Improved Water Collection from Short-Term Fog on a Patterned Surface with Interconnected Microchannels.

Fog harvesting is considered a promising freshwater collection strategy for overcoming water scarcity, because of its environmental friendliness and strong sustainability. Typically, fogging occurs briefly at night and in the early morning in most arid and semiarid regions. However, studies on water collection from short-term fog are scarce. Herein, we developed a patterned surface with highly hydrophilic interconnected microchannels on a superhydrophobic surface to improve droplet convergence driven by the Young-Laplace pressure difference. With a rationally designed surface structure, the optimized water collection rate from mild fog could reach up to 67.31 g m-2 h-1 (6.731 mg cm-2 h-1) in 6 h; this value was over 130% higher than that observed on the pristine surface. The patterned surface with interconnected microchannels significantly shortened the startup time, which was counted from the fog contact to the first droplet falling from the fog-harvesting surface. The patterned surface was also facilely prepared via a controllable strategy combining laser ablation and chemical vapor deposition. The results obtained in outdoor environments indicate that the rationally designed surface has the potential for short-term fog harvesting. This work can be considered as a meaningful attempt to address the practical issues encountered in fog-harvesting research.

Laser Promoting Oxygen Vacancies Generation in Alloy via Mo for HMF Electrochemical Oxidation.

It is well known that nickel-based catalysts have high electrocatalytic activity for the 5-hydroxymethylfurfural oxidation reaction (HMFOR), and NiOOH is the main active component. However, the price of nickel and the catalyst's lifetime still need to be solved. In this work, NiOOH containing oxygen vacancies is formed on the surface of Ni alloy by UV laser (1J85-laser). X-ray absorption fine structure (XAFS) analyses indicate an interaction between Mo and Ni, which affects the coordination environment of Ni with oxygen. The chemical valence of Ni is between 0 and 2, indicating the generation of oxygen vacancies. Density functional theory (DFT) suggests that Mo can increase the defect energy and form more oxygen vacancies. In situ Raman electrochemical spectroscopy shows that Mo can promote the formation of NiOOH, thus enhancing the HMFOR activity. The 1J85-laser electrode shows a longer electrocatalytic lifetime than Ni-laser. After 15 cycles, the conversion of HMF is 95.92%.

Magnetic Non-Spherical Particles Inducing Vortices in Microchannel for Effective Mixing.

Mixing in microfluidic channels is dominated by diffusion owing to the absence of chaotic flow. However, high-efficiency microscale mixing over short distances is desired for the development of lab-on-chip systems. Here, enhanced mixing in microchannels achieved using magnetic nonspherical particles (MNSPs), is reported. Benefiting from the nonspherical shape of the MNSPs, secondary vortices exhibiting cyclical characteristics appear in microchannels when the MNSPs rotate under an external magnetic field. Increasing the rotation rate enlarges the secondary vortices, expanding the mixing zone and enhancing the mixing, resulting in a mixing efficiency exceeding 0.9 at Re of 0.069-0.69. Complementary micro-particle image velocimetry (µPIV) for flow field analysis clarifies the mixing mechanism. In addition, a chaotic vortex area is generated in the presence of two MNSPs, which shortens the distance required for achieving an appropriate mixing efficiency. This study demonstrates the potential of employing MNSPs as efficient mixers in lab-on-chip devices.

Synthesis of Micro-/Nanohydroxyapatite Assisted by the Taylor-Couette Flow Reactor.

Hydroxyapatite (HAP) has received increasing attention as an essential chemical product with good biocompatibility and adsorption properties. Generally, amorphous calcium phosphate (ACP) was generated first in the reactor and transformed into HAP after a period of crystallization. In this work, a series of Taylor-Couette flow reactors with different inner diameters were designed to assist in synthesizing HAP micro-/nanocrystals. ACP was obtained in a Taylor-Couette flow reactor at Re = 247 and successfully transformed into needle-like HAP crystals with a length of about 200 nm and a uniform particle size distribution after crystallization transformation. The yield of a single reactor can reach 2.16 kg per day. The finite element analysis results and time-space diagram of flow pattern variation showed that the Taylor-Couette flow reactor could improve the mixing behavior and the flow field distribution. The Taylor-Couette flow reactor provides a valuable reference for synthesizing inorganic micro-/nanomaterials.

Coemissive luminescent nanoparticles combining aggregation-induced emission and quenching dyes prepared in continuous flow.

Achieving an ideal light-harvesting system at a low cost remains a challenge. Herein, we report the synthesis of a hybrid dye system based on tetraphenylene (TPE) encapsulated organic dyes in a continuous flow microreactor. The composite dye nanoparticles (NPs) are synthesized based on supramolecular self-assembly to achieve the co-emission of aggregation-induced emission dyes and aggregation-caused quenching dyes (CEAA). Numerical simulations and molecular spectroscopy were used to investigate the synthesis mechanism of the CEAA dyes. Nanoparticles of CEAA dyes provide a platform for efficient cascade Förster resonance energy transfer (FRET). Composite dye nanoparticles of TPE and Nile red (NiR) are synthesized for an ideal light-harvesting system using coumarin 6 (C-6) as an energy intermediate. The light-harvesting system has a considerable red-shift distance (~126 nm), high energy-transfer efficiency (ΦET) of 99.37%, and an antenna effect of 26.23. Finally, the versatility of the preparation method and the diversity of CEAA dyes are demonstrated.

Copper-Based Integral Catalytic Impeller for the Rapid Catalytic Reduction of 4-Nitrophenol.

The integral catalytic impeller can simultaneously improve reaction efficiency and avoid the problem of catalyst separation, which has great potential in applying heterogeneous catalysis. This paper introduced a strategy of combining electroless copper plating with 3D printing technology to construct a pluggable copper-based integral catalytic agitating impeller (Cu-ICAI) and applied it to the catalytic reduction of 4-nitrophenol (4-NP). The obtained Cu-ICAI exhibits very excellent catalytic activity. The 4-NP conversion rate reaches almost 100% within 90 s. Furthermore, the Cu-ICAI can be easily pulled out from the reactor to be repeatedly used more than 15 times with high performance. Energy-dispersive spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy characterizations show that the catalyst obtained by electroless copper plating is a ternary Cu-Cu2O-CuO composite catalyst, which is conducive to the electron transfer process. This low-cost, facile, and versatile strategy, combining electroless plating and 3D printing, may provide a new idea for the preparation of the integral impeller with other metal catalytic activities.

Bodipy-Containing Porous Microcapsules for Flow Heterogeneous Photocatalysis.

Photocatalysis is a facile strategy for complex chemical transformations. Heterogeneous photocatalysis, especially in the flow system, has attracted much attention as it avoids the separation of catalysts. Herein, a kind of a Bodipy-containing porous microcapsule heterogeneous photocatalyst was rationally constructed with modulation on a multiscale. The diiodo-Bodipy with methacrylate (MA-2IBDP) was synthesized as a polymerizable photosensitizer. After immobilization in a polymer matrix, the intersystem crossing rate constant of MA-2IBDP increased to 2.7 × 1010 s-1 and its triplet excited-state lifetime prolonged to ∼1 ms. Porous structures in microcapsules were created to facilitate mass transfer. A flat plate flow reactor was constructed to fix the catalytic microcapsules and improve light utilization. With the combination of all the above benefits, the reaction rate constant (0.896 s-1) is 10 times faster than that of MA-2IBDP in a homogeneous system for juglone synthesis. The continuous production can last for 30 h without yield decrease. The photocatalyst can also be used in aza-Henry reaction, Alder-Ene reaction, and oxidation of thiols to disulfides with conversion rates above 95%. This study provides a means for the construction of heterogeneous catalysts and the flow reaction system.

Laser-Induced Carbon Electrodes in a Three-Dimensionally Printed Flow Reactor for Detecting Lead Ions.

Nowadays, heavy metal pollution has attracted wide attention. Many electrochemical methods have been developed to detect heavy metal ions. The electrode surface usually needs to be modified, and the process is complicated. Herein, we demonstrate the fabrication of electrodes by direct laser sintering on commercial polymer films. The prepared porous carbon electrodes can be used directly without any modification. The electrodes were fixed in a 3D-printed flow reactor, which led to very little analyte required during the detection process. The velocities of the analyte under stirring and flowing conditions were simulated numerically. The results prove that flow detection is more conducive to improving detection sensitivity. The limit of detection is about 0.0330 mg/L for Pb2+. Moreover, the electrode has been proved to have good repeatability and stability.

A Hierarchical-Structured Impeller with Engineered Pd Nanoparticles Catalyzing Suzuki Coupling Reactions for High-Purity Biphenyl.

Suzuki cross-coupling reactions catalyzed by palladium are authoritative protocols in fine-chemical synthesis. Mass transfer and catalyst activity are both significant factors affecting the reaction efficiency in heterogeneous reactions. Although the holistic catalysts hold great promise in heterogeneous reactions due to the enhanced mass transport and convenient recycling, the unsatisfied catalytic activity has impeded further large-scale applications. In addition, another pronounced barrier is the product separation in the intricate system. Here, the catalytic production and separation of biphenyl (purity of 99.7%) were achieved by integrating the Suzuki cross-coupling reactions and the crystallization separation for the first time. A hierarchical-structured impeller with Pd nanoparticles (NPs) loaded on the Ni(OH)2 nanosheets was prepared to catalyze the Suzuki reactions for bromobenzene, which exhibits a high turnover frequency (TOF) value of 25,976 h-1 and a yield of 99.5%. The X-ray absorption fine structure (XAFS) analysis has unveiled that the electron transfer between the Pd NPs and Ni(OH)2 accounts for the greatly enhanced catalytic activity. The findings inspire new insights toward rational engineering of highly efficient holistic catalysts for Suzuki reaction, and the innovative integrated technology offers an avenue for the separation and collection of products.

Laser-Induced Patterned Photonic Crystal Heterostructure for Multimetal Ion Recognition.

In this work, a new method of direct laser writing patterned photonic crystal heterostructure on a glass surface is proposed. A multi-heterostructure photonic crystal (MHPC) is predeposited on the glass surface and then the laser spot is focused on it and moves according to the set program, leading to the formation of patterned MHPC. Scanning electron microscopy (SEM) and finite element simulation show that the patterning is caused by the local thermal annealing of the polymer colloidal spheres through the thermal conduction effect of the substrate on the laser energy. The patterned area presents a function of the water confinement effect and can be used as a high-performance droplet analysis chip. By integrating the patterned MHPC array and seven fluorescent dyes, nine metal ions can be successfully recognized and discriminated. This approach is quite facile and fast for designing colloidal photonic crystals with controllable patterns. Moreover, it is of considerable significance for the practical application of photonic crystal heterostructure in the detection, sensing, anti-counterfeiting, and display fields.

Fabrication of a porous NiFeP/Ni electrode for highly efficient hydrazine oxidation boosted H2 evolution.

Rational optimization of the surface electronic states and physical structures of non-noble metal nanomaterials is essential to improve their electrocatalytic performance. Herein, we report a facile dual-regulation strategy to fabricate NiFeP/Ni (P-NiFeP/Ni) porous nanoflowers, which involves Fe-doping and creating pores on nanosheets. The as-prepared P-NiFeP/Ni has a hierarchically porous surface, which exposes more electrochemically active sites and dramatically enhances the electron transfer rate. Thus, it exhibits excellent catalytic activity in both anodic hydrazine oxidation reaction (HzOR) and cathodic hydrogen evolution reaction (HER). Interestingly, the coupled electrolysis cell only offers a potential of 0.162 V at 10 mA cm-2 to enable HzOR boosted H2 evolution, highlighting an energy-saving hydrogen evolution strategy.

Rational 3D Coiled Morphology for Efficient Solar-Driven Desalination.

Aiming at the global water scarcity, solar-driven desalination based on photothermal materials is identified as a promising strategy for freshwater production because of sustainability, spontaneity, and flexibility. Water transfer in photothermal materials, especially ones with 3D morphologies, can adjust the evaporation efficiency as a critical factor. In this work, a rationally designed roll morphology has been introduced into photothermal to advance the water transfer evaporation via controllable capillary action. The vertical intervals of the roll, similar to slit pore, can pump the water up to the entire materials to not only keep a stable vapor generation rate but reject salt precipitation. Additionally, the roll morphology also improves the light-harvesting via both the high roughness surface and confinement absorption inside the intervals. With excellent water transfer and energy management, photothermal roll showed an evaporation rate up to 1.93 ± 0.05 kg m-2 h-1, which was over 44% higher than the flat sample in the same constituents. Under actual conditions, the freshwater generation rate was achieved up to 1.09 kg m-2 h-1 on average of the whole daylight hours. The work provides novel insights into the design of efficient morphology in photothermal materials and advances their practical applications in sustainable water generation.

Scale-up Design of a Fluorescent Fluid Photochemical Microreactor by 3D Printing.

The integration of light-converting media and microflow chemistry renders new opportunities for high-efficient utilization of solar energy to drive chemical reactions. Recently, we proposed a design of fluorescent fluid photochemical microreactor (FFPM) with a separate light channel and reaction channel, which displays excellent advantages in energy efficiency, flexibility, and general use. However, the limitations of the scalability of the microchannel reactor are still a big challenge to be overcome. Herein, we illustrate the scalability of such an FFPM via a 2 n numbering-up strategy by 3D printing technology. Channel shape, number, and interchannel spacing have been optimized, and the serpentine FFPM shows the best scalability with an excellent conversion rate and massive throughput. Reactors with up to eight channels have been fabricated and displayed conversions comparable to that obtained in a single-channel reactor, which provides a feasible strategy and an optimized structure model for batch production of fine chemicals.

Self-Assembly of Nanoparticles in a Modular Fashion to Prepare Multifunctional Catalysts for Cascade Reactions: From Simplicity to Complexity.

One-pot cascade reactions can simplify the synthetic route and reduce the use of solvents and energy. The critical part of the completion of the cascade reaction is the preparation of multifunctional catalysts. In this work, a novel and simple pathway was developed to construct multifunctional catalysts with acidic, basic, and magnetic properties at the same time. Mesoporous silica materials modified with different metal oxides were used as catalytic elements. Microspheres that assembled with catalytic components have a diameter of 150 µm and a specific surface area larger than 400 m2 g-1 and can be used as catalysts for cascade reactions. The yield of the final product in the deacetalization-Knoevenagel reaction is 92%. Microspheres integrated with Fe3O4 nanoparticles have a magnetic susceptibility of 7.2 emu g-1 and can be easily removed from the reaction system by applying an external magnetic field. This multimodule assembly method fully reflects the enormous power of complexity resulting from simplicity. This method provides a reference and practical technical support for the preparation of other multifunctional materials.

Fluorescent Fluid in 3D-Printed Microreactors for the Acceleration of Photocatalytic Reactions.

The photochemical microreactor has been a burgeoning field with important application in promoting photocatalytic reactions. The integration of light-converting media and microflow chemistry renders new opportunity for efficient utilization of light and high conversion rate. However, the flexibility of emission light wavelength regulation and the universality of the microreactor remain significant problems to be solved. Here, a photochemical microreactor filled with fluorescent fluid is fabricated by a 3D printing technique. The light-converting medium in the fluorescent fluid is used to collect and convert light, and then delivers light energy to the embedded continuous-flow reaction channels to promote the chemical reaction process. With the merits of flowability, different light-converting media can be replaced, making it a general tool for photocatalytic reactions in rapid screening, parameters optimization, and kinetic mechanism research.

Preparation of Hollow Cu and CuO x Microspheres with a Hierarchical Structure for Heterogeneous Catalysis.

Diffusion is one of the most critical factors which affect the performance of porous catalysts in heterogeneous reactions. Hollow spheres with a hierarchical structure could significantly improve the mass transfer in the spherical catalyst. Therefore, preparation of such kind of microspheres is an important work in the field of inorganic synthesis. Herein, we combine microfluidic technology and electroless deposition to prepare hollow Cu and CuO x microspheres with a hierarchically porous structure. These microspheres have a controllable diameter (100-500 µm) and shell thickness (10-60 µm). Numerical simulation and experimental results indicate that the hollow structure is beneficial for the diffusion and utilization of the catalyst in heterogeneous reactions. The Cu and CuO x microspheres were used to catalyze the hydrogenation and Fenton-like reactions in a flow reactor, respectively. The conversion of all reactants can reach more than 95%, and catalysts can maintain their reactivity in long reaction times. Thus, the strategy in the present research should apply in the construction of other porous catalysts with high performance.

Fabrication of multi-functional porous microspheres in a modular fashion for the detection, adsorption, and removal of pollutants in wastewater.

Water pollution control has become significant challenges in recent years because of their extensive species diversity. It is critical to developing general-purpose materials for environmental rehabilitation. In this paper, a novel module-assembly method is developed to prepare multi-functional materials for treating pollutants in water. Building blocks are porous nanoparticles with a different function. Microspheres (MS) with a diameter of 90 µm are prepared and have a coefficient of variation of 6.8%. The modular fashion of self-assembly process in a microfluidic chip is the crucial factor in fabricating the multifunction material. The assembled microspheres with different building modules still have a specific surface area larger than 400 m2 g-1, and exhibit excellent performance in adsorbing various pollutants in water, such as heavy metal ions and organic dyes. The adsorption capacities of them to Hg2+ and orange II reach 150 mg g-1 and 333 mg g-1, respectively. The integrated fluorescence probes in microspheres can detect low concentration (9.8 ppb) of Hg2+. Microspheres integrated with Fe3O4 nanoparticles have a magnetic susceptibility of 6.01 emu g-1 and can be easily removed from wastewater by applying an external magnetic. Due to the stability of inorganic building blocks, each function in the assembled system is well performed, and multi-functional "All-in-One" materials can be easily fabricated.

A general strategy to fabricate photonic crystal heterostructure with Programmed photonic stopband.

In this paper, we present a general fabrication strategy to achieve the structure control and the flexible photonic stop band regulation of (2+1) D photonic crystal heterostructures (PCHs) by layer-by-layer depositing the annealed colloidal crystal monolayers of different sphere size. The optical properties of the resulting (2+1) DPCHs with different lattice constants were systematically studied and a universal photonic stopband variation rule was proposed, which makes it possible to program any kind of stopband structure as required, such as dual- or multi-stopbands PCH and ultra-wide stopband PCH. Furthermore, PCH with dual-stopbands overlapping the excitation wavelength (E) and emission wavelength(F) of Ru complex was fabricated by finely manipulating the spheres' diameter of colloidal monolayers. And an additional 2-fold fluorescence enhancement in comparison to that on the single stopband sample was achieved. This strategy affords new opportunities for delicate engineering the photonic behaviour of PCH, and also is of great significance for the practical application based on their bandgap property.

Porous TiO2 with large surface area is an efficient catalyst carrier for the recovery of wastewater containing an ultrahigh concentration of dye.

The preparation of porous TiO2 as a carrier for the Fenton reaction is reported. Porous TiO2 is an excellent carrier to load with elemental iron due to the large specific surface area and negative surface charge. Porous TiO2 was synthesized in the form of a hierarchically porous silica monolith that was used as a microreactor, and a block copolymer served as a template for mesoporous forms. The crystalline TiO2 growing in confined spaces maintained the porous structure and high crystallinity. The surface area of our synthesized porous TiO2 can reach 205 m2 g-1. The zeta potential of the TiO2 was as low as -36.5 mV (pH 7). Elemental iron was highly and uniformly dispersed over the channel of the porous TiO2 via an impregnation method and served as the catalyst for the Fenton reaction. In the Fenton reaction, the synthesized catalyst performed strong catalytic activity during the degradation of wastewater containing an ultrahigh concentration of aqueous dye, at 400 ppm. The aqueous dye solution was degraded over 95% in 30 min, and the catalyst could be reused many times.

Preparation of magnetic hierarchically porous microspheres with temperature-controlled wettability for removal of oils.

A series of monodispersed microspheres with hierarchically porous structures were prepared by microfluidic devices. Phase separation of the silica sol in microdroplets was adopted to construct these structures. The effects of velocity ratios (for both the continuous and the dispersed phases), collection solvents and calcination temperatures were investigated. The diameters of the microspheres were tuned from 148µm to 940µm by adjusting the velocity ratio. Tests revealed that the surface areas and pore volumes of the microspheres can reach 495m2g-1 and 0.6068mlg-1, respectively. The macroporous structure can be controlled by the collection solvents, and the wettability of the microspheres is determined by the calcination temperature. A calcination temperature of 450°C leads to a hydrophilic surface property. Fe3O4 nanoparticles were added to the silica sol to form magnetic microspheres, and the porous structure was not affected. This kind of hybrid microsphere adsorbs 3.29 times its own weight in toluene. These spheres can adsorb oil on water surfaces, and then be removed from the water with an external magnetic field. The microspheres can be recovered and reused more than 10 times.