Halas and her co-workers reported the gold nanoshells

with strong surface plasma resonance(SPR)absorption band in near-infrared(NIR)region of 800~1200 nm

the transparent window of biological tissues.This kind of gold nanoshells was successfully used in thermal ablative therapy for cancer by NIR photo-thermal conversion.The noble metal nanomaterials with strong NIR absorption are also an ideal candidate for diffuse optical tomography

which is a promising imaging modality for early detection of diseases.Silver nanomatertials

as the metal with the highest electrical and thermal conductivity

if their SPR absorption were extended to NIR region

should have more excellent photothermal conversion property.One-dimensional silver nanomaterials

such as silver nanowires or wire-like nanostructures

have both transverse and longitudinal SPR absorption modes.The absorption location for the transverse SPR mode is fixed at ~400 nm

while that of the longitudinal SPR mode varies depending on the ratio of length to width of the nanostructures.Therefore

if the ratios of length to width of the silver nanowires are modified

then the longitudinal SPR absorption should be broaden inhomogeneously and may extended to NIR region.In this work

cross-sectional Ag nanochains with diameters of 10~30 nm were prepared using the method of water/oil emulsion.This kind of Ag nanochains demonstrated strong and super-wide SPR absorption extending from 400 to 1 200 nm.It exhibited better photothermal conversion property than that of the well-known gold nanoshells

and thus is more suitable to be used in biomedicine as the photothermal converters and in diffuses optical tomography as the contrast agent.