Benliang Liang

Bioinspired Design and Assembly of Layered Double Hydroxide/Poly(vinyl alcohol) Film with High Mechanical Performance

Inspired by the hierarchical structure and excellent mechanical performance of nacre, LDH nanosheets with an appropriate aspect ratio to withstand significant loads and at the same time allow for rupture under the pull-out mode were synthesized as artificial building blocks for the fabrication of nacre-like films. Multilayered PVA/LDH films with a high tensile strength and ductility were prepared for the first time by bottom-up layer-by-layer assembly of pretreated LDH nanosheets and spin-coating of PVA. The weight fraction of inorganic LDH platelets in the hybrid PVA/LDH films (wp) was controlled by changing the concentration of PVA solution applied in the spin-coating process. The resulting films revealed that the PVA/LDH hybrid films were piled close together to form a well-defined stratified structure resembling the brick-and-mortar structure of natural nacre. In the hybrid films, the content of inorganic LDH platelets was comparable to the value in nacre, up to 96.9 wt %. It could be clearly seen that the mechanical performance of the as-prepared PVA/LDH films was greatly improved by increasing the rigid building-block LDHs. The tensile strength of the 2 wt % PVA/LDH hybrid film reached a value of 169.36 MPa, thus exceeding the strength of natural nacre and reaching 4 times that of a pure PVA film. Meanwhile, its elastic modulus was comparable to that of lamellar bone.

Tuning plasmonic and chemical enhancement for SERS detection on graphene-based Au hybrids

Various graphene-based Au nanocomposites have been developed as surface-enhanced Raman scattering (SERS) substrates recently. However, efficient use of SERS has been impeded by the difficulty of tuning SERS enhancement effects induced from chemical and plasmonic enhancement by different preparation methods of graphene. Herein, we developed graphene-based Au hybrids through physical sputtering gold NPs on monolayer graphene prepared by chemical vapor deposition (CVD) as a CVD-G/Au hybrid, as well as graphene oxide-gold (GO/Au) and reduced-graphene oxide (rGO/Au) hybrids prepared using the chemical in situ crystallization growth method. Plasmonic and chemical enhancements were tuned effectively by simple methods in these as-prepared graphene-based Au systems. SERS performances of CVD-G/Au, rGO/Au and GO/Au showed a gradually monotonic increasing tendency of enhancement factors (EFs) for adsorbed Rhodamine 6G (R6G) molecules, which show clear dependence on chemical bonds between graphene and Au, indicating that the chemical enhancement can be steadily controlled by chemical groups in a graphene-based Au hybrid system. Most notably, we demonstrate that the optimized GO/Au was able to detect biomolecules of adenine, which displayed high sensitivity with a detection limit of 10(-7) M as well as good reproducibility and uniformity.

Layer by layer assembly of heparin/layered double hydroxide completely renewable ultrathin films with enhanced strength and blood compatibility

Renewable nacre-like heparin (HEP)/layered double hydroxide (LDH) ultrathin films were first fabricated via a bottom-up layer by layer (LBL) deposition technique, which simultaneously showed largely enhanced mechanical properties and good blood compatibility. The results of UV-vis, FTIR, XRD and SEM analysis indicate that the HEP/LDH ultrathin films stacked densely together to form a well-defined brick-and-mortar structure. A strong electrostatic and hydrogen bond network at the organic–inorganic interface allowed the modulus of the film reach ca. 23 GPa, which was remarkably enhanced compared to previously reported polymer–LDH hybrid films. Due to the interlamellar heparin, the (HEP/LDH)n film may prove to be beneficial for new medical applications or as a replacement for conventional petroleum based plastics.

Ca2+ Enhanced Nacre-Inspired Montmorillonite–Alginate Film with Superior Mechanical, Transparent, Fire Retardancy, and Shape Memory Properties

Inspired by nacre, this is the first time that using the cross-linking of alginate with Ca ions to fabricate organic-inorganic nacre-inspired films we have successfully prepared a new class of Ca2+ ion enhanced montmorillonite (MMT)-alginate (ALG) composites, realizing an optimum combination of high strength (∼280 MPa) and high toughness (∼7.2 MJ m-3) compared with other MMT based artificial nacre. Furthermore, high temperature performance of the composites (with a maximum strength of ∼170 MPa at 100 °C) along with excellent transmittance, fire retardancy, and unique shape memory response to alcohols could greatly expand the application of the mutilfunctional composites, which are believed to show competitive advantages in transportion, construction, and insulations, protection of a flammable biological material, etc.

Nacre-inspired green artificial bionanocomposite films from the layerby-layer assembly of montmorillonite and chitosan

The simple LBL technique was introduced to fabricate green nacre-like chatosan/montmorillonite (CHI/MMT) films. The results of SEM and XRD analysis demonstrate that the produced CHI/MMT composites films stacked densely together to bring out well-defined nacre-like brick-mortar structure. The nanoindentation technique is used to characterize the mechanical properties of the layered nanocomposite films, which show enhanced mechanical modulus (up to ∼6.64 GPa) compared with the pure chitosan.

Nacre-inspired Polyglutamic Acid/Layered Double Hydroxide Bionanocomposite Film with High Mechanical, Translucence and UV-blocking Properties

Due to the various needs in the current applications, multifunctional composite materials with high strength and high toughness were highly desired now. Many scholars dedicated their time to find a simple, green and fast method for the preparation of multi-functional materials. In this study, inspired by the hierarchical “brick-and-mortar” structure and excellent mechanical performance of nacre, a fast green vacuum-filtration method was used to fabricate strong and multifunctional polyglutamic acid/layered double hydroxide (PGA/LDH) films mimicking nacre. The experimental results confirm that the artificial nacre has hierarchical “brick-and-mortar” structure. It exhibits excellent strength (93.5 MPa) and flexibility (easily bendable fold), combining with outstanding properties of UV-blocking and translucence properties. This work provides a way of fabricating multifunctional organic-inorganic hybrid films, which has potential applications in the areas of optical, transportation and construction fields.

A CO2-tunable plasmonic nanosensor based on the interfacial assembly of gold nanoparticles on diblock copolymers grafted from gold surfaces

A general stepwise strategy for the fabrication of CO2-tunable plasmonic nanosensors was described for the first time, based on gold surface functionalization by CO2-responsive poly(N,N-diethylaminoethyl methacrylate) (PDEAEMA) brushes via a surface-initiated atom transfer radical polymerization (SI-ATRP) method, then the extremity of PDEAEMA was functionalized by linking the polyacrylamide (PAAm) brushes via ATRP, where they were assembled with gold nanoparticles (AuNPs) efficiently by altering the deposition time. The swelling–shrinking states of the PDEAEMA brushes can be tuned just by passing CO2 and N2 through a solution alternately. The unique plasmonic surface-enhanced Raman scattering (SERS) sensing properties of these stimulable substrates were investigated using 4-mercaptophenol (4MPh) as a molecular probe. When alternating CO2 and N2 bubbling in the water solution, the reversible switching of the SERS signals was complete. By in situ contact-mode atomic force microscopy, the thickness of the polymer layer was observed to be 26 nm in CO2 saturated water, and after N2 bubbling to remove CO2 it decreased to 15 nm, causing the AuNPs to move near to the gold surface. Meanwhile, the distance between the nearby AuNPs becomes smaller, and the surface coverage (φ) of the AuNPs increased from 27% to 35%. The reported CO2-responsive plasmonic nanosensor provided a dynamic SERS platform, with reversible regulation for electromagnetic coupling between the AuNPs and the gold surface, and between nearby AuNPs.

A biomimetic ion-crosslinked layered double hydroxide/alginate hybrid film

Natural nacre has an ordered layered arrangement of calcium carbonate platelets and ion-crosslinked protein, which enable it to achieve outstanding mechanical properties. Inspired by the relationship between structure and mechanical properties of natural nacre, we fabricate a Ca2+-crosslinked layered double hydroxide/alginate (LDH/ALG-Ca2+) hybrid film through filtration of Ca2+-crosslinked LDH/ALG hybrid building blocks. The LDH nanoplatelets and alginate were alternately stacked giving an ordered layered structure, in which alginate was crosslinked by Ca2+. The effect of LDH content and Ca2+ crosslinking on the microstructure and interfacial interaction of LDH/ALG-Ca2+ hybrid films was studied systematically. The optimized nacre-like hybrid film exhibits good flexibility and high strength (194 MPa), superior to natural nacre. The ordered layered structure and small diameter of LDH give the hybrid film a high transparency of 74–94% in the visible light wavelength range.