Further progress in the applications of self-assembled nanostructures critically depends on developing a fundamental understanding of the relation between the properties of nanoparticle ensembles and their time-dependent structural characteristics. Following dynamic generation of hot-spots in the self-assembled chains of gold nanorods, we established a direct correlation between ensemble-averaged surface-enhanced Raman scattering and extinction properties of the chains. Experimental results were supported with comprehensive finite-difference time-domain simulations. The established relationship between the structure of nanorod ensembles and their optical properties provides the basis for creating dynamic, solution-based, plasmonic platforms that can be utilized in applications ranging from sensing to nanoelectronics.

No abstract

Silver nanoparticles (AgNPs) have been broadly used as antibacterial and antiviral agents. Further, interests for green AgNP synthesis have increased in recent years and several results for AgNP biological synthesis have been reported using bacteria, fungi and plant extracts. The understanding of the role and nature of fungal proteins, their interaction with AgNPs and the subsequent stabilization of nanosilver is yet to be deeply investigated. Therefore, in an attempt to better understand biogenic AgNP stabilization with the extracellular fungal proteins and to describe these supramolecular interactions between proteins and silver nanoparticles, AgNPs, produced extracellularly by Aspergillus tubingensis—isolated as an endophytic fungus from Rizophora mangle—were characterized in order to study their physical characteristics, identify the involved proteins, and shed light into the interactions among protein-NPs by several techniques. AgNPs of around 35 nm in diameter as measured by TEM and a positive zeta potential of +8.48 mV were obtained. These AgNPs exhibited a surface plasmon resonance (SPR) band at 440 nm, indicating the nanoparticles formation, and another band at 280 nm, attributed to the electronic excitations in tryptophan, tyrosine, and/or phenylalanine residues in fungal proteins. Fungal proteins were covalently bounded to the AgNPs, mainly through S–Ag bonds due to cysteine residues (HS–) and with few N–Ag bonds from H2N– groups, as verified by Raman spectroscopy. Observed supramolecular interactions also occur by electrostatic and other protein–protein interactions. Furthermore, proteins that remain free on AgNP surface may perform hydrogen bonds with other proteins or water increasing thus the capping layer around the AgNPs and consequently expanding the hydrodynamic diameter of the particles (~264 nm, measured by DLS). FTIR results enabled us to state that proteins adsorbed to the AgNPs did not suffer relevant secondary structure alteration upon their physical interaction with the AgNPs or when covalently bonded to them. Eight proteins in the AgNP dispersion were identified by mass spectrometry analyses. All these proteins are involved in metabolic pathways of the fungus and are important for carbon, phosphorous and nitrogen uptake, and for the fungal growth. Thereby, important proteins for fungi are also involved in the formation and stabilization of the biogenic AgNPs.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1538-y) contains supplementary material, which is available to authorized users.

No abstract

The SERS enhancement factor (SERS-EF) is one of the most important parameters that characterizes the ability of a given substrate to enhance the Raman signal for SERS applications. The comparison of SERS intensities and SERS-EF values across different substrates is a common practice to unravel the performance of a given substrate. In this study, it is shown that such a comparison may lack significance if we compare substrates of very distinct nature and optical properties. It is specifically shown that the SERS-EF values for static substrates (e.g. immobilized metallic nanostructures) cannot be compared to those of dynamic ones (e.g. colloidal metal nanoparticle solutions), and that the optical properties for the latter show strong dependence on the metal-molecule interaction dynamics. The most representative experimental results concerning the dynamic substrates have been supported by generalized Mie theory simulations, which are tools used to describe the substrate complexity and the microscopic information not usually taken into account.

No abstract

OBJETIVO: Estudar a prevalência da síndrome metabólica em adolescentes acompanhados em ambulatório de obesidade. MÉTODOS: Foram avaliados 84 adolescentes com idades entre dez e 19 anos, divididos em dois grupos, de acordo com o escore Z do índice de massa corpórea (Z IMC), sendo um o grupo de adolescentes com sobrepeso (GSP) e o outro, o grupo de adolescentes obesos (GOB). GSP: Z IMC>1 e <2 (1,6±0,2, 13M/13F), e GOB: Z IMC>2 (2,4±0,6, 32M/26F). Três ou mais dos critérios a seguir foram considerados no diagnóstico da síndrome metabólica e avaliados pelo teste do qui-quadrado entre os grupos: Z IMC>2; triglicérides em jejum >130mg/dL; lipoproteína de alta densidade <35mg/dL; glicemia em jejum >100mg/dL ou homeostatic model assessment index (HOMA) >2,5; elevação da pressão arterial acima do percentil 90 ajustada para gênero, estatura e idade. RESULTADOS: A prevalência da síndrome metabólica esteve significantimente elevada nos adolescentes obesos (GOB: 40% versus GSP: 4%, p=0,0008). O grupo GOB mostrou maiores valores referentes a insulinismo (54% versus 19%, p=0,003), HOMA (66% versus 38%, p=0,01) e trigliceridemia (21% versus 4%; p=0,04). CONCLUSÕES: É importante que o pediatra fique atento aos sinais de síndrome metabólica em adolescentes obesos. A detecção precoce pode ser feita por meio de simples parâmetros e permite a adoção de medidas preventivas para o desenvolvimento da doença cardiovascular em adolescentes.

No abstract