Photosensitive caged compounds have enhanced our ability to address the complexity of biological systems by generating effectors with remarkable spatial/temporal resolutions1-3. The caging effect is typically removed by photolysis with ultraviolet light to liberate the bioactive species. Although this technique has been successfully applied to many biological problems, it suffers from a number of intrinsic drawbacks. For example, it requires dedicated efforts to design and synthesize a precursor compound to the effector. The ultraviolet light may cause damage to biological samples and is only suitable for in vitro studies because of its quick attenuation in tissue4. Here we address these issues by developing a platform based on the photothermal effect of gold nanocages. Gold nanocages represent a class of nanostructures with hollow interiors and porous walls5. They can have strong absorption (for the photothermal effect) in the near-infrared (NIR) while maintaining a compact size. When the surface of a gold nanocage is covered with a smart polymer, the pre-loaded effector can be released in a controllable fashion using a NIR laser. This system works well with various effectors without involving sophiscated syntheses, and is well-suited for in vivo studies due to the high transparency of soft tissue in NIR6.

This Communication describes a facile route to the preparation of ultrathin gold nanowires using linear chains formed from [(oleylamine)AuCl] complex via aurophilic interaction. The linear chains, with AuI...AuI bonds as the backbone and surrounded by oleylamines, can group together to form bundles of polymeric strands. When the AuI was reduced to Au0 by reacting with Ag nanoparticles in hexane, the polymeric strands functioned as both the source of Au and the template to mediate the nucleation and growth of Au nanowires. Using this method, we were able to produce Au nanowires with an average diameter of approximately 1.8 nm and an aspect ratio of >1000 in high yields (approximately 70%).

This article reports a simple method for functionalizing the surface of TiO 2 (both anatase and rutile) and ZrO 2 nanofibre membranes with Pt, Pd, and Rh nanoparticles. The TiO 2 membranes were prepared in the form of nonwoven mats by electrospinning with a solution containing both poly(vinyl pyrrolidone) and titanium tetraisopropoxide, followed by calcination in air to generate anatase (at 510 C) or rutile (at 800 C). The ZrO 2 membranes were fabricated with a solution of poly(vinyl pyrrolidone) and zirconium acetylacetonate, followed by calcination in air at 550 C to yield the tetragonal phase. The fibre mats were then immersed in a polyol reduction bath to coat the surface of the nanofibres with Pt, Pd, or Rh nanoparticles of 2-5 nm in size. In addition, the ceramic fibres decorated with Pt nanoparticles could serve as a substrate to grow Pt nanowires $7 nm in diameter with lengths up to 125 nm. We subsequently demonstrated the use of Pd-coated anatase fibre membranes as a catalytic system for cross-coupling reactions in a continuous flow reactor. Contrary to the conventional setup for an organic synthesis, a continuous flow system has advantages such as short reaction time and no need for separation. The membrane-based catalytic system can also be fully regenerated for reuse.

The detection of molecules at an ultralow level by Surface-Enhanced Raman Spectroscopy (SERS) has recently attracted enormous interest for various applications especially in biological, medical, and environmental fields. Despite the significant progress, SERS systems are still facing challenges for practical applications related to their sensitivity, reliability, and selectivity. To overcome these limitations, in this study, we have proposed a simple yet facile concept by combining 3-D anisotropic gold nanorod arrays with colloidal gold nanoparticles having different shapes for highly reliable, selective, and sensitive detection of some hazardous chemical and biological warfare agents in trace amounts through SERS. The gold nanorod arrays were created on the BK7 glass slides or silicon wafer surfaces via the oblique angle deposition (OAD) technique without using any template material or lithography technique and their surface densities were adjusted by manipulating the deposition angle (α). It is found that gold nanorod arrays fabricated at α = 10° exhibited the highest SERS enhancement in the absence of colloidal gold nanoparticles. Synergetic enhancement was obviously observed in SERS signals when combining gold nanorod arrays with colloidal gold nanoparticles having different shapes (i.e., spherical, rod, and cage). Due to their ability to produce localized surface plasmons (LSPs) in transverse and longitudinal directions, utilization of colloidal gold nanorods as a synergetic agent led to an increase in the enhancement factor by about tenfold compared to plain gold nanorod arrays. Moreover, we have tested our approach to detect some chemical and biological toxins namely dipicolinic acid (DIP), methyl parathion (MP), and diethyl phosphoramidate (DP). For all toxins, Raman spectra with high signal-to-noise ratios and reproducibility were successfully obtained over a broad concentration range (5 ppm-10 ppb). Our results suggest that the slightly tangled and closely-packed anisotropic gold nanorod arrays reinforced by the gold nanoparticles may serve as an ideal SERS substrate to detect any analyte in trace amounts.

Soluble precursor polymers are processed and assembled into solid‐state devices and subsequently converted in the devices to conjugated electrochromic materials. This method, termed in situ conversion, requires no rigorous cleaning step for the electrode substrate. It eliminates the use of a costly electrolyte bath during the assembly process. This methodology results in high yields for the resultant conjugated system.

In this work, we have developed a general methodology for constructing an activatable biosensor utilizing a thermoresponsive polymer and two-dimensional nanosheet. We have demonstrated the detection of four different types of biological compounds using the smart PEGMA (poly(ethylene glycol) methyl ether methacrylate), oligonucleotides, and graphene oxide nanoassembly. The activity of the functional nanodevice is controlled with a thermo-switch at 39 °C. In this design, the nanosized graphene oxide serves as a template for fluorophore labeled probe oligonucleotides while quenching the fluorescence intensities dramatically. On the other hand, the PEGMA polymer serves as an activatable protecting layer covering the graphene oxide and entrapping the probe oligonucleotides on the surface. The PEGMA polymers are hydrophobic above their lower critical solution temperature (LCST) and therefore interact strongly with the hydrophobic surface of graphene oxide, creating a closed configuration (OFF state) of the nanodevice. However, once the temperature decreases below the LCST, the polymer undergoes conformational change and becomes hydrophilic. This opens up the surface of the graphene oxide (open configuration, ON state), freeing the encapsulated payload on the surface. We have tuned the activity of the nanodevice for the detection of a sequence-specific DNA, miR-10b, thrombin, and adenosine. The activity of our functional system can be decreased by ∼80% with a thermo-switch at 39 °C. Our approach can be extended to other antisense oligonucleotide, aptamer, or DNAzyme based sensing strategies.

Herein we describe a protocol that generates Au icosahedra in high yields by simply mixing aqueous solutions of HAuCl(4) and N-vinyl pyrrolidone. Our mechanistic study reveals that water plays an important role in this synthesis: as a nucleophile, it attacks the gold-vinyl complex, leading to the production of an alcohol-based Au(I) intermediate. This intermediate then undergoes a redox reaction in which Au(I) is reduced to Au(0), leading to the formation of Au atoms and then Au icosahedra of about 18 nm in size at a yield of 94 %, together with a carboxylic acid in the final product. This new protocol has also been employed to prepare multiply twinned nanoparticles of Ag (15-20 nm in size), spherical aggregates (25-30 nm in size) of Pd nanoparticles, and very small nanoparticles of Pt (2 nm in size). Since no organic solvent, surfactant, or polymer stabilizer is needed for all these syntheses, this protocol may provide a simple, versatile, and environmentally benign route to noble-metal nanoparticles having various compositions and morphologies.

Herein we report the synthesis of symmetrical bis(thieno[3,4-b]thiophene)s and their electrochemical polymerization. The 2,2‘-bis(T34bT) has an oxidation peak at 0.73 V for electropolymerization whereas both 4,4‘-bisT34bT and 6,6‘-bisT34bT have peak oxidation potentials for polymerization at 0.49 and 0.53 V (0.44 V vs NHE), respectively. For comparison, thieno[3,4-b]thiophene (T34bT) polymerizes with an oxidation peak at 0.9 V. Conjugated T34bT polymers prepared from T34bT, 4,4‘-bisT34bT, and 6,6‘-bisT34bT exhibit similar redox behavior showing oxidation and reduction peaks located at ca. 0.1 V and ca. −0.3 V, respectively, and optical band gaps of ca. 0.9 eV (1377 nm), whereas the conjugated polymer from 2,2‘-bisT34bT has redox peaks centered at 0.5 and 0.4 V. Like PT34bT prepared from T34bT, both PT34bTs prepared from 4,4‘-bisT34bT and 6,6‘-bisT34bT are pale blue to colorless in their oxidized states and sky blue in their neutral forms. PT34bT prepared from 2,2‘-bisT34bT is brown in the oxidized state. The conductivities of the PT34bTs from both 4,4‘- and 6,6-bisT34bTs were found to be ca. 2 × 10-5 S/cm in the undoped state, increasing to 0.2 S/cm after iodine doping. The conductivity of PT34bT from 2,2‘-bisT34bT was 2 × 10-5 and 0.007 S/cm in the neutral and oxidized forms, respectively.