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Developing strategies for the production of porous particles with controllable structures using a spray-drying method has attracted attention of researchers for decades. Although many papers have reported their successful production of porous particles using this method, information on how to create and control the porous structures as well as what parameters involving and what formation mechanism occurring during the synthesis process are still not clear. To meet these demands, the present review covers strategies in the spray-drying developments for the fabrication of porous particles with controllable structure. This information is important for optimizing the production of porous particles with desirable properties. Regulation of process conditions and precursor formulations are also explained, including composition, type, and physicochemical properties of droplet and raw components used (i.e., host component, template, and solvent). The electrostatic interactions between the individual components and the droplets are also presented, while this information tends to be neglected in the conventional spray-drying process. To clarify how the porous particles are designed, current experimental results completed with illustrations for the proposal particle formation mechanism are presented. The review also completed with the opportunities and potential roles of the changing porous structures in practical uses. This review would provide information on how to produce porous particles that can be used for advanced functional materials, such as catalysts, adsorbents, and sensors.

Magnetic wires in highly dense arrays, possessing unique magnetic properties, are eagerly anticipated for inexpensive and scalable fabrication technologies. This study reports a facile method to fabricate arrays of magnetic wires directly assembled from well-dispersed α ″ -Fe 16 N 2 /Al 2 O 3 and Fe 3 O 4 nanoparticles with average diameters of 45 nm and 65 nm, respectively. The magnetic arrays with a height scale of the order of 10 mm were formed on substrate surfaces, which were perpendicular to an applied magnetic field of 15 T. The applied magnetic field aligned the easy axis of the magnetic nanoparticles (MNPs) and resulted in a significant enhancement of the magnetic performance. Hysteresis curves reveal that values of magnetic coercivity and remanent magnetization in the preferred magnetization direction are both higher than that of the nanoparticles, while these values in the perpendicular direction are both lower. Enhancement in the magnetic property for arrays made from spindle-shape α ″ -Fe 16 N 2 /Al 2 O 3 nanoparticles is higher than that made from cube-like α ″ -Fe 16 N 2 /Al 2 O 3 ones, owing to the shape anisotropy of MNPs. Furthermore, the assembled highly magnetic α ″ -Fe 16 N 2 /Al 2 O 3 arrays produced a detectable magnetic field with an intensity of approximately 0.2 T. Although high-intensity external field benefits for the fabrication of magnetic arrays, the newly developed technique provides an environmentally friendly and feasible approach to fabricate magnetic wires in highly dense arrays in open environment condition.

Degrading organic dyes via catalytic processes for waste water purification is an important research topic from the environmental conservation point of view. Herein, the catalytic performance of tungsten blue oxide (WO x ) nanoparticles was investigated systematically by varying the reduction temperature. The optimum reduction temperature to obtain the most stable WO x phase was obtained when plasma-synthesized WO3 nanoparticles were thermally reduced at 425 °C. The as-synthesized nanoparticles had an average diameter of 10 nm and a calculated band gap of 2.37 eV, which is lower than that of the WO3 nanoparticles (2.61 eV). The WO x nanoparticles exhibited an excellent performance in degrading rhodamine B under dark conditions and visible light irradiation, with a reaction rate constant 93 times higher than that of the WO3 nanoparticles.

Template selection is a critical step to determining an effective and efficient method for the synthesis of porous materials. We introduce the use of the low-cost poly(methyl methacrylate) (PMMA) as a template in a spray pyrolysis process for the synthesis of a porous carbon particle. Monodisperse, negatively charged, three sizes of PMMA particles are used to evaluate the porous structure formation. The highest surface area of the prepared porous carbon particle is 172 m2/g, which is double that of carbon particles produced using a polystyrene latex (PSL) template. The high surface area is attributed to the low PMMA decomposition residue and the formation of a micropore and a mesopore. The use of PMMA reduces the energy consumption for template decomposition by 32% compared with PSL. This benefit suggests an excellent potential for the use of PMMA in the scaled-up production of porous materials.

Demand for tantalum (Ta) is dramatically increasing and Ta recovery from waste products is essential to attempt to avoid social conflicts caused by escalating Ta mining. Here, we developed a rapid and facile guanidine-assisted precipitation method for recovering Ta from an aqueous solution containing Ta, tungsten (W), and silicon (Si). The guanidine showed high selectivity for removal of Ta over W or Si, and the highest 99.96% of the Ta was recovered as a precipitate in 3 min. The calcined precipitate was very pure crystalline Ta2O5. The method performed well at room temperature without requiring pH adjustment. The proposed method can be regarded as environmentally benign because it minimizes energy consumption, produces little liquid waste, and enables sustainable supply of useful resources.

Pyrrolic-N-rich carbon dots (CDs) that exhibit an absorption peak in the first near-infrared (NIR) window region were developed using a one-step microwave-assisted hydrothermal synthesis. A high concentration of urea enabled the introduction of a large amount of pyrrolic-nitrogen on the CD surfaces. Upon optimization of the experimental conditions, the absorption peak of the CDs red-shifted from 550 to 650 nm. The resulting pyrrolic-N-rich CDs exhibited photothermal effects with high NIR photothermal efficiency (54.3%) and photoluminescence. The prepared CDs, which show a first NIR window absorption peak, photoluminescence, and negative surface charge, have the potential to be used as multifunctional nanocarriers for cell imaging and drug delivery and as photothermal agents in cancer therapy.

Herein, we present a charged amino group assisted precipitation (CAAP) method for recovery and recycling of high-purity tungsten from a solution obtained by alkaline leaching of cemented carbide (WC–Co alloy) scrap. When lysine hydrochloride, which contains a charged amino group (NH3+), was added to an alkaline leaching solution containing tungsten (307 mmol L–1), sodium (1236 mmol L–1), and vanadium (1.7 mmol L–1), over 90% of the tungsten was rapidly recovered as a lysine–tungsten precipitate. The sodium in the precipitate was successfully removed by a simple washing process. Calcination was then performed to obtain 99.6% high-purity tungsten oxide, and reduction and carburization of the obtained tungsten oxide resulted in tungsten carbide. A pilot study using the CAAP method demonstrated a considerable decrease (60%) in the displacement (i.e., volume of chemicals used/waste created) compared with that required for the conventional ion-exchange method for tungsten recycling.

Monodisperse, nitrogen-doped hollow carbon spheres of submicron size were synthesized using hexamethoxymethylmelamine as both a carbon and nitrogen source in a short (1 h) microwave-assisted synthesis. After carbonization at 550 °C, porous carbon spheres with a remarkably high nitrogen content of 37.1% were obtained, which consisting mainly of highly basic pyridinic moieties. The synthesized hollow spheres exhibited high selectivity for carbon dioxide (CO2) over nitrogen and oxygen gases, with a capture capacity up to 1.56 mmol CO2 g–1. The low adsorption enthalpy of the synthesized hollow carbon spheres permits good adsorbent regeneration. Evaluation of the feasibility of scaling up shows their potential for large-scale applications.

In this work, Pt nanoparticles were deposited onto the surface of Magneli phase titanium suboxide (TiOx) nanoparticles using a microwave-assisted deposition method. The effect of different concentrations of Pt nanoparticles was investigated to evaluate the strong metal-support interactions (SMSIs) between Pt and TiOx based on their performance for the degradation of organic pollutant molecules. The adsorption and catalytic performance of the as-synthesized Pt/TiOx nanoparticles were evaluated with respect to the degradation of rhodamine B (RhB) molecules without any external energy source. The Pt/TiOx nanoparticles with Pt loading at 10 wt% (10%Pt/TiOx) exhibited a remarkable performance. The XPS, CV, and FTIR analyses confirmed the presence of RhB degradation reactions under dark condition. This remarkable performance of the Pt/TiOx nanoparticles was attributed to the SMSIs between Pt and Ti3+ atoms, which improves their performance compared with Pt/TiO2 nanoparticles, and high density of active sites due to their nanometer size, which results in better performance compared with that of Pt/TiOx submicron particles.

Dual-size nanofibers consisting of a random mixture of nano- and submicron-size nanofibers are promising structures for specific applications such as air filters because of their increased specific surface area and low pressure drop. Synthesis of dual-size nanofibers using one-step electrospinning was reported here for the first time. The formation of well-mixed nano- and submicron-size cellulose–polyvinylpyrrolidone nanofiber composites was accomplished utilizing the physical properties of TEMPO-oxidized cellulose nanofibers (i.e., high thixotropy and high magnitude of zeta potential) and tuning the charge of the polymer jet, which influences the formation and shape of Taylor cone, and Coulombic explosion. The dual-size nanofibers were then spun on the surface of a HEPA filter to obtain a multilayer air filter. Aerosol filtration measurements show that this multilayer air filter has an incredibly high performance, shown by the high quality factor (Qf), 0.117 Pa–1, which is 10 times the Qf of commercial H...

Herein, we present the first successful silica coating of poly(lactic acid) (PLA) nanoparticles, resulting in fully coated PLA–silica core–shell nanoparticles. Subsequent dissolution treatment efficiently dissolved the PLA core template and exclusively yielded hollow silica spheres with a shell thickness of 16 ± 1 nm. The collected PLA could then be directly recycled from the template removal solution and reused to synthesize PLA nanoparticles for a next batch of hollow silica nanospheres. Such hollow particles are of interest in next-generation insulation materials and as lightweight fillers in polymers for fuel-efficient mobility.

Complex fabrication methods for carbon nanotubes limit their potential for scale-up and use in practical applications. This study developed a simple method to deposit multiwall carbon nanotube (MWCNT) forest-like films from polyacrylonitrile and MWCNT solutions by coaxial electrospray. A MWCNT solution was used as the shell flow to generate vertically aligned tree-like structures at mesoscopic scale (∼10−5 m) on aluminum, silicon, and fiber membrane substrates. These forest-like structures assembled from highly conductive core-shell polymer/MWCNT particles with diameter of about 1 μm. The fabricated MWCNT films show good potential for applications in flexible electronics and as conductive filters.

We present a facile method for tungsten ion removal using lysine for the development of an environmentally friendly and sustainable recycling technique. Lysine addition to the tungsten solution achieved 100% tungsten removal within 5 min, as a white lysine–tungsten precipitate. Electrospray ionization mass spectrometry analyses of the tungsten and lysine mixed solutions showed that lysine promoted dehydration condensation reactions of anionic tungsten species such as HWO4– and W6O192– through the electrostatic interactions between positively charged lysine and negatively charged tungsten ions. Calcination of the lysine–tungsten precipitate produced tungsten oxide powder of high purity (99.6%) because the lysine is completely decomposed. This facile and useful metal removal method can be used for polyoxometalates of other metals such as molybdenum, tantalum, and niobium.

A modified emulsion polymerisation synthesis route for preparing highly dispersed cationic polystyrene (PS) nanoparticles is reported. The combined use of 2,2′-azobis[2-(2-imidazolin- 2-yl)propane] di-hydrochloride (VA-044) as the initiator and acetone/water as the solvent medium afforded successful synthesis of cationic PS particles as small as 31 nm in diameter. A formation mechanism for the preparation of PS nanoparticles was proposed, whereby the occurrence of rapid acetone diffusion caused spontaneous rupture of emulsion droplets into smaller droplets. Additionally, acetone helped to reduce the surface tension and increase the solubility of styrene, thus inhibiting aggregation and coagulation among the particles. In contrast, VA-044 initiator could effectively regulate the stability of the PS nanoparticles including both the surface charge and size. Other reaction parameters i.e. VA-044 concentration and reaction time were examined to establish the optimum polymerisation conditions.

On April 6, 2020, Prof. Emi passed away at the age of 82. He graduated in 1961 from Kyoto University, and continued his studies at the Graduate School of Kyoto University. In 1969 until his retirement in 2003 he worked at Kanazawa University. He started as an associate professor and obtained his doctoral degree from Kyoto University in 1969. He became a full professor of Kanazawa University in 1977 and was the dean of engineering at Kanazawa University from 1995 to 1997.

Numerous studies of the synthesis of mesoporous silica (MPS) particles with tailored properties have been published. Among those studies, tetraethyl orthosilicate (TEOS) is commonly used as a silica source, but tetramethyl orthosilicate (TMOS) is rarely used because its reaction is fast and difficult to control. In this study, MPS particles were synthesized via one-step controlled polymerization of styrene and hydrolysis of TMOS, followed by the addition of hexadecyltrimethylammonium bromide (CTAB) and n-octane. The MPS particles obtained from TMOS generally have small inner pores, but the MPS particles obtained in this study had a unique radially oriented structure, a high surface area up to 800 m2 g–1, and large pores, of size 20 nm. The content of styrene in the emulsion system played a key role in increasing pore sizes of the MPS particles. A plausible mechanism for particle formation based on the phase behavior and type of the emulsion system is proposed. For further research, this material is expect...

Carbon quantum dots (CQDs) were characterized and their synthesis optimized extensively over recent years. It is becoming more and more important to develop synthesis solutions for CQDs applications to allow simple and cheap applications with composite materials. Here, we present a one-pot CQDs reaction in an aqueous polyvinyl alcohol (PVA) solution and the synthesis of transparent UV protection films. The synthesis solution was tuned in a way that transparent UV-protection films cast from unpurified CQDs–PVA solutions could be obtained without the need of yield consuming purification steps. Measuring the impact of varying PVA, branched polyethylene imine (b-PEI), and citric acid (CA) concentrations on the solution's and film's UV/Vis transmission and absorbance allowed elucidating important factors influencing the solution to film property transition. Applying CQDs–PVA films on commercially available PET bottle films resulted in high transparency of the composite film in the visible range (>80%) and UV absorption of over 90%. Lastly, our CQDs–PVA film performed stable UV-blocking and did not show any bleaching effects over several days of UV-exposure.

Catalytic decomposition of organic air pollutants is attractive in environmental remediation but challenging because such a reaction must take place at ambient temperature. To achieve sufficient catalytic activity under these conditions, the size, morphology and electric state of catalysts are critical. In particular, the interaction between noble metals and their ceramic supports is crucial for these catalysts. Herein we elucidate the significance of strong metal–support interactions (SMSIs) and strong oxide–support interactions (SOSIs) in such catalysts. The SMSIs lead to embedded metal nanoparticles into ceramic supports, hindering metal particle growth. For example, SMSIs in Pt–TiO2 formed by reduction of NaBH4 at room temperature allows stabilization of Pt clusters of 1–2 nm in diameter. On the other hand, SMSIs in Ag–TiO2 composites form crystalline TiOx (x < 2) that is a highly active photocatalyst under the full range of visible light (400–800 nm). Furthermore, such embedded structures could enhance visible light absorption by plasmonic materials. The SOSIs take place between metals and supports through oxygen ligands forming their hetero-bimetallic structure (e.g. Cu–O–Ti). This enables absorption of visible light and facilitates the transfer of photo-excited electrons to the co-catalysts (e.g. TiO2 to Cu), resulting in superior visible-light activity with a quantum yield of over 50%. Also, such interactions allow stabilization of small metal clusters and even single atoms on the supports to significantly facilitate the catalytic oxidation of pollutants at ambient temperature. For example, single Pd atoms on TiO2 increase its photocatalytic NOx removal by 9 times while only doubling its cost.

This work reports for the first time the preparation and evaluation of aligned Fe3O4 nanoparticle films via a magneto-electrospray method, i.e., electrospray under a magnetic field. The magnetic field was applied to align the magnetic moment of Fe3O4 particles. Well-dispersed Fe3O4 nanoparticles (NPs) with average sizes of 10, 25, and 45 nm were obtained using a bead-mill dispersion. The Fe3O4 nanoparticle slurries were mixed with a polyvinyl alcohol (PVA) solution and then deposited on Si-wafers under a 0.1 T magnetic field. The Fe3O4 crystalline structures were maintained after both dispersion and deposition, as characterized by X-ray diffraction patterns. Hysteresis curves revealed that the magnetic coercivity (Hc) of the well-dispersed nanoparticle slurries decreased owing to magnetic interactions among particles. However, the Hc values of the films were larger than those of the nanoparticle slurries. The values further increased from the application of a magnetic field during film deposition. This enhancement was attributed to alignment of the magnetic moments of the Fe3O4 NPs. These results show that tuning of the magnetic properties of materials, such as Fe3O4 NPs, can be achieved by controlling the alignment of their magnetic moment.

α″-Fe 16 N 2 nanoparticles (NPs) have been identified as one of the most promising rare-earth-free magnetic materials and synthesized with high purity in laboratory investigation recently. This study reports characteristics and magnetic performance of spindle shaped core–shell α″-Fe 16 N 2 /Al 2 O 3 NPs successfully synthesized from hematite NPs. A two-step reaction process, i.e., hydrogen reduction and ammonia nitridation treatments, was employed to produce the α″-Fe 16 N 2 phase (making up to ∼99 wt.% of the core content). The high-purity NPs exhibited saturation magnetization and coercivity of 186 emu/g and 2.2 kOe, respectively, at 300 K. The obtained α″-Fe 16 N 2 /Al 2 O 3 NPs possessed a spindle shape with an internal pore structure. Their porosity increased from ∼10% to 50–60% during the two-step synthesis process, however, at the expense of crystallite size. The combined use of the present synthesis method and hematite NP enables reduction in the synthesis reaction time, as well as the fabrication of NPs with excellent magnetic performance. Furthermore, the present results suggest the potential of rare-earth-free magnetic core–shell α″-Fe 16 N 2 /Al 2 O 3 NPs in industrial applications.

With a high surface area to volume ratio and good transport properties, hollow carbon spheres are one of the candidate materials for energy storage devices. Furthermore, highly capacitive and conductive hollow carbon spheres obtained through an effective synthesis route are in high demand for future commercialization. In this study, nitrogen-doped hollow carbon is synthesized utilizing microwave irradiation. 3-aminophenol is used as a carbon and nitrogen source, while the hollow structure is obtained using a polystyrene latex (PSL) template. The carbon shell thickness is easily adjusted by changing the mass ratio of 3-aminophenol to PSL, while control of the particles size is accomplished by changing the size of PSL particles. The steps in shell formation are explained based on the changes in the ζ-potential measured using a zetasizer. The synthesis duration was 50% shorter than that required by the common hydrothermal method, making this synthesis route promising for future development toward mass production. The high nitrogen content, primarily composed of pyridinic, pyrollic, and graphitic nitrogen, contribute to a volume-specific capacitance of 16.3 F cm−3. 93.1% of the total capacitance is maintained after 1600 charge-discharge cycles and the energy and power densities are superior to that of activated carbon.

Adsorption performance in the biosorption of tungsten using Escherichia coli cells can be significantly improved by using cell suspensions that have been heat-treated at ⩽100°C. In the case of E. coli cells suspension heated at 100°C, the aqueous tungsten ions concentration rapidly decreased from 0.8mmol/L to practically zero within 1h. This biosorption time is much shorter than that of non-heat treated E. coli cells (7h). Furthermore, the adsorption saturation amount for cells heat-treated at 100°C was significantly increased up to 1.62mmol-W/g-E. coli compared to the unheated E. coli cells case (0.62mmol-W/g-E. coli). Determination of the surface potential and surface structure along with quantitative analyses of free amino acids of heat-treated E. coli cells were also carried out and revealed that heated cells have a high zeta potential and express a higher concentration of amino acids on the cell surface.

N-doped TiO 2 was further doped with SiO 2 to prepare SiO 2 /N-doped TiO 2 photoelectrodes with high activity in the visible region. A sol-gel process was employed to produce nanoparticles of SiO 2 /N-doped TiO 2 . The addition of SiO 2 to the metal oxide enhanced charge transfer and reduced charge recombination. With the addition of sufficient amounts of SiO 2 and N, the photoelectrodes exhibited a high surface area and strong absorption of light because of their altered absorptivity in the visible wavelength region. These characteristics enabled the production of photoelectrodes with increased charge transfer and reduced charge recombination, resulting in dye-sensitized solar cells (DSSCs) with enhanced J sc values. The SiO 2 /N-doped TiO 2 photoelectrodes were characterized using a range of analysis techniques. After the J-V curve measurements, the DSSCs fabricated with the 0.1 mM SiO 2 /N-doped TiO 2 photoelectrodes exhibited the highest energy conversion efficiency of 8.68%, which was approximately 3% higher than that of the N-doped TiO 2 control groups. This high energy efficiency with the addition of SiO 2 might be due to the enhanced surface area of the photoelectrodes, allowing more dye absorption, and a decrease in electron recombination.

Tungsten (W) is present in the waste products of used scrap metal. The recovery of W from urban mines has become increasingly warranted because of the growing demand for W in the manufacturing of advanced materials and for use within key industries (e.g., the automotive industry). In this study, processes involving the biosorption of W from urban mines by microbes (e.g., Escherichia coli and beer yeast) were evaluated for their adoptability as an environmentally friendly recycling process. Selective biosorption of W and molybdenum (Mo) ions from multicomponent metal solutions containing W, Mo, and vanadium(V) ions was successfully achieved by controlling the concentration of both cells (2.58 × 108 cells/mL) and the solution pH (1.4). These biosorption tests were also applied to a real waste solution composed of used scrap comprising tungsten carbide (WC). It was shown that E. coli cells and beer yeast successfully and preferentially adsorbed the W ion from the real waste solution. To confirm the feasibili...

The requirements of advanced technologies, green chemistry, and air pollution remediation drive the development of heterogeneous catalysis. Two important factors defining catalyst quality are its efficiency and selectivity for a target reaction. Designing an effective catalyst structure requires understanding of the roles of particular scales of transport phenomena of chemical species during the catalytic process. Such phenomena include mass transfer in the bulk and on the surface of the catalyst and the chemical reaction mechanism at the catalyst active sites. Catalysts with controlled pore and surface topography can be fabricated by advanced aerosol methods such as spray drying and spray pyrolysis. Here, the principles of particle formation of desired morphology, including the topological background for obtaining allowed packing forms and conflict set theory to describe the self-organization process, are presented. Supporting nanostructures produced by spray drying and spray pyrolysis have been decorated with chemically active materials for use in selective catalytic processes.

In this work, we reported the synthesis of an engineered novel nanocarrier composed of biodegradable charged polyester vectors (BCPVs) and graphene quantum dots (GQDs) for pancreatic cancer (MiaPaCa-2 cells) therapy applications. Such a nanocarrier was utilized to co-load doxorubicin (DOX) and small interfering ribonucleic acid (siRNA), resulting in the formation of GQD/DOX/BCPV/siRNA nanocomplexes. The resulting nanocomplexes have demonstrated high stability in physiologically mimicking media, excellent K-ras downregulation activity, and effective bioactivity inhibition for MiaPaCa-2 cells. More importantly, laser light was used to generate heat for the nanocomplexes via the photothermal effect to damage the cells, which was further employed to trigger the release of payloads from the nanocomplexes. Such triggered release function greatly enhanced the anticancer activity of the nanocomplexes. Preliminary colony formation study also suggested that GQD/DOX/BCPV/siRNA nanocomplexes are qualified carrier candidates in subsequent in vivo tests. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University This work was supported by the Singapore Ministry of Education (Grants Tier 2 MOE2010-T2-2-010 (M4020020.040 ARC2/11) the NTU-NHG Innovation Collaboration Grant (M4061202.040), the NTU-ASTAR Silicon Technologies, Centre of Excellence, under the program grant no. 11235100003, the NEWRI seed funding (grant no. NEWRI SF20140901) the research grants (nos. MOST 106-2221-E-224-058-; MOST 107-2221-E-224-059-MY2) supported by the Ministry of Science and Technology of Taiwan, and the grants from the National Natural Science Foundation of China (NSFC) (81400591).

Degrading organic dyes via catalytic processes for waste water purification is an important research topic from the environmental conservation point of view. Herein, the catalytic performance of tungsten blue oxide (WOx) nanoparticles was investigated systematically by varying the reduction temperature. The optimum reduction temperature to obtain the most stable WOx phase was obtained when plasma-synthesized WO3 nanoparticles were thermally reduced at 425 °C. The as-synthesized nanoparticles had an average diameter of 10 nm and a calculated band gap of 2.37 eV, which is lower than that of the WO3 nanoparticles (2.61 eV). The WOx nanoparticles exhibited an excellent performance in degrading rhodamine B under dark conditions and visible light irradiation, with a reaction rate constant 93 times higher than that of the WO3 nanoparticles.

Slip flow phenomena are of great concern in aerosol filtration because of their ability to develop low-pressure drops and high collection efficiency air filters by using nanofibers. However, it is a difficult task to verify the slip flow effect on the reduction in pressure drop because the inhomogeneity in fiber packing also results in a decrease in pressure drop. In the present work, we propose pressure drop measurements at low pressures to verify the slip flow effect by distinguishing the effects of filter inhomogeneity. We found that the experimental dimensionless drag at low-pressure conditions, which was obtained with correction by the inhomogeneity factor measured at atmospheric pressure, followed the theoretical prediction that includes the slip flow correction (Kirsch and Stechkina, 1978) for both conventional PTFE and newly developed fluororesin nanofiber filter media. Because the dimensionless drags of both nanofiber filters decreased inversely proportional to the Knudsen number, we concluded that these nanofiber filters have low-pressure drops because of slip flow effects.

The influence of Cu doping on the function of dye-sensitized solar cells (DSSCs) dependent on Cu/N-doped TiO 2 photoelectrodes was examined. Cu/N-doped TiO 2 photoelectrodes with diverse Cu concentration were synthesized using the sol–gel process. Upon adequate addition of Cu, the nanoparticles exhibited small particle sizes, high surface area, and a significant red alteration of their absorption to the visible region in relation to Degussa P25 nanomaterials. Furthermore, the traces of Cu/N-doped TiO 2 nanoparticles enhanced the charge transfer and reduced the charge recombination. The addition of sufficient Cu and N increased the surface area, elevating the dye adsorption degree, and decreasing the level of electron recombination. A DSSC fabricated with a 1 mM Cu/N-doped TiO 2 nanoparticles accomplished 11.35% of the highest power conversion efficiency, with a short-circuit current of 22.5 mA/cm 2 . The energy conversion efficiency of this photoelectrode was approximately 37% greater than that of the control, Degussa P25. The increased energy efficiency can be resulted from the extension in surface area, which enabled larger dye charging amount, and the deduction in charge recombination, which accelerated the charge transfer.