## 4 Conclusions  
In this work, we have presented experimental evidence for the production of polyynes as well as C-NMs by a fs laser ablation of a bulk graphite target in DI water. C-NMs are formed for high as well as low fluences. However, for low fluences ranging from 4 and up to 20 J/cm\({}^{2}\) (800 nm laser beam wavelength), polyynes are also detected in the produced solutions, whereas for high fluences of 250 J/cm\({}^{2}\) (343 nm laser beam wavelength), polyynes are detected when the ablation for the total ablation time duration was performed in two split intervals with a pause of ablation between them. The ablation products consist of large NPs (\(\sim\)50-200 nm), small NPs (\(\sim\)2-5 nm), and large, flake-like structures. The products have a hexagonal graphite crystal structure. The LIBS spectra in DI water are dominated by neutral or singly ionized carbon atoms rather than C\({}_{2}\) dimers.  
Figure 7: LIBS spectra measured with different time delays upon ablation (50 J/6 kHz) of the target in DI water, showing the CI line at 808.37 nm (**a**) and CII line at 868.25 nm (**b**).  
**Supplementary Materials:** The following can be downloaded at: [[https://www.mdpi.com/article/10.390/app131810388/s1](https://www.mdpi.com/article/10.390/app131810388/s1)]([https://www.mdpi.com/article/10.390/app131810388/s1](https://www.mdpi.com/article/10.390/app131810388/s1)). Figure S1: LIBS spectra measured upon ablation of the target in air at 50 uJ/6 kHz and 30 uJ/6 kHz; Figure S2: LIBS spectra measured upon ablation of the target in air at 50 uJ/6 kHz and for different time delays in the region of 465-475 (a), 512-518 (b), and 553-565 nm (c) where the C\({}_{2}\) Swan bands due to \(\Delta\
u=+1\), 0, and \(-1\) transitions appear, respectively; Figure S3: LIBS spectra measured for different time delays in the region of 553-565 nm where the C\({}_{2}\) Swan bands corresponding to \(\Delta\
u=-1\) transitions appear. The blue lines correspond to theoretical fitting to the experimentally measured spectra (red lines); Figure S4: Vibrational/rotational temperature of the C\({}_{2}\) molecules versus the time delay as determined from the theoretical fitting of Figure S3; Figure S5: LIBS spectra measured with different time delays upon ablation (50 uJ/6 kHz) of the target in air, showing the CI line at 833.65 nm (a) and CII line at 868.25 nm (b); Figure S6: TEM image of the sheet-like structures in the ablation products (DI water, 80 uJ/6 kHz, 33 min). The large NPs are distinguished on the sheets and in the spaces between them; Figure S7: TEM images of the ablation products (DI water, 800 nm/110 uJ).  
**Author Contributions:** Conceptualization, N.G.S.; methodology, N.G.S., O.B., R.J., A.D. and G.N.; formal analysis, N.G.S., O.B., R.J. and G.N.; investigation, N.G.S.; resources, N.G.S., O.B. and E.H.; data curation, N.G.S., O.B., R.J., A.D. and G.N.; writing--original draft preparation, N.G.S.; writing--review and editing, N.G.S., O.B., R.J., A.D., G.N. and E.H.; supervision, O.B., R.J. and E.H.; project administration, N.G.S., O.B. and E.H.; funding acquisition, N.G.S., O.B. and E.H. All authors have read and agreed to the published version of the manuscript.  
**Funding:** Part of the research leading to these results has received funding from LASERLAB-EUROPE (grant agreement No. 871124, European Union's Horizon 2020 research and innovation programme).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available from the corresponding author upon reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest.