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A novel approach for the synthesis of colloidal silver nanoprisms (AgNPrs) with controllable localized surface plasmon resonance (LSPR) via a chemical shape transformation of silver nanospheres (AgNSs) is presented. The shape conversion is carried out by feeding hydrogen peroxide (H 2 O 2 ) solution into a starchstabilized AgNS colloid under ambient conditions. Oxidative dissolution and the mild reducing action of H 2 O 2 under alkaline conditions serve as the principal reactions for the shape transformation process. After addition of H 2 O 2 , the instantaneous shape transformation events can be visualized by the naked eye through the color change of the colloid. Initial concentration of AgNSs, molar ratio of H 2 O 2 : AgNSs, H 2 O 2 injection rate, and mixing efficiency are the key parameters for controlling the LSPR wavelengths of AgNPrs as the in-plane dipole plasmon resonance can be selectively tuned across visible and near infrared regions (i.e., 460-850 nm). The obtained AgNPrs exhibited mixed geometries e.g. hexagonal, truncated triangular, rounded-tip triangular prisms, and circular disks with average bisector lengths of 30 to 120 nm and the thickness of 10 to 20 nm. A colloid of highly concentrated AgNPrs having a final concentration up to 11 mM can be produced within 10 min.

Triphenylamine-based fluorophores containing pyrene or corannulene show variable fluorescence quenching sensitivity toward nitro explosives. The most sensitive fluorophore is capable of detecting TNT on the ng cm(-2) scale; the array is useful for identifying nitro aromatics.

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Gold nanoparticles stabilized by thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM-AuNPs) were prepared by surface grafting of thiol-terminated PNIPAM onto citrate-stabilized AuNPs. The color change of the PNIPAM-AuNPs solution from red to blue-purple without precipitation when the solution was heated to 40 °C, above the lower critical solution temperature (LCST) of PNIPAM, indicated the thermoresponsive property of the synthesized AuNPs. PNIPAM-AuNPs were used to detect proteins by chemical nose approach based on fluorescence quenching of fluorophore by AuNPs. An array-based sensing platform for detection of six proteins, namely bovine serum albumin, lysozyme, fibrinogen, concanavalin A, hemoglobin, holo-transferrin human can be successfully developed from the PNIPAM-AuNPs having different molecular weights (4 and 8 kDa) and conformation (varied heat treatment from 25 to 40 °C) in combination with a tricationic branched phenylene-ethynylene fluorophore. From principal component analysis (PCA) followed by linear discriminant analysis (LDA), 100% accuracy of protein classification using a leave-one-out (LOO) approach can be achieved by using only two types of PNIPAM-AuNPs.