Graphene oxide as inhibitor on the hydrolysis of fats under simulated in vitro duodenal conditions.

Obesity is a global pandemic, thus novel developments that reduce the absorption of fats is of interest. We have evaluated the effect of graphene oxide (GO) on the lipase catalyzed hydrolysis of fats (tributyrin, sunflower and olive oil) under simulated duodenal conditions. Results indicate that the presence of GO in the digestion mixture can inhibit lipase activity up to a 90% of the initial reaction rate, and this inhibition lasts even during 2 h of digestion. The inhibition mechanism seems non competitive and could be opposite to the effect of bile salts, although the direct interaction between GO and the enzyme cannot be discarded. The inhibition is found also in alimentary fats suggesting that GO could be a strong inhibitor for fat hydrolysis.

New fluorescent Schiff base modified nanocellulose-based chemosensors for the selective detection of Fe3+, Zn2+ and Cu2+ in semi-aqueous media and application in seawater sample.

Stimulus-responsive fluorescent-modified biopolymers have received significant attention in the field of chemosensors. Herein, four new fluorescent dyes, namely, S1: (PDA-DANC), S2: (SAL-PDA-DANC), S3: (BrSAL-PDA-DANC) and S4: (ClSAL-PDA-DANC) have been successfully synthesized from 2,3-dialdehyde nanocellulose (DANC) for the detection of heavy metals. The microstructural and photophysical properties of nanocellulose (NC), microcrystalline cellulose (DANC) and the synthesized S1 to S4 dyes were investigated by FT-IR, SEM-EDX, XRD, TGA, DLS and photoluminescence. NC, obtained from conversion of MCC, shows an average size of 802.4 nm with 0.141 of polydispersity index (PdI), and a crystalline index (CI) of 82.40 % and crystallite size of 4.68 nm. The synthesized dyes present good fluorescent properties and have been therefore exploited for developing new probes for heavy metal ions detection. Remarkable "turn off" and/or "turn on" behaviors with Fe3+ and Cu2+ and with Zn2+ in DMF/water solution have been demonstrated, allowing the sensitive and selective determination of these heavy metal ions with a low limit of detection (LOD). Finally, the evaluation of the Fe3+ sensing in a real seawater sample was investigated.

Synthesis and Catalytic Activity for 2, 3, and 4-Nitrophenol Reduction of Green Catalysts Based on Cu, Ag and Au Nanoparticles Deposited on Polydopamine-Magnetite Porous Supports.

This work reports on the synthesis of nine materials containing Cu, Ag, Au, and Ag/Cu nanoparticles (NPs) deposited on magnetite particles coated with polydopamine (PDA). Ag NPs were deposited on two PDA@Fe3O4 supports differing in the thickness of the PDA film. The film thickness was adjusted to impart a textural porosity to the material. During synthesis, Ag(I) was reduced with ascorbic acid (HA), photochemically, or with NaBH4, whereas Au(III), with HA, with the PDA cathecol groups, or NaBH4. For the material characterization, TGA, XRD, SEM, EDX, TEM, STEM-HAADF, and DLS were used. The catalytic activity towards reduction of 4-, 3- and 2-nitrophenol was tested and correlated with the synthesis method, film thickness, metal particle size and NO2 group position. An evaluation of the recyclability of the materials was carried out. In general, the catalysts prepared by using soft reducing agents and/or thin PDA films were the most active, while the materials reduced with NaBH4 remained unchanged longer in the reactor. The activity varied in the direction Au > Ag > Cu. However, the Ag-based materials showed a higher recyclability than those based on gold. It is worth noting that the Cu-containing catalyst, the most environmentally friendly, was as active as the best Ag-based catalyst.

Novel Microwave-Assisted Synthesis of COFs: 2020-2022.

Covalent organic frameworks (COFs) have emerged as a new type of crystalline porous polymers of great interest. However, their preparation requires long reaction times. Microwave-assisted synthesis (MAS) offers an interesting approach to increasing the reaction rate of chemical processes. Thus, microwaves can be a key tool for the fast and scalable synthesis of COFs. Since our previous review on the topic, the preparation of COFs with microwaves has been evolving. Herein, we present a compilation of COFs studies and experiments published in the last three years on the synthesis of COFs using microwave-assisted synthesis as a source of energy. The articles include imine, triazine, and other 2D COFs synthesized using MAS. The 3D COFs have also been compiled. The chemical structure of the monomers and the COFs and their main parameters of synthesis and application are summarized for each article.

Fast Microwave-Assisted Synthesis, Calcination and Functionalization of a Silica Mesoporous Nanomaterial: UVM-7.

We report here, for the first time, the use of a solid state microwave source for the synthesis, calcination and functionalization of a UVM-7 based hybrid mesoporous silica material. The synthesis of the UVM-7 material is obtained in 2 min at low power (50 W) by the combination of a microwave irradiation and the atrane route. Moreover, it has been successfully calcined and functionalized in just 13 and 4 min respectively with microwave assisted procedures. A total synthesis comprising each individually optimized step, can be executed in only 4 h including work-up, by contrast to a typical synthesis that comprises several days. Savings higher than one order or magnitude are obtained in time and energy. Our example is a proof of concept of the potential use of solid state microwave generators for the ultrafast on-command preparation of hybrid nanomaterials due to their accurate control and accelerating properties.

Metal-organic frameworks as promising solid-phase sorbents for the isolation of third-generation synthetic cannabinoids in biological samples.

In this work, metal-organic frameworks (MOFs) were used for the first time as solid-phase extraction (SPE) sorbents for the isolation of synthetic cannabinoids (SCs) from oral fluids and subsequently quantified by LC-fluorescence detection (FLD). In this context, different MOF families were synthesized and tested under SPE mode. UiO-66 was the family selected, being the amino functionalized (NH2-UiO-66) the best candidate in terms of extraction performance. After the method optimization, several analytical parameters of interest were obtained, reaching limits of detection (LODs) as low as 0.6-0.8 µg L-1 and precision values (expressed as RSD) lower than 10.6%. The developed method was successfully applied to the determination of 8 SCs in different oral fluids at three spiked levels with recoveries between 67 and 114%. This method claims to be a real alternative for screening purposes, being a cost-effective procedure due to the price of the sorbent (<0.5 €/cartridge) and its recyclability (up to 12 uses), among others good features.

An optimized sono-heterogeneous Fenton degradation of olive-oil mill wastewater organic matter by new magnetic glutarlaldehyde-crosslinked developed cellulose.

The present study highlights the olive mill wastewater (OMW) treatment characteristics through a sono-heterogeneous Fenton process using new designed [GTA-(PDA-g-DAC) @Fe3O4] and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), magnetic properties measurements, and point of zero charge (pH pzc) analysis. A preliminary removal study showed significant degradation efficiency (75%) occurred combining the magnetic synthesized catalyst [GTA-(PDA-g-DAC)@Fe3O4] ([catalyst] = 2 g/L) with US /H2O2 and maintaining 500WL-1 ultrasonic power (US). The values obtained by US only were (13%), H2O2/US (18%), US/Fe3O4 (28%), and US /Fe3O4/H2O2(35%). The catalytic findings have shown that [GTA-(PDA-g-DAC)@Fe3O4] exhibited good properties for OMW compound's degradation. The sonocatalytic process coupling and extra oxidant addition resulted in the degradation substantial levels. For instance, the concomitant effect of degradation optimized parameters; H2O2 10 mM, [GTA-(PDA-g-DAC) @Fe3O4] nanocomposites 2.5 g/L, at pH 3, and T 35 °C for 70 min resulted in an almost complete mineralization of aqueous OMW solution followed by a significant decolorization. Oxidation results exhibited efficient degradation rates in total phenolic compounds (TPC), total amino compounds (TAC), and chemical oxygen demand (COD) oxidation rate were 89.88, 92.75, and 95.66 respectively following the optimized sono-heterogeneous catalytic Fenton process. The prepared magnetic catalyst exhibited a good stability during repeated cycles. The gathered findings gave the evidence that sono-heterogeneous catalytic Fenton process is a promising treatment technology for OMW effluents.

One-Pot Synthesis of MnOx-SiO2 Porous Composites as Nanozymes with ROS-Scavenging Properties.

The development of nanomaterials that mimic the activity of enzymes is a topic of interest, for the decomposition of reactive oxygen species (ROS). We report the preparation of a novel nanocomposite of MnOx needles covered with SiO2 porous material. The material was prepared in one pot with a two-step procedure. The material was characterized by EDX, SEM, TEM, XRD, nitrogen adsorption-desorption isotherms, and XPS. The synthesis protocol took advantage of the atrane method, favoring the nucleation and initial growth of manganese oxide needles that remained embedded and homogeneously dispersed in a mesoporous silica matrix. The final composite had a high concentration of Mn (Si/Mn molar ratio of ca. 1). The nanozyme presented bimodal porosity: intraparticle and interparticle association with the surfactant micelles and the gaps between silica particles and MnOx needles, respectively. The porosity favored the migration of the reagent to the surface of the catalytic MnOx. The nanozyme showed very efficient SOD and catalase activities, thus improving other materials previously described. The kinetics were studied in detail, and the reaction mechanisms were proposed. It was shown that silica does not play an innocent role in the case of catalase activity, increasing the reaction rate.

Batch and Flow Synthesis of CeO2 Nanomaterials Using Solid-State Microwave Generators.

Microwave-assisted synthesis in combination with flow synthesis offers an interesting approach to develop faster and more sustainable procedures for the preparation of homogeneous nanomaterials. Recently, solid-state generators of microwaves appeared as a tool with improved control over power and frequency. Cerium oxide, despite its excellent catalytic activity, has not been prepared before using solid-state generators or microwave-assisted flow chemistry. We report a procedure for the preparation of nanoparticulated CeO2 (around 4 nm) under 2.45 GHz microwaves in only 30 s. The materials are further calcined at 800 °C to increase particle size, with a better defined particle size and crystallinity. The procedure was tested in batch at pH 11 and 12 and diverse potencies, and the products were characterized by TEM, XRD, DLS, and N2 adsorption-desorption isotherms. The materials were similar at the diverse pH values and potencies. XRD confirms the crystallinity of the CeO2 material with a fluorite-like structure. They are composed of particles around 40 nm that aggregate as structures of around 100 nm. The procedure was successfully adapted to flow synthesis, obtaining materials with structure and properties equivalent to batch synthesis. The batch and flow materials offer peroxidase properties, opening the door for their use as ROS scavengers.

Iron-Doped Bimodal Mesoporous Silica Nanomaterials as Sorbents for Solid-Phase Extraction of Perfluoroalkyl Substances in Environmental Water Samples.

In this work, sorbets based on UVM-7 mesoporous silica doped with Fe were synthesized and applied to solid-phase extraction of perfluoroalkyl substances from environmental water samples. These emerging pollutants were then determined by liquid chromatography coupled with a mass spectrometry detector. Thus, Fe-UVM-7 mesoporous silica materials with different contents of iron, as well as different pore sizes (by using alkyltrimethilamonium bromide surfactants with different organic tail lengths) were synthesized, and their structure was confirmed for the first time by transmission electron microscopy, nitrogen adsorption-desorption, X-ray diffraction, and Raman spectroscopy. After comparison, Fe50-UVM-7-C12 was selected as the best material for analyte retention, and several extraction parameters were optimized regarding the loading and elution step. Once the method was developed and applied to real matrices, extraction efficiencies in the range of 61-110% were obtained for analytes with C8-C14 chain length, both perfluoroalkyl carboxylates, and perfluoroalkyl sulfonates. Likewise, limits of detection in the range of 3.0-8.1 ng L-1 were obtained for all target analytes. In the analysis of real well-water samples, no target compounds were detected. Spiked samples were analyzed in comparison to Oasis WAX cartridges, and statistically comparable results were achieved.

Mesoporous silica sorbent with gold nanoparticles for solid-phase extraction of organochlorine pesticides in water samples.

In this work, a novel sorbent, based on UVM-7 mesoporous silica doped with Au, has been proposed for organochlorine pesticides extraction. Cartridges containing this material have been applied to the preconcentration of 20 pesticides from water samples, through a solid-phase extraction (SPE) protocol, with their later determination by gas chromatography with an electron capture detector. First, UVM-7 materials were properly characterized by X-ray diffraction, N2 adsorption-desorption, electron microscopy techniques, and UV-Vis spectroscopy, thus confirming their structure and Au incorporation. After optimization of main extraction parameters, recoveries in the range of 80-110% were obtained for most of the analytes, with enrichment factors comprised between 275 and 430. The obtained sensitivity was comparable with other reported methods, with limits of quantification in the range of 0.3-20 ng L-1, thus allowing the determination of these compounds according to European legislation. The developed method has been successfully applied to the analysis of real spiked samples in comparison with a reference method, thus being this sorbent an alternative for organochlorine pesticide enrichment, through a simple, reusable, cheap, and environmentally friendly SPE procedure.

Assessment of migrating endocrine-disrupting chemicals in bottled acidic juice using type UVM-7 mesoporous silica modified with cyclodextrin.

An innovative material based in type UVM-7 mesoporous silica containing analyte-accessible cyclodextrin units is described and assessed as a selectivity-enhancing sorbent for extracting endocrine-disrupting chemicals from bottled apple juice to subsequently quantify them. The synthesis procedure has been carried out using both ß- and γ-cyclodextrin for their later comparison. Then, a complete analytical method for the isolation and determination of the above analytes has been validated. Following the optimized procedure, recoveries between 94% and 100% have been achieved and good repeatability is obtained with deviations under 6.8% for intra-day and inter-day experiments. The detection limits of the method have been established in the ng L-1 level, which demonstrates the ability to quantify the trace concentrations established by sanitary restrictions. A low matrix effect is found when working with real samples. To end, a comparison with an alternative extraction method using C18 extraction cartridges has been carried out and the results obtained with both procedures are comparable.

Chromogenic Chemodosimeter Based on Capped Silica Particles to Detect Spermine and Spermidine.

A new hybrid organic-inorganic material for sensing spermine (Spm) and spermidine (Spd) has been prepared and characterized. The material is based on MCM-41 particles functionalized with an N-hydroxysuccinimide derivative and loaded with Rhodamine 6G. The cargo is kept inside the porous material due to the formation of a double layer of organic matter. The inner layer is covalently bound to the silica particles, while the external layer is formed through hydrogen and hydrophobic interactions. The limits of detection determined by fluorimetric titration are 27 µM and 45 µM for Spm and Spd, respectively. The sensor remains silent in the presence of other biologically important amines and is able to detect Spm and Spd in both aqueous solution and cells.

In situ growth of metal-organic framework HKUST-1 in an organic polymer as sorbent for nitrated and oxygenated polycyclic aromatic hydrocarbon in environmental water samples prior to quantitation by HPLC-UV.

An in situ preparation of metal-organic framework (HKUST-1) on the surface of an organic polymer is reported. The hybrid material was evaluated as sorbent for solid-phase extraction (SPE) of oxygenated and nitrated polycyclic aromatic hydrocarbons (PAHs). The growth of HKUST-1 on MAA-based polymer was accomplished using a layer-by-layer assembly strategy. The HKUST-1-polymer was characterized using powder X-ray diffraction and scanning electron microscopy to demonstrate the incorporation of MOF crystals onto the polymer surface. The MOF (nano)crystals were characterized using high-resolution transmission electron microscopy and high-angle annular-dark-field scanning transmission electron microscopy. The water-stable MOF-polymer was evaluated as SPE sorbent, and several variables that can influence the extraction recoveries of PAH derivatives were investigated. Under the selected conditions, the detection limits varied between 4 and 21 ng·L-1, and the precision (relative standard deviation) was below 12%. The recovery values for spiked solutions ranged from 95 to 104%, and the enrichment factor achieved was close to 1000-fold using a high sample volume (100 mL) and very low desorption volume (100 µL). The SPE enrichment combined with HPLC and DAD detector was successfully applied to the extraction and determination of polycyclic hydrocarbons in environmental water samples. Graphical abstract A layer-by-layer synthesis of HKUST-1 onto polymer surface was performed and applied to isolation of PAH derivatives in environmental water samples.

Comparison of silica-based materials for organophosphorus pesticides sampling and occupational risk assessment.

A novel air sampler has been designed containing a sorbent based on UVM-7 mesoporous silica doped with Ti. The sorbent has been applied for the determination of organophosphorus pesticides in occupational air, followed by gas chromatography with mass spectrometry detection. Thus, several silica materials with different structures (mesoporous UVM-7 and microporous xerogels) were synthesized, and modified with the addition of Ti and Fe. The structure of these materials was proved by transmission electronic microscopy, energy-dispersive X-ray, X-ray diffraction, nitrogen adsorption-desorption and UV-Vis and Raman spectroscopy. The potential of these materials for the retention of pesticides was evaluated and Ti25-UVM-7 was selected as the best solid phase for analyte sorption. Then, several sampling parameters were optimized and analytical features such as breakthrough volume were determined. Using the designed samplers, quantitative retentions were achieved with recoveries in the range 93-107% for all analytes except for diazinon (82%). RSD values below 13% were obtained. Likewise, the sensitivity of the method was studied, and limits of quantification below 0.5 µg m-3 were obtained for all pesticides. The reusability of the material was also proved. The developed procedure has been applied to the air sampling and occupational risk assessment, during and after methyl-chlorpyrifos application in orange plantations. High concentrations and exposure rates above the limit value for ensure safe work conditions were obtained. At the same time, the air was sampled with XAD-2 samplers as a reference method, and results obtained with both devices were statistically comparable.

Extraction of aflatoxins by using mesoporous silica (type UVM-7), and their quantitation by HPLC-MS.

A solid-phase extraction procedure has been developed by using a sorbent derived from UVM-7 mesoporous silica. The sorbent was applied to the extraction of aflatoxins B1, B2, G1 and G2 from tea samples followed by HPLC with mass spectrometric detection. The sorbent was characterized by transmission electron microscopy, nuclear magnetic resonance, X-ray diffraction and nitrogen adsorption-desorption. UVM-7 is found to be the best solid phase. The amount of solid-phase, type and volume of eluent, pH value and ionic strength and breakthrough volume were optimized. Following the recommended procedure, recoveries between 96.0 and 98.2% were achieved, with RSD values of <5.1%, and the limits of detection are in the range from 0.14 to 0.7 µg·kg-1. The material is reusable. The method was applied to the analysis of real tea samples. A low matrix effect is found, and recoveries are >88%. The results were compared with those obtained by immunoaffinity columns as a reference method. Only low concentrations of aflatoxin G2 were found in some samples, and results obtained with both methods are shown to be statistically sound and comparable. Graphical abstractSchematic representation of a mesoporous silica sorbent (type UVM-7) for the extraction of aflatoxins (AF) from tea by solid-phase extraction (SPE), and its determination by liquid chromatography. The morphology of the material allows to retain the analytes very well.

Not always what closes best opens better: mesoporous nanoparticles capped with organic gates.

Four types of calcined MCM-41 silica nanoparticles, loaded with dyes and capped with different gating ensembles are prepared and characterized. N1 and N2 nanoparticles are loaded with rhodamine 6G and capped with bulky poly(ethylene glycol) derivatives bearing ester groups (1 and 2). N3-N4 nanoparticles are loaded with sulforhodamine B and capped with self-immolative derivatives bearing ester moieties. In the absence of esterase enzyme negligible cargo release from N1, N3 and N4 nanoparticles is observed whereas a remarkable release for N2 is obtained most likely due to the formation of an irregular coating on the outer surface of the nanoparticles. In contrast, a marked delivery is found in N1, N3, and N4 in the presence of esterase enzyme. The delivery rate is related to the hydrophilic/hydrophobic character of the coating shell. The use of hydrophilic poly(ethylene glycol) derivatives as gating ensembles on N1 and N2 enables an easy access of esterase to the ester moieties with subsequent fast cargo release. On the other hand, the presence of a hydrophobic monolayer on N3 and N4 partially hinders esterase enzyme access to the ester groups and the rate of cargo release was decreased.

Layered-Expanded Mesostructured Silicas: Generalized Synthesis and Functionalization.

Mesostructured layered silicas have been prepared through a surfactant-assisted procedure using neutral alkylamines as templates and starting from atrane complexes as hydrolytic inorganic precursors. By adjusting the synthetic parameters, this kinetically controlled reproducible one-pot method allows for obtaining both pure and functionalized (inorganic or organically) lamellar silica frameworks. These are easily deconstructed and built up again, which provides a simple way for expanding the interlamellar space. The materials present high dispersibility, which results in stable colloidal suspensions.

Mesoporous silica microparticles gated with a bulky azo derivative for the controlled release of dyes/drugs in colon.

Mesoporous silica microparticles were prepared, loaded with the dye safranin O (M-Saf) or with the drug budesonide (M-Bud) and capped by the grafting of a bulky azo derivative. Cargo release from M-Saf at different pH values (mimicking those found in the gastrointestinal tract) in the absence or presence of sodium dithionite (a reducing agent mimicking azoreductase enzyme present in the colon) was tested. Negligible safranin O release was observed at pH 6.8 and 4.5, whereas a moderate delivery at pH 1.2 was noted and attributed to the hydrolysis of the urea bond that linked the azo derivative onto the external surface of the inorganic scaffold. Moreover, a marked release was observed when sodium dithionite was present and was ascribed to the rupture of the azo bond in the molecular gate. Budesonide release from M-Bud in the presence of sodium dithionite was also assessed by ultraviolet-visible spectroscopy and high performance liquid chromatography measurements. In addition, preliminary in vivo experiments with M-Saf carried out in mice indicated that the chemical integrity of the microparticles remained unaltered in the stomach and the small intestine, and safranin O seemed to be released in the colon.

Study of silica-structured materials as sorbents for organophosphorus pesticides determination in environmental water samples.

A novel sorbent based on a UVM-7 mesoporous silica doped with Ti has been synthesized and used for solid-phase extraction of several organophosphorus pesticides in environmental water samples followed by gas chromatography coupled to a nitrogen-phosphorus selective detector. Thus, mesoporous silica materials doped with Ti and Fe as well as immobilized cyclodextrin silica-based supports were prepared and morphologically characterized by several techniques such as transmission electronic microscopy, nitrogen adsorption-desorption and X-ray diffraction. These sorbents were comparatively evaluated, and Ti25-UVM-7 material was selected as the best solid phase. After optimization of extraction parameters such as amount of solid-phase, type and volume of eluent, pH and ionic strength and breakthrough volume, recoveries between 81% and 104.5% were achieved, with RSD values below 7.8% and 12% for intra-day and inter-day repeatability respectively. Moreover, limits of quantification in the range 0.5-4.4 µg L-1 were achieved for all target compounds using mass spectrometry detector. In addition, the developed method was applied for analysis of real water samples and it was validated with commercial C18 cartridges. Matrix effect was demonstrated in complex environmental matrices and the good reusability of synthesized material was also proved.