LB Thin Film Research Articles

Surface plasmon resonance chemical sensor modified with α-naphthylmethacrylate nano thin film for chloroform detection

The research on the rapid and sensitive detection of pollution caused by the products and technologies used has recently attracted attention in the literature. In the detection of volatile organic compounds (VOCs), polymers/monomers are used in the production of sensitive, fast-responding, reversible thin-film gas sensor elements. In this work, the monomer α-Naphthylmethacrylate was selected as thin film sensor element. The α-Naphthylmethacrylate-based nano thin films were prepared with technique of LB. Monomer LB thin films fabricated onto gold-coated glass substrate to investigate their vapour sensing properties by using Surface Plasmon Resonance (SPR) optical technique. This prepared monomer-based thin film sensor exposed to five different concentrations of chloroform vapors varying between 13.98x103-69.9x103 ppm and the sensor response values were recorded. Swelling dynamics’ of this monomer thin film sensor was also illuminated by using Fick's early-time diffusion law. Diffusion coefficients of α-Naphthylmethacrylate LB thin film sensor materials exposed to the five different concentrations of chloroform vapor were calculated with the help of reflected light intensity graph data and Fick's Law as a function of time. It was determined that the diffusion coefficient values of the first and second slope regions as varying between 5.72x10-17-21.97x10-17 cm2s-1 and 3.06x10-17-6.25x10-17 cm2s-1, respectively. SPR kinetic measurement results showed that α-Naphthylmethacrylate material is promising for the detection of chloroform vapor.

Aromatik hidrokarbonların dedekte edilmesi için kaliksaren bazlı diamid kimyasal sensor çiplerinin geliştirilmesi

In the present work, a new macrocycle materials (SB77) was selected and Langmuir-Blodgett thin films of this macrocycle compounds were examined for its vapor sensing capabilities against vapor of aromatic BTX hydrocarbons (benzene, toluene, xylene) through Quartz Crystal Microbalance (QCM) technique. In accordance with this aim, the calix[4]arene LB thin films were prepared onto quartz crystal substrates. The characterization of SB77 LB thin film was performed for nine LB layers fabricated onto the quartz crystal. The frequency shifts and the mass changes for monolayer of these LB thin films were obtained as 32.35 Hz / per layer and 2206.65 ng (8.32 ng mm-2), respectively. All QCM results indicated that SB77 LB thin film chemical sensors exhibits high response, a good sensitivity and selectivity for benzene vapor at saturated or different concentrations than other aromatic hydrocarbon vapors. These LB thin film sensors with SB77 calix [4]arene macrocycle materials have been potential candidates for organic vapor sensing applications with simple and low cost preparation at room temperature.

Optical and Vapor Sensing Properties of Calix[4]arene Langmuir-Blodgett Thin Films with Host–Guest Principles

ABSTRACT25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene was used as a chemical sensor material in this work. The calix[4]arene LB thin films were prepared onto a gold-coated glass and quartz glass substrates to fabricate a thin film chemical sensor element. Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques were used to characterize all the calix[4]arene LB thin films. The film thickness and the refractive index of thin films can be evaluated with the fitted experimental SPR datas. The refractive index and the thickness per monolayer of LB films were determined as a 1.58 ± 0.04 and 1.27 ± 0.09 nm, respectively. The calix[4]arene LB thin film chemical sensor element was exposed to dichloromethane, chloroform, benzene and toluene vapors. The SPR kinetic measurements displayed that, the photodetector response change, ΔIrf for saturated dichloromethane vapor is much larger than the other vapors with the ΔIrf value of 48 au and the diffusion coefficient value of 5.1 × 10−16 cm2s−1. Swelling process was analyzed by well known Fick's Equations. In this approach diffusion coefficients () for swelling were conformed to the square root of time and were correlated with the volatile organic compounds. Our results showed that calix[4]arene thin film has a highly selective with a large response to dichloromethane vapor.

Tadpole-Shaped POSS-Based Copolymers and the Aggregation Behavior at Air/Water Interface

The aggregation behavior of three tadpole-shaped Polyhedral oligomeric silsesquioxane (POSS) based block copolymers using different blocks poly(methyl methacrylate) (PMMA) and poly(trifluoroethyl methacrylate) (PTFEMA) with different block sequence and ratio (POSS-PTFEMA161-b-PMMA236, POSS-PMMA277-b-PTFEMA130, and POSS-PMMA466-b-PTFEMA172) was investigated on the air-water interface. The interfacial rheology of three block copolymers was studied by surface pressure isotherm, compression modulus measurements, and compression and expansion hysteresis analysis on the Langmuir trough. The block sequence and ratio play a great role in self-assembly behavior at the interface. Based on surface pressure isotherm analysis, a thin film with low elasticity was achieved for the POSS-PTFEMA161-b-PMMA236. Moreover, for the block copolymer with same segment sequence (POSS-PMMA2-b-PTFEMA), the thin film compression capability is increased with increasing the PMMA ratio. The morphology of the deposited LB thin film was illustrated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). We observed that a thin film was composed by crater-shaped quasi-2D micelles for POSS-PTFEMA-b-PMMA, while it was proved that only flaky texture was observed for both POSS-PMMA277-b-PTFEMA130 and POSS-PMMA466-b-PTFEMA172. The thickness and area of flaky aggregates were greatly related to PMMA ratio. The different interface self-assembly structure evolution was proposed based on the interfacial rheology and thin film morphology studies.

Swelling behavior of the 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate monomer LB thin film exposed to various organic vapors by quartz crystal microbalance technique

In this work FT-IR, 1H and 13C-NMR spectra are used to analyze the structure of a novel 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate (MPAEMA) materials. MPAEMA LB thin films are characterized by UV-Vis spectroscopy and Quartz Crystal Microbalance (QCM) techniques. The sensing behaviors of the films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs (dichloromethane, chloroform, benzene and toluene) were measured by the QCM method. It was found that the MPAEMA films exhibited good response, reversibility, stability and faster response and recovery characteristic to VOCs. The changes in resonance frequency associated with mass changes can be attributed to the swelling behavior of monomeric thin films during vapor absorption. This swelling is due to the capturing of organic vapor molecules in the sensor environment. Fick's law for early-time diffusion was adopted to quantify real time QCM data for the swelling processes. It was observed that diffusion coefficients ( ) for swelling obeyed the law and could be correlated with the VOCs used. The response of MPAEMA films to the chosen VOCs has been investigated in conditions of physical properties of the solvents, and the films were obtain to be largely sensitive to dichloromethane vapor compared to other studied vapors.

Characterization and organic vapor sensing properties of Langmuir-Blodgett film using perylendiimide material

LB thin film characterization and vapor sensing applications of 1,7-dibromo- N,N’-(bicyclohexyl)-3,4:9,10- perylendiimide (FY3) materials are reported in this study. The thin film deposition conditions of FY3 materials, which are prepared by LB film technique, are characterized by UV-vis spectroscopy and Quartz Crystal Microbalance (QCM) techniques. The typical frequency shift per layer is obtained as 50.15 Hz / layer and the deposited mass onto a quartz crystal is calculated as 399.36 ng / layer (1.50 ng mm-2). Vapor sensing properties of these LB films against three different volatile organic compounds (chloroform, benzene and toluene) are studied using the QCM technique. The sensitivities to vapors are determined between 3.62 x 10-4 and 1.60 x 10-4 Hz ppm-1. FY3 LB film is more sensitive to chloroform than other vapors. Responses of the FY3 LB film to these vapors are fast, large and reversible. Detection limits are calculated between 0.83 x 104 and 1.88 x 104 ppm. It can be concluded that this FY3 material is promising as a vapor sensing device at room temperature.

Characterization of 1,7-dibromo-N,N′-(bicyclohexyl)-3,4:9,10-perylendiimide Langmuir–Blodgett film for organic vapor sensing application

1,7-Dibromo-N,N′-(bicyclohexyl)-3,4:9,10-perylendiimide material (FY3) was used as a sensor element in this work. Different number of LB thin film layer was deposited onto a gold-coated glass substrate to produce a thin film sensor element. Fabrication processes were monitored by surface plasmon resonance (SPR) technique. The experimental SPR data were fitted using the Winspall software to evaluate the film thickness and refractive index of this material. Values of the thickness and refractive index of LB films were determined as 0.54±0.01nm for the thickness per monolayer, and 0.46±0.08 for the refractive index. LB thin film sensor element was exposed to chloroform, benzene, toluene and ethyl alcohol vapors. In-situ SPR measurements showed that the response of the FY3 LB film for saturated chloroform vapor is much larger than the other vapors with 4s recovery times and 5s response time. The photodetector response change, ΔIrf was monitored when FY3 LB film was exposed to these organic vapors and the response of the FY3 LB film to chloroform was also the largest among organic vapors with the ΔIrf value of 0.11au. It can be proposed that this sensing element deposited onto gold-coated glass substrates has a good sensitivity and selectivity for saturated chloroform vapor.

Comparative study of optical, structural and electrical properties of zinc phthalocyanine Langmuir–Blodgett thin film on annealing

Model representing growth mechanism in the LB thin film during phase transformation from α- to β-phase on annealing.

Ab Initio Semi-Quantitative Analysis of Micro-Beam Grazing-Incidence Small-Angle X-Ray Scattering (Μ-GISAXS) during Protein Crystal Nucleation and Growth

Micro-beam Grazing-Incidence Small-Angle X-ray scattering (μ-GISAXS), exploiting both the advantages of elastic X-ray scattering and the highly focused third-generation synchrotron radiation micro-beams, is an advanced scattering technique that enables scientists to unravel the details of crystal growth processes and to investigate large-scale structures in thin films, including nanobiofilms or other different kinds of surfaces, such as surface gradients or confined surfaces. In this study, we analyze semi-quantitatively and we simulate our previously acquired μ-GISAXS experiments of Thaumatin and Lysozyme Langmuir-Blodgett (LB)-film, shedding light on nucleation and crystal growth processes. Here, we show that, during LB-thin film facilitated nucleation, the particle radius of Thaumatin and of Lysozyme crystal increases while the film thickness reduces. Structural re-organization inside and within the LB-thin film are likely to lead to the crystal nucleation and growth. These semi-quantitative findings are in agreement with the model previously hypothesized. New insights and implications for protein nanocrystallography are also discussed.

Preparation and Dielectric Properties of Oriented PZT Thin Films by LB Technique

The oriented La modified PZT thin films were prepared on Pt/Ti/SiO2/Si substrate by the LB technique. The pre-sintering temperatures and the annealing temperatures for La modified PZT were determined by TG-DTA curves and XRD detect results. XRD detection of PZT and PZT with different La amount illustrated the crystal constructions and the effects by modification. The AFM observation of PLZT thin films with organic acid indicated that the LB technique could obtain smooth and flat film with the deposition of PLZT particles within nanometers on substrate. The detection results of the electrical properties indicated that the modification of La had great influence on the electric properties of LB thin film. PLZT thin film by annealing at 650°C had better dielectric constant of 569.2 and dielectric loss of 0.4915 at 5 kHz. And the amount of La of 2% in mass gave the piezoelectric constant of 14pC/N.

Poly[bis‐(p‐toluene sulphonate) of 2,4‐Hexadiyne‐1,6‐diol] Langmuir‐Blodgett Thin Film Formation and Characterization

Coherent thin films of bis‐(p‐toluene sulphonate) of 2,4‐hexadiyne‐1,6‐diol (TS) and its polymer, PTS, were prepared by the Langmuir‐Blodgett method. Even though TS has no amphiphilic groups at each end, it has an isotherm curve similar to stearic acid and can be transferred to a flat solid substrate under a certain pressure. Polarized UV‐Vis spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize this kind of LB thin film's anisotropy, surface morphology, and topography.

Structure of the U(VI)-PARC18 Complex Studied by EXAFS

We applied photo-responsive 5-octadecyloxy-2-(2-pyridylazo)phenol (PARC18) LB film to selective isolation of the uranyl cation from aqueous solutions. In the case of a mixed aqueous solutions of Cu2+/UO22+, UO22+ could be collected less than Cu2+, while, in the case of separate solution containing only Cu2+ or UO22+, UO22+ could be collected more preferentially than Cu2+. Surface pressure-area (π-A) isotherms indicated the complexation-induced expansion of molecular moiety. More detailed structural studies were carried out by EXAFS. An analysis of the results showed the complexed species with longer bond length and smaller coordination number, compared to the complexed species prepared in ethanol solutions, were formed in the LB thin film. From these results we proposed "spreading effect of molecular packing" to explain efficiency of diffusion and adsorption of metal cations and complexation-induced expansion of molecular span. This hypothesis could consistently explain the observed phenomena. Therefore, while the molecular rotation was strongly restricted and complexation with metal cation hardly proceeded via dark reaction in LB film, effective complexation in czs-form and the resulting spreading effect of molecular packing could be available by photo-illumination.

A Study on the Deposition and Surface Structure Analysis of LB Thin Film

The physicochemical properties of the LB films surface structure has been studied by AFM. We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 2, 10, 30[mN/m](gas state, liquid state, solid state). Formation that prevent when gas phase state and liquid phase state measure but could know organic matter that molecules form equal and stable film when molecules were not distributed evenly, and accumulated in solid state only.

A Study on the Deposition and Surface Structure Analysis of LB Thin Film

The physicochemical properties of the LB films surface structure has been studied by AFM. We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 2, 10, 30[mN/m](gas state, liquid state, solid state). Formation that prevent when gas phase state and liquid phase state measure but could know organic matter that molecules form equal and stable film when molecules were not distributed evenly, and accumulated in solid state only.

InP EFFECTS ON CuPc LB FILM AND THE PHASE CHANGE

Interaction between the rough surface of InP and LB thin film of CuPc have been studied, and the reversible structure phase transition are found at room temperature and liquid nitrogen temperature, respectively.