Highly　stable　dispersions　of　nanosized　copper　(Cu)　particles　with　an　average　size　of　(2.6 ± 0.5)　nm　were　synthesized　by　in　situ　reduction　of　Cu(II)　to　immobilize　Cu　nanoparticles　on　the　amino-enriched　surface　of　chitosan　(CTS).　The　synthetic　process　and　stability　of　the　l-ascorbic　acid-stabilized　Cu-CTS　nanocomposites　were　investigated　by　X-ray　photoelectron　spectroscopy　and　Fourier　transform　Infrared　spectroscopy.　The　antimicrobial　efficiency　and　potency　of　the　Cu-CTS　nanocomposites　were　studied.　The　Cu-CTS　nanocomposites　were　found　to　exhibit　a　broad　antimicrobial　spectrum　and　high　antimicrobial　activity　against　Gram-positive　bacterial　pathogen　Staphylococcus　aureus　and　fungal　pathogen　Monilia　albican.　The　minimum　inhibitory　concentration　of　the　Cu-CTS　nanocomposites　toward　S.　aureus　was　found　to　be　6.4 µg mL−1,　much　lower　than　those　reported　in　the　literature.　Furthermore,　the　Cu-CTS　nanocomposites　were　stable　and　maintained　good　disinfection　potential　even　after　90-day　shelf-time　under　ambient　conditions.　©　2014,　Science　China　Press　and　Springer-Verlag　Berlin　Heidelberg.