Xuemin Lu

Electrically Conductive PEDOT Coating with Self-Healing Superhydrophobicity

A self-healing electrically conductive superhydrophobic poly(3,4-ethylenedioxythiophene) (PEDOT) coating has been prepared by chemical vapor deposition of a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by electrochemical deposition. The coating not only maintained high conductivity with a low resistivity of 3.2 × 10(-4) Ω·m, but also displayed a water contact angle larger than 156° and a sliding angle smaller than 10°. After being etched with O2 plasma, the coating showed an excellent self-healing ability, spontaneously regaining its superhydrophobicity when left under ambient conditions for 20 h. This superhydrophobicity recovery process was found to be humidity-dependent, and could be accelerated and completed within 2 h under a high humidity of 84%. The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at pH 1 or strong base solution at pH 14 for 3 h.

Dual-Responsive Controlled Drug Delivery Based on Ionically Assembled Nanoparticles

Ionically assembled nanoparticles (INPs) have been formed from poly(ionic liquid-co-N-isopropylacrylamide) with deoxycholic acid through electrostatic interaction. The structure and properties of the INPs were investigated by using (1)H NMR, Fourier transform infrared (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), and so on. Due to pH-responsive deoxycholic acid (pK(a) = 6.2) and thermo responsive N-isopropylacrylamide included in the ionic complex, the INPs exhibit highly pH and thermal dual-responsive properties. The potential practical applications as drug delivery carriers were demonstrated using doxorubicin (DOX) as a model drug. With a lower pH (pH 5.2) and higher temperature (above 37 °C), structural collapse of the INPs occurred as well as release of DOX owing to protonated DA departure from the INPs and a lower LCST (lower critical solution temperature) at the pathological conditions. The result shows that 80% of DOX molecules were released from INPs within 48 h at pH 5.2, 43 °C, but only 30% of the drug was released within 48 h at 37 °C and pH 7.4. Moreover, drug-loaded INPs exhibit an inhibitory effect on cell growth.

A Facile Method to Prepare Macroscopically Oriented Mesostructured Silica Film: Controlling the Orientation of Mesochannels in Multilayer Films by Air Flow

Mesoporous silica film with oriented mesochannels in three dimensions was supposed to have significant potential in preparing a new kind of optical or microelectronic device. Here we reported a new approach to preparing an oriented mesostructured silica film by just employing rapid and hot air flow. Based on this approach, 3D control of mesochannel orientation was also carried out.

Transparent, thermally and mechanically stable superhydrophobic coating prepared by an electrochemical template strategy

By mimicking nature, the preparation of artificial self-cleaning surfaces has gradually matured both in theory and technology, but their actual application has been hampered by enormous difficulties. The main challenge is that their design principle (i.e., their requirement for micro- and nano-structures) is difficult to reconcile with the need for coating strength and transparency. Here, we have exploited a porous structured silica coating with the help of an electrodeposited porous PEDOT template. This porous silica coating not only provides the requisite roughness for the final superhydrophobic surface, but also has a low refractive index, thereby enhancing the transparency of the silica coating. After fluorination, a highly transparent, thermally and mechanically stable superhydrophobic coating was obtained. The silica coating is found to withstand tests of harsh environments, such as mechanical resistance and ultra-high hydraulic pressure tests. This large-area superhydrophobic coating has great potential for use in solar cells and self-cleaning windows.

A facile approach for controlling the orientation of one-dimensional mesochannels in mesoporous titania films.

Controlling of the orientation of mesochannels in mesostructured thin films is important for the development of novel molecular devices and, in particular, generating vertically aligned mesochannels with respect to the substrate plane is extremely challenging for nonsiliceous materials. We describe a facile and highly effective air flow method, which is able to control the unidirectional alignment of titania mesochannels in a desired direction (e.g., parallel, perpendicular, or oblique) on a large scale, via manipulation of the air flow rate and incident angle. The titania mesochannels were characterized by TEM, SEM, SAXRD, and GISAXS. The unidirectional, vertically aligned mesostructured titania films were found to exhibit excellent ion conductivity.

Fluorescent Nanoparticles of Chitosan Complex for Real-Time Monitoring Drug Release

New types of fluorescent nanoparticles (FNPs) were prepared through ionic self-assembly of anthracene derivative and chitosan for applications as drug delivery carriers with real-time monitoring of the process of drug release. Because of the presence of the hydrophilic groups, these FNPs showed excellent dispersion and stability in aqueous solution. The structure and properties of the FNPs were investigated by using means of (1)H NMR, FTIR, SEM, dynamic light scattering (DLS), and so on. The potential practical applications as drug delivery carriers for real-time detection of the drug release process were demonstrated using Nicardipine as a model drug. Upon loading the drug, the strong blue fluorescence of FNPs was quenched due to electron transfer and fluorescence resonance energy transfer (FRET). With release of drug in vitro, the fluorescence was recovered again. The relationship between the accumulative drug release of FNPs and the recovered fluorescence intensity has been established. Such FNPs may open up new perspectives for designing a new class of detection system for monitoring drug release.

Electro-Responsively Reversible Transition of Polythiophene Films from Superhydrophobicity to Superhydrophilicity

An electro-responsively reversible switching of wettability between superhydrophobicity and superhydrophilicity has been obtained from a highly porous structured polythiophene film. The polythiophene film was prepared by two-step electrochemical deposition on an indium tin oxide (ITO) substrate. The underlying poly(3,4-ethylenedioxythiophene) (PEDOT) provides a highly porous structured conductive support, and poly(3-methylthiophene) (P(3-MTH)) deposited thereon plays the role of a low-surface-energy conductive coating. The wettability switching of this double-layer film between superhydrophobicity and superhydrophilicity has been investigated by doping and dedoping in an electrolyte solution containing ClO4(-). Electrochromism of the film was also seen to accompany the electrochemical process of conversion between the two superwetting states. On the basis of this porous electro-active film, an in situ electro-wetting device was also demonstrated.

Thermally tunable circular dichroism and circularly polarized luminescence of tetraphenylethene with two cholesterol pendants

This work provides a novel strategy for the construction of materials exhibiting circularly polarized luminescence (CPL) with a thermal tunability and a high efficiency in the solid state. In this strategy, cholesterol pendants were introduced into tetraphenylethene, a typical aggregation-induced emission (AIE) molecule using long undecyl spacers as a covalent connection bridge. The resulting AIE molecule (2CTPE) exhibited CPL with a high dissymmetry factor (∼10−2) and a high fluorescence efficiency (42%) in the solid state. The presence of the long spacer led to the formation of a liquid crystal (LC) phase of 2CTPE with a typical focal conic texture of cholesteric LC, as revealed by polarizing optical microscopy (POM) investigation. Furthermore, circular dichroism (CD) and CPL properties of 2CTPE could be thermally regulated. These results give evidence to the synthesis of new, tunable CPL materials with a high fluorescence efficiency in the solid state.

Preparation of aggregation-induced emission dots for long-term two-photon cell imaging

Two-photon fluorescence imaging has attracted increasing interest in the biological and medical fields because of its low cell damage, high resolution, large imaging depth, and easy dynamic observation. A high-performance two-photon probe with long-term imaging capability was proposed for this imaging technology. In this work, a new two-photon probe compound was synthesized from tetraphenylethylene fluorogen with aggregation-induced emission. A phenyl-[phenyl-(1,2,5-thialdiazol)] amine group was induced to red-shift the absorption and emission wavelengths of the compound. After self-assembly, fluorescent dots with aggregation-induced emission cores and hydrophobic shells terminated by -COOH were formed. Cell experiments proved that the 4-(7-(phenyl(4-(1,2,2-triphenylvinyl)phenyl)amino)benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid (TPECOOH) dots with red emission showed good biocompatibility and excellent two-photon imaging ability. TPECOOH dots were used successfully in direct long-term cell imaging with high efficiency. Even after twelve days, fluorescence imaging could still be observed in live HeLa cells.

Self-healing polymers with PEG oligomer side chains based on multiple H-bonding and adhesion properties

In an attempt to prepare polymers able to function as self-healing materials, a quadruple hydrogen-bonding ureidopyrimidinone (UPy) moiety was introduced to polymer systems. Low crosslinking materials based on hydroxyethyl acrylate (HEA) and poly(ethylene glycol) methacrylate (PEGMA) containing 10% of UPy moieties were synthesized, and their thermal and rheological properties were investigated by dynamic mechanical analysis (DMA) and a rotational rheometer. The hydroxyethyl group and a PEG oligomer with high molecular polarity as side chains provided high surface energies and adhesion properties. The fastest self-healing of these polymer films can be achieved within 20 min. The adhesion strength tests via the tensile mode revealed the potential of these self-healing polymers in application as adhesives.