## 2 Materials and Methods  
The fs laser sources that were used in this work for polyyne and NM synthesis by laser ablation of the bulk target material in liquid had a beam wavelength/pulse width/pulse repetition rate/focused beam diameter on the sample surface of either 800 nm/90 fs/1 kHz/\(\sim\)36 \(\upmu\)m or 343 nm/190 fs/1-6 kHz/\(\sim\)7 \(\upmu\)m. The UV wavelength was obtained by converting the fundamental IR laser beam wavelength (1030 nm) using a standard optical setup consisting of BBO crystals, half- and quarter-waveplates, and mirrors. The bulk target material was a piece of pyrolytic graphite (dimensions of 10 \(\times\) 10 \(\times\) 2-mm) and was ablated while lying at the bottom of a beaker filled with deionized (DI) water (Sigma-Aldrich (St. Louis, MO, USA) 38796-1L). The liquid volume in the beaker was kept to the minimum possible volume of \(\sim\)3 mL to also ensure a minimum liquid height above the target surface of \(\sim\)1 mm, thus avoiding the induction of non-linear optical effects of self-focusing and filamentation in the liquid by the laser beam. The beam was vertically impinging onto the horizontally lying target at the bottom of the beaker, and it scanned the target surface under the stationary beam in a meandering fashion (5 mm length, 0.01 mm pitch, and 1 mm/s scanning speed) using a computer-controlled translational stage. The optical emission spectrum of the laser ablation plasma plume was measured by collecting the plume emission light using an achromatic lens positioned at a 45\({}^{\circ}\) angle relative to the normal and by focusing it at the entrance of an optical fiber that was coupled to an echelle spectrometer ([PERSON] (Oxford Instruments, Abingdon, UK) 5000) equipped with a gateable, intensified charge-coupled device (ICCD) camera (iStar 334T, (Oxford Instruments, Abingdon, UK)). The ICCD camera detector was synchronized with the trigger of the laser pulse using a digital delay generator (AtomTrace (Brno-Kralovo Pole, Czech Republic), AC-DDG-4). The time delay of the ICCD (t\({}_{\text{d}}\)) was chosen to be between 2 and 50 ns, the gate window (t\({}_{\text{w}}\)) between 100 and 200 ns, the number of pulses for each shot between 1000 and 6000 (corresponding to the laser pulse repetition rate), the number of accumulations for each shot between 1 and 50, and the spectral resolution to be 0.1 nm to maximize the signal-to-noise ratio (SNR) in the measured spectra. All spectral measurements were completed soon after starting the ablation (typically within the first minute or earlier). For comparison purposes, experiments were also performed on the target in ambient air using the same ablation and detetion parameters. Following ablation of the target in liquid, the produced solutions were characterized using UV-vis absorption spectroscopy. The ablation products from solution droplets that were dried out on carbon-coated grids were characterized using TEM, whereas those obtained from droplets that were dried out on clean glass substrates were characterized using XRD, a diffractometer with a Cu K\({}_{\alpha}\) source (\(\uplambda\) = 1.5406 A), and Raman spectroscopy (excitation beam wavelength of 532 nm, power \(<\) 0.06 mW). The emission lines in the LIBS spectra were identified using the NIST database [21] and Plasus SpecLine software Version 2.1.