Co-deposition of gold nanoparticles and metalloporphyrin using the langmuir-blodgett (LB) technique for Surface-Enhanced Raman Scattering (SERS)

The synergistic effect produced by metallic nanoparticles when incorporated into different systems empowers a research field that is growing rapidly. In addition, organometallic materials are at the center of intensive research with diverse applications such as light-emitting devices, transistors, solar cells, and sensors. The Langmuir-Blodgett (LB) technique has proven to be suitable to address challenges inherent to organic devices, since the film properties can be tuned at the molecular level. Here we report a strategy to incorporate gold nanoparticles (AuNPs) into the LB film by co-deposition in order to achieve surface-enhanced Raman scattering (SERS) of the zinc(II)-protoporphyrin (IX) dimethyl ester (ZnPPIX-DME). Prior to the LB co-deposition, the properties of the Langmuir monolayer of ZnPPIX-DME at the air-water interface, containing AuNPs in the subphase, are studied through the surface-pressure versus mean molecular area (π-A) isotherms. The ZnPPIX-DME+AuNPs π-A isotherm presented a significant shift to higher molecular area, suggesting an interaction between both ZnPPIX-DME molecules and AuNPs. Those interactions are a key factor allowing the co-deposition of both AuNPs and ZnPPIX-DME molecules onto a solid substrate, thus forming the LB film. SERS of ZnPPIX-DME was successfully attained, ensuring the spatial distribution of the AuNPs. Higher enhancement factors were found at AuNP aggregates, as a result of the intense local electromagnetic field found in the metal nanoparticle aggregates. The main vibrational bands observed in the SERS spectra suggest a physical adsorption of the ZnPPIX-DME onto the surface of AuNPs. The latter is not only in agreement with the interactions pointed out by the π-A isotherms but also suggests that this interaction is kept upon LB film co-deposition.

Liquid crystalline formulations containing modified surface TiO2 nanoparticles obtained by sol-gel process

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

New label free CA125 detection based on gold nanostructured screen-printed electrode

This paper describes the optimisation and the analytical performances of a label-free impedimetric immunosensor for the detection of tumour marker CA125 based on gold nanoparticles modified screen-printed graphite electrode. Experimental conditions of each step for the developed immunosensor were studied and optimised. The immunosensor response varied linearly (r2 = 0.996) with antigen concentration between 0 and 100 U/mL. The estimated detection limit was 6.7 U/mL. The electrochemical immunosensor allowed unambiguous identification of CA125, while no significant non-specific signal was detected in the case of all negative controls. The analytical usefulness of the impedimetric immunosensor was finally demonstrated analysing serum samples. © 2012 Elsevier B.V. All rights reserved.

Multifunction hexagonal liquid-crystal containing modified surface TiO2 nanoparticles and terpinen-4-ol for controlled release

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Double-Tagging Polymerase Chain Reaction with a Thiolated Primer and Electrochemical Genosensing based on Gold Nanocomposite Sensor for Food Safety

A novel material for electrochemical biosensing based on rigid conducting gold nanocomposite (nano-AuGEC) is presented. Islands of chemisorbing material (gold nanoparticles) surrounded by nonreactive, rigid, and conducting graphite epoxy composite are thus achieved to avoid the stringent control of surface coverage parameters required during immobilization of thiolated oligos in continuous gold surfaces. The spatial resolution of the immobilized thiolated DNA was easily controlled by merely varying the percentage of gold nanoparticles in the composition of the composite. As low as 9 fmol (60 pM) of synthetic DNA were detected in hybridization experiments when using a thiolated probe. Moreover, for the first time a double tagging PCR strategy was performed with a thiolated primer for the detection of Salmonella sp., one of the most important foodborne pathogens affecting food safety. Ibis assay was performed by double-labeling the amplicon during the PCR with a -DIG and -SH set of labeled primers. The thiolated end allows the immobilization of the amplicon on the nano-AuGEC electrode, while digoxigenin allows the electrochemical detection with the antiDIG-HRP reporter in the femtomole range. Rigid conducting gold nanocomposite represents a good material for the improved and oriented immobilization of biomolecules with excellent transducing properties for the construction of a wide range of electrochemical biosensors such as immunosensors, genosensors, and enzymosensors.

Orange pectin mediated growth and stability of aqueous gold and silver nanocolloids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Characterization and application of nanostructured films containing Au and TiO2 nanoparticles supported in bacterial cellulose

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A label-free electrochemical affisensor for cancer marker detection: the case of HER2

In this paper, we report the development of a sensitive label-free impedimetric biosensor based on the use of affibody as bioreceptor and gold nanostructured screen-printed graphite as a sensor platform for the detection of human epidermal growth factor receptor 2 (HER2). The affisensor is realized by immobilizing a terminal cysteine-modified affibody on gold nanoparticles. The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Furthermore, surface plasmon resonance (SPR) technology was also applied to explore the potential of affibodies as small-molecule discriminating tools. Using optimized experimental conditions, a single-use affisensor showed a good analytical performance for HER2 detection from 0 to 40μg/L. The estimated limit of detection was 6.0μg/L. Finally, the realized affisensor was applied to human serum samples.

The influence of natural rubber/Au nanoparticle membranes on the physiology of Leishmania brasiliensis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Portable smart films for ultrasensitive detection and chemical analysis using SERS and SERRS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Características ópticas e morfológicas de nanoestruturas de ouro

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Plasmonic Coupling in Er3+:Au Tellurite Glass

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efficient plasmonic coupling between Er3+:(Ag/Au) in tellurite glasses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Modifying glassy carbon (GC) electrodes to confer selectivity for the voltammetric detection of L-cysteine in the presence of DL-homocysteine and glutathione

In this communication we report a proof of concept study of the use of cyclic voltammetry with a polyeugenol-modified glassy carbon (GC) electrode to selectively detect L-cysteine in the presence of both DL-homocysteine and glutathione in perchloric acid. The formation of a polyeugenol-modified gold electrode is also reported for the first time.

Ultrafast reflectivity dynamics in bis (n-butylimido) perylene thin films

Using pump-probe reflectometry, we study the ultrafast excited-state dynamics in thin films of BuPTCD, an organic semiconductor, deposited on gold nanoparticles. We observe depletion of the ground state and excited state absorption after photo-excitation. © 2008 Optical Society of America.