthesized via one-step hydrothermal carbonization of glucose, citric acid, and hydroxyethylsulfonic acid at 180 °C for only 4 h. The novel carbon had an acidity of 1.7 mmol/g with the carbonyl to sulfonic acid groups molar ratio of 1:3, which was confirmed by IR, XPS, TPD, SEM, and BET analyses. The catalytic activities of the carbon were investigated through esterification and oxathioketalization. The results showed that the carbon owned the comparable activities to sulfuric acid, which indicated that the carbon holds great potential for the green processes.     

Mini‐Sized Carbon Nitride Nanosheets with Double Excitation‐ and pH‐Dependent Fluorescence Behaviors for Two‐Photon Cell Imaging

Synthesis of mini‐sized carbon nitride nanosheets (CNNSs) by traditional methods remains a challenge. Herein, size‐tunable and uniform mini‐sized CNNSs are synthesized by hydrothermal carbonization of a single polyethyleneimine (PEI) precursor. The as‐obtained mini‐sized CNNSs possess uniform size, good hydrophilicity and abundant nitrogen active sites, which not only exhibit double excitation‐ and pH‐dependent fluorescence behaviors, but also two‐photon excitation fluorescence. áThe resulting CNNSs display low toxicity and can be efficiently delivered into live cells for two‐photon fluorescence imaging, offering great potential as fluorescence probes in biochemical applications.     

A Soft‐Template‐Conversion Route to Fabricate Nanopatterned Hybrid Pt/Carbon for Potential Use in Counter Electrodes of Dye‐Sensitized Solar Cells

Hybrid Pt(platinum)/carbon nanopatterns with an extremely low loading level of Pt catalysts derived from block copolymer templates as an alternative type of counter electrodes (CEs) in dye‐sensitized solar cells (DSSCs) are proposed. DSSCs employing hybrid Pt/carbon with tailored configuration as CEs exhibit higher short‐circuit current and conversion efficiencies as well as stability with a lapse of time compared with conventional cells on the basis of sputtered Pt thin films, evidencing that the new class of hybrid nanostructures possess high potential for cost‐effective electrodes in energy conversion devices.

     

Facile Polymer Functionalization of Hydrothermal‐Carbonization‐Derived Carbons

A simple and efficient polymer grafting onto hydrothermal carbonization (HTC)‐derived materials is described. The method pertains to the Diels–Alder cycloaddition reaction of furan moieties present on the surface of a HTC material with the maleimide groups stemming from a maleimide protected poly(ethylene glycol) (Me‐PEG‐MI) by a retro Diels‐Alder reaction. The precursor polymer, HTC material, and final product are characterized. Successful grafting is confirmed by elemental analysis, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and dispersion studies.