Dezhong Shen

Label-Free Colorimetric Detection of Trace Atrazine in Aqueous Solution by Using Molecularly Imprinted Photonic Polymers

Based on the combination of colloidal-crystal templating and a molecular imprinting technique, a sensor platform for efficient detection of atrazine in aqueous solution has been developed. The sensor is characterized by a 3D-ordered interconnected macroporous structure in which numerous nanocavities derived from atrazine imprinting are distributed in the thin wall of the formed inverse polymer opal. Owing to the special hierarchical porous structure, the molecularly imprinted polymer opals (or molecularly imprinted photonic polymer; MIPP) allow rapid and ultrasensitive detection of the target analyte. The interconnected macropores are favorable for the rapid transport of atrazine in polymer films, whereas the inherent high affinity of nanocavites distributed in thin polymer walls allows MIPP to recognize atrazine with high specificity. More importantly, the atrazine recognition events of the created nanocavities can be directly transferred (label-free) into a readable optical signal through a change in Bragg diffraction of the ordered macropores array of MIPP and thereby induce color changes that can be detected by the naked eye. With this novel sensory system, direct, ultrasensitive (as low as 10(-8) ng mL(-1)), rapid (less than 30 s) and selective detection of atrazine with a broad concentration range varying from 10(-16) M to 10(-6) M in aqueous media is achieved without the use of label techniques and expensive instruments.

Polydopamine-coated nanofibrous mats as a versatile platform for producing porous functional membranes

In this work, polydopamine-coated electrospun polystyrene (PS) nanofibrous mats were successfully prepared by simply immersing the PS mats into dopamine alkaline Tris buffer solution for 24 h. The successful growth of polydopamine (Pdop) was confirmed with X-ray photoelectron spectroscopy (XPS). The thickness of the Pdop layer was about 20 nm observed by transmission electron microscope (TEM). The wetting behavior was changed tremendously into superhydrophilicity. Combining the unique characteristics of Pdop as active secondary reaction sites and electrospun mat as a flexible porous support, this hierarchically structured nanofibrous mat can serve as a useful platform for developing porous functional membranes. As demonstrated, oil/water separation and molecule gating membranes were fabricated by using the Michael reaction of Pdop coating with undecanethiol (UT) or 11-mercaptoundecanoic acid (MUA), respectively. As an oil/water separation membrane, the long alkyl chains of UT anchored on the membrane surface increased the contact angle (CA) of water distinctly, and water was blockaded completely while oil smoothly passed through the membrane. Similarly, a molecule gating membrane was constructed based on the pH-induced deprotonation of the carboxyl group of MUA, and its permeation selectivity was confirmed by cyclic voltammetry (CV) with an electrochemical probe. Moreover, the reductive property of the Pdop coating was also utilized to facilely introduce various metal nanoparticles into membrane systems for potential applications, for example, a silver nanoparticle-decorated membrane can be used as an effective antibacterial film as confirmed by the modified Kirby-Bauer method. All performed experiments demonstrate that polydopamine-coated nanofibrous mats can serve as a versatile platform for producing porous functional membranes.

Direct and label-free detection of cholic acid based on molecularly imprinted photonic hydrogels

Here we report the design and preparation of a novel self-reporting sensor for cholic acid, an important biological compound produced in hepatocytes. Traditional detection methods of cholic acid are mostly dependent on analytical equipment, and are either time-consuming or require a derivatization process. In this work, a new approach based on molecularly imprinted photonic hydrogels (IPHs) is described, by which direct, sensitive and label-free detection of cholic acid can be achieved without any derivatization treatment and expensive instruments. The unique 3D ordered porous hydrogels that reveal optical changes in responsive to cholic acid concentration were prepared by combining colloidal crystal templating with the molecular imprinting technique. Due to their special hierarchical porous structure, which consists of 3D-ordered interconnected macroporous arrays with nanocavities derived from molecular imprinting, the formed photonic hydrogels allow rapid and ultrasensitive detection of the target analyte. The interconnected macropores are favorable for the rapid transport of the analyte in the hydrogel, while the inherent high affinity of nanocavities distributed in thin hydrogel walls allows IPHs to recognize the analyte with high specificity.

Enhancement of Light Output Power from LEDs Based on Monolayer Colloidal Crystal

One of the major challenges for the application of GaN-based light emitting diodes (LEDs) in solid-state lighting lies in the low light output power (LOP). Embedding nanostructures in LEDs has attracted considerable interest because they may improve the LOP of GaN-based LEDs efficiently. Recent advances in nanostructures derived from monolayer colloidal crystal (MCC) have made remarkable progress in enhancing the performance of GaN-based LEDs. In this review, the current state of the art in this field is highlighted with an emphasis on the fabrication of ordered nanostructures using large-area, high-quality MCCs and their demonstrated applications in enhancement of LOP from GaN-based LEDs. We describe the remarkable achievements that have improved the internal quantum efficiency, the light extraction efficiency, or both from LEDs by taking advantages of diverse functions that the nanostructures provided. Finally, a perspective on the future development of enhancement of LOP by using the nanostructures derived from MCC is presented.

Maleimide-containing polymer inverse opals: a new kind of reactive photonic structure with significant extendibility

In this work, maleimide-containing polymer inverse opals have been successfully prepared by utilization of an acrylate monomer bearing a masked (protected) maleimide unit. As an ideal clickable functional group, maleimide can promote the Michael addition of thiol-containing molecules and the thermoreversible Diels–Alder reaction of furan derivatives, providing tremendous opportunities to produce various functional materials from one maleimide-containing polymer. As a demonstration, four chemical systems were facilely evolved from the prepared maleimide-containing inverse opal. By exploiting the nucleophilic thiol–ene reaction of maleimide, the zwitterionic pH-responsive inverse opal and electroactive inverse opal were first fabricated by reacting with cysteine and thiol-containing ferrocene derivatives, respectively. Based on the same reaction, it was also found that the maleimide-containing inverse opal could serve as a self-reporting sensing platform to sensitively detect the reduction of oxidized glutathione by specific enzymes. On the other hand, the thermoreversible nature of the Diels–Alder reaction of the maleimide groups made it possible to construct a dynamic molecule gating system by reacting with alkyl-chain-substituted furan derivatives from the prepared interconnected macroporous film. In fact, due to the unlimited variety provided by the two kinds of reactions mentioned above, the described photonic material exhibits a significant extendibility and could be easily post-modified for special purposes with maintenance of the opaline structure. Thus, this novel clickable maleimide-containing polymer inverse opal could serve as a reactive platform for producing a variety of functional photonic materials.