Growth Kinetics and Sensing Features of Colloidal Silver Nanoplates

This paper presents the growth mechanisms and the plasmon sensing features for a large class of silver nanoplates obtained in the colloidal form. The synthesis is conducted by seed-mediated growth and leads to plates with aspect ratios as large as 20, having localized surface plasmon resonances extending deeply into the infrared spectral region (1000 nm and above). We measure plasmon sensitivity by varying the colloidal local refractive index, and Δλ/Δn sensitivity values up to 500 nm/RIU are obtained. Theoretical considerations regarding the correlation between the refractive index sensitivity and the position of the main localized plasmon resonance band demonstrate that plasmon sensitivity does not depend directly on the nanoparticle shape and aspect ratio

Optical trapping of silver nanoplatelets

Optical trapping of silver nanoplatelets obtained with a simple room temperature chemical synthesis technique is reported. Trap spring constants are measured for platelets with different diameters to investigate the size-scaling behaviour. Experimental data are compared with models of optical forces based on the dipole approximation and on electromagnetic scattering within a T-matrix framework. Finally, we discuss applications of these nanoplatelets for surface-enhanced Raman spectroscopy

Reduction of Graphene Oxide by Laser Scribing in Different Atmospheres and Application in Humidity Sensing

Laser scribing, by far proposed as a method for efficiently transforming graphene oxide into reduced graphene, has been employed, using a CW laser beam, to study the modifications of graphene oxide scribed under different controlled atmospheres, including air, N2, Ar, and a 95 : 5 (v/v) Ar/H2 mixture. We have found that laser scribing effects, including chemical composition, order degree, and electrical properties, strongly depend upon the atmosphere during the irradiation. The electrical properties of the various materials, obtained in different atmospheres, have been evaluated with respect to the sensing properties towards humidity, the materials produced in pure Argon yielding the highest sensitivity and the fastest response, while related Raman microspectroscopy measurements showed that both Ar and Ar-H2 mixture produce the highest order among the various samples. The results stress the importance and the potentialities of controlling the irradiation atmosphere in order to tune the composition and electrical properties of the laser-scribed graphene oxide materials

Hierarchical Route for the Fabrication of Cavitand-Modified Nanostructured ZnO Fibers for Volatile Organic Compound Detection

A hierarchical hybrid inorganic-organic system suited for the recognition of aromatic volatile organic compounds on brushlike ZnO fibers was synthetized. The hybrid material was obtained by a multistep approach based on the growth of ZnO nanorods onto electrospun ZnO fibers (average diameter 200 nm). The obtained nanostructured ZnO brushlike fibers (overall diameter 2 μm) were functionalized through the grafting of a bifunctional phosphonic linker (12-azidododecylphosphonic acid) followed by the anchoring of a specific cavitand receptor. The linker was anchored on ZnO fibers through the phosphonic group while the azide terminations reacted with a quinoxaline-bridged cavitand (QxCav) having four alkyne groups via "click" reaction. The anchoring steps were monitored through the evolution of the FT-IR features in the 3200-2800 cm-1 region due to C-Hx stretches and in the 2200-2000 cm-1 region due to the azide and alkyne groups of the phosphonic linker and QxCav. The recognition properties of this hybrid nanostructure toward α,α,α-trifluorotoluene vapors were evaluated by XPS and Raman measurements

Self-Assembly of Discrete Porphyrin/Calix[4]tube Complexes Promoted by Potassium Ion Encapsulation

The pivotal role played by potassium ions in the noncovalent synthesis of discrete porphyrin-calixarene nanostructures has been examined. The flattened-cone conformation adopted by the two cavities of octa-cationic calix[4]tube C4T was found to prevent the formation of complexes with well-defined stoichiometry between this novel water-soluble calixarene and the tetra-anionic phenylsulfonate porphyrin CuTPPS. Conversely, preorganization of C4T into a C4v-symmetrical scaffold, triggered by potassium ion encapsulation (C4T@K+), allowed us to carry out an efficient hierarchical self-assembly process leading to 2D and 3D nanostructures. The stepwise formation of discrete CuTPPS/C4T@K+ noncovalent assemblies, containing up to 33 molecular elements, was conveniently monitored by UV/vis spectroscopy by following the absorbance of the porphyrin Soret band