Recent years have witnessed an increasing interest in highly-efficient absorbers of visible light for the conversion of solar energy into electrochemical energy. This study presents a TiO2-Au bilayer that consists of a rough Au film under a TiO2 film, which aims to enhance the photocurrent of TiO2 over the whole visible region and may be the first attempt to use rough Au films to sensitize TiO2. Experiments show that the bilayer structure gives the optimal optical and photoelectrochemical performance when the TiO2 layer is 30 nm thick and the Au film is 100 nm, measuring the absorption 80–90% over 400–800 nm and the photocurrent intensity of 15 μA·cm−2, much better than those of the TiO2-AuNP hybrid (i.e., Au nanoparticle covered by the TiO2 film) and the bare TiO2 film. The superior properties of the TiO2-Au bilayer can be attributed to the rough Au film as the plasmonic visible-light sensitizer and the photoactive TiO2 film as the electron accepter. As the Au film is fully covered by the TiO2 film, the TiO2-Au bilayer avoids the photocorrosion and leakage of Au materials and is expected to be stable for long-term operation, making it an excellent photoelectrode for the conversion of solar energy into electrochemical energy in the applications of water splitting, photocatalysis and photosynthesis.

Chloroplast of plants is a natural microfluidic reactor for natural photosynthesis, in which, the multi-enzymatic Calvin cycle is the key. In chloroplast, the Calvin cycle enzymes are reportedly attached to...

On-chip integration of optical detection units into the microfluidic systems for online monitoring is highly desirable for many applications and is also well in line with the spirit of optofluidics technology–fusion of optics and microfluidics for advanced functionalities. This paper reports the construction of a UV-Vis spectrophotometer on a microreactor, and demonstrates the online monitoring of the photocatalytic degradations of methylene blue and methyl orange under different flow rates and different pH values by detecting the intensity change and/or the peak shift. The integrated device consists of a TiO2-coated glass substrate, a PDMS micro-sized reaction chamber and two flow cells. By comparing with the results of commercial equipment, we have found that the measuring range and the sensitivity are acceptable, especially when the transmittance is in the range of 0.01–0.9. This integrated optofluidic device can significantly cut down the test time and the sample volume, and would provide a versatile platform for real-time characterization of photochemical performance. Moreover, its online monitoring capability may enable to access the usually hidden information in biochemical reactions like intermediate products, time-dependent processes and reaction kinetics.

A reconfigurable in-plane optofluidic lens that enables significant suppression or even elimination of longitudinal spherical aberration using discrete electrode strips.

Plasmon-enhanced photocatalysis has emerged as a promising technology for solar-to-chemical energy conversion. Compared to isolated or disordered metal nanostructures, by controlling the morphology, composition, size, spacing, and dispersion of individual nanocomponents, plasmonic nanostructure arrays with coupling architectures yield strong broadband light-harvesting capability, efficient charge transfer, enhanced local electromagnetic fields, and large contact interfaces. Although metallic nanostructure arrays are extensively studied for various applications, such as refractive index sensing, surface-enhanced spectroscopy, plasmon-enhanced luminescence, plasmon nanolasing, and perfect light absorption, the connection between surface plasmon resonance and enhanced photocatalysis remains relatively unexplored. In this study, an overview of plasmonic nanostructure arrays over a broad range, from 0D to 3D, for efficient photocatalysis is presented. By reviewing the fundamental mechanisms, recent applications, and latest developments of plasmonic nanostructure arrays in solar-driven chemical conversion, this study reports on the latest guidance toward the integration of plasmonic nanostructures for functional devices in the fields of plasmonic, photonics, photodetection, and solar-energy harvesting.

This work reports a microfluidic reactor that utilizes gold nanoparticles (AuNPs) for the highly efficient photocatalytic degradation of organic pollutants under visible light. The bottom of microchamber has a TiO 2 film covering a layer of AuNPs (namely, TiO 2 /AuNP film) deposited on the F-doped SnO 2 (FTO) substrate. The rough surface of FTO helps to increase the surface area and the AuNPs enables the strong absorption of visible light to excite electron/hole pairs, which are then transferred to the TiO 2 film for photodegradation. The TiO 2 film also isolates the AuNPs from the solution to avoid detachment and photocorrosion. Experiments show that the TiO 2 /AuNP film has a strong absorption over 400-800 nm and enhances the reaction rate constant by 13 times with respect to the bare TiO 2 film for the photodegradation of methylene blue. In addition, the TiO 2 /AuNP microreactor exhibits a negligible reduction of photoactivity after five cycles of repeated tests, which verifies the protective function of the TiO 2 layer. This plasmonic photocatalytic microreactor draws the strengths of microfluidics and plasmonics, and may find potential applications in continuous photocatalytic water treatment and photosynthesis. The fabrication of the microreactor uses manual operation and requires no photolithography, making it simple, easy, and of low cost for real laboratory and field tests.2 of 11 resonance (LSPR) due to the collective oscillation of free electrons in response to the excitation of irradiant light. The LSPR effect can drastically enhance the visible response of TiO 2 photocatalysis for solar energy capture, environmental redemption, and selective organic photosynthesis [5,7,9,10]. Moreover, the direct physical contact of the noble metal NPs and the TiO 2 photocatalysts would form a Schottky junction to suppress the recombination of electron-hole pairs [8,11].Typical photodegradation systems involve the suspension of TiO 2 nanopowders in an aqueous solution of a bulky container. With the stirring, the TiO 2 nanopowders have full contact with the dissolved organic pollutants, resulting in a large specific surface area (SSA, defined as the total surface area per unit of mass) and high photodegradation efficiency. However, the suspended TiO 2 nanopowders absorb and scatter light, causing rapid decay, and thus an uneven distribution of the irradiant light. What is more problematic is the requirement of post processing, namely the nanopowders have to be separated from the solution after the reaction [12][13][14]. To avoid these problems, immobilized systems have been developed to fix the TiO 2 photocatalysts on a support, but they tend to have a small SSA and low efficiency [15].Microfluidic reactors have attracted much attention and have been proposed to tackle the drawbacks of photocatalytic processes [14,[16][17][18][19][20]. They inherit many advantages from microfluidics technology, such as small dimensions, high surface-to-volume (S/V) ratio, easy control of flow rates, short molecular diffusion distance,...

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Photocatalytic regeneration of valuable cofactors by using sunlight has emerged as a promising strategy for biosynthesis and pharmaceutical manufacturing. Graphitic carbon nitride (g-C 3 N 4 ) is very suitable for photocatalytic nicotinamide cofactor regeneration since it is metal-free, visible-light responsive and has strong binding with nicotinamide cofactor. However, its great potential is hindered by some intrinsic drawbacks such as low visible absorption, fast electron/hole recombination, and limited active sites. Here, we demonstrate dual-defect g-C 3 N 4 (DDCN) with controllable defects of nitrogen vacancies and cyano groups for efficient photocatalytic cofactor regeneration via a KOH-assisted thermal polymerization by using urea as a precursor. Although DDCN is widely used for other photocatalytic applications such as organic degradation and hydrogen peroxide production, this work is original in its application to photocatalytic cofactor regeneration. Material characterizations confirm the successful introduction of nitrogen vacancies and cyano groups. Measurements of nicotinamide-cofactor generation show that the DDCN samples assisted with 0.1 g and 0.01 g KOH are 3.0 and 2.5 times that of pristine g-C 3 N 4 in terms of nicotinamide cofactor yield, respectively. The high yields are attributed to the synergetic effect of both enhanced light absorption and improved charge separation, achieved through the introduction of energy levels and trap states via dual defects. This work provides a green, energy-saving, and promising strategy for nicotinamide cofactor regeneration and would promote its application in biosynthesis and drug manufacturing.