Surface Amino Research Articles

Enhanced visible-light photocatalytic hydrogen evolution using two-dimensional carbon nitride sheets with the removal of amine groups

Two-dimensional (2D) carbon nitride sheets (CNs) with atomically thin structures are regarded as one of the most promising materials for solar energy conversion. However, due to their substantially enlarged bandgap caused by the strong quantum size effect and their incomplete polymerisation with a large number of non-condensed surface amino groups, the practical applicability of CNs in photocatalysis is limited. In this study, CNs with broad visible-light absorption were synthesised using a 5-min fast thermal annealing. The removal of uncondensed amine groups reduces the bandgap of CNs from 3.06 eV to 2.60 eV, increasing their absorption of visible light. Interestingly, the CNs were distorted after annealing, which can differentiate the spatial positions of electrons and holes, enhancing the visible-light absorption efficiency. As a result, when exposed to visible light, the photocatalytic hydrogen production activity of atomically thin 2D CNs rose by 8.38 times. This research presents a dependable and speedy method for creating highly effective visible-light photocatalysts with narrowed bandgaps and improved visible-light absorption.

Synthesis of easily renewable and recoverable magnetic PEI-modified Fe3O4 nanoparticles and its application for adsorption and enrichment of tungsten from aqueous solutions

Tungsten is a hazardous metal to human health and the environment, but it is also valuable. Previous studies have been limited to the adsorption and removal of tungsten, without considering its recovery and utilization. In this article, a renewable magnetic material, Fe3O4 nanoparticles coated by polyethyleneimine (Fe3O4@PEI NPs), is synthesized and used for the adsorption of tungsten in water. Tungsten adsorption experiments were conducted under different initial tungsten concentrations, contact times, solution pH values, and co-existing anions. The results show that Fe3O4@PEI NPs efficiently and rapidly adsorb tungsten from water, with a maximum adsorption capacity of 43.24 mg/g. Under acidic conditions (pH ∼2), the adsorption performance of the NPs maximized. This is because tungstate ions polymerize under such conditions to form polytungstic anions. These are attracted to the positively charged surface of Fe3O4@PEI NPs by electrostatic attraction, followed by complexation reactions with the surface hydroxyl and amino groups of NPs, as evidenced by multiple spectroscopic methods. The NPs can be recovered and renewed and provide a potential application for the enrichment and recycling of high-value tungsten (W(VI)).

Amino group functionalized pitch-based carbocatalyst for the Henry reaction of furfural

BackgroundTo transform the commodity wastes into high performance materials such as catalyst supports can facilitate the circular economy. Therefore, pitch-based carbon (MPC) which is mainly regarded as a premium carbon byproduct from the petroleum refinery was used to synthesize the supported amino catalyst for the Henry reaction of furfural. MethodsThe amino functionalized pitch-based carbon was prepared by the facile chemical nitration and reduction. The surface textures of the functionalized carbon materials were carefully scrutinized by various characterization techniques, including PXRD, XPS, FT-IR, 13C SSNMR, and Raman spectroscopy. Meanwhile, the amount of surface accessible amino groups was quantified by the colorimetric method using 2-iminothiolane hydrochloride (ITL) as molecular probe. Significant findingThe results reveal that the surface amino groups were immobilized and quantified as 0.391 mmol/g at the periphery of MPC. Moreover, this amino functionalized carbon denoted NRE-MPC could catalyze the Henry reaction of furfural with nitromethane in isopropanol at 90 °C for 6 h to yield 2-(2-nitrovinyl)furan (NVF) as the major product in 65% with 87% furfural conversion. NRE-MPC can be also easily recycled at least four times and the peripheral amino groups alongside the graphitic domains of MPC were still chemically active with perceptible reactivity reduction.

Fabrication of polydopamine-boehmite modified superhydrophobic coating for self-cleaning, oil-water separation, oil sorption and flame retardancy

A facile approach for fabricating multifunctional superhydrophobic coating was developed through a simple dip-coating process. The boehmite particles (BMPs) were adhered and modified onto stainless steel (SS) mesh through polydopamine (PDA), which was formed by the oxygen-induced polymerization of dopamine (DA). Therefore, the roughness structure (SS-PDA@BMPs mesh) was obtained. Meanwhile, due to the catechol group of the PDA, cetylamine (CTA) with low surface energy and amino group was grafted onto PDA via the Michael addition reaction to construct the superhydrophobic coating (CTA@PDA@BMPs). The effects of the morphology of BMPs, the ratio of BMPs to DA, the reaction time, and the concentration of CTA on superhydrophobicity of SS-CTA@PDA@BMPs mesh were discussed, which showed the water contact angle of 164° and the sliding angle of 3° for the SS-CTA@PDA@BMPs mesh fabricated under optimal conditions. The SS-CTA@PDA@BMPs mesh with great chemical stability and mechanical durability displayed excellent self-cleaning property and oil/water separation efficiency. When the PU sponge was coated with CTA@PDA@BMPs coating by the same process, the superhydrophobic PU sponge was obtained, which exhibited superior reusability and flame retardancy property. Thus, the prepared superhydrophobic materials are multifunctional and environmentally friendly.

Numerous defects induced by exfoliation of boron-doped g-C3N4 towards active sites modulation for highly efficient solar-to-fuel conversion

Graphitic carbon nitride (CN) has emerged as a highly promising material in the photocatalysis field. However, its bulk structure suffers from a lack of active sites, limiting its practical application. Herein, a boron-doped CN (BCN) was prepared by a green gas-blowing-assisted thermal polymerization and then subjected to different exfoliation processes in order to delaminate the layered structure and tune the surface-active sites. A thorough comparative study shows that thermal exfoliation creates unsaturated nitrogen sites and induces the formation of interconnected layers that act as an electron diffusion channel for better charge transport. Furthermore, the thermally exfoliated BCN is rich in structural disorders that serve as dissociation defects for photoinduced charge carriers with a low exciton binding energy of 27 meV. Experimental results supported by theoretical calculations show that the nitrogen adjacent to boron is activated by the surrounding surface amino groups and the perforated texture to serve as an active adsorption site towards CO2 and H2O. Consequently, the exfoliated BCN acts as an outstanding bifunctional photocatalyst towards CO2 reduction into CO (40.41 μmol g−1 h−1) and prominent hydrogen evolution (4740 μmol g−1 h−1, 12.2% apparent quantum yield (AQY)).

Polydopamine-encapsulated cap-like mesoporous silica based delivery system for responsive pesticide release and high retention

Nanopesticides formulation has been applied in modern agriculture, but the effective deposition of pesticides on plant surfaces is still a critical challenge. Here, we developed a cap-like mesoporous silica (C-mSiO2) carrier for pesticide delivery. The C-mSiO2 carriers with surface amino groups present uniform cap-like shape and have an mean diameter of 300 nm and width of 100 nm. This structure would reduce the rolling and bouncing of carriers on plant leaves, leading to improving the foliage deposition and retention. After loading dinotefuran (DIN), polydopamine (PDA) was used to encapsulate the pesticide (DIN@C-mSiO2@PDA). The C-mSiO2 carriers exhibit high drug loading efficiency (24.7%) and benign biocompatibility on bacteria and seed. Except for pH/NIR response release, the DIN@C-mSiO2@PDA exhibited excellent photostability under UV irradiation. Moreover, the insecticidal activity of DIN@C-mSiO2@PDA was comparable to that of pure DIN and DIN commercial suspension (CS-DIN). This carrier system has the potential for improving the foliage retention and utilization of pesticides.

Highly (2 2 2)-oriented flexible hollow fiber-supported metal-organic framework membranes for ultra-permeable and selective H2/CO2 separation

Metal-organic framework (MOF) membranes demonstrate enormous potential for energy-efficient gas separations, while the construction of flexible and oriented MOF-based membranes remains a significant challenge. Herein, we prepared an ultrathin and highly (222)-oriented ZIF-8 layer with unique honeycomb cellular structures on porous aminated polyethersulfone (PES) hollow fibers (HF) via UV radiation-induced surface amino-grafting followed by a homogeneous fluidic processing method, and the reaction conditions including amino-grafting density, radiation power, flow rate, and reaction time et al. were systematically investigated and optimized. The orientation of reflection originated from the difference in attachment energy of crystal planes induced by the surface amino groups. The coherent (222)-oriented NH2-ZIF-8@HF membrane exhibited distinguished H2/CO2 separation performance with a mixed-gas H2 permeance of 75711 ± 610 GPU, among the highest values of previously reported hollow fiber supported ZIF membranes, and the H2/CO2 selectivity of 21.2 ± 0.11 at 150 °C. Additionally, the NH2-ZIF-8@HF membrane displayed outstanding mechanical and thermal stability with negligible deterioration of gas separation performance after folding and unfolding at 180° for 20 times and several temperature-swing cycles. ZIF-7 and ZIF-67 composite membranes were also prepared with outstanding H2/CO2 separation performance following the same strategy. The facile membrane fabrication method and exceptional separation performance make NH2-ZIF@HF membranes attractive for important industrial energy-efficient H2 recovery from steam cracking and similar processes.

Covalent Immobilization of Natural Biomolecules on Chitin Nanocrystals.

As a highly crystalline and renewable natural polymer nanomaterial, chitin nanocrystals (ChNCs) have attracted intense interest in the biomedical field. The structure of a ChNC is composed of an acetylglucosamine unit containing two hydroxyl groups and an acetyl group. The acetyl group can be converted to the active amino group through deacetylation, which is under the condition of maintaining the rod-like morphology and high crystalline property and is beneficial for the following modification and potential application. We investigated the relationship between different treatments and varied crystallinities of the modified ChNC, which obtained surface amino groups and aldehyde groups and retained high crystallinity. The natural biomolecules were covalently immobilized on the surface of the ChNC. The etherification was performed based on the hydroxyl groups. Based on the amino groups and the aldehyde groups, the carboxyamine and Knoevenagel condensation reactions were realized on ChNCs. Finally, natural biomolecule-modified ChNCs showed no or low cytotoxicity, antibacterial properties, and high antioxidant properties, which extended their potential biomedical applications.

Surface reaction mechanism of atomic layer deposition of titanium nitride using Tetrakis(dimethylamino)titanium and ammonia

Atomic layer deposition (ALD) is an excellent technology used for the preparation of various nanomaterials in microelectronics, energy, catalysis, optics and coatings. Titanium nitride (TiN) is an interesting member of the refractory transition metal nitrides family exhibiting chemical and thermal stability. Using density functional theory calculations, the reaction mechanisms of the ALD of TiN using tetra(dimethylamino)titanium (TDMAT) and ammonia as precursors was investigated. The results showed that the mechanism consisted of two reactions: the TDMAT reaction and NH3 reaction. In the TDMAT reaction, the precursor achieved the elimination of dimethylamine via a substitution reaction with the surface amino groups. In the NH3 reaction, the reaction process was complicated. They mainly included exchange reactions between the amino and dimethylamino ligands and coupling reactions forming bridged products and by-products, such as NH3 or HN(CH3)2. As a whole, all of these surface reactions were thermodynamically and kinetically favorable. All these insights into surface reactions of the ALD of TiN provided the guidance for precursor design and the ALD growth of other nitride and titanium-based compounds.

Highly Dispersed Vanadia Anchored on Protonated g-C3N4 as an Efficient and Selective Catalyst for the Hydroxylation of Benzene into Phenol

The direct hydroxylation of benzene is a green and economical-efficient alternative to the existing cumene process for phenol production. However, the undesired phenol selectivity at high benzene conversion hinders its wide application. Here, we develop a one-pot synthesis of protonated g-C3N4 supporting vanadia catalysts (V-pg-C3N4) for the efficient and selective hydroxylation of benzene. Characterizations suggest that protonating g-C3N4 in diluted HCl can boost the generation of amino groups (NH/NH2) without changing the bulk structure. The content of surface amino groups, which determines the dispersion of vanadia, can be easily regulated by the amount of HCl added in the preparation. Increasing the content of surface amino groups benefits the dispersion of vanadia, which eventually leads to improved H2O2 activation and benzene hydroxylation. The optimal catalyst, V-pg-C3N4-0.46, achieves 60% benzene conversion and 99.7% phenol selectivity at 60 oC with H2O2 as the oxidant.

Automated prediction of site and sequence of protein modification with ATRP initiators.

One of the most straightforward and commonly used chemical modifications of proteins is to react surface amino groups (lysine residues) with activated esters. This chemistry has been used to generate protein-polymer conjugates, many of which are now approved therapeutics. Similar conjugates have also been generated by reacting activated ester atom transfer polymerization initiators with lysine residues to create biomacromolecular initiators for polymerization reactions. The reaction between activated esters and lysine amino groups is rapid and has been consistently described in almost every publication on the topic as a “random reaction”. A random reaction implies that every accessible lysine amino group on a protein molecule is equally reactive, and as a result, that the reaction is indiscriminate. Nonetheless, the literature contradicts itself by also suggesting that some lysine amino groups are more reactive than others (as a function of pKa, surface accessibility, temperature, and local environment). If the latter assumption is correct, then the outcome of these reactions cannot be random at all, and we should be able to predict the outcome from the structure of the protein. Predicting the non-random outcome of a reaction between surface lysines and reactive esters could transform the speed at which active bioconjugates can be developed and engineered. Herein, we describe a robust integrated tool that predicts the activated ester reactivity of every lysine in a protein, thereby allowing us to calculate the non-random sequence of reaction as a function of reaction conditions. Specifically, we have predicted the intrinsic reactivity of each lysine in multiple proteins with a bromine-functionalised N-hydroxysuccinimide initiator molecule. We have also shown that the model applied to PEGylation. The rules-based analysis has been coupled together in a single Python program that can bypass tedious trial and error experiments usually needed in protein-polymer conjugate design and synthesis.

Polyaniline-Grafted Chitin Nanocrystals as Conductive Reinforcing Nanofillers for Waterborne Polymer Dispersions.

Due to its intrinsic electrical conductivity, polyaniline (PANI) is one of the most promising conducting polymers for high-performance applications in a wide range of technological fields. However, its poor dispersibility in water and organic solvents markedly imparts its processability and electrical conductivity. Herein, we report a green and one-step approach to preparing stable colloidal dispersions of highly dispersible hybrid nanoparticles by polymerizing PANI onto chitin nanocrystals (ChNCs) as biotemplates, via initiation through the surface amino groups of ChNCs. Evidence of the grafting of PANI onto ChNCs was supported by transmission electron microscopy (TEM), as well as Raman and Fourier transform infrared (FTIR) spectroscopies. Nanocomposite films were prepared by mixing the PANI-g-ChNCs with a waterborne poly(vinyl acetate) latex dispersion followed by casting and film formation at room temperature. The mechanical properties were tested as a function of the PANI-g-ChNC content. In addition, it was shown that at a proper content of PANI in ChNCs, and over a critical loading in the PANI-g-ChNCs, a conductive film was obtained, without sacrificing the reinforcing effect of the rodlike nanofiller. As a potential application, conductive waterborne adhesives for wood were prepared and the performance of the adhesives was tested. This research provides a facile route to fabricating a new class of hybrid nanofiller from a biobased origin, stable in water and easy to mix with waterborne dispersions, combining the merits of the ChNC nanofiller with the conductivity of PANI.

ANN-GA based biosorption of As(III) from water through chemo-tailored and iron impregnated fungal biofilter system

The iron impregnated fungal bio-filter (IIFB) discs of luffa sponge containing Phanerochaete chrysosporium mycelia have been used for the removal of As(III) from water. Two different forms of same biomass viz. free fungal biomass (FFB) and modified free fungal biomass (chemically modified and iron impregnated; CFB and IIFB) have been simultaneously investigated to compare the performance of immobilization, chemo-tailoring and iron impregnation for remediation of As(III). IIFB showed highest uptake capacity and percentage removal of As(III), 1.32 mg/g and 92.4% respectively among FFB, CFB and IIFB. Further, the application of RSM and ANN-GA based mathematical model showed a substantial increase in removal i.e. 99.2% of As(III) was filtered out from water at optimised conditions i.e. biomass dose 0.72 g/L, pH 7.31, temperature 42 °C, and initial As(III) concentration 1.1 mg/L. Isotherm, kinetic and thermodynamic studies proved that the process followed monolayer sorption pattern in spontaneous and endothermic way through pseudo-second order kinetic pathway. Continuous mode of As(III) removal in IIFB packed bed bioreactor, revealed increased removal of As(III) from 76.40 to 88.23% with increased column height from 5 to 25 cm whereas the removal decreased from 88.23 to 69.45% while increasing flow rate from 1.66 to 8.30 mL/min. Moreover, the IIFB discs was regenerated by using 10% NaOH as eluting agent and evaluated for As(III) removal for four sorption–desorption cycles, showing slight decrease of their efficiency by 1–2%. SEM–EDX, pHzpc, and FTIR analysis, revealed the involvement of hydroxyl and amino surface groups following a non-electrostatic legend exchange sorption mechanism during removal of As(III).

L-histidine functionalized ZiF-8 with aggregation-induced emission for detection of tetracycline

In this study, we constructed zinc based metal–organic framework functionalized by L-histidine (His@ZiF-8). The His@ZiF-8 had high porosity, large surface area, abundant carboxyl and amino group, which has been found to greatly enhance the aggregation-induced emission (AIE) of tetracycline (TC). After the His@ZiF-8 enrichment with TC, the TC exhibited strong fluorescence emission peak at 565 nm based on AIE. Under the optimal conditions, the fluorescence intensity of TC exhibited a good linear relationship with TC concentration within 0.1–80 μM with a low limit of detection of 28.6 nM. Antibiotic analogs such as neomycin, chloramphenico, ampicillin, kanamycin, and erythromycin have no obvious interference. In addition, the developed method was successfully used to the detection of TC in milk, river water, and honey.

Surface amino group modulation of carbon dots with blue, green and red emission as Cu2+ ion reversible detector

The surface functional groups of carbon dots (CDs) play a significant role in the luminescence performances, but it is still unclear about the effects of special groups on the luminescence mechanism since there are different groups on the surface of prepared CDs. Here, electrochemical method was adopted to synthesize initial CDs and graphite rods served as raw materials, and initial CDs were only modified with amino groups to regulate their surface states, which lead to the blue, green and red luminescence for the modified CDs. The amino groups with different contents are only introduced on the surface of CDs without affecting carbon core. With the increased contents of amino groups, the luminescence spectra of CDs can be successfully modulated from blue to red emission. In addition, the blue emitting carbon dots (B-CDs) have a specific response to Cu2+ ions and can be applied as a fluorescent probe to detect Cu2+ ions in the solution. Moreover, the addition of DL-serine can restore the blue emission of B-CDs quenched by Cu2+ ions. Therefore, the B-CDs have great potential application as a fluorescent reversible ion detector.

Amino Surface Modification and Fluorescent Labelling of Porous Hollow Organosilica Particles: Optimization and Characterization

Surface modification of silica nanoparticles with organic functional groups while maintaining colloidal stability remains a synthetic challenge. This work aimed to prepare highly dispersed porous hollow organosilica particles (pHOPs) with amino surface modification. The amino-surface modification of pHOPs was carried out with 3-aminopropyl(diethoxy)methylsilane (APDEMS) under various reaction parameters, and the optimal pHOP-NH2 sample was selected and labelled with fluorescein isothiocyanate (FITC) to achieve fluorescent pHOPs (F-HOPs). The prepared pHOPs were thoroughly characterized by transmission electron microscopy, dynamic light scattering, FT-IR, UV-Vis and fluorescence spectroscopies, and microfluidic resistive pulse sensing. The optimal amino surface modification of pHOPs with APDEMS was at pH 10.2, at 60 °C temperature with 10 min reaction time. The positive Zeta potential of pHOP-NH2 in an acidic environment and the appearance of vibrations characteristic to the surface amino groups on the FT-IR spectra prove the successful surface modification. A red-shift in the absorbance spectrum and the appearance of bands characteristic to secondary amines in the FTIR spectrum of F-HOP confirmed the covalent attachment of FITC to pHOP-NH2. This study provides a step-by-step synthetic optimization and characterization of fluorescently labelled organosilica particles to enhance their optical properties and extend their applications.

Magnetically recyclable HPW@ mSiO2/hydrophobic GO with adjustable polarity used for oxidative desulfurization in Pickering emulsion

A series of amphiphilic particles were prepared using Janus graphene oxide (GO) and magnetic SiO2-NH2 (mSiO2-NH2) as starting materials. Then, H3PW12O40 (HPW) was supported on the particles through the interaction between surface amino groups and HPW to obtain catalytic emulsion stabilizers for oxidative desulfurization. The characterization analysis showed that the prepared materials exhibited the sheet structure of GO which was connected by several core–shell microspheres of mSiO2 on one side, and the other side of the materials was grafted by carbon chains to increase hydrophobicity. The catalytic performance of prepared materials increased with the grafted carbon chain length, and the one grafted by hexadecylamine had the best performance with a final desulfurization ratio of 99.21%. That was because it had the most appropriate amphipathy, which can convert the bi-phase system into a stable Pickering emulsion with enlarged contact area between oil and extractant, thus largely promoting mass transfer even without stirring. With the excellent magnetism, the catalytic emulsion stabilizers can be magnetically separated to realize the emulsion breaking, thus easily recycling the catalyst and value-added reaction products after reaction.

Bifunctional ZnCo2S4@CoZn13 hybrid electrocatalysts for high efficient overall water splitting

To develop highly active and low-cost electrocatalyst is very important to improve the efficiency of water splitting. However, the current catalysts still present serious challenges due to the poor intrinsic activity and high overpotential. Herein, we report several amino induced Co-based composite catalysts. As a structure-mediating agent, ethylenediamine (EDA) can not only regulate the crystal structure and but also provide many surface amino groups. The obtained ZnCo2S4/CoZn13 catalysts show an excellent oxygen evolution reaction (OER) performance (274 mV@50 mA cm−2) and the overpotential of 160 mV at −10 mA cm−2 for hydrogen evolution reaction (HER). For electrolysis of water, the electrocatalysts deliver a cell voltage of 1.61 V at 50 mA cm−2. This study provides a facile synthetic strategy to construct advanced electrocatalysts for future applications.

High performance Pt(II) complex and its hybridized carbon quantum dots: Synthesis and the synergistic enhanced optical limiting property

A new strategy is launched to develop efficient nonlinear optical (NLO) materials by incorporating organometallic Pt(II) complexes into carbon quantum dots (CQDs), which exhibits the synergistic effect for the optical limiting performance of hybrid materials. m1-CDs were further functionalized with Pt(II) complex for the smaller sizes (2.3 nm) and more surface amino groups (54.6 %), and the Pt(II) complex also shows long triplet-excited lifetime (482 ns) and satisfactory reverse saturable absorption (RSA). The hybrid material N-CD-Pt exhibits the special π − π* transitions and broader metal-to-ligand/intraligand/ligand-to-ligand charge transfer transitions in the visible region (∼675 nm). The electron/energy transfer process occurred among the system causes a significant emission quenching for the nanohybrid, which is benefit for the occurrence of excited-state absorption process and the enhancement of the RSA. The covalent modification also endows nanohybrid N-CD-Pt with improved NLO performance, including RSA behaviors mainly from the Pt(II) complexes and nonlinear scattering responses from CQDs. The limiting threshold (F50) of N-CD-Pt reaches 0.62 J·cm−2 at 532 nm, which is better than Pt(II) complex (1.0 J·cm−2).

Analysis of Constituent Elements and Brownian Motion of the Conjugates of anti-CD3 Antibody and Magnetic Nanoparticles

An Fc-directed conjugate (mAb-MNP) of the anti-CD3 monoclonal antibody (mAb), Foralumab, and the surface amino groups on magnetic nanoparticles (MNPs) was prepared using the SiteClick antibody labeling kit. The conjugate was imaged by transmission electron microscopy and analyzed using energy dispersive spectrum and a nanoparticle tracking analyses. The average values of drift velocities (pix/frame) due to the Brownian motion of MNPs and mAb-MNPs in phosphate-buffered saline were 3.16/0.76 and 6.70/1.98 on the x-/yaxes, respectively. Two different hydrodynamic diameters of 180.0 nm and 258.8 nm were found for the MNPs and the mAb-MNPs with an actual size of 35 nm, respectively. The drift velocity was 2 times (2×) higher for mAb-MNPs than MNPs in proportion to the 2× higher value of the square of the hydrodynamic diameter of the conjugate relative to the MNPs as calculated by Stokes