Study and Optimization of Self‐Assembled Polymeric Multilayer Structures with Neutral Red for pH Sensing Applications

Abstract

The characterization of nanostructured thin films is critical in the design and fabrication of optical sensors. Particularly, this work is a detailed study of the properties of layer-by-layer electrostatic self-assembled multilayer (LbL) structures fabricated using poly(allylamine hydrochloride) (PAH) and Neutral Red (NR) as cations, and poly(acrylic acid) (PAA) as polyanion. These LbL films, due to the colorimetric properties of the NR, are suitable for sensor applications such as pH sensing in the physiological range. In the (PAH+NR/PAA) LbL structure, it has been observed a very important influence of the pH of the solutions in the properties of the resultant films. Different techniques such as spectroscopy and atomic force microscopy (AFM) are combined to characterize the films, and the results are analyzed showing coherence with previous works. The LbL structure is finally optimized and dramatically improved nanostructured films were fabricated, showing good sensing properties, short response times, and good stability.

New azine compounds as photoantimicrobial agents against Staphylococcus aureus

“…Besides, the pK a of NR was determined (pK a NR ¼ 7.0 ± 0.8) following the same procedure to corroborate the value previously reported in the literature [31,32]. Fig.…”

Photonic Crystal Fiber Temperature Sensor Based on Quantum Dot Nanocoatings

“…The technique is based on the attraction between oppositely charged polyelectrolytes. Its main advantage is the possibility of controling the thickness of the coating on the nanometer scale, building the film by creating bilayers of both cationic and anionic solutions consecutively [10][11][12][13][14]. More specifically, in order to fabricate temperature sensing nanofilms inside the holes of the PCF, quantum dots (QDs) have been used as one of the colloids of the deposition process.…”

Fiber-optic pH sensors fabrication based on selective deposition of Neutral Red

“…The materials used in this study are represented in Fig. 1, composed basically by Neutral Red as the pH sensitive molecule [12][13] and the polymers poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) used as polycation and polyanion respectively. …”

“…The main governing parameters of this fabrication method are well known and have been extensively studied in literature [4][5][6]. As a consequence, LbL has motivated numerous applications in many diverse areas such as biological sensors, organo-electronic devices or hydrophobic surfaces allowing the fabrication of multipurpose structures [7][8][9][10][11][12][13].…”