Query: Acrylamide COF

title: Effect of contact geometry on the friction of acrylamide hydrogels with different surface structures
abstract: Polyacrylamide (PAAm) hydrogels with brush covered or crosslinked surfaces were produced and their tribological behavior was studied over a wide range of sliding speeds for two different contact geometries: sphere on flat and flat pin on flat. Irrespective of the contact geometry, the brushy hydrogel surfaces displayed up to an order of magnitude lower coefficients of friction m (COF) compared to the crosslinked surfaces, even achieving superlubricity (m 0.01) In general, a hydrogel sphere showed a lower coefficient of friction than a flat hydrogel pin at a similar contact pressure over the entire range of sliding speeds. However, after normalizing the friction force by the contact area, the shear stress of hydrogels with either crosslinked or brushy surfaces was found to be similar for both contact geometries at low speeds, indicating that hydrogel friction is unaffected by the contact geometry at these speeds. At high sliding speeds, the shear stress was found to be lower for a sphere on flat configuration compared to a flat pin on flat configuration. This can be attributed to the larger equivalent hydrodynamic thickness due to the convergent inlet zone ahead of the sphere on flat contact, which presumably enhances the water supply in the contact, promotes rehydration, and thus reduces the friction at high sliding speeds compared to that measured for the flat pin on flat contact.

title: Analysis of coffee for the presence of acrylamide by LC MS/MS.
abstract: A variety of popular instant, ground, and brewed coffees were analyzed using a modified liquid chromatography tandem mass spectrometry (LC MS/MS) method specifically developed for the determination of acrylamide in foods. Coffee test portions were spiked with 13C3 labeled acrylamide as an internal standard prior to their extraction and cleanup. Ground coffees (1 g) and instant coffees (0.5 g) were extracted by shaking with 9 mL of water for 20 min. Brewed coffee test portions (9 mL) were taken through the cleanup procedure without further dilution with extraction solvent. Coffee test portions were cleaned up by passing 1.5 mL first through an Oasis HLB (hydrophilic/lipophilic copolymer sorbent) solid phase extraction (SPE) cartridge and then a Bond Elut Accucat (cation and anion exchange sorbent) SPE cartridge. The cleaned up extracts were analyzed by positive ion electrospray LC MS/MS. The MS/MS data was used to detect, confirm, and quantitate acrylamide. The limit of quantitation of the method was 10 ng/g for ground and instant coffees and 1.0 ng/mL for brewed coffee. The levels of acrylamide ranged from 45 to 374 ng/g in unbrewed coffee grounds, from 172 to 539 ng/g in instant coffee crystals, and from 6 to 16 ng/mL in brewed coffee.

title: Improving cold storage and processing traits in potato through targeted gene knockout.
abstract: Cold storage of potato tubers is commonly used to reduce sprouting and extend postharvest shelf life. However, cold temperature stimulates the accumulation of reducing sugars in potato tubers. Upon high temperature processing, these reducing sugars react with free amino acids, resulting in brown, bitter tasting products and elevated levels of acrylamide a potential carcinogen. To minimize the accumulation of reducing sugars, RNA interference (RNAi) technology was used to silence the vacuolar invertase gene (VInv) which encodes a protein that breaks down sucrose to glucose and fructose. Because RNAi often results in incomplete gene silencing and requires the plant to be transgenic, here we used transcription activator like effector nucleases (TALENs) to knockout VInv within the commercial potato variety, Ranger Russet. We isolated 18 plants containing mutations in at least one VInv allele, and five of these plants had mutations in all VInv alleles. Tubers from full VInv knockout plants had undetectable levels of reducing sugars, and processed chips contained reduced levels of acrylamide and were lightly coloured. Furthermore, seven of the 18 modified plant lines appeared to contain no TALEN DNA insertions in the potato genome. These results provide a framework for using TALENs to quickly improve traits in commercially relevant autotetraploid potato lines.

title: Bulk COFs and COF nanosheets for electrochemical energy storage and conversion.
abstract: Covalent organic frameworks (COFs) as an emerging class of crystalline porous materials have received much attention due to their tunable porosity, modifiable skeletons, and atomically precise structures. Besides, COFs can provide multiple high rate charge carrier transport (electron, hole, and ion) pathways, including conjugated skeletons, overlapped p electron clouds among the stacked layers, and open channels with a variable chemical environment. Therefore, they have shown great potential in electrochemical energy storage (EES) and conversion (EEC) However, in bulk COFs, the defects always impede charge carrier conduction, and the difficulties in reaching deep buried active sites by either electrons or ions lead to limited performance. To overcome these obstacles, numerous research studies have been carried out to obtain COF nanosheets (NSs) This review first describes the preparation strategies of COF NSs via bottom up and top down approaches. Then, the applications of bulk COFs and COF NSs in EES and EEC are summarized, such as in batteries, supercapacitors, and fuel cells. Finally, key challenges and future directions in these areas are discussed.

title: Two dimensional MOF and COF nanosheets: synthesis and applications in electrochemistry.
abstract: Metal organic framework (MOF) and covalent organic framework (COF) nanosheets are a new type of two dimensional (2D) materials with unique design principles and various synthesis methods. It is considered an ideal electrochemical device due to the ultrathin thickness, easily tunable molecular structure, large porosity and other unique properties. There are two common methods to synthesize 2D MOF/COF nanosheets: bottom up and top down. The top down strategy mainly includes ultrasonic assisted exfoliation electrochemical exfoliation and mechanical exfoliation. Another strategy mainly includes interface synthesis, modulation synthesis, surfactant assisted synthesis. In this review, the development of ultrathin 2D nanosheets in the field of electrochemistry supercapacitors, batteries, oxygen reduction, and hydrogen evolution) is introduced, and highlight their unique dimensional advantages.

title: Covalently integrated core shell MOF@COF hybrids as efficient visible light driven photocatalysts for selective oxidation of alcohols
abstract: Building a covalently connected structure with accelerated photo induced electrons and charge carrier separation between semiconductors could enhance the photocatalytic performance. In this work, we report a facile and novel seed growth method to coat NH2 MIL 125 MOFs with crystalline and porous covalent organic frameworks (COFs) materials and form a range of NH2 MIL 125@TAPB PDA nanocomposites with different thicknesses of COF shell. The introduction of appropriate content of COF could not only modify the intrinsic electronic and optical properties, but also enhance the photocatalytic activity distinctly. Especially, NH2 MIL 125@TAPB PDA 3 with COF shell thickness of around 20 nm exhibited the highest yield (94.7% of benzaldehyde which is approximately 2.5 and 15.5 times as that of parental NH2 MIL 125 and COF, respectively. The promoted photocatalytic performance of hybrid materials was mainly owing to the enhanced photo induced charge carriers transfer between the MOF and COF through the covalent bond. In addition, a possible mechanism to elucidate the process of photocatalysis was explored. Therefore, this kind of MOF based photocatalysts possesses great potentials in future green organic synthesis.

title: Dummy molecularly imprinted polymers based on a green synthesis strategy for magnetic solid phase extraction of acrylamide in food samples.
abstract: In this work, novel dummy molecularly imprinted polymers (DMIP) with propanamide as a dummy template molecule were prepared based on a green synthesis strategy of less consumption of hazardous/organic reagents and at mild conditions for magnetic solid phase extraction (MSPE) of acrylamide in biscuit samples, followed by high performance liquid chromatography (HPLC) determination. The resultant DMIP was well characterized by FT IR, SEM, TEM and VSM, exhibiting uniform nanoscale coreshell structure and good magnetic property in favor of simple rapid separation. Several main variables influencing MSPE efficiency were investigated, including DMIP dosage, sample solution pH, extraction time and desorption solvent; central composite design (CCD) and response surface methodology (RSM) were employed to assist in the MSPE condition optimization with rapidity and reliability. Under optimized conditions, excellent linearity for acrylamide was obtained in the range of 5.0 5000.0 ug kg 1, and low detection and quantification limits were 1.3 ug kg 1 and 4.4 ug kg 1, respectively. The method recoveries at five spiked concentrations were found within 86.0 98.3% with relative standard deviations (RSDs) of 1.2 4.1% Furthermore, endogenous acrylamide was detected in five different biscuit samples and the RSDs values were lower than 3.3% The present study suggested promising perspectives of water compatible eco friendly DMIP based MSPE HPLC method for highly effective sample pretreatment and targeted analytes determination in complicated matrices.

title: Novel nanoarchitecture of Co MOF on TPN COF hybrid: Ultralowly sensitive bioplatform of electrochemical aptasensor toward ampicillin.
abstract: Owning to the misuse of the antibiotics in animal husbandry and agriculture, it is highly urgent to determine the quantification of antibiotics in biological systems by the simple, sensitive, and fast method. In this work, a novel nanoarchitecture of Co based metal organic frameworks (Co MOF) and terephthalonitrile based covalent organic framework (TPN COF) was synthesized (represented by Co MOF@TPN COF) followed by the exploitation as the bioplatform of non label aptasensor for detecting the most frequently used b lactam antibiotics, ampicillin (AMP) The new porous hybrid material of Co MOF@TPN COF was synthesized by adding the as prepared TPN COF into the Co MOF preparation system. The multilayered Co MOF@TPN COF nanosheets exhibit a high specific surface area (52.64 m2 g 1) nitrogen rich groups and excellent electrochemical activity. As a result, large amounts of aptamer strands can be bound over the Co MOF@TPN COF nanosheets owning to the strong p p stacking and hydrogen bonds. When detecting AMP by the electrochemical impedance spectroscopy, the fabricated Co MOF@TPN COF based aptasensor exhibits an ultra low detection limit of 0.217 fg mL 1 within the AMP concentration from 1.0 fg mL 1 to 2.0 ng mL 1, which was superior to those previously reported in literatures. In addition, this proposed aptasensor also shows high selectivity, good reproducibility and stability, acceptable regenerability, and favorable applicability in human serum, river water and milk. Therefore, the proposed Co MOF@TPN COF based aptasensor has a great promise to be applied as a powerful tool in the fields of food safety.

title: Mixed matrix membranes containing MOF@COF hybrid fillers for efficient CO2/CH4 separation
abstract: Membrane technology has aroused great attention for gas separations due to its high energy efficiency, small capital investment, easy and continuous operation. Mixed matrix membranes (MMMs) constructed from a continuous polymer phase and a dispersed filler phase offer new opportunities to achieve a breakthrough in fabricating high performance membranes. Metal organic frameworks (MOFs) have been regarded as potential fillers to boost the MMM separation performance. However, MOFs occasionally exhibit limited compatibility with the polymer matrixes owing to their partially inorganic structure and tendency of agglomeration in the membranes. Here, an interfacial design strategy is demonstrated by coating size selective MOF cores with covalent organic framework (COF) layers to construct MOF@COF hybrids as fillers in MMMs for enhanced polymer filler compatibility. The pure organic COF layers exhibit high affinity to the polymer matrix, thereby preventing the formation of nonselective interfacial voids and alleviating filler agglomeration. With the incorporation of only 5 wt% of MOF@COF fillers, the resultant MMM exhibits 48% and 79% enhancements in CO2 permeability and CO2/CH4 selectivity, respectively, with better operational stability compared to that of the pure polymeric membrane. These results reveal a novel filler design strategy for the tailored synthesis of high performance MMMs for natural gas and biogas purification.

title: Construction of Ce MOF@COF hybrid nanostructure: Label free aptasensor for the ultrasensitive detection of oxytetracycline residues in aqueous solution environments.
abstract: Porous organic framework (COF) nanomaterials have drawn increasing attention and showed promising potential in the applications of various fields. Nevertheless, its applications in biosensing or biomedical fields are still in the early stage. In this work, we designed and synthesized a series of nanohybrids of COF and Ce based metal organic framework (Ce MOF) for the first time as label free bioplatforms for a sensitive electrochemical aptasensor to detect oxytetracycline (OTC) A novel kinds of Ce MOF@COF hybrids were prepared by adding different dosages of COF, into the preparation system of Ce MOF, for which COF was synthesized using melamine and cyanutic acidmonomers through polycondensation (represented by MCA) Basic characterizations revealed that Ce MOF@MCA nanohybrids not only remained their orignal crystal and chemical structure and features, such as different Ce species containing in Ce MOF (Ce3+ and Ce4+ various functional amino groups of MCA, and individual frameworks, but also showed a large specific surface area and interpenetrated morphologies. As a result, the Ce MOF@MCA hybrid with high content of MCA exhibited high bioaffinity toward the OTC targeted aptamer, further leading to the incremental detection effect for OTC detection. Among different hybrid based aptasensors, the Ce MOF@MCA based one with an MCA dosage of 500 mg exhibited the lowest limit of detection at 17.4 fg mL 1 within a wider linearity of the OTC concentration within 0.1 0.5 ng mL 1. Additionally, the fabricated aptasensor displayed excellent analytical performance with great reproducibility, high selectivity and stability, and acceptable applicability for detecting OTC in various aqueous solutions, including milk, wastewater, and urine samples. This new Ce MOF@MCA hybrid will become an excellent aptasensors platform for detecting various analytes, such as antibiotics, heavy metal ions, or cancer markers, and it have shown the promissing application potentials in the fields of biomedicine, food safety and environmental monitoring.