Holographic sol–gel monoliths: optical properties and application for humidity sensing

Abstract

Sol–gel monoliths based on SiO2, TiO2 and ZrO2 with holographic colourful diffraction on their surfaces were obtained via a sol–gel synthesis and soft lithography combined method. The production was carried out without any additional equipment at near room temperature and atmospheric pressure. The accurately replicated wavy structure with nanoscale size of material particles yields holographic effect and its visibility strongly depends on refractive index (RI) of materials. Addition of multi-walled carbon nanotubes (MWCNTs) in systems increases their RI and lends absorbing properties due to extremely high light absorption constant. Further prospective and intriguing applications based on the most successful samples, MWCNTs-doped titania, were investigated as reversible optical humidity sensor. Owing to such property as reversible resuspension of TiO2 nanoparticles while interacting with water, it was proved that holographic xerogels can repeatedly act as humidity sensors. Materials which can be applied as humidity sensors in dependence on holographic response were discovered for the first time.

Synthesis of Fast Curing, Water‐Resistant and Photopolymerizable Glass for Recording of Holographic Structures by One‐ and Two‐Photon Lithography

“…The sensitivity of a holographic recording material to changes in the environmental humidity can have a profound influence on the performance of photonic structures created in the material: 1) Bragg angle shift/wavelength shift due to dimensional changes of transmission/reflection gratings; 2) diffraction efficiency alterations caused by RIM change. While humidity-sensitive holographic materials can be beneficial for holographic sensor development and have received much attention in the literature, [40][41][42][43] most holographic applications require robust materials that ensure stable performance of the photonic structure at different humidity levels. The PHSG can provide advantages in terms of stability of photonic structures under water exposure due to the material's water resistance as discussed below.…”

Environmentally friendly Au@CNC hybrid systems as prospective humidity sensors

“…Au@CNC hybrid lm response to changes in humidity was determined using two different approaches: laser diffraction method and uorescence measurements. For the rst approach, laser diffraction was carried out using the method described by Ilatovskii et al 23 Ambient humidity was gradually increased to 90% and then gradually lowered to ascertain how the Au@CNC lm responded to changes in humidity. As can be seen from Fig.…”

Robust method for uniform coating of carbon nanotubes with V2O5 for next-generation transparent electrodes and Li-ion batteries

“…30 Hydrolysis-polycondensation reaction is a promising approach to the formation of metal oxides under ambient conditions and has several advantages: the process usually occurs at room temperature and atmospheric pressure allowing formation of a homogenous layer with tailored thickness and composition. [31][32][33][34][35][36] Though this method is highly suitable for the ne deposition of V 2 O 5 , it has never been employed for coating carbon nanotubes.…”