scholarly journals New insights in polydopamine formation via surface adsorption

Author(s):  
Hamoon Hemmatpour ◽  
Oreste De Luca ◽  
Dominic Crestani ◽  
Alessia Lasorsa ◽  
Patrick van der Wel ◽  
...  

Abstract Polydopamine is a biomimetic self-adherent polymer, which can be easily deposited on a wide variety of materials. Despite the rapidly increasing interest in polydopamine-based coatings, the polymerization mechanism and the key intermediate species formed during the deposition process are still controversial. Herein, we report a systematic investigation of polydopamine formation on halloysite nanotubes; the negative charge and high surface area of halloysite nanotubes favour the capture of intermediates that are involved in polydopamine formation and decelerate the kinetics of the process, to unravel the various polymerization steps. Data from X-ray photoelectron and solid-state nuclear magnetic resonance spectroscopies demonstrate that in the initial stage of polydopamine deposition, oxidative coupling reaction of the dopaminechrome molecules is the main reaction pathway that leads to formation of polycatecholamine oligomers as an intermediate and the post cyclization of the linear oligomers occurs subsequently. Furthermore, Tris molecules are incorporated into the initially formed oligomers.

2021 ◽  
Author(s):  
Ayat Nuri ◽  
Abolfazl Bezaatpour ◽  
Mandana Amiri ◽  
Nemanja Vucetic ◽  
Jyri-Pekka Mikkola ◽  
...  

AbstractMesoporous SBA-15 silicate with a high surface area was prepared by a hydrothermal method, successively modified by organic melamine ligands and then used for deposition of Pd nanoparticles onto it. The synthesized materials were characterized with infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen physisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP-OES). The catalyst was effectively used in the Mizoroki–Heck coupling reaction of various reactants in the presence of an organic base giving the desired products in a short reaction time and with small catalysts loadings. The reaction parameters such as the base type, amounts of catalyst, solvents, and the temperature were optimized. The catalyst was easily recovered and reused at least seven times without significant activity losses. Graphic Abstract


NANO ◽  
2015 ◽  
Vol 10 (01) ◽  
pp. 1550005 ◽  
Author(s):  
Yaling Xie ◽  
Aidong Tang ◽  
Huaming Yang

Nanoporous materials Al -MCM-41 with varying Si / Al molar ratios have been successfully synthesized from natural clay mineral halloysite nanotubes (HNTs). Hydrothermal treatment of acid-pretreated HNTs and NaOH solution resulted in the one-step synthesis of final nanoporous products by using surfactant. The effects of Si / Al molar ratios (7.7, 61.0 and 176.5) on the surface area, porosity and degree of structural order of Al -MCM-41 materials have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption–desorption measurements and Fourier transform infrared (FTIR) spectra techniques. The results indicated that Si / Al molar ratio had important effect on the characteristics of nanoporous materials, and Al -MCM-41 with an intermediate Si / Al molar ratio of 61.0 exhibited excellent characteristics with high degree of order, high surface area (S BET ) of 1033 m2/g and pore volume of 0.92 mL/g.


2021 ◽  
Vol 92 (2) ◽  
pp. 025115
Author(s):  
K. Knemeyer ◽  
R. Baumgarten ◽  
P. Ingale ◽  
R. Naumann d’Alnoncourt ◽  
M. Driess ◽  
...  

2021 ◽  
Author(s):  
Xin Zhao ◽  
Fengliang Wang ◽  
Xiangpeng Kong ◽  
Ruiqi Fang ◽  
Yingwei Li

Abstract Single cluster catalysts (SCCs) are considered as versatile boosters in heterogeneous catalysis due to their modifiable single cluster sites and supports. In this work, we report subnanometric Cu clusters dispersed on Fe-doped MoO2 support for biomass-derived furfural upgrading. Systematical characterizations suggest uniform Cu clusters (composing four Cu atoms in average) are homogeneously immobilized on the atomically Fe-doped ultrafine MoO2 nanocrystals (Cu4/Fe0.3Mo0.7O2@C). The atomic doping of Fe into MoO2 leads to significantly modified electronic structure and consequently charge redistribution inside the supported Cu clusters. The as-prepared Cu4/Fe0.3Mo0.7O2@C shows superior catalytic performance in the oxidative coupling of furfural with C3~C10 primary/secondary alcohols to produce C8~C15 aldehydes/ketones (aviation biofuel intermediates), outperforming the conventionally prepared counterparts. DFT calculations and control experiments are further carried out to interpret the structural and compositional merits of Cu4/Fe0.3Mo0.7O2@C in the oxidative coupling reaction, and elucidate the reaction pathway and related intermediates.


2013 ◽  
Vol 11 (1) ◽  
pp. 407-415 ◽  
Author(s):  
Sharad V. Lande ◽  
A. Sakthivel, ◽  
K. V. V. S. B. S. R. Murthy ◽  
Unnikrishnan Sreedharan ◽  
Jagannath Das ◽  
...  

Abstract In this paper, we report loading of ZnCl2 on microporous medium pore high surface area zeolite, which was achieved by incipient wetness method. The zinc-modified mobil composite material -22 (Zn-MCM-22) was systematically characterized by powder X-ray diffraction, N2 adsorption-desorption analysis, scanning electron microscopy and Fourier transform infrared spectroscopy. The acidity of the materials was studied by temperature programmed desorption of ammonia analysis. The well-characterized Zn-MCM-22 catalyst was investigated for the Friedel–Crafts alkylation of benzene by benzyl chloride in liquid phase medium. A systematic investigation of various operating parameters like effect of different temperature, catalyst loading and reactant molar ratio was carried out. The Zn-MCM-22 found to be promising, further the catalytic activity remains stable over several recycles.


Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 672 ◽  
Author(s):  
Bianca R. Gevers ◽  
Frederick J.W.J. Labuschagné

Hydrocalumite is a layered double hydroxide (LDH) that is finding increased application in numerous scientific fields. Typically, this material is produced through environmentally polluting methods such as co-precipitation, sol-gel synthesis and urea-hydrolysis. Here, the hydrothermal green (environmentally friendly) synthesis of hydrocalumite (CaAl-OH) from Ca(OH)2 and Al(OH)3 in water and the parameters that influence its formation are discussed. The parameters investigated include the reaction temperature, reaction time, molar calcium-to-aluminium ratio, the morphology/crystallinity of reactants used, mixing and the water-to-solids ratio. Hydrocalumite formation was favoured in all experiments, making up between approximately 50% and 85% of the final crystalline phases obtained. Factors that were found to encourage higher hydrocalumite purity include a low water-to-solids ratio, an increase in the reaction time, sufficient mixing, the use of amorphous Al(OH)3 with a high surface area, reaction at an adequate temperature and, most surprisingly, the use of a calcium-to-aluminium ratio that stoichiometrically favours katoite formation. X-ray diffraction (XRD) and Rietveld refinement were used to determine the composition and crystal structures of the materials formed. Scanning electron microscopy (SEM) was used to determine morphological differences and Fourier-transform infrared analysis with attenuated total reflectance (FTIR-ATR) was used to identify possible carbonate contamination, inter alia. While the synthesis was conducted in an inert environment, some carbonate contamination could not be avoided. A thorough discussion on the topic of carbonate contamination in the hydrothermal synthesis of hydrocalumite was given, and the route to improved conversion as well as the possible reaction pathway were discussed.


Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 248 ◽  
Author(s):  
Athanasios Papaderakis ◽  
Olga Spyridou ◽  
Nikolaos Karanasios ◽  
Aikaterini Touni ◽  
Angeliki Banti ◽  
...  

The oxidation of methanol is studied at TiO2-supported Pt electrodes of varied high surface area carbon content (in the 30-5% w/w range) and C÷Ti atom ratio (in the 3.0-0.4 ratio). The Pt-TiO2 catalyst is prepared by a photo-deposition process and C nanoparticles (Vulcan XC72R) are added by simple ultrasonic mixing. The optimum C÷Ti atom ratio of the prepared catalyst for methanol electro-oxidation is found to be 1.5, resulting from the interplay of C properties (increased electronic conductivity and methanol adsorption), those of TiO2 (synergistic effect on Pt and photo-activity), as well as the catalyst film thickness. The intrinsic catalytic activity of the best Pt-TiO2/C catalyst is better than that of a commercial Pt/C catalyst and could be further improved by nearly 25% upon UV illumination, whose periodic application can also limit current deterioration.


2018 ◽  
Vol 54 (27) ◽  
pp. 3391-3394 ◽  
Author(s):  
Qian Liang ◽  
Sainan Cui ◽  
Song Xu ◽  
Chao Yao ◽  
Mark J. MacLachlan ◽  
...  

A novel triptycene-based covalent polymer (TCP) with a high surface area was constructed through the Suzuki coupling reaction.


2021 ◽  
Vol 59 (12) ◽  
pp. 880-885
Author(s):  
Tae Wan Park ◽  
Woon Ik Park

Nanopatterning methods for pattern formation of high-resolution nanostructures are essential for the fabrication of various electronic devices, including wearable displays, high-performance semiconductor devices, and smart biosensor systems. Among advanced nanopatterning methods, nanotransfer printing (nTP) has attracted considerable attention due to its process simplicity, low cost, and great pattern resolution. However, to diversify the pattern geometries for wide device applications, more effective and useful nTP based patterning methods must be developed. Here, we introduce a facile and practical nanofabrication method to obtain various three-dimensional (3D) ultra-thin metallic films via thermally assisted nTP (T-nTP). We show how to generate surface-wrinkled 3D nanostructures, such as angular line, concave-valley, and convex-hill structures. We also demonstrate the principle for effectively forming 3D nanosheets by T-nTP, using Si master molds with a low aspect ratio (A/R ≤ 1). In addition, we explain how to obtain a 3D wavy structure when using a mold with high A/R (≥ 3), based on the isotropic deposition process. We also produced a highly ordered 3D Au nanosheet on flexible PET over a large area (> 15 µm). We expect that this T-nTP approach using various Si mold shapes will be applied for the useful fabrication of various metal/oxide nanostructured devices with high surface area.


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