The　role　of　reactive　environment　and　hydrogen　specifically　in　growth　and　structure　of　molybdenum　selenide　(MoSe2)　nanomaterials　is　presently　debated,　and　it　is　not　clear　whether　hydrogen　can　promote　the　growth　of　MoSe2　sheets　and　alter　their　electronic　properties.　To　find　efficient,　convenient　methods　for　controlling　the　nucleation,　growth　and　resultant　properties　of　MoSe2　nanomaterials,　MoSe2　nanoflakes　were　synthesized　on　silicon　substrates　by　hot　filament　chemical　vapor　deposition　using　molybdenum　trioxide　and　selenium　powders　in　pure　hydrogen,　nitrogen　gases　and　hydrogen-nitrogen　mixtures.　The　structures　and　composition　of　synthesized　MoSe2　nanoflakes　were　studied　using　the　advanced　characterization　instruments　including　field　emission　scanning　electron　microscopy,　micro-Raman　spectroscopy,　X-ray　photoelectron　spectroscopy,　transmission　electron　microscopy　and　energy　dispersive　X-ray　spectrometry.　The　analysis　of　the　growth　process　indicates　that　hydrogen　can　improve　the　formation　of　MoSe2　nanoflakes　and　significantly　alter　their　properties　due　to　the　high　reduction　capacity　of　hydrogen　and　the　creation　of　more　nucleation　centers　of　MoSe2　nanoflakes　on　the　silicon　surface.　The　study　of　photoluminescent　(PL)　properties　reveals　that　the　MoSe2　nanoflakes　can　generate　a　strong　PL　band　at　about　631　nm,　differently　from　the　plain　MoSe2　nanoflakes.　The　major　difference　in　the　PL　properties　may　be　related　to　the　edges　of　MoSe2　nanoflakes.　These　results　can　be　used　to　control　the　growth　and　structure　of　MoSe2-based　nanomaterials　and　contribute　to　the　development　of　advanced　MoSe2-based　optoelectronic　devices.　(C)　2017　Elsevier　B.V.　All　rights　reserved.