6 research outputs found
Design of 1D photonic crystals for colorimetric and ratiometric refractive index sensing
Abstract Photonic crystals can be employed effectively as simple and low-cost colorimetric sensors for monitoring variation in the environmental refractive index. In most cases, the photonic colorimetric approach relies on the use of porous and permeable materials to highlight refractive index (RI) modulation, although a fine control over the size distribution and free volume can be complex to achieve. Here, we propose nonporous low-layer count distributed Bragg reflectors (DBRs) as simple optical devices for colorimetric refractive index sensing. In our feasibility study, we simulated the reflectance of DBRs consisting of two to five SiO2/TiO2 bilayers upon variation of the external refractive index. We found that the 2-bilayers sample exhibits the highest sensitivity to RI variations, and identified the ratio between the first and third order reflectance intensity as simple yet efficient ratiometric parameter to discern analytes with different refractive indices. This approach can provide a promising perspective for the development of cheap and portable devices for environmental detection of a wide range of substances
The Impact of Bacteria Exposure on the Plasmonic Response of Silver Nanostructured Surfaces
Silver, especially in the form of nanostructures, is widely employed as an
antimicrobial agent in a large range of commercial products. The origin of the
biocidal mechanism has been elucidated in the last decades, and most likely
originates from silver cation release due to oxidative dissolution followed by
cellular uptake of silver ions, a process that causes a severe disruption of
bacterial metabolism and eventually leads to eradication. Despite the large
number of works dealing with the effects of nanosilver shape/size on the
antibacterial mechanism and on the (bio)physical chemistry pathways that drive
bacterial eradication, little effort has been devoted to the investigation of
the silver NPs plasmon response upon interaction with bacteria. Here we present
a detailed investigation of the bacteria-induced changes of the plasmon
spectral and dynamical features after exposure to one of the most studied
bacterial models, Escherichia Coli. Ultrafast pump-probe measurements indicate
that the dramatic changes on particle size/shape and crystallinity, which stem
from a bacteria-induced oxidative dissolution process, translate into a clear
modification of the plasmon spectral and dynamical features. This study may
open innovative new avenues in the field of biophysics of bio-responsive
materials, with the aim of providing new and reliable biophysical signatures of
the interaction of these materials with complex biological environments
Bringing the interaction of silver nanoparticles with bacteria to light
In the last decades the exploitation of silver nanoparticles in novel
antibacterial and detection devices have risen to prominence for their
well-known specific interaction with bacteria. The vast majority of studies
focus on the investigation over the mechanism of action underpinning bacterial
eradication, while little efforts have been devoted to the modification of
silver optical properties upon interaction with bacteria. Specifically, given
the characteristic localized surface plasmon resonance of silver
nanostructures, which is sensitive to changes in the charge carrier density or
in the dielectric environment, these systems can offer a handle in the
detection of bacteria pathogens. In this review, we present the state of art of
the research activity on the interaction of silver nanoparticles with bacteria,
with emphasis on the modification of their optical properties. This may indeed
lead to easy color reading of bacterial tests and pave the way to the
development of nanotechnology silver based bacterial detection.Comment: This article has been submitted to the journal Biophysics Review
Hybrid plasmonic/photonic crystals for optical detection of bacterial contaminants
Here, we show that a hybrid plasmonic/photonic crystal consisting of a thin layer of bioactive plasmonic material (i.e. silver) deposited on top a 1D PhC can detect one of the most common bacterial contaminant, namely Escherichia coli. We speculate that the change in the plasmon charge density brought about by metal/bacterium interaction results in a variation of the plasmon resonance that, in turns, translates in a shift of the photonic structural color
Hybrid plasmonic/photonic crystals for optical detection of bacterial contaminants
Here, we show that a hybrid plasmonic/photonic crystal consisting of a thin layer of bioactive plasmonic material (i.e. silver) deposited on top a 1D PhC can detect one of the most common bacterial contaminant, namely Escherichia coli. We speculate that the change in the plasmon charge density brought about by metal/bacterium interaction results in a variation of the plasmon resonance that, in turns, translates in a shift of the photonic structural color