Dihydroxyacetone aerosols with particle diameters around 50 nm were produced in an electrospray at ambient temperature and pressure. The vibrational spectra of the aerosols between 800 and 4000 cm(-1) were recorded with a Fourier transform infrared spectrometer. Depending on the experimental conditions, an appreciable amount of gas-phase 1,3-dihydroxy-2-propanone appeared in the infrared spectra of the particulate phase. In contrast to the gas phase, the particulate phase was found to consist of the chemically bound dimer 2,5-dihydroxymethyl-2,5-dihydroxy-1,4-dioxane. Temperature-dependent gas-phase spectra of dihydroxyacetone monomer between 310 and 440 K reveal interesting torsional dynamics, which are analyzed with the help of a detailed four-dimensional model. Experimental spectra of the nanoparticles were simulated using a Kramers-Heisenberg dielectric function. The comparison with ab initio calculations of the free molecule and small clusters leads to a first microscopic picture of the intermolecular interactions in the condensed phase.