Substructure imaging of heterogeneous nanomaterials with enhanced refractive index contrast by using a functionalized tip in photoinduced force microscopy

查看全文 作　　者：Junghoon [1]Jahng;Heejae [2]Yang;Eun Seong [1]Lee 机构地区：[1]Center for Nanocharacterization,Korea Research Institute of Standards and Science(KRISS),Daejeon 34113,Republic of Korea;[2]Department of Materials Engineering,Advanced Fibrous Materials Laboratory,University of British Columbia,Vancouver,BC V6T 1Z4,Canada 出　　处：《Light(Science & Applications)》索引2018年第7卷第1期,共9页 基　　金：supported by the Nano Material Technology Development Program(2014M3A7B6020163);by the Korea Research Fellowship Program(2016H1D3A1938071)through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT. 摘　　要：The opto-mechanical force response from light-illuminated nanoscale materials has been exploited in many tip-based imaging applications to characterize various heterogeneous nanostructures.Such a force can have two origins:thermal expansion and induced dipoles.The thermal expansion reflects the absorption of the material,which enables one to chemically characterize a material at the absorption resonance.The induced dipole interaction reflects the local refractive indices of the material underneath the tip,which is useful to characterize a material in the spectral region where no absorption resonance occurs,as in the infrared(IR)-inactive region.Unfortunately,the dipole force is relatively small,and the contrast is rarely discernible for most organic materials and biomaterials,which only show a small difference in refractive indices for their components.In this letter,we demonstrate that refractive index contrast can be greatly enhanced with the assistance of a functionalized tip.With the enhanced contrast,we can visualize the substructure of heterogeneous biomaterials,such as a polyacrylonitrile-nanocrystalline cellulose(PAN-NCC)nanofiber.From substructural visualization,we address the issue of the tensile strength of PAN-NCC fibers fabricated by several different mixing methods.Our understanding from the present study will open up a new opportunity to provide enhanced sensitivity for substructure mapping of nanobiomaterials,as well as local field mapping of photonic devices,such as surface polaritons on semiconductors,metals and van der Waals materials. 关 键 词：refractive BIOMATERIALS functional