Low-cost synthesis of nanoaggregate SAPO-34 and its application in the catalytic alcoholysis of furfuryl alcohol

Silicoaluminophosphate-34(SAPO-34) molecular sieves have important applications in the petrochemical industry as a result of their shape selectivity and suitable acidity. In this work, nanoaggregate SAPO-34 with a large external surface area was obtained by dissolving pseudoboehmite and tetraethylorthosilicate in an aqueous solution of tetraethylammonium hydroxide and subsequently adding phosphoric acid. After hydrolysis in an alkaline solution, the aluminum and silicon precursors exist as Al(OH)4-and SiO2(OH)-, respectively;this is beneficial for rapid nucleation and the formation of nanoaggregates in the following crystallization process. Additionally, to study the effect of the external surface area and pore size on the catalytic performance of different SAPO-34 structures, the alcoholysis of furfuryl alcohol to ethyl levulinate(EL) was chosen as a model reaction. In a comparison with the traditional cube-like SAPO-34, nanoaggregate SAPO-34 generated a higher yield of 74.1% of EL, whereas that with cube-like SAPO-34 was only 19.9%. Moreover, the stability was remarkably enhanced for nanoaggregate SAPO-34. The greater external surface area and larger number of external surface acid sites are helpful in improving the catalytic performance and avoiding coke deposition.

Micro-sized nanoaggregates:Spray-drying-assisted fabrication and applications

The applications of nanoparticles suffer from their extremely small size and intrinsic trend of agglom-eration.Rearranging nanoparticles to form micro-sized nanoaggregates(MNAs)with increased size,ordered structure,as well as controllable size,shape,and morphology is a crucial step in various fields of science and technology to maintain the unique characteristics of nanoparticles while obtaining greatly enhanced or new performance at the microscale.The structure of MNAs prominently affects their functionality,which is determined by the arrangement of nanoparticles and the interaction between primary particles.Several methods have been proposed to prepare the MNAs,in which spray-drying technology stands out considering the feasibility,scalability for industry,cost,and efficiency.Forced assembly of nanoparticles through spray-drying under tunable process parameters yields diverse physical properties and structural arrangements of nanoparticles of the MNAs,they therefore exhibit enormous potential in a wide range of application fields.This review presents the construction and applications of spray-dried MNAs.The factors that influence the size,morphology,and structure of the MNAs are discussed in detail.In addition,the outstanding application performance resulting from the tightly packed nanoparticles in regular-shaped MNAs obtained by the spray-drying process is illustrated.

Efficient construction of calcium fluoride nanoaggregates for enhanced water vapor adsorption

Calcium fluoride(CaF_(2))is an ideal adsorbent for the dehydration of gaseous hydrogen fluoride(HF)containing water vapor.In this work,a novel CaF_(2)absorbent,spherical CaF_(2)nanoaggregates(NAs)with a closely packed structure,was proposed and efficiently fabricated by spray drying technology.As the building blocks of CaF_(2)NAs,the CaF_(2)nanoparticles(NPs)were prepared by the addition of excess calcium ions(Ca^(2+))or fluorine ions(F−)in the synthesis.The results indicated that the CaF_(2)NPs synthesized by excess Ca^(2+)and the corresponding NAs exhibited much better water vapor adsorption properties than their counterparts by excess F−,owing to higher zeta potentials.More importantly,whether excess Ca^(2+)or F^(−),CaF_(2)NAs had further enhanced water vapor adsorption capacity compared to primary CaF_(2)NPs,possibly owing to their unique nano-micro secondary structures and higher surface areas.This work has great potential in the development of high-performance absorbents for separating moisture from corrosive gas HF.

Highly ordered arrangement of meso-tetrakis(4-aminophenyl)porphyrin in self-assembled nanoaggregates via hydrogen bonding

meso-Tetrakis（4-aminophenyl）porphyrin（TAPP） can self-assemble into nanostructures with different morphologies by a phase-transfer method.The morphologies（nanospheres,nanorods and nanothorns）of porphyrin nanoaggregates could be easily tuned just by changing the concentration of porphyrin in a proper solvent at room temperature.HRTEM images revealed the formation of highly ordered supramolecular arrays of TAPP,i.e. superlattice of TAPP molecules in nanoaggregates,which agreed well with the size of one molecule of TAPP.UV–vis absorption spectra showed an obvious red shift of the Soret band of TAPP,indicating the formation of J-aggregates of TAPP in nanoaggregates.

Thermally Induced Nanocrystal Array of Poly(N-Vinylcarbazole) on Si-Wafer Substrate

Recently, nanostructures such as nanocrystals and nanoaggregates have attracted much attention in many quarters of materials, electronics, and biology to create higher-value-added functional nanoscale materials and films. In this research, the fabrication of nanoaggregates on ultrathin photoconductive films of poly(N-vinylcarbazole) (PVCz) by applying thermal treatment is demonstrated. The structure and size are discussed on the basis of the results of atomic force microscope images. As a result, after thermal treatment of these films above the glass transition temperature (Tg) of PVCz, different types of surface morphological changes were induced showing a dependence on the tacticity of PVCz. Radically polymerized PVCz(r) ultrathin film showed small aggregates with heights of ~8 nm on the film surface after thermal treatment, while cationically polymerized PVCz(c), which has higher isotactic diad fractions than PVCz(r), indicated similar aggregates on the film surface, although the number of aggregates was smaller than PVCz(r). It is considered that these different phenomena depend on the tacticity of PVCz and the interaction between PVCz molecules and the substrate surface.

Biomineralized nanoparticles for the immobilization and degradation of crude oil-contaminated soil

Accidental oil leaks and spills often cause server soil pollution,and in situ remediation is a powerful and economical treatment technology.While during in situ remediation process,unpredicted migration of petroleum hydrocarbon in heterogeneous soil will lead to a long-term source of persistent aquifer contamination.To reduce the migration of petroleum hydrocarbon and effectively improve the in situ remediation efficiency,herein,fungal biomineralization strategy was proposed for the immobilization of petroleum contaminants.A ureolytic fungi strain with crude oil-degradation ability was screened and identified as Chaetomium globosum.When incubated in medium containing Ca2+and crude oil,a mineral corona with spiny nanoparticles was formed at the edge of oil and the interface characters were analyzed using fluorescent pH and dissolved oxygen(DO)sensing films,respectively.Results indicated that biominerals preferred to aggregate around the edge of crude oil,providing favorable microenvironment for fungal growth and then leading to the increase of pH in the microenvironment,eventually accompanied by the formation of mineral corona.The mineral corona with numerous nanoparticles may act as a solid and stable shell,limiting or reducing the mobility of crude oil,and providing enough time for fungal biodegradation.After 28 days incubation,oilcontaminated soil treated with fungal biomineralization showed better immobilization ability for total petroleum hydrocarbon(TPH)under simulated acid-rain condition and higher TPH removal efficiency.This is the first demonstration for the immobilization of oil through fungal biomineralized nanoparticles,thus providing a novel strategy for the in situ remediation of oilcontaminated sites.

Pure redox-sensitive paclitaxelemaleimide prodrug nanoparticles: Endogenous albumininduced size switching and improved antitumor efficiency

A commercial albumin-bound paclitaxel nano-formulation has been considered a gold standard against breast cancer.However,its application still restricted unfavorable pharmacokinetics and the immunogenicity of exogenous albumin carrier.Herein,we report an albumin-bound tumor redoxresponsive paclitaxel prodrugs nano-delivery strategy.Using diverse linkages(thioether bond and disulfide bond),paclitaxel(PTX)was conjugated with an albumin-binding maleimide(MAL)functional group.These pure PTX prodrugs could self-assemble to form uniform and spherical nanoparticles(NPs)in aqueous solution without any excipients.By immediately binding to blood circulating albumin after intravenous administration,NPs are rapidly disintegrated into small prodrug/albumin nanoaggregates in vivo,facilitating PTX prodrugs accumulation in the tumor region via albumin receptormediated active targeting.The tumor redox dual-responsive drug release property of prodrugs improves the selectivity of cytotoxicity between normal and cancer cells.Moreover,disulfide bond-containing prodrug/albumin nanoaggregates exhibit long circulation time and superior antitumor efficacy in vivo.This simple and facile strategy integrates the biomimetic characteristic of albumin,tumor redox-responsive on-demand drug release,and provides new opportunities for the development of the high-efficiency antitumor nanomedicines.

Unusual self-assembled nanoaggregation of the thermally stable metal-free slipped-cofacial J-type phthalocyanine dimer

Nanoaggregation of the thermally stable bis（2-hydroxy-9（10）,16（17）,23（24）-tri-tert-butylphthalocyanine） of J-type was observed by the field emission scanning electron microscopy（FE-SEM）. Ordered phases, represented as threads composed of about 200 nm diameter circles were discovered, unlike the parent dimeric magnesium complex, in which similar circles combine together to give visually distinguishable zones with widths of about 600 nm and the same distance between them.