Magnetic Field-Enhancing Photocatalytic Reaction in Micro Optofluidic Chip Reactor

Abstract

A small external magnetic field (100–1000 Oe) was demonstrated to enhance the photocatalytic degradation of methyl orange (MO) using TiO2 NPs in micro optofluidic chip (MOFC) reactors. The rectangular shape of the fluidic channel and TiO2 deposited only onto the lower glass substrate leads to a selectively enhancing photocatalytic reactions by magnetic field in specific directions. Utilizing ethyl alcohol as a scavenger presented the difference between generated hot-hole (hVB+) and hot-electron (eCB−) pathways of photocatalytic reactions. Effects of dissolved oxygen (DO) and hydroxyl ions (OH−) are all demonstrated in a magnetic field-enhancing photocatalytic reaction. The experimental results demonstrate great potential for practical applications utilizing low-price fixed magnets in the field of green chemistry.

Review of Experimental Setups for Plasmonic Photocatalytic Reactions

“…These reactors characterized by a small size, low power consumption, and waste reduction properties, rendering them green technologies. MOFC reactors [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85] have been used in some photocatalytic reactions. Although they have low processing volume, MOFC reactors have features that contribute to high processing efficiency in many applications: (i) Their small fluid channel size results in a high mass transfer rate, thus enabling effective transportation of reactants and products.…”

“…(ii) The plasmon or light converted into heat results in increased temperature in localized area in micro fluids that further enhances mass transfer in fluidics. (iii) The external magnetic field and large variation in flow speed in the fluid channel lead to distinctive ion condensation of OH − , thus enhancing active OH * radical generation [85]. (iv) Their highly efficient light illumination engenders low energy loss.…”

“…Reactors with waveguide features or the potential to couple with light for an increased wavevector variation are particularly suitable for studying plasmonic photocatalytic reactions. Fixed-bed or MOFC reactors [71,81,85] with thin and flat glass substrates are also suitable for use as waveguides for delivering light energy. These reactors might help studies on plasmonic photocatalytic reactions.…”

Recent Advances in Noncontact External-Field-Assisted Photocatalysis: From Fundamentals to Applications

“…However, the catalyst rotates along the stirring direction, so the Lorentz force here is not conducive to charge transfer and can only inhibit the recombination of electron–hole pairs. In addition, Huang et al developed microfluidic technology based on promotion of the reaction of nonmagnetic photocatalysts by a magnetic field, in which TiO 2 was fixed in a microfluidic chip reactor, and the photocatalytic degradation was enhanced by a small external magnetic field (100–1000 Oe) (Figure b). The design of a rectangular fluid channel and fixed catalyst provides convenience for studying the effect of the magnetic field in a specific direction.…”

Perfect Dual-Band Absorber Based on Plasmonic Effect with the Cross-Hair/Nanorod Combination

“…With the ability of efficaciously transforming electromagnetic (EM) waves from free space into the sub-wavelength scale, plasmonic nanomaterials disclose a broad range of applications in nanophotonics [1][2][3][4][5][6]. Metal nanoparticles (MNPs) with the behavior of surface plasmon polaritons (SPPs) and resonant couplings lead to EM wave confinement that can be applied in nanophotonic and optoelectronic fields [7][8][9][10][11][12]. Surface plasmon resonance (SPR) is an extraordinary phenomenon, which originates from coupling an EM wave with collective electron oscillations between the interface of an MNP and dielectric [13][14][15][16][17].…”