Wavelength-sensitive photocatalytic H2 evolution from H2S splitting over g-C3N4 with S,N-codoped carbon dots as the photosensitizer

Photocatalytic splitting of hydrogen sulfide(H2S) for hydrogen evolution is a promising method to solve the energy and environmental issues.In this work,S,N-codoped carbon dots(S,N-CDs)/graphitic carbon nitride(g-C3N4) nanosheet is synthesized by hydrothermal method as an efficient photocatalyst for the decomposition of H2S.In addition to the characterization of the morphology and structure,chemical state,optical and electrochemical performances of S,N-CDs/g-C3N4,hydrogen evolution tests show that the activity of g-C3N4 is improved by introducing S,N-CDs,and the enhancement depends strongly on the wavelength of incident light.The photocatalytic hydrogen production rate of S,N-CDs/g-C3N4 composite reaches 832 μmol g-1h-1, which is 38 times to that of g-C3N4 under irradiation at 460 nm.Density functional theory calculations and electron paramagnetic resonance as well as photoluminescence technologies have altogether authenticated that the unique wavelength-dependent photosensitization of S,N-CDs on g-C3N4;meanwhile,a good match between the energy level of S,N-CDs and g-C3N4 is pivotal for the effective photocatalytic activity.Our work has unveiled the detailed mechanism of the photocatalytic activity enhancement in S,N-CDs/g-C3N4 composite and showed its potential in photocatalytic splitting of H2S for hydrogen evolution.

Quick photofabrication of functional nanospheres from de novo designed peptides for NIR fluorescence and MR imaging

Combining the noncovalent and covalent interactions,a series of peptide amphiphiles were designed de novo and synthesized to architect functional assemblies by means of photochemistry.The strand of peptide sequence was structurally capped with photoactive tyrosine-tyrosine(YY)motifs at both termini,and the spacing was filled by alternating of hydrophilic D(L-aspartate)and hydrophobic X(ε-aminocaproic acid)structure.Upon visible-light irradiation,these de novo designed peptides underwent rapid photocrosslinking within merely 10 min.Interestingly,the modulation of alternating D-X pairs in occupying spacer would adjust molecular amphiphilicity,regulate charge distribution,and control particle size and loading capacity of peptide nanospheres(PNS)in aqueous media.With entirely peptide-based matrix,this PNS system could host cationic indicators of fluorescent rhodamine and magnetic GdIII for exemplar near infrared(NIR)fluorescence and magnetic resonance(MR)imaging,which paves a pathway to biomaterial and biomedical applications using de novo designed peptides.