**4. Conclusions**

Nanoassemblies of gold clusters and J-aggregated porphyrins were synthesized and characterized by spectroscopic techniques. The aggregated porphyrin showed a chirality related to the amino acid used in the synthesis of the metal nanostructures. A simple procedure for the deposition of gold nanoparticles on glass substrates was described, which starts with the preparation of easily synthesized and highly reactive Au10 clusters. In fact, we found that acidification of aqueous solutions of Au10 sub-nanometer clusters led to the formation of plate-like and regular nano-objects on glass surfaces. Our procedure o ffers the advantage of not requiring the use of expensive and sophisticated equipment and hazardous reagents. The growth of the metallic nanostructures with the co-deposition of TPPS J-aggregates on the substrates was exploited as a test system for the potential use of these nanoparticles in SERS applications. In fact, a significant increase of the Raman signals for the porphyrin J-aggregates deposited on gold plated surfaces was observed compared with J-aggregates deposited on bare glass. Furthermore, these J-aggregates maintained their peculiar CD signals on the glass surface, showing a chirality that is related to the configuration of the amino acid (<sup>d</sup>- and l-histidine) used in the metal cluster synthesis. This latter observation suggests that the Au10 clusters, analogously to other templating systems [62,63], have a role as chiral seeds in the growth of J-aggregates.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2079-4991/9/7/1026/s1, Figure S1: UV-vis spectra of Au10 solution after addition of the positively charged H2TMPyP<sup>4</sup>+. Figure S2: Spectral changes of Au10 clusters upon addition of HCl (pH 2) within 1 h. Figure S3: Photographs of gold plated cuvettes on dark and white backgrounds. Figure S4: UV-vis spectra of Au10 solutions upon acidification. Figure S5: AuNPs prepared from histidine and NaBH4 and of a glass dipped in the corresponding solutions at acidic pH. Figure S6: UV-vis and CD spectra of residual TPPS solution after formation of co-deposit. Figure S7: Circular dichroism (CD) spectra of co-deposit J-aggregates and AuNPs. Figure S8: Histograms of the height and diameter distributions, height profiles of Au nanostructures and TPPS J-aggregates deposited on glass surfaces. Figure S9. AFM image and relative profile.

**Author Contributions:** Conceptualization, L.M.S. and G.S.; investigation, M.T., N.M, B.D.H and G.D.L; data curation, M.T., A.R. and M.A.C.; writing—original draft preparation, M.A.C., M.T. and B.D.H.; writing—review and editing, L.M.S., A.R., G.S.; visualization, A.R.; Authorship must be limited to those who have contributed substantially to the work reported.

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

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