lbl assembly
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2021 ◽  
Vol 43 (12) ◽  
pp. 731-738
Author(s):  
Bok Seong Kim ◽  
Sung Won Kang

Objectives : The purpose of this study was to develop an adsorbent to which Prussian blue (PB) is stably immobilized to remove radioactive cesium (Cs).Methods : Prussian blue-Alginate (PA) bead and Prussian blue-Alginate with Layer-by-layer synthesis (PAL) bead were synthesized by immobilizing PB respectively.Results and Discussion : As a results of XRD and FT-IR analysis, PB was successfuuly immobilized in alginate bead and PA, PAL bead. SEM (EDS) and TG analysis data were confirmed that the PB content of the PAL bead to which the LBL synthesis method was applied was improved by 6.31%. It was confirmed that the Cs adsorption capacity was improved through the LBL assembly process. The maximum adsorption amount (qm) of PA bead was 25.783 mg/g, and PAL bead was mg/g. In addition, as a result of UV-vis analysis of washing water after synthesis of PA bead and PAL bead, it was confirmed that the PB desorption of the PAL bead was lower indicating that the stability was also improved by LBL synthesis.Conclusions : We developed an adsorbent which prussianblue immobilized on alginate bead for selective removal cesium in aqueous solution. PB was immobilized by LBL synthesis method qm of PAL beads was 28.294 mg/g. It was expected to applied effectively and stably to radioactive cesium contaminated water.


Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2992
Author(s):  
Putri Bintang Dea Firda ◽  
Yoga Trianzar Malik ◽  
Jun Kyun Oh ◽  
Evan K. Wujcik ◽  
Ju-Won Jeon

Polyaniline (PANI) has been widely used as an electroactive material in various applications including sensors, electrochromic devices, solar cells, electroluminescence, and electrochemical energy storage, owing to PANI’s unique redox properties. However, the chemical and electrochemical stability of PANI-based materials is not sufficiently high to maintain the performance of devices under many practical applications. Herein, we report a route to enhancing the chemical and electrochemical stability of PANI through layer-by-layer (LbL) assembly. PANI was assembled with different types of polyelectrolytes, and a comparative study between three different PANI-based layer-by-layer (LbL) films is presented here. Polyacids of different acidity and molecular structure, i.e., poly(acrylic acid) (PAA), polystyrene sulfonate (PSS), and tannic acid (TA), were used. The effect of polyacids’ acidity on film growth, conductivity, and chemical and electrochemical stability of PANI was investigated. The results showed that the film growth of the LbL system depended on the acidic strength of the polyacids. All LbL films exhibited improved chemical and electrochemical stability compared to PANI films. The doping level of PANI was strongly affected by the type of dopants, resulting in different chemical and electrochemical properties; the strongest polyacid (PSS) can provide the highest conductivity and chemical stability of conductive PANI. However, the electrochemical stability of PANI/PAA was found to be better than all the other films.


2021 ◽  
Author(s):  
Xinhua Liu ◽  
Hailong Liu ◽  
Yinchun Fang

Abstract In this study, intumescent flame retardant coating of polyethylenimine/phytic acid (PEI/PA) with gradient structure was constructed on cotton fabric through facile layer-by-layer (LBL) assembly method. The LOI value of coated cotton fabric reached over 40% indicating excellent flame retardancy. Reasonable controlling the LBL assembly process of PEI/PA coating brought less influence to the physical properties of cotton fabrics. And the coated cotton fabric revealed good flame retardant washing durability. Thermogravimetric analysis results of coated cotton fabrics showed that PEI/PA flame retardant coating changed the thermal decomposition process and promoted char formation revealing the obviously condensed phase flame retardant action. SEM images of char residues revealed that PEI/PA flame retardant coating promoted to form the intumescent flame retardant (IFR) char layer showing obvious IFR action. This research provides novel strategy for the development of high-efficiency flame retardant cotton fabric with good durability and physical properties using simple LBL assembly method.


Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2254
Author(s):  
Miryam Criado-Gonzalez ◽  
Carmen Mijangos ◽  
Rebeca Hernández

Natural polymers are of great interest in the biomedical field due to their intrinsic properties such as biodegradability, biocompatibility, and non-toxicity. Layer-by-layer (LbL) assembly of natural polymers is a versatile, simple, efficient, reproducible, and flexible bottom-up technique for the development of nanostructured materials in a controlled manner. The multiple morphological and structural advantages of LbL compared to traditional coating methods (i.e., precise control over the thickness and compositions at the nanoscale, simplicity, versatility, suitability, and flexibility to coat surfaces with irregular shapes and sizes), make LbL one of the most useful techniques for building up advanced multilayer polymer structures for application in several fields, e.g., biomedicine, energy, and optics. This review article collects the main advances concerning multilayer assembly of natural polymers employing the most used LbL techniques (i.e., dipping, spray, and spin coating) leading to multilayer polymer structures and the influence of several variables (i.e., pH, molar mass, and method of preparation) in this LbL assembly process. Finally, the employment of these multilayer biopolymer films as platforms for tissue engineering, drug delivery, and thermal therapies will be discussed.


2021 ◽  
Vol 8 ◽  
Author(s):  
Peng Lin ◽  
Yuchen Xu ◽  
Junfeng Hou ◽  
Xiaochun Zhang ◽  
Lingfei Ma ◽  
...  

Bamboo is a rich natural resource in the Asia Pacific, and it is widely used in the construction and decoration industry. Meanwhile, bamboo is an extremely combustible natural polymer material. Herein, the bamboo slices were treated with melamine and phytic acid using layer-by-layer (LBL) assembly technology to improve their flame retardancy properties. The morphology and chemical composition of untreated and treated bamboo slices were measured by scanning electron microscopy equipped with energy dispersive X-ray analysis and Fourier transform infrared spectra. The results showed that two-dimensional melamine–phytate (MP) nanoflakes were successfully formed and deposited on the bamboo surface. The deposition of the MP coating caused the earlier degradation of the bamboo to form char, according to thermogravimetric analysis. The peak heat release rates of the treated bamboo slices were reduced by more than 28% compared to those of the untreated ones. The MP coating promoted the formation of thermally stable char, which was responsible for the significant improvement in flame retardancy. Besides, the char layer with excellent thermal resistance performed a vital role in suppressing flame spread.


2021 ◽  
Vol 5 (2) ◽  
pp. 20
Author(s):  
Tomasz Kruk ◽  
Piotr Warszyński

We demonstrate a method for the formation of multilayers composed of reduced graphene oxide (rGO), which can be used for transparent, conducting thin films. Using the layer-by-layer (LbL) assembly of positively and negatively charged GO sheets, we could obtain thin films with highly controllable sheet resistance. The natural negative charge of graphene oxide was turned to positive by the amidation reaction. After forming the multilayer films, the graphene oxide underwent thermal reduction at temperatures above 150 °C. The (rGO+/rGO−) films were characterized by UV-Vis and scanning electron microscopy (SEM), and their conductivity was measured by the four-point method. We found that after deposition of five (rGO+/rGO−), the coating structure reached the percolation limit, and the film resistance decreased more gradually to around 20 kΩ/sq for the films obtained by eleven deposition cycles with graphene oxide reduced at 250 °C. The formation of thin films on polyimide allows the forming of new flexible conductive materials, which can find applications, e.g., in biomedicine as new electroactive, low-cost, disposable sensors.


2021 ◽  
Author(s):  
Yunbo Chen ◽  
Xiangyu Zhu ◽  
Xiang Li ◽  
Bijia Wang ◽  
Zhiping Mao ◽  
...  

Abstract The lack of thermo-regulation functionality and high flammability of cotton fabrics greatly restrict their application in high-performance fields. Herein, we report a versatile layer-by-layer (LbL) assembly strategy for introducing to cotton fabrics a multilayered coating consisted of phase change microcapsules and ammonium polyphosphate, endowing them with thermo-regulating and flame retardancy. The coated fabrics were characterized by limiting oxygen index (LOI), scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorimetry (DSC) and infrared thermal imaging. The fabric deposited with 20 bilayers (MCPM/APP-20) showed improved flame retardancy with a LOI of 24.4% and residual carbon of 34.24%. It also shows a melting enthalpy of 30.16 J/g, which transferred to a temperature difference of 6.4 ℃ compared with pristine cotton. The functional endowed by the LbL assembly was reasonably durable, with melting enthalpy and residual carbon of MPCM/APP-20 reduced to 17.14 J/g and 19.82% after 30 laundering cycles. These results suggest that LbL assembly was a convenient way for functionalization of cotton fabrics.


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