Bachelor (Undeclared), National Chiao Tung University (2007)
Doctor of Philosophy, National Taiwan University (2013)
General Self-Assembly Method for Deposition of Graphene Oxide into Uniform Close-Packed Monolayer Films
AMER CHEMICAL SOC. 2019: 4460–70
Depositing a morphologically uniform monolayer film of graphene oxide (GO) single-layer sheets is an important step in the processing of many composites and devices. Conventional Langmuir-Blodgett (LB) deposition is often considered to give the highest degree of morphology control, but film microstructures still vary widely between GO samples. The main challenge is in the sensitive self-assembly of GO samples with different sheet sizes and degrees of oxidation. To overcome this drawback, here, we identify a general method that relies on robust assembly between GO and a cationic surfactant (cationic surfactant-assisted LB). We systematically compared conventional LB and cationic surfactant-assisted LB for three common GO samples of widely different sheet sizes and degrees of oxidation. Although conventional LB may occasionally provide satisfactory film morphology, cationic surfactant-assisted LB is general and allows deposition of films with tunable and uniform morphologies-ranging from close-packed to overlapping single layers-from all three types of GO samples investigated. Because cationic surfactant-assisted LB is robust and general, we expect this method to broaden and facilitate the use of GO in many applications where precise control over film morphology is crucial.
View details for DOI 10.1021/acs.langmuir.8b03994
View details for Web of Science ID 000463679300007
View details for PubMedID 30836748
Photocatalytic CO2 reduction using hybrid nanoporous catalysts
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478860505729
Langmuir-Blodgett Deposition of Graphene Oxide-Identifying Marangoni Flow as a Process that Fundamentally Limits Deposition Control.
Langmuir : the ACS journal of surfaces and colloids
Langmuir-Blodgett deposition is a popular route to produce thin films of graphene oxide for applications such as transparent conductors and biosensors. Unfortunately, film morphologies vary from sample to sample, often with undesirable characteristics such as folded sheets and patchwise depositions. In conventional Langmuir-Blodgett deposition of graphene oxide, alcohol (typically methanol) is used to spread the graphene oxide sheets onto an air-water interface before deposition onto substrates. Here we show that methanol gives rise to Marangoni flow, which fundamentally limits control over Langmuir-Blodgett depositions of graphene oxide. We directly identified the presence of Marangoni flow by using photography, and we evaluated depositions with atomic force microscopy and scanning electron microscopy. The disruptive effect of Marangoni flow was demonstrated by comparing conventional Langmuir-Blodgett depositions to depositions where Marangoni flow was suppressed by a surfactant. Because methanol is the standard spreading solvent for conventional Langmuir-Blodgett deposition of graphene oxide, Marangoni flow is a general problem and may partly explain the wide variety of undesirable film morphologies reported in the literature.
View details for PubMedID 30025460