Polymer Monolith Research Articles

A promising sensing platform for explosive markers: Zeolite-like metal-organic framework based monolithic composite as a case study

Preconcentration for on-site detection or subsequent determination is a promising technique for selective sensing explosive markers at low concentrations. Here, we report divinylbenzene monolithic polymer in its blank form (neat-DVB) and as a composite incorporated with sodalite topology zeolite-like metal-organic frameworks (3-ZMOF@DVB), as a sensitive, selective, and cost-effective porous preconcentrator for aliphatic nitroalkanes in the vapor phase as explosive markers at infinite dilution. The developed materials were fabricated as 18 cm gas chromatography (GC) monolithic capillary columns to study their separation performance of nitroalkane mixture and the subsequent physicochemical study of adsorption using the inverse gas chromatography (IGC) technique. A strong preconcentration effect was indicated by a specific retention volume adsorption/desorption ratio equal to 3 for nitromethane on the neat-DVB monolith host-guest interaction, and a 14% higher ratio was observed using the 3-ZMOF@DVB monolithic composite despite the low percentage of 0.7 wt.% of sod-ZMOF added. Furthermore, Incorporating ZMOF resulted in a higher percentage of micropores, increasing the degree of freedom more than bringing stronger adsorption and entropic-driven interaction more than enthalpic. The specific free energy of adsorption (ΔGS) values increased for polar probes and nitroalkanes, denoting that adding ZMOFs earned the DVB monolithic matrix a more specific character. Afterward, Lewis acid-base properties were calculated, estimating the electron acceptor (KA) and electron donor (KB) constants. The neat-DVB was found to have a Lewis basic character with KB/KA = 7.71, and the 3-ZMOF@DVB had a less Lewis basic character with KB/KA = 3.82. An increased electron-accepting nature can be directly related to incorporating sod-ZMOF into the DVB monolithic matrix. This work considers the initial step in presenting a portable explosives detector or preconcentrating explosive markers trace prior to more sophisticated analysis. Additionally, the IGC technique allows for understanding the factors that led to the superior adsorption of nitroalkanes for the developed materials.

Diethylene glycolamine-assisted rapid synthesis of mechanically robust pyrogallol-based carbon monoliths for CO2 capture and separation

Carbon monoliths have the advantages of good heat resistance and no need for molding during use. However, in practical applications, due to its low strength, it often suffers from wear and breakage during multiple adsorption-desorption cycles, which is not conducive to CO2 adsorption. Pyrogallol and formaldehyde-based polymers were used as carbon precursors, triblock copolymer Pluronic F127 was used as a structural directing agent, and diethylene glycolamine (DGA) as both the polymerization crosslinking agent and structural assembly promoter. In the presence of DGA, the solution can quickly gel within 15–20 min at 90 °C. No catalyst required, no environmental pollution, low cost, and mild reaction. Hydrogen bond interaction and poly(benzoxazine-co-resol) self-assembly synthesized homogeneous and crack-free polymer monoliths. A sturdy framework of carbon monoliths was obtained by adjusting the content of DGA and carbonization temperature. The kind of carbon monolith not only has a fully interconnected mesoporous structure and maintains good shape even after being magnified three times. The tight network skeleton enables it to have good mechanical strength and withstand a pressure of 8.1 MPa, which is 41 times greater than that of nano-casting and soft template carbon monoliths (0.19 and 0.2 MPa). The presence of nitrogen-containing groups and pore structures gives it good CO2 capture ability (0.9–2.8 mmol/g, 1 bar, 298 K), superior to the regular mesoporous carbon prepared by soft and hard template methods (1.5 and 1.7 mmol/g). Meanwhile, it exhibits high selectivity for capturing CO2 over N2 from a 15% (v%) CO2/N2 mixture. They undergo a facile CO2 release in an argon stream at 25 °C, indicating a good regeneration capacity. After five testing cycles, the carbon monolith still maintained good adsorption and separation performance, with adsorption capacity maintained at 98–100% of the initial adsorption capacity.

Sponge-nested polymer monoliths: Versatile materials for the solid-phase extraction of bisphenols.

Polymer monoliths are promising materials for sample preparation due to their high porosity, pH stability, and simple preparation. The use of melamine formaldehyde foams has been reported as an effective support to prepare highly robust silica and polymer monoliths. Herein, divinylbenzene monoliths based on a 50:50 (%, w/w) crosslinker/porogen ratio have been nested within a melamine-formaldehyde sponge, resulting in monoliths with a surface area higher than 400 m2 /g. The extraction performance of these monoliths was evaluated for the extraction of endocrine-disrupting bisphenols from aqueous solutions. We evaluated for the first time the versatility of sponge-nested polymer monoliths by comparing three different extraction modes (vortex mixing, magnetic stirring, and orbital shaking). Vortex mixing showed a comparable recovery of bisphenols (39%-81%) in a shorter extraction time (30min, instead of 2h). In addition, the robustness of the sponge-nested polymer monoliths was demonstrated for the first time by reshaping a larger monolithic cube (0.125 cm3 ) into four smaller pieces (4×0.03125 cm3 ) leading to a 16%-21% increase in extraction efficiency. This effect was attributed to an increase in the effective contact area with the sample, obtaining a higher analyte extraction capacity.

Porous polymer monoliths with complementary retention mechanisms for online solid-phase extraction liquid chromatography to determine lysozyme in egg white

Porous polymer monoliths with complementary retention mechanisms for online solid-phase extraction liquid chromatography to determine lysozyme in egg white

Reprocessible Triketoenamine‐Based Vitrimers with Closed‐Loop Recyclability

AbstractDevelopment of thermosets that can be repeatedly recycled via both chemical route (closed‐loop) and thermo‐mechanical process is attractive and remains an imperative task. In this work, we reported a triketoenamine based dynamic covalent network derived from 2,4,6‐triformylphloroglucinol and secondary amines. The resulting triketoenamine based network does not have intramolecular hydrogen bonds, thus reducing its π‐electron delocalization, lowering the stability of the tautomer structure, and enabling its dynamic feature. By virtue of the highly reversible bond exchange, this novel dynamic covalent bond enables the easy construction of highly crosslinked and chemically reprocessable networks from commercially available monomers. The as‐made polymer monoliths exhibit high mechanical properties (tensile strength of 79.4 MPa and Young's modulus of 571.4 MPa) and can undergo a monomer‐network‐monomer (yields up to 90 %) recycling mediated by an aqueous solution, with the new‐generation polymer capable of restoring the material strength to its original state. In addition, owing to its dynamic nature, a catalyst‐free and low‐temperature reprogrammable covalent adaptable network (vitrimer) was achieved. The design concept reported herein can be applied to the development of other novel vitrimers with high repressibility and recyclability, and sheds light on future design of sustainable polymers with minimal environmental impact.

Reprocessible Triketoenamine-Based Vitrimers with Closed-Loop Recyclability.

Development of thermosets that can be repeatedly recycled via both chemical route (closed-loop) and thermo-mechanical process is attractive and remains an imperative task. In this work, we reported a triketoenamine based dynamic covalent network derived from 2,4,6-triformylphloroglucinol and secondary amines. The resulting triketoenamine based network does not have intramolecular hydrogen bonds, thus reducing its π-electron delocalization, lowering the stability of the tautomer structure, and enabling its dynamic feature. By virtue of the highly reversible bond exchange, this novel dynamic covalent bond enables the easy construction of highly crosslinked and chemically reprocessable networks from commercially available monomers. The as-made polymer monoliths exhibit high mechanical properties (tensile strength of 79.4 MPa and Young's modulus of 571.4 MPa) and can undergo a monomer-network-monomer (yields up to 90 %) recycling mediated by an aqueous solution, with the new-generation polymer capable of restoring the material strength to its original state. In addition, owing to its dynamic nature, a catalyst-free and low-temperature reprogrammable covalent adaptable network (vitrimer) was achieved. The design concept reported herein can be applied to the development of other novel vitrimers with high repressibility and recyclability, and sheds light on future design of sustainable polymers with minimal environmental impact.

Chromoionophoric probe imbued porous polymer monolith as a Three-in-One Solid-state Naked-eye sensor for the selective sensing and recovery of Ultra-trace Lead, Mercury, and cadmium ions from Industrial/Environmental samples

This article presents a simple, low-cost, eco-benign, and portable naked-eye solid-state sensor for the selective and sensitive colorimetric detection and recovery of ultra-trace concentrations of Pb(II), Hg(II) and Cd(II) from environmental/industrial sources. For solid-state sensing, an indigenously synthesized polymer monolith, i.e., poly(VAn-EGDMA), in-built with high surface area and interlinked meso-/macro-pore network serves as a template for the voluminous and uniform decoration of chromoionophoric probe molecules, i.e., 2-((1H-benzo[d]imidazol-2-yl)diazenyl)-4-methoxyphenol (IDMP) onto the monolith perforations via. direct immobilization technique. The structural and surface topological properties of poly(VAn-EGDMA) monolith and probe-loaded polymer, i.e., IDMP@poly(VAn-EGDMA) sensor, are characterized through FE-SEM, HR-TEM, EDAX, XPS, p-XRD, SAED, FT-IR, BET and BJH analysis. The IDMP@poly(VAn-EGDMA) sensor forms a selective/stable metal complex through visually imposing enhanced charge transfer color transitions from its original canary yellow to dark denim blue, brownish green and lapis blue for varying concentrations of Pb(II), Hg(II) and Cd(II), respectively. The sensor reusability has been tested by decomplexing the IDMP-Mn+ complex with 0.1 M HCl and repeating the sensor performance consistently for eight consecutive cycles. The IDMP@poly(VAn-EGDMA) sensor exhibits pH-dependent ion-sensing, demonstrating a wide linear response range for Pb(II) (0–200 ppb), Hg(II) (0–150 ppb), and Cd(II) (0–150 ppb), with a detection limit of 0.44, 0.56, and 0.52 ppb, respectively. The three-in-one sensor exhibits pH-dependent sequential selectivity, chemical/thermal stability, and data reliability/reproducibility, thus proving effective for on-spot sensing of various sources of contaminated samples.

NH2-MIL-125 MOF integrated translucent mesoporous polymer monolith as dual-light responsive new-generation photocatalyst for the expeditious decontamination of perennial pharmaceuticals

We have synthesized a dual (UV-Visible) light-responsive heterocomposite photocatalyst of NH2-MIL-125 metal-organic framework (MOF) integrated on a translucent bimodal macro-/meso-porous polymer monolith for decontaminating pharmaceutical pollutants from aqueous medium. FE-SEM-EDAX, HR-TEM-SAED, p-XRD, BET/BJH, XPS, UV-Vis-DRS and PLS instrumental analysis were used to characterize the structural and morphological features of the synthesized MOF-poly(EGDMA) photocatalyst. The electron microscopic analysis confirmed the homogeneous dispersion of MOF across the well-defined porous network of polymer monolith, ensuring easy transport/interaction of pollutant molecules to the photoactive sites for faster dissipation. The hetero composite photocatalyst offered an intriguing band gap energy state that favored excellent dual light-responsive performance for fast decontamination of perennial pharmaceutical organic compounds. The superior photocatalytic performance was guaranteed by optimizing parameters such as solution pH, drug concentration, photocatalyst dosage, sensitizers, matrix tolerance, and light intensity. Under UV and visible light illumination, the maximum drug degradation was achieved using 50 mg of photocatalyst within 0.5 h in the pH range of 6.0–7.0. The drug degradation pathway was monitored using HRMS analysis, and the toxicity evaluation of the identified photoproducts was studied using the ECOSAR program. The MOF-poly(EGDMA) photocatalyst had excellent reusability and durability apart from its superior photocatalytic performance in clean-up applications.

Emulsion-Templated Monoliths Based on PIM-1 Monomers: Hierarchical Porosity and Dye Adsorption

Polymers of intrinsic microporosity (PIMs) are linear macromolecules from rigid, twisted monomers. PolyHIPEs, macroporous polymer monoliths templated within high internal phase emulsions (HIPEs), are of interest for adsorption applications. Here, PIM-like linear polymers synthesized within oil-in-oil HIPEs generated powders. However, the addition of a cross-linking comonomer enabled, and was essential for, the generation of monoliths with densities of ∼0.08 g/cm3 and uniform, highly interconnected, open-cell structures. Interestingly, the void diameters strongly depended upon the internal phase, ∼3 μm for silicone oil and ∼52 μm for hexadecane. The unexpectedly flexible polyHIPEs exhibited poor thermal stabilities compared to PIM-1, indicating significant macromolecular differences that originate in the emulsion-templated synthesis and in the cross-linking. While the polyHIPEs synthesized at 80 °C exhibited relatively high specific surface areas (∼154 m2/g), they were far smaller than that of PIM-1. The polyHIPEs adsorbed up to ∼28 mg/g of a cationic dye but only negligible amounts (∼1 mg/g) of an anionic dye. These results demonstrate that hierarchically porous monoliths that may be of interest for adsorption applications can be generated through PIM-like syntheses within HIPEs.

Facile fabrication of novel In2S3–BiOCl nanocomposite-supported porous polymer monolith as new generation visible-light-responsive photocatalyst for decontaminating persistent toxic pollutants

We report synthesizing a novel p-In2S3 and n-BiOCl heterojunction nanocomposite of varying β-In2S3 stoichiometry (10–50%) fabricated via. The hydrothermal and combustion methods. In2S3–BiOCl nanocomposites were homogeneously integrated onto a porous poly(ethylene glycol dimethacrylate) monolith to serve as a high-performance visible-light-responsive renewable photocatalyst decontaminating toxic organic pollutants such as Rhodamine B. The photocatalyst's structural and surface features were characterized using ppowder X-ray diffraction, X-ray photoelectron spectrometer, high-resolution transmission electron microscopy–selected area electron diffraction, field-emission scanning electron microscopy-energy-dispersive X-ray spectral, UV–Vis-diffuse reflectance spectral, photoluminescence spectral, Fourier transforms infrared, electrochemical impedance spectroscopy, and Brunauer–Emmett–Teller/Barrett-Joyner-Halenda (BJH) analysis. Using 20 wt% of In2S3 composition in the In2S3–BiOCl nanocomposite facilitated better electron–hole pair separation with excellent visible light responsive photocatalytic activity, confirmed through electrochemical impedance spectroscopy, photoluminescence spectral and bandgap measurements. The Brunauer–Emmett–Teller/BJH analysis revealed that the In2S3–BiOCl nanocomposite-loaded poly(ethylene glycol dimethacrylate) monolith had high surface area and pore dimensions, with voluminous photoactive sites. The role of analytical parameters such as pH, nanocomposite ratio, photocatalyst dosage, dye concentration, photosensitizers/oxidizers, and light intensity were studied/optimized. Under the optimized conditions of pH 2.0, 100 mg photocatalyst dosage, 30 ppm dye concentration, 1.0 mM KBrO3, and 300 W/cm2 visible light intensity, the monolithic photocatalyst showed a dissipation efficiency of ≥98.6% for Rhodamine B in ≤0.3 h. The renewable photocatalyst can be reused for six cycles without loss in efficiency/performance and proved promising in efficiently decontaminating persistent organic pollutants at an affordable cost and time.

Development of biomimetic hexapeptide functionalized monolithic material for capillary microextraction of microcystins in environmental waters

In this work, a histidine-tagged hexapeptide functionalized monolithic material is described for the efficient capillary microextraction (CME) of microcystins (MCs) from environment waters. 1-Vinylimidazole (VIM) monomer was utilized to synthesize the matrix polymer monolith by the copolymerization with divinylbenzene (DVB) crosslinker in the presence of radical initiator azobisisobutyronitrile (AIBN). The affinity sorbent was then prepared by a metal ion chelation-based multi-step approach, in which the histidine tag peptide Trp-His-Trp-Leu-Gln-Trp (WHWLQW) was functionalized on a Cu2+ modified polymer monolith via a chelation reaction between the imidazole group of histidine and Cu2+. The resultant WHWLQW functionalized monolithic material had high affinity, hierarchical porosity and good mechanical stability. Especially, it exhibited favorable enrichment capacity for MCs compared to other affinity materials as previously reported. With the optimized CME protocol, MCs at ultra-trace level can be analyzed by CME coupled to high performance liquid chromatography-mass spectrometry (HPLC-MS) in different aqueous environmental matrices. The average recoveries were ranged from 89.3% to 104.5% with relative standard deviations (RSD%) of 2.1–8.4, demonstrating high extraction efficiency and repeatability. The limits of detection (LODs) of MCs were determined to be 0.28–0.45 ng L-1. This novel biomimetic sorbent shows promising potential for the enrichment of ultra-trace pollutants in environment waters.

Pore Structure Tuning of Poly-EGDMA Biomedical Material by Varying the O-Quinone Photoinitiator.

Porous polymer monoliths with thicknesses of 2 and 4 mm were obtained via polymerization of ethylene glycol dimethacrylate (EGDMA) under the influence visible-light irradiation in the presence of a 70 wt% 1-butanol porogenic agent and o-quinone photoinitiators. The o-quinones used were: 3,5-di-tret-butyl-benzoquinone-1,2 (35Q), 3,6-di-tret-butyl-benzoquinone-1,2 (36Q), camphorquinone (CQ), and 9,10-phenanthrenequinone (PQ). Porous monoliths were also synthesized from the same mixture but using 2,2'-azo-bis(iso-butyronitrile) (AIBN) at 100 °C instead o-quinones. According to the results of scanning electron microscopy, all the resulting samples were conglomerates of spherical, polymeric particles with pores between them. Use of mercury porometry showed that the interconnected pore systems of all the polymers were open. The average pore size, Dmod, in such polymers strongly depended on both the nature of the initiator and the method of initiation of polymerization. For polymers obtained in the presence of AIBN, the Dmod value was as low as 0.8 μm. For polymers obtained via photoinitiation in the presence of 36Q, 35Q, CQ, and PQ, the Dmod values were significantly greater, i.e., 9.9, 6.4, 3.6, and 3.7 μm, respectively. The compressive strength and Young's modulus of the porous monoliths increased symbatically in the series PQ < CQ < 36Q < 35Q < AIBN with decreasing proportions of large pores (over 12 μm) in their polymer structures. The photopolymerization rate of the EGDMA and 1-butanol, 30:70 wt% mixture was maximal for PQ and minimal for 35Q. All polymers tested were non-cytotoxic. Based on the data from MTT testing, it can be noted that the polymers obtained via photoinitiation were characterized by their positive effect on the proliferative activity of human dermal fibroblasts. This makes them promising osteoplastic materials for clinical trials.

Photoactive aurivillius oxide integrated porous polymer monoliths as renewable visible light catalyst for decontaminating persistent organic pollutants

Photoactive aurivillius oxide integrated porous polymer monoliths as renewable visible light catalyst for decontaminating persistent organic pollutants

Neglected Applications of Monolithic Structures: The Beginnings of Planar Chromatography with Mass Spectrometric Detection

Thin layer chromatography (TLC) has been first reported by N. A. Izmailov and M. S. Schreiber in the late 1930s. The liquid mobile phase usually moves in pores of a layer supported by a rigid plate placed vertically in a simple container, e.g., a beaker. The flow is driven by capillary forces in the pores only and no sophisticated instrumentation is required. The individual components of the mixture are separated based on differences in their affinity for the solid stationary and the liquid mobile phases. The typical format of the stationary phase represents a thin layer coated on a glass, aluminium, or plastic plate. The porous sorbents can be silicon dioxide (silica), aluminium oxide (alumina), and cellulose, held together, e.g., with gypsum. The main advantages of TLC are the ease of carrying out the separations, which can also take place in parallel lines on the same plate, simple equipment, stationary phase for single use, static detection, and the possibility of archiving the separation result in a dried layer. However, the typical 100–250 μm thick layers are not well suited for combination of TLC with mass spectrometry (MS). This has led to the commercialization of ultrathin 10 μm thick monolithic silica layers. Unfortunately, their production was soon discontinued. Alternative solutions to that problem originated from the academic environment. In one approach, the layers were formed from nanofibers prepared by electrospinning. Alternatively, the layers were porous monolithic polymers produced by polymerization in situ and a variety of separations of both small and large molecules was demonstrated. The use of MS detection then enabled determination of molecular mass of the compounds in the separated spots. Although preparation of the thin monolithic layers originally appeared straightforward, some unexpected problems had to be solved. This review details issues related to the history of the monolithic TLC and presents approaches leading to well behaving layers suitable for the desired separations.

Titanium particles incorporated polymer monolith microcolumn for phosphoprotein enrichment from biological samples

In proteomic studies, selective enrichment of target phosphoproteins from biological samples is of importance. Of various enrichment methods, affinity chromatography is widely preferred method. Development of micro-affinity columns with simple strategies are in constant demand. Here in this report, for the first time, we have embedded TiO2 particles within the monolith structure in a single step. Fourier transform infrared spectroscopy and scanning electron microscope analysis has confirmed the successful incorporation of TiO2 particles within the polymer monolith. Incorporation of 3-(trimethoxy silyl) propyl methacrylate within the poly(hydroxyethyl methacrylate) based monolith composition has enhanced its rigidity and one fold phosphoprotein (α-casein) adsorption capacity. Presence of only 66.6 µg of TiO2 particles within the monolith has displayed a four-fold higher affinity to α-casein over the non-phosphoprotein i.e. bovine serum albumin. Under optimized conditions (TiO2 particle and acrylate silane), the affinity monolith has a maximum adsorption capacity of ∼ 72 mg per gram monolith. Translation of TiO2 particles-monolith into a microcolumn of 3 cm long and 19 µL volume was successful. α-casein was selectively separated from an artificial protein mixture of α-casein and BSA, α-casein spiked human plasma, and cow milk within 7 min

Incorporation of metal-organic framework MOFs-5 into the polymer monolith via the surface covalent immobilization method for enhanced capillary liquid chromatographic separation of benzene homologues

In this study, metal organic framework material MOFs-5 was immobilized covalently on the surface of polymer monolith to improve the separation efficiency of small molecular compounds in the mode of capillary liquid chromatography (cLC) firstly. Scanning electron microscopy, fourier transform infrared spectroscopy and flow-through property test were applied to characterize the novel [email protected] monolith, confirming that MOFs-5 was effectively immobilized on the surface of polymer monolith via covalent reactions. More importantly, Benzene homologues (benzene and phenol) which could be separated by the commercialized C18 packed chromatographic column have been well separated via the [email protected] monolith. By contrast, there wasn't any separation between benzene and phenol via the original polymer monolith. Moreover, the relative standard deviation was less than 2.2 % for run-to-run. These results showed that the [email protected] monolith is a kind of potential commercialized material for small molecular compound separation in the mode of cLC.

Porogen Concentration Effect on the Pore Structure and Properties Evolution of Polymer Monolith Based on Oligocarbonate Dimethacrylate OCM-2.

Porous polymer monolith materials of 2-mm thickness were obtained by visible light-induced radical polymerization of oligocarbonate dimethacrylate (OCM-2) in the presence of 1-butanol (10 to 70 wt %) as a porogenic additive. The pore characteristics and morphology of polymers were studied by mercury intrusion porosimetry and scanning electron microscopy. Monolithic polymers with both open and closed pores up to 100 nm in size are formed when the alcohol content in the initial composition is up to 20 wt %. The pore structure in such materials is a system of holes in the bulk of the polymer (hole-type pores). Open interconnected pores with a specific volume up to 2.22 cm3/g and modal pore size up to 10 microns are formed in the volume of the polymer with 1-butanol content of more than 30 wt %. Such porous monoliths are a structure of covalently bonded polymer globules (interparticle-type pores). The free space between the globules represents a system of open interconnected pores. In the transition region of 1-butanol concentrations (from 20 to 30 wt %), areas with both structures and intermediate frameworks, as well as honeycomb structures of polymer globules connected by bridges, are fixed on the polymer surface. It was found that the transition from one type of pore system to another is accompanied by a sharp change in the strength characteristics of the polymer. Approximation of experimental data using the sigmoid function made it possible to determine the concentration of the porogenic agent in the vicinity of which the percolation threshold is observed.

Structurally engineered ion-receptor probe immobilized porous polymer platform as reusable solid-state chromogenic sensor for the ultra-trace sensing and recovery of mercury ions

This study reports an efficacious solid-state optical sensor through the synergistic coalescences of an original chromoionophoric probe and a structurally engineered porous polymer monolith for the selective and sensitive colorimetric spotting of ultra-trace toxic mercury ions. The unique properties of the bimodal macro-/meso-pore structured polymer, i.e., poly(AAm-co-EGDMA) monolith, offer voluminous and uniform anchoring of probe molecules, i.e., (Z)-N-phenyl-2-(quinoline-4-yl-methylene)hydrazine-1-carbothioamide (PQMHC). The structure/surface features of the sensory system, i.e., surface area, pore dimensions, monolith framework, elemental mapping, and phase composition, were examined by p-XRD, XPS, FT-IR, HR-TEM-SAED, FE-SEM-EDAX, and BET/BJH analysis. The sensor's ion-capturing ability was established through naked eye color transition and UV-Vis-DRS response. The sensor exhibits a strong binding affinity for Hg2+, with a linear signal response in the concentration range of 0–200 μg/L (r2 >0.999), with a detection limit of 0.33 μg/L. The analytical parameters were optimized to facilitate pH-dependent visual sensing of ultra-trace Hg2+ in ≤ 30 s. The sensor exhibits high chemical/physical stability characteristics, with reliable data reproducibility (RSD ≤1.94 %), while testing with natural/synthetic water and cigarette samples. The proposed work offers a cost-effective and reusable naked-eye sensory system for the selective sensing of ultra-trace Hg2+, with potential prospects of commercialization considering their simplicity, viability, and reliability.

In-Depth Performance Analysis and Comparison of Monolithic and Particulate Zwitterionic Hydrophilic Interaction Liquid Chromatography Polymer Columns.

The kinetic performance of different zwitterionic hydrophilic interaction liquid chromatography polymer columns is evaluated and compared in-depth. For this purpose, two lab-made monolithic columns, synthesized with different crosslinkers, and a commercial particle packed column are considered. It is found that performance evaluation techniques, such as comparing plate height curves or fitted A-, B- and C-terms, obtained by fitting experimental plate height data to a plate height model, are complicated by the determination of a reliable characteristic length. This is due to the very different morphology of these column types, and the heterogeneity of the monolithic columns. The occurrence of a convective flow through the packed particle column further complicates the interpretation of the obtained fitting parameters, as part of the C-term is wrongfully attributed to the A-term. Therefore, the use of the kinetic plot method is suggested for the comparative evaluation of these columns, as kinetic plots do not require the determination of a characteristic length, nor rely on any fitting parameters. With the kinetic plot method, it is demonstrated that the lab-made monolithic columns outperform the packed particle column for plate counts between 10,000 and 800,000. This is attributed to the higher column efficiency of these columns, due to their small domain and skeleton sizes, and their high permeability, resulting from their high external porosity and the occasional occurrence of preferential flow paths.

Renewable terpene-based highly porous polymer monoliths for the effective removal of persistent pharmaceuticals of tetracycline and ibuprofen

Adsorptive removal of residual pharmaceuticals from wastewater has become an important issue from an environmental aspect. Macroporous polymer-based monoliths are being used as efficient adsorbents to remove such toxic materials. Regarding this, the ease of preparation, sustainability and low production cost are the most demanded properties from polymer-based monoliths. This work describes the synthesis of the first sustainable β-myrcene (My) and d-limonene (Lim) derived adsorbents by free radical copolymerization crosslinking in water-in-oil (w/o) high internal phase emulsions (HIPEs). To demonstrate the influence of purification and drying steps on the pore morphology of the monoliths, the samples were either vacuum dried (PMLE-E) or freeze-dried (PMLE-L). Characterization tests indicated that the specific surface area of the PMLE-E monolith (64.71 m2/g) was much higher than that of PMLE-L monolith (19.38 m2/g), which was attributed to the abundant pore throats. The adsorption efficiencies of the monoliths were investigated towards removal of tetracycline (TC) and ibuprofen (IBU) from aqueous solution. The effects of solution pH, contact time, and temperature on the adsorption were investigated and the experimental data fitted to isotherm, kinetic and thermodynamic models. The maximum TC and IBU adsorption capacities were found as 23.8 mg/g and 10.6 mg/g over PMLE-E adsorbent, respectively. The highest TC removal (95%) was achieved within 30 min by using PMLE-E monolith, which was ascribed to its more permeable porous structure as well as higher surface area, boosting diffusion rate of antibiotic molecules. In the reusability tests, the PMLE-E adsorbent exhibited higher performance than PMLE-L sample after eight adsorption-desorption cycles. The polymer monoliths also exhibited considerable adsorption efficiencies towards different kinds of dye molecules, demonstrating their effectiveness in the removal of water pollutants.