Fine-tuned gold and silver nanoshells were produced via an entirely reformulated synthesis. The new method yielded ultramonodisperse samples, with polydispersity indexes (PI) as low as 0.02 and narrow extinction bands suited for multiplex analysis. A library of nanoshell samples with localized surface plasmon resonances (LSPR) spanning across the visible range was synthesized. Hyperspectral analysis revealed that the average scattering spectrum of 100 nanoshells matched closely to the spectrum of a single nanoshell, indicating an unprecedented low level of nanoparticle-to-nanoparticle variation for this type of system. A cell labeling experiment, targeting different subcellular compartments in MCF-7 human breast cancer cells, demonstrated that these monodisperse nanoparticles can be used as a multiplex platform for single cell analysis at the intracellular and extracellular level. Antibody-coated gold nanoshells targeted the plasma membrane, while silver nanoshells coated with a nuclear localization signal (NLS) targeted the nuclear membrane. A fluorescence counterstaining experiment, as well as single cell hyperspectral microscopy showed the excellent selectivity and specificity of each type of nanoparticle for its designed subcellular compartment. A time-lapse photodegradation experiment confirmed the enhanced stability of the nanoshells over fluorescent labeling and their capabilities for long-term live cell imaging.

Department of Chemistry, University of Vict 5C2, Canada. E-mail: agbrolo@uvic.ca British Columbia Cancer Agency – Vancou Research Centre, 2410 Lee Ave., Victoria, BC Department of Mathematics, Statistics, Phy British Columbia Okanagan, 3187 Universit Department of Biochemistry and Microbiol Road, Victoria BC V8P 5C2, Canada † Electronic supplementary information ( instruments, table for different SiO2 c optical images. See DOI: 10.1039/c6sc0412 ‡ Current address Biophotonics Researc Foundation Trust, Gloucester, UK. Cite this: Chem. Sci., 2017, 8, 3038

We studied the random laser (RL) bichromatic emission (BCE) from a powder consisting of silica particles infiltrated with Rhodamine 640 (Rh640) molecules. The BCE is attributed to Rh640 monomers and dimers. Because of the efficient monomer-dimer energy transfer, we observed RL wavelength switching from ≈ 620 nm to ≈650 nm and the control of the emitted wavelength was made by changing only the excitation laser intensity. None of external parameters such as excitation laser spot size or radiation detector position was changed as in previous experiments. Two laser thresholds associated either to monomers or dimers were clearly observed. Moreover, an effect analog to frequency-pulling among two coupled oscillators was identified measuring the RL spectra as a function of the excitation laser intensity. A wavelength shift, Δλ, was measured between the monomer and dimer resonance wavelengths, changing only the excitation laser intensity. The maximum value of Δλ ≈ 16 cm−1 was obtained for laser pulses of 7 ns with 30 μJ.

The synthesis and spectroscopic properties of multicore cadmium telluride (CdTe) quantum dots-zinc oxide (ZnO) shell nanoparticles (mc-CdTe@ZnO) as a new charge transfer material are presented. This colloidal system is easy to process, suitable for large scale production, and adaptable to be used in different solvents. The fabrication process employed a water-in-oil (w/o) reverse microemulsion of Triton X-100/hexanol/cyclohexane. Fluorescence and lifetime measurements for different sizes of CdTe quantum dots and their respective mc-CdTe@ZnO nanoparticles were acquired. Charge injection from CdTe multicores to the ZnO shell was confirmed by pump-probe transient absorption experiments. The presence of multicores increases the net interfacial interaction between CdTe and ZnO when compared to a structure with a single quantum dot core. The mc-CdTe@ZnO particles displayed electron-transfer rates as high as 10(12) s(-1), a value in the high-end of those reported in the literature for other type II semiconductor composites. Hydrogen production experiments further confirmed the establishment of a type II junction between the CdTe multicore and the ZnO shell.

Metallic nanoshells have been in evidence as multifunctional particles for optical and biomedical applications. Their surface plasmon resonance can be tuned over the electromagnetic spectrum by simply adjusting the shell thickness. Obtaining these particles, however, is a complex and time-consuming process, which involves the preparation and functionalization of silica nanoparticles, synthesis of very small metallic nanoparticles seeds, attachment of these seeds to the silica core, and, finally, growing of the shells in a solution commonly referred as K-gold. Here we present synthetic modifications that allow metallic nanoshells to be obtained in a faster and highly reproducible manner. The main improved steps include a procedure for quick preparation of 2.3 ± 0.5 nm gold particles and a faster approach to synthesize the silica cores. An investigation on the effect of the stirring speed on the shell growth showed that the optimal stirring speeds for gold and silver shells were 190 and 1500 rpm, respectively. In order to demonstrate the performance of the nanoshells fabricated by our method in a typical plasmonic application, a method to immobilize these particles on a glass slide was implemented. The immobilized nanoshells were used as substrates for the surface-enhanced Raman scattering from Nile Blue A.

Summary form only given. The charge-transfer mechanisms from dye to semiconductor nanoparticles and the time scales involved in these processes are a matter of interest for diverse applications, such as dye-sensitized solar cells (DSC) [1] and photocatalysis [2]. In DSC, the primary mechanism encompasses light-induced electron excitation following electron transfer from excited LUMO states of the dye to the conduction band (CB) of the semiconductor. To take place this electron transfer, the semiconductor CB must have a lower energy than the LUMO states of the sensitizer. Titanium dioxide (TiO2) often meets this requisition and therefore is the most widely semiconductor employed in DSC. Fast electron transfer is mandatory to avoid exciton recombination before charge-transfer and therefore, improve the efficiency of a DSC. Conversely, slow backward charge transfer (from the semiconductor to the dye) increases the efficiency of a DSC.the dye) increases the efficiency of a DSC.Charge transfer from rhodamine 590 (Rh6G) to amorphous TiO2 nanoparticles in colloidal suspension is investigated here via pump-probe transient absorption (TA). The TA kinetics is analyzed taking into account the relevant energy levels of the hybrid nanocomposite and electron transfer rates are estimated from the TA absorption signals. The pump-probe TA experimental apparatus used, as pump beam, a regeneratively amplified Ti:Sapphire laser (800 nm, 100 fs, 1 kHz repetition rate), which was frequency doubled (λ = 400 nm) by a 1 mm long nonlinear BiBO crystal. The pump beam was modulated by an optical chopper operating at 461 Hz and its optical path was controlled by a mechanical delay line. The probe beam was derived from an optical parametric amplifier (OPA) pumped by the Ti:Sapphire laser whose output beam wavelength was tuned to λ = 530 nm at the maximum of the S0-S1 transition of Rh6G. The photodiode signals of the reference and signal beams were sent to two differen- boxcar averagers. The analog processor output voltage was sent to a lock-in amplifier locked at the chopper frequency. With this system, absorbance changes as low as 10-5 could be accurately measured. To functionalize the TiO2 nanoparticles with rhodamine 6G, a modified methanolic dye solution (Si:Rh6G) was prepared by reacting the dye with a silane molecule (3-isocyanatepropyltriethoxysilane) according to [3]. After the reaction, 10 mL of the Si:Rh6G solution was mixed to 5 mL of the TiO2 colloidal solution. The dye is proposed to anchor to the TiO2 nanoparticles via OH groups at the particles surface formed during the hydrolysis reaction. The colloid was kept under reflux at 80 °C for 24 hours. The resulting colloid was washed several times and redispersed in ethanol. The normalized transient bleaching signal shows curves that could be fitted by exponential functions. In this case, the bleaching recovery time is ≈ (2.9 ± 0.5) ns, which is smaller than the rhodamine 590 lifetime in ethanol (≈ 4.0 ns). However, for the dye binded to TiO2, the signal could be fitted by a sum of two exponential functions plus an offset. The time constants derived from the exponential fits to the TA kinetics for the Rh6Gfunctionalized TiO2 particles were τ1 = (160 ± 70) ps and τ2 = (1.0 ± 0.2) ns. The faster decay is assigned as charge transfer from thermalized excited states of the dye to the TiO2 conduction band, while the slower one corresponds to the back electron transfer from TiO2 to the dye. Direct exciton recombination and triplet states also contribute to the slower decay dynamics. The offset is a signature that the bleaching recovery is not completed during the time scale investigated due to trapping of electrons at in-gap states of the semiconductor or trapping of molecules in triplet states. Using the values of extracted from the TA data, the charge transfer rate is in the range (0.5-6.0)x109 s-1. This value

We investigate charge transfer dynamics in Rh6G-functionalized amorphous TiO2 nanoparticles using transient absorption (TA) spectroscopy. The TA shows a bleaching signal that is shortened compared to the bleaching of the free dye in solution.

Localized surface plasmon dephasing times for aqueous colloidal silver nanoparticles (NPs) stabilized with three different capping agents (trisodium citrate-TSC, poly(vinylpyrrolidone)-PVP, and poly(vinylalcohol)- PVA) were measured using the persistent spectral hole burning technique. The results obtained by fitting a theoretical curve to the experimental data show that the dephasing times are dependent on the chosen stabilizer (3.0, 2.3, and 1.8 fs for TSC, PVP, and PVA, respectively), and the differences are attributed to changes in the electronic density of states due to the interaction between the NPs and the capping agents. The results are supported by ab initio calculations for the chemisorbate and metallic cluster interaction.

The nonlinear response of silica-gold-nanoshells (SGNS) in chloroform was studied at 1560nm, and an analytical approach that allowed extraction of the third- and the fifth- nonlinear susceptibility of a SGNS from the data is presented.

The dephasing times of localized surface plasmons in silver colloidal nanoparticles stabilized with different capping agents are measured. The short T2 measured are strongly dependent on the stabilizer. The results are supported by DFT calculations.

In this communication, we used the persistent spectral hole burning technique to measure T2 in aqueous colloidal silver NPs with different stabilizing agents.

A new three-dimensional plasmonic lithography method is presented. The direct writing with an optical beam in a polymeric matrix is demonstrated. The plasmonic structure induced by the light beam can be erased chemically.

The nonlinear response of silica--gold nanoshells (SGNs) in chloroform was studied using laser pulses of 65 fs at 1560 nm. The experiments were performed using the thermally managed Z--scan technique that allows measurements of the electronic contribution for the nonlinear response, free from thermal influence. The results were analyzed using an analytical approach based on the quasi--static approximation that allowed extraction of the nonlinear susceptibility of a SGN from the data. High third--order susceptibility, χsh((3)) = - 1.5 x 10(-11) m(2)/V(2), approximately four orders of magnitude larger than for gold nanospheres in the visible, and large fifth--order susceptibility, χsh((5)) = - 1.4 x 10(-24) m(4)/V(4), were obtained. The present results offers new perspectives for nonlinear plasmonics in the near--infrared.

Random laser action is obtained in a diffusive weakly scattering regime using an alcohol solution of rhodamine 640 with silica nanoparticles prepared by the Stöber method, with different average diameters of 49, 90, 219, and 490 nm. Particle size and concentration has proven to affect the random laser performance. It is also shown that silica nanoparticles contributes for a much slower photodegradation of the dye molecules than titania nanoparticles that has been used in the majority of the dye random lasers. This fact makes it advantageous to use silica nanoparticles for the fundamental studies of random laser, due to its increase in lifetime under pumping conditions.

This article describes the formation of silver nanoparticles (NPs) within preformed unsaturated polyester/styrene resins in which the resulting color could be tuned by changing the silver load, time, and method used to grow the NPs. NP size and aggregation are responsible for the resulting sample color, and the samples present very good optical transparency. The silver ions were first added to the prepolymer that was crosslinked by free radical polymerization in the absence of light. NP formation was subsequently induced by submitting the transparent and colorless samples to heat or UV irradiation. Within the heated samples, isolated spherical particles ranging from 3 to 40 nm were observed. UV irradiation led to the formation of particle aggregates; however, as the exposure time was increased, silver NPs became well dispersed within the matrix within a particle diameter range of 9 to 24 nm. The particle formation is faster when induced by UV irradiation. Samples were also prepared by first dissolving rhodamine 6G in the resin. The emission bandwidth of samples prepared in this way showed a dependence on the silver particles amount and size. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

In this paper we report on the fabrication of gold nanoshells (GNS) and present a study of their nonlinear optical properties. GNS were studied and the results exhibit large third and fifth order susceptibilities.

Poly(vinyl-pyrrolidone) (PVP) stabilized silver nanoparticles with an average particle size ranging from 4.3 to 4.9nm were synthesized by laser ablation in preformed colloids in methanol, acetone, ethylene glycol, and glycerin. Aqueous colloids obtained using PVP, poly(vinyl-alcohol) (PVA), and sodium citrate as stabilizing agents also lead to a good control over particle size distribution. Silver ions were reduced with sodium borohydride. The smaller average particle size and narrower dispersivity in comparison to previously reported data were ascribed to the relatively small size of the particles formed in the chemical reduction step, laser fluence, and the use of PVP, which was not previously used as the stabilizing agent in "top-down" routes. The surface plasmon resonance band maximum wavelength shifted from 398nm in methanol to 425nm in glycerin. This shift must be due to solvent effects since all other variables were the same.

The hyper-Rayleigh scattering technique was applied to measure the first-order hyperpolarizability, β, of ferroelectric BaTiO3 and PbTiO3 nanoparticles (NPs) dissolved in methanol. The crystalline particles have average diameter of ≈50nm as determined by scanning electron microscopy. A 8ns pulsed laser operating at 1064nm was used as the excitation source to generate the second harmonic scattered light. The results show that the per nanoparticle β value is 10−24esu and the β value per unit volume of NPs is two orders of magnitude larger than that observed for antiferroelectric NaNbO3 nanoparticles.

This paper presents the synthesis of the coordination polymers (infinity)[Ln(DPA)(HDPA)] (DPA=2,6-pyridinedicarboxylate; Ln=Tb and Gd), their structural and spectroscopic properties. The structural study reveals that the (infinity)[Ln(DPA) (HDPA)] has a single Ln(+3) ion coordinated with two H(2)DPA ligands in tridentade coordination mode, while two others H(2)DPA establish a syn-bridge with a symmetry-related Ln(3+), forming a two-dimensional structure. The spectroscopic studies show that (infinity)[Tb(DPA)(HDPA)] compound has high quantum yield (q(x)approximate to 50.0%), due to the large contribution of radiative decay rate. Moreover triplet level is localized sufficiently over the emitter level D-5(4) of the Tb3+ ion, avoiding a retrotransference process between these states.