**4. Conclusions**

We have successfully achieved to obtain novel plasmonic heterostructures by the close conjunction of plasmonic metals, specifically Au and Ag nanoparticles and gallium partially substituted hydrotalcite layered matrix. The catalysts were obtained by a facile synthesis procedure, via calcination-reconstruction of MgGaAl in the solutions of gold acetate and silver sulphate, respectively. The analysis of photocatalytic degradation of 4-NPh and 2-DCB from aqueous solutions, under irradiation by solar light, revealed that the plasmonic behavior of the newly designed catalysts plays a key role in establishing high photocatalytic performances for the removal of the studied pollutants from the aqueous mediums.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/catal12111351/s1, Figure S1: EDS analysis for (a) Ag\_MgGaAl and (b) Au\_MgGaAl catalysts; Figure S2: High resolution XPS spectra of Ga2p in both Ag\_MgGaAl and Au\_MgGaAl catalysts. Figure S3: Effect of different scavengers on the degradation of 4-NP in the presence of Ag-MgGaAl.

**Author Contributions:** Conceptualization, G.C.; Methodology, E.C.I.; Validation, E.C.I., G.A.; Formal analysis, D.L., G.C.; Investigation, G.A., E.C.I.; Data curation, D.L.; Writing—original draft preparation, D.L.; Writing—review and editing, G.C., D.L.; Visualization, G.C.; Supervision, G.C.; Funding acquisition, E.C.I. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors are grateful for the financial supports from the Grant-in-Aid for Scientific Research from Romanian National Authority for Scientific Research, CNCS-UEFISCDI (PN-II-ID-1751).

**Conflicts of Interest:** The authors declare no conflict of interest.
