Nanophase of Ga2O3 has potentially important applications in photocatalysis. We report the synthesis of nanophase of the metastable gamma- and stable beta-Ga2O3 and demonstrate that it is possible to prepare a continuously varying mixture starting from the pure metastable gamma- to the pure beta-phase. This is achieved by employing a facile and reliable combustion route, using urea as a fuel. Typical grain sizes, as estimated from XRD studies, are about 3 nm. Given the importance of surface chemistry for potential applications, thermogravimetric coupled with mass spectrometry is used in conjunction with FTIR to elucidate the chemistry of the adsorbed surface layer. Studies on the gamma-Ga2O3 phase indicate the occurrence of weight loss of 8.1% in multiple steps. Evolved gas analysis and FTIR studies show presence of physisorbed H2O molecules and chemisorbed -(OH) ions bonded to active surface states and accounts predominantly for the observed weight loss.