Research Summary 

　   Our group works on validation, evaluation and standardization of nanomaterial testing methods, to improve their accuracy, reliability, and applicability in research and industry setting. This motivates us to understand the measurement principles, fabricate nanoscale reference materials, perform uncertainty assessment, and develop new methods for chemical metrology of nanomaterials.

　　We study gold, silica, bimetallic alloy nanoparticle, quantum dots, graphene, and carbon nanotubes, using various techniques including CPS, QCM, ITC, AUC, low-field NMR and single-particle ICP-MS. Besides authoring 5 ISO/IEC standards and 12 national standards, we are interested in the following research directions:

　　1) Deveopment of model nanomaterial/nanostructures for method validation and homogenoeity evaluation

　　We obtained monolayers of gold nanorod vertical arrays to study the correlation between SERS and coupled plasmonics. The spatial variation of SERS signal is less than 5%. We also sorted carbon nanotubes into fractions using density gradient centrifugation, which provided new insights into biological effects of nanomaterials as functions of their structural variation.

　　2) Validation of characterization methods on various nanomaterials

　　We studied the sedimentation of gold nanorods with different aspect ratio and diameter, and detected protein adsorption onto nanoparticles in a mixture, using Differential Centrifugal Sedimentation.

　　These research activities involve collaboration with national metrology institutes (NIM China, DIN, NPL, etc.), Chinese Academy of Inspection and Quarantine, National Institute for Food and Drug Control, and research groups in various universities.