In order to obtain visible light response, doping or modifying titania by nonmetal elements such as nitrogen has been investigated extensively in recent years. In this paper, recent progress in mechanism of titania doping by nitrogen, carbon, sulphur, fluorine is reviewed. Methods for preparing nitrogen doped titania are follows: i) reduce titania by ammonia gas under high temperature; ii) sputter titania target in nitrogen gas; iii)pulsed laser deposition in nitrogen gas; iv) mechanochemical processing titania in ammonia; v)direct oxidation titanic nitride; vi)forming organic titanic nitride and then thermal treated; vii)hydrolysis a titanic precursor in ammonia solution then thermal treated the precipitate. Structure and mechanism of visible light response of the nitrogen doped titania are discussed according to literature reports although there had many inconsistent conclusions. Narrowing the band gap of titania or forming a new isolated level in band gap may be the most probable reason for visible response. Titania doping by carbon, sulphur or fluorine can also give rise to visible light response and high photo efficiency, but there had many inconsistent conclusions too.
Transition metal dichalcogenides (TMDCs) have been widely concerned due to dependence of its energy band on the number of layers. Especially the two. dimensional molybdenum disulfide (MoS2) film has become a research hot spot because of its excellent photoelectric properties. So far, chemical vapor deposition (CVD) and exfoliation have become the main methods for preparing MoS2 films, but it is very difficult to precisely control the layers of MoS2 using these methods. Research confirms that the MoS2 films can be further processed by etching methods so as to obtain the sample with a monolayer or a specific number of layers. Therefore, in this paper the research progress about etching technology of MoS2 films based on different etching mechanisms is reviewed and the influence of different etching techniques on the quality of etched films is analyzed. Moreover, the application and prospects of these etching methods in field effect transistor (FET) and other optoelectronic devices are also introduced. Finally, problems that need to be solved in the future study are prospected.
In recent years, one-dimensional (1D) polymer-inorganic nanocomposites have attracted considerable attention due to their unique structures, excellent properties and tremendous application prospects. Since the composite of the inorganic phase and polymer phase in the nanoscale could remarkably promote the intrinsic properties and the functions, the corresponding materials exhibit outstanding performances in electron transmission, optical properties, mechanical properties and so on. Many of them possess application potentials in the fields of electronic devices, energy storage devices, photochemical sensors, catalysts and other fields. By enumerating several different 1D polymer-inorganic composite nanostructures, three commonly used strategies, including template synthesis method, electrospinning method and 1D assembly method are summarized herein. The principles and the characteristics of various preparation methods are introduced. Finally, the outlook for future development is prospected.
Mercury pollution has posed increasingly severe threat to environment all over the world. Dealing with the problem of mercury contamination in water bodies is extremely urgent. The iron-based nanoparticles like FeSx, Fe3O4, Fe-0 are used to remove mercury from aqueous solutions due to their high adsorption capacity and large surface area. In addition, using particle stabilization techniques and functional group modification could increase the dispersion of iron-based nanoparticles, offer more adsorption sites for the adsorption of mercury, which could enhance the effect of mercury removal. This paper emphasizes on the stabilization of FeSx nanoparticles, thiol-functionalization and amino-functionalization of Fe3O4, etc. The applications of functionalized iron-based nano-materials are summarized. The influential factors of mercury removal by iron based materials are further discussed, and then the adsorption mechanisms of mercury by functionalized iron based nanoparticles are also explored. Finally, the outlook of mercury removal in water environment by modified iron-based nano-materials are presented.
Hierarchically porous aluminophosphate molecular sieves possessing both micropores and mesopores recently receive increasing interest because they can reduce diffusion limitations in the reactions involving bulky molecules. This paper mainly focuses on the latest development of synthesis, characterizations and catalytic applications of hierarchically porous aluminophosphate molecular sieves. According to the formation mechanism of hierarchical pores, the synthetic methods of the hierarchical structured aluminophosphate molecular sieves can be classified into four categories: hard template, soft template, nontemplated and post-synthesis method. The advantages and disadvantages of these synthetic methods are systematically compared with each other. From the point view of industrial application, the nontemplated and post-synthesis methods are more promising compared to other synthetic routes. In addition, various techniques characterizing the acid properties and pore textures of hierarchically porous molecular sieves are described, taking silicoaluminophosphate molecular sieve as an example. However, most of these measurements need to be performed on complex expensive instruments, and the process is time-consuming. Thus, to develop some facile and general characterization techniques is highly desirable. Finally, the catalytic applications of these hierarchically porous materials in three kinds of important reactions (such as alkylation reaction, isomerization reaction and, methanol to olefins) are reviewed. The relationships between the catalytic performances and the properties of catalysts are analyzed in detail.
Molecular beacons are stem-loop hairpin-structured fluorescence probes with a fluorescent dye at 5' end and a fluorescence quencher at 3' end. When a target complementary sequence is absent, the molecular beacons do not fluoresce, because the formation of the hairpin structure brings the quencher and fluorophore into close proximity, whereby fluorescence is quenched with high efficiency. When a target molecule is present, the hybridization between the target and the loop sequence of the molecular beacon results in the spatial separation of the fluorophore and quencher, which opens the stem-loop structure of molecular beacons to emit fluorescence. Locked nucleic acid is a nucleic acid analogue containing one or more LNA nucleotide monomers with a bicyclic furanose unit locked in an RNA mimicking sugar conformation. It possesses excellent binding affinity to nucleic acid, high biostability and resists to nuclease degradation. Due to the excellent sensitivity and high specificity, the combination of the molecular beacons and locked nucleic acid has aroused wide concern. In this review, we intensively summarize the structure, function, design essentials, current research topics and some important progress. In addition, we also discuss the applications, potential problems and perspective of locked nucleic acid molecular beacons in molecular recognition and bioanalysis.
Development of dual-stimuli-responsive and multi-stimuli-responsive smart polymeric materials becomes more and more important. The recent progresses in molecular-recognition and thermo-responsive composite smart linear polymers, smart microspheres and smart membranes based on poly(N-isopropylacrylamide) (PNIPAM) and beta-cyclodextrin (beta-CD) are reviewed in detail. The different kinds of smart materials are prepared by the same reaction mechanism, namely polymerization of N-isopropylacrylamide (NIPAM) with glycidyl methacrylate (GMA) into poly(N-isopropylacrylamide-co-glycidyl methacrylate) (PNG) polymer at first, followed by introduction of modified mono-6-deoxy-6-ethylenediamino-beta-cyclodextrin (ECD) or mono-6-deoxy-6-hexnediamino-beta-cyclodextrin (HCD) onto PNG polymer by virture of reaction between primary amino groups and epoxy groups. The effects of preparation conditions, the molar ratio of NIPAM to GMA, grafting yields, the types and concentrations of guest molecules on the thermo-responsibility and molecular-recognition characteristics of different composite smart polymeric materials are discussed. Moreover, the applications of composite smart polymeric membranes in affinity separation, controlled release and chrial separation are also discussed. The significance and future of molecular-recognition and thermo-responsive composite polymeric materials are commented.
During last several decades, optical fiber has been applied in many disciplines and areas. Among its kinds of applications, optical fiber sensors have become an interesting research project due to the advantages of optical fiber, such as immunity to electromagnetic interferences, capability of remote measurements, multiplexed detection, small size and low weight and so on. Optical fiber has been applied in fiber-optic sensors based on polyelectrolyte layer-by-layer (LbL) self-assembly multilayers have become into a hot research field since it was reported in 2000. It has widely application in measuring trace substances. In this paper, layer-by-layer self-assembly polyelectrolytes on the surface of optical fibers as well as test of fiber-optic sensors are introduced. The fiber-optic structures, assembly materials, detection principle and performance of different fiber-optic sensors based on multilayers nanocoating are also summarized. Particularly, the preparation, test and application of fiber-optic pH sensors, fiber-optic humidity sensors, fiber-optic gas sensors and fiber-optic biosensors in last decade are reviewed. The outlook of fiber-optic sensors based on LbL polyelectrolyte self-assembly multilayers is suggested.
The basic principle of zonation technology is described in detail. The effects of ozone dosage, temperature, pH, UV, H2O2 and catalyst on the treatment of antibiotics wastewater by ozonation are discussed. The recent developments about ozonation of six kinds of antibiotic wastewater, including beta-lactam antibiotics, macrolide antibiotics, sulfonamide antibiotics, quinolone antibiotics, tetracycline antibiotics, and chloramphenicol antibiotics, are reviewed. Moreover, existing problems and development trend of wastewater treatment by ozonation technology are presented.
The main physical-chemical processes of secondary organic aerosols (SOA) formation from volatile and semi-volatile compounds can be summarized as photooxidation mechanism, nucleation process, condensation, gas/particle partition and heterogeneous reaction mechanism according to the research about SOA formation mechanism of the last twenty years. These physical-chemical processes and their influence factors are discussed in detail in this paper. Isoprene, toluene and its homologs are focused to illustrate the photooxidation of alkene and aromatic compounds. Two important theories of gas/particle partition, absorption mechanism and adsorption mechanism are analyzed. Heterogeneous reaction is proposed for its substantial effect for SOA formation. At last, the prospects for the study direction of the formation mechanism of SOA are given.
This paper has reviewed recent progress in preparation, characterization and application of mesoporous alumina (MA). We introduce the preparation methods of MA contrastively and respectively, and overview the post treatment method of precursors. Subsequently, by contrasting the average pore size, specific surface areas and morphology of MA, we discuss the influence factors on the preparation and thermal stability of MA, which involve preparation method, aluminum sources, template, reactant ratio, pH value, post treatment method of precursors and so on. In addition, analysis and characterization methods utilized in preparation of MA, including transmission electron microscopy (TEM) and selected area electron diffraction (SAED), X-ray powder diffraction (XRD) and low angle X-ray powder diffraction(LAXRD), gas adsorption-desorption method, different thermal and thermo gravimetry analysis ( DT-TGA) and Al-27 magic angle spinning nuclear magnetic resonance (Al-27 MAS NMR), are introduced in detail. Meanwhile, the development trend of preparation and application of MA for the field of catalytic, adsorption, optics and other fields is prospected.