The tunable photoluminescent and photocatalytic properties of carbon dots (CDs) via chemical surface modification have drawn increased attention to this emerging class of carbon nanomaterials. Herein, we summarize the advances in CD synthesis and modification, with a focus on surface functionalization, element doping, passivation, and nanocomposite formation with metal oxides, transition metal chalcogenides, or graphitic carbon nitrides. The effects of CD size and functionalization on photocatalytic properties are discussed, along with the photocatalytic applications of CDs in energy conversion, water splitting, hydrogen evolution, water treatment, and chemical degradation. In particular, the enzyme-mimetic and photodynamic applications of CDs for bio-related uses are thoroughly reviewed.
We demonstrate highly efficient liquefaction of alkali lignin with a very high yield of THF‐soluble bio‐oil (91.5 wt %) using formic acid (FA) and Rh/C catalyst under relatively mild reaction conditions (250 °C, 6 h) in EtOH−H2O co‐solvent system. The monomeric products are identified in which alkyl guaiacols accounts for the main proportion. The role of FA was not only used as a liquid‐phase in‐situ hydrogen source but also acts as organic acid which can catalyze the hydrolysis reaction of −C−O−C ether bonds of lignin. Moreover, in the present study, the role of Rh/C and FA is demonstrated for the liquefaction of lignin. The replacement of pure H2 gas by the liquid‐phase FA (hydrogen source) can effectively prevent the char formation. The utilization of Rh/C catalyst helps for the conversion of alkenyl guaiacols to alkyl guaiacols suggesting the hydrogenation of phenolic monomers and further cleavage by hydrogenation results in the formation of bio‐oil with lower molecular weight (Mn=466 g mol−1) as well as lower O/C ratio (0.26).
Recently,
lignin utilization in advanced applications has gained
much interest. Due to the limitation of the current use of standard
lignin, lignin particles have recently gained attention in overcoming
the challenge. In this work, the spherical lignin particles obtained
from organosolv lignin (OL) were prepared using the dialysis method
with tetrahydrofuran (THF) or ethanol as the solvent. From the result,
it was found that the types of lignin and solvent, initial lignin
concentration, and stirring rate strongly affected the size of fabricated
particles. Moreover, the preparation of lignin particles using THF
as a solvent showed more uniform and symmetric spherical lignin particles.
The stability of the particle dispersion was examined under various
pH conditions. Moreover, lignin samples were also introduced into
the poly(vinyl alcohol) (PVA) for the production of ultraviolet (UV)-blocking
composite film. Mechanical and optical properties of composite film
were also observed. As a result, the prepared lignin–PVA composite
film showed great ultraviolet (UV) protective potential in both UVA
and UVB regions.
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