The synthesis of nanoparticles (e.g. TiO2) is investigated experimentally and computationally in low-pressure H2/O2/N2 burner-stabilized flat flames in a stagnation point geometry, using a metal-organic (e.g. titanium tetra-iso-propoxide, TTIP) precursor. The flow field is modeled with detailed chemical kinetics and transport, and is compared with measurements using laser induced fluorescence (LIF) to map gas-phase temperature and OH-radical concentration. A sectional model, coupled with the simulated flow field and flame structure, is employed to model particle growth dynamics, computing aggregate particle size distribution, geometric standard deviation, and average primary particle size. The computations are compared with the experiments, for which in-situ characterization of the nanoparticles in the flow field is facilitated by a low-pressure aerosol sampling system connected to a nano scanning mobility particle sizer (nano-SMPS). Effects of operating pressures and precursor-loading rates on particle growth are also examined. Higher pressures produce larger aggregate particles, but with smaller primary particles, due to longer residence times. Higher precursor-loading rates result in larger aggregate particles, with slightly smaller primary particles.