Gold nanoflowers (AuNF) were synthesized according to an established procedure and subsequently drop-cast onto a silicon substrate (see the methods section for more details on the preparation and supplementary information (SI) for TEM images of the particles and a micrograph of the film). The extinction spectrum of the AuNFs in aqueous solution is characterized by a broad, but well-defined localized surface plasmon resonance (LSPR) at approximately 550 nm (Figure , black, dashed line), and by characteristic interband absorption at the blue side of the spectrum. The latter can also be clearly distinguished in the absorption spectrum of the films (Figure , orange line). However, in contrast to the particle dispersion, the film spectrum transitions to a broad continuous absorption for wavelengths longer than 480 nm. This response is typical for rough gold films and likely originates from a large ensemble of plasmon resonances in the various hot spots of the nanoparticle aggregates. The presence of local hot spots is confirmed by the well-known strong SERS enhancement observed for these films (see also Figure ). Figure presents the emission spectrum of the AuNF film for an excitation wavelength of λ ex = 355 nm (blue line). The emission strongly resembles the LSPR absorption of the AuNFs in solution (black, dashed line). This correlation between emission and plasmon resonance has been reported for many particles and is generally interpreted as evidence of plasmon-enhanced emission from single particles. The only investigation we could find in the literature on the emission of AuNFs 55 reported the emission for single particles for wavelengths above 530 nm. In this spectral range, the observed emission aligns closely with our measurements. Given the pronounced similarity between the measured emission spectrum of the film and the absorption spectrum of the individual particles, we can reasonably conclude that the emission from the film originates from individual nanoparticles, despite the dense packing.