Porous Polymer Monoliths Research Articles

Effect of binary porogen mixtures on polymer monoliths prepared by gamma-radiation initiated polymerization

Gamma-radiation initiated polymerization is an easy-to-use and simple technique for the preparation of porous polymer monoliths widely used as active materials in separation columns. Herein, binary porogen mixtures of ethyl acetate/acetone/acetonitrile with methanol were used to synthesize diethylene glycol dimethacrylate monoliths with this technique. Systematic studies have been performed to determine the effect of the composition of the solvent mixture on the morphology and the reaction kinetics, including the growth mechanism and the growth rate. The irradiation dose-dependent conversion profiles showed that with binary solvents the polymerization is much faster than with the same compounds used as single solvents. Depending on the type and the composition of the solvent one-, two- and three-dimensional, and fractal growth mechanisms were identified.

Morphological Control and Mechanical Properties of Porous Phenolic Resins Derived from Poly(4‐Vinylphenol): Effects of Molecular Weight and Polydispersity of Prepolymer

Improvement of mechanical stability for porous polymer monoliths is one of the prime concerns as represented by the long‐standing research efforts on resorcinol‐formaldehyde (RF) aerogels. To this end, it is imperative not only to tailor mechanically robust porous morphology but also to design macromolecular structure of polymer scaffolds. Previously, we have developed porous RF gels showing a unique mechanical feature combining high mechanical strength and outstanding flexibility against uniaxial compression. Comparison of mechanical properties between the porous gels with varied morphologies has elucidated the influence of porous structure, whereas effects of macromolecular structure still remain elusive. Herein, we have fabricated a series of macroporous phenolic resins from three types of linear prepolymers with phenol pendant groups, poly(4‐vinylphenol) or poly(4‐hydroxystyrene), which differ in molecular‐weight properties, by the sol–gel process in conjunction with spinodal decomposition. The difference in gelation and phase separation behaviors observed for the discrete systems indicates the dissimilar cross‐linked networks developed in the respective gels, which consequently influence the mechanical strength and flexibility against uniaxial compression. This study also demonstrates the improvement of mechanical features by thermal treatment for the porous monoliths derived from the high‐molecular‐weight prepolymer with a view to the application in mechanical energy absorption.

Hybrid NiCo2O4-BiOCOOH heterostructure nanocomposite impregnated porous polymer monolith as high-performance visible light photocatalyst for the decontamination of antimicrobial pollutants

We report a first-of-its-kind preparation of a NiCo2O4-BiOCOOH heterostructure as visible light-responsive nanocomposites (NCs) for the fast decontamination of moxifloxacin drug molecules, with longer persistence and non-biodegradability nature that could promote gene-resistance bacteria in aqueous medium. Further, a reusable/recoverable photocatalyst is fabricated through the uniform decoration of NiCo2O4(15 %)-BiOCOOH(85 %), i.e., NB-15 NCs across a tailor-made poly(EGDMA) monolith (PEM) that serves as the host template for the photoactive NCs. The electron microscopy, optical spectroscopy, diffraction, and surface analysis techniques confirm the photocatalyst's superior structural morphology, surface topography, and porosity features that assist in high-performance photocatalysis. The inorganic-organic hybrid photocatalyst exhibits a narrow energy bandgap that promotes ample generation of reactive oxygen species upon visible light irradiation, as confirmed by the electrochemical and spectroscopic analysis. The BET/BJH plot for the photocatalyst reveals a large surface area of 345 m2/g, with voluminous pore distributions (2–80 nm), indicating the coexistence of mesopores-infused macroporous framework that offers better contact/equilibration of the pollutant molecules with the abundantly dispersed photoactive sites. The optimized parameters reveal ≥99.2 % drug dissipation in ≤0.33 h and drug mineralization in ≤2.0 h, using a mere 50 mg of photocatalyst irradiated with a 150 W/cm2 tungsten lamp. The synthesized photocatalyst has a simple/cost-saving procedure that can transform into scalable, cheaper, and eco-friendly products for the real-time monitoring of toxic pollutants. Besides, the photocatalyst exhibits excellent stability and reusability characteristics for efficiently decontaminating organic pollutants, thus highlighting an innovative approach for fabricating high-performance photocatalysts.

Influence of the Polymerization Parameters on the Porosity and Thermal Stability of Polymeric Monoliths.

Rigid porous polymeric monoliths are robust, highly efficient, versatile stationary phases. They offer simple preparation and convenient modification provided by a whole range of synthesis factors, e.g., starting monomers, cross-linkers, initiators, porogens, polymerization techniques, and temperature. The main aim of this study was to synthesize polymeric monoliths and determine the correlation between polymerization parameters and the porosity and thermal stability of the obtained materials. Polymeric monoliths were synthesized directly in HPLC columns using N-vinyl-2-pyrrolidone (NVP) and 4-vinylpiridine (4VP) as functional monomers, with trimethylolpropane trimethacrylate (TRIM) serving as the cross-linking monomer. During copolymerization a mixture of cyclohexanol/decane-1-ol was used as the pore-forming diluent. Polymerization was carried out at two different temperatures: 55 and 75 °C. As a result, monoliths with highly developed internal structure were synthesized. The value of their specific surface area was in the range of 92 m2/g to 598 m2/g, depending on the monomer composition and polymerization temperature. Thermal properties of the obtained materials were investigated by means of thermogravimetry (TG). Significant differences in thermal behavior were noticed between monoliths synthesized at 55 and 75 °C. Additionally, the poly(NVP-co-TRIM) monolith was successfully applied in GC analyses.

Molecular receptors integrated bimodal porous polymer scaffolds as portable solid-state optical ion-sensors and extractors for the selective capturing of ultra-trace toxic copper ions

BackgroundEnvironmental contamination by heavy metal ions has caused growing ecological and public health concerns. In this line, monitoring of copper toxicity gains importance due to its application in industrial, agricultural, domestic, medical and technological sectors. Although noteworthy breakthroughs were made, critical issues, such as portability, the need for well-trained personnel, costly/complex instrumentations, long response time, and the introduction of secondary contaminants, required attention. Hence, developing a low-cost, user-friendly, real-time, portable analytical platform for rapid and on-site analysis remained imperative. Solid-state colorimetric sensors have gained widespread popularity due to their low cost, ease of use, and brilliant sensitivity/selectivity. ResultsWe have successfully unfolded an ultra-portable azomethine-infused structurally interwoven polymer monolith as the solid-state chromatic sensor for the quantitative naked-eye detection of ultra-trace Cu2+ in industrial/environmental samples. For the sensor fabrication, non-hygroscopic conjugated Schiff-base receptors, namely N-(1E,2E)-3-(4-dimethylamino)phenyl)allylidene)-3-nitrobenzohydrazide (DPAN) and 2,3-bis(((1E,2E)-3-(4-dimethylamino)phenyl)allylidene)amino)malononitrile (DPAM) were synthesized in-house and voluminously immobilized onto a crack-free porous poly(4VP-co-EGDMA) monolith framework. The topological structure and functionalities of the porous polymer monolith and chromatic sensor materials were examined using various surface analytical and microscopic techniques. The excellent surface area and intriguing interlaced porosity features of the tailor-made polymer monolith facilitated the voluminous anchoring of the chromatic receptors for the selective/sensitive targeting of Cu2+. The DPAN and DPAM receptor-loaded poly(4VP-co-EGDMA) sensors exhibited a linear range of 0–150 μg/L, with the limit of detection of 0.11 and 0.13 μg/L for Cu2+, respectively. The sensors manifested Cu2+ specificity amidst concomitant matrix ions to highlight the relevance of the proposed solid-state sensor. SignificanceThe sensor materials offered a reliable approach for detecting and quantifying environmentally toxic and industrially pertinent Cu2+ from aqueous samples, with the prospect of large-scale production, owing to the sensor's integrated compact design that can be reused for repeated real-time surveillance. The sensor's ability to sense/trap traces of toxic Cu2+ can provide an early warning about the growing toxicity in a particular resource, thereby providing an opportunity to initiate remediation protocols for speedy decontamination.

3D Carbonaceous Foams Derived from High Internal Phase Emulsion for Energy Applications

AbstractIn recent years, there has been a notable increase in interest regarding monolithic porous polymers known as poly(High Internal Phase Emulsion) – poly(HIPE) – which are synthesized from high internal phase emulsions. This is due to their exceptional capability to produce three‐dimensional structures with substantial porosity. Nevertheless, the exploitation of this family of materials in energy‐driven applications is still limited, mainly because of their lack of conductivity. The exploration of conducting materials with 3D polymeric frameworks remains a promising avenue for research. In this context, pyrolysed poly(HIPE) seems to be the simplest and most cost‐effective strategy to directly transform a 3D polymer into a 3D conductive carbon foam, that is, carboHIPE. Currently, CarboHIPE and its derivatives are becoming alternatives to commercially available activated carbon/graphite or expensive graphene and carbon nanotube‐based materials. Accordingly, gaining insight into the formation of these materials is crucial to accelerate their use in commercial energy devices. This review aims to provide a comprehensive summary of various synthesis pathways utilized to modify the characteristics of CarboHIPEs, as well as the recent developments in their application as active components in energy‐based systems.

Structurally engineered probe infused porous polymer monolith as a solid-state visual sensing platform for Cd2+ ions

This work describes an effective optical on-site sensor strategy for quantifying Cd2+ in aqueous samples using a tailor-made physically modified probe-immobilized porous polymer monolithic sensor. The bimodal macro/mesoporous polymer, namely poly(2-(trifluoromethyl) acrylic acid-co-trimethylolpropane triacrylate) (poly(TFMAA-co-TMPTA)) matrix, was fabricated by simple bulk polymerization, and was uniformly encapsulated with a chromophoric ligand, namely (E)− 5-(quinoline-8-yl-diazenyl)quinoline-8-ol (QDQ) by a direct impregnation process. The designed monolithic template and the concocted sensor were characterized using FE-SEM, EDAX, HR-TEM, SAED, XPS, N2 adsorption isotherms, p-XRD, TGA and FT-IR. The optical sensor benefits from a uniformly interconnected mesostructured polymer template and showcased a superior sensing performance in selectively capturing the ultra-trace amounts of Cd2+. Furthermore, it displayed a dynamic optical property by enabling a distinct progressive visual color change from light orange to brick red due to the selective complexation of the QDQ probe with Cd2+. The solution pH, probe concentration, contact time, temperature, selectivity, and sensitivity were optimized to evaluate the best sensing performance, and the sensor showed a linear response range from 1.5–100 μg/L, with the lowest detection limit (LOD) of 0.53 μg/L. The theoretical calculations about the binding mechanism of QDQ probe molecules with Cd2+ were studied using density functional theory (DFT). The newly fabricated solid-state sensor affords a promising tool for detecting trace amounts of Cd2+ in real water and cigarette samples.

Mesoporous degradable chitosan-based monoliths: synthesis and applications toward water purification

A synthetic strategy is presented for the preparation of degradable chitosan based functional porous polymer monoliths with tunable surface area, which are capable to efficiently remove multiple pollutants from water.

Chromogenic probe adhered porous polymer monolith as real-time solid-state sensor for the detection of ultra-trace toxic mercury ions

The escalating predicament of water pollution has spurred the development of new chromogenic materials for the efficient detection/screening of toxic mercuric (Hg2+) ions. In this study, we report a simple and efficient detection stratagem by infusing a chromogenic ion-receptor (BTDA), i.e., 4-(benzothiazol-2-yl)-N, N-dimethylaniline onto a structurally intertwined meso-/macro-pore polymer template for the target-specific sensing of ultra-trace Hg2+. The structural/surface features of the monolithic polymer template, prepared from glycidyl methacrylate (GMA) monomer crosslinked with ethylene glycol dimethacrylate (EGDMA), facilitate voluminous infusion and uniform decoration of ion-receptor molecules across the continuous porous poly(GMA-co-EGDMA) framework, resulting in a solid-state colorimetric sensory system. The bimodal polymer network's intriguing surface and structural morphology of the chromogenic sensor material are interpreted using scanning/transmission electron microscopy, X-ray diffraction, photoelectron spectroscopy, energy dispersive X-ray spectrometry, optical spectroscopy, surface area, porosity and thermal analysis. The proposed Hg2+ sensor offers a linear response range of 1–150 μg/L, with a detection and quantification limit of 0.29 and 0.97 μg/L, respectively. The poly(GMA-co-EGDMA)-BTDA sensor exhibits a quick ion-sensing response (40 s) with distinct color transitions from pastel yellow to olive as a function of increasing Hg2+ concentration. The matrix tolerance studies for the proposed sensory system reveal high selectivity for Hg2+, with a recovery of ≥99.2% in on-site environmental samples. The sensor material exhibits excellent data reproducibility and reliability up to seven cycles of reusability.

Metal-organic framework and porous polymer monolith as ion-receptor carrier templates for the solid-state naked-eye sensing of ultra-trace Cr(III) from aqueous medium

We report on an effective onsite optical sensor strategy using probe-decorated porous polymer monolith (PPM) and aluminum-based metal-organic framework (MIL-53 (Al) MOF) as a reliable colorimetric sensor for the detection of ultra-trace levels of Cr3+. MOFs and PPMs have attracted considerable interest in environmental applications due to their high surface area, perpetual porosity, and tunable structural network. Here, Al-MOF and PPM materials were used as porous templates for the uniform infusion of a chromoionophoric probe, i.e., (Z)-1,2-diphenyl-2-((4-(E)-phenyldiazenyl)phenyl)imino)ethan-1-ol (DPPE), for the solid-state colorimetric recognition and capturing of Cr3+ from aqueous medium. The structural morphology and surface topography of the sensor materials have been characterized using the transmission/scanning electron microscopy, optical spectroscopy, X-ray/electron diffraction, elemental mapping, surface area/pore volume and thermal analysis to understand the surface properties and stability features of the long-range ordered porous framework. The sensor's superior structural and surface features tender faster ion diffusion to the anchored probe sites within 60 s. The sensor induces a selective ligand-to-metal charge transfer (LMCT) chelation with Cr3+, resulting in a sequence of color transition from pale orange to sepia-brown, with incremental levels of Cr3+. The significance of physicochemical factors, such as pH, probe content, sensor dose, kinetics, temperature, reusability, selectivity, sensitivity, and stability, has been optimized to maximize the ion-sensing performance. The sensors' reusability has been tested by replicating the ion-sensing performance up to eight cycles. The solid-state sensor exhibited a linear range of 1.0–200 ppb for Cr3+, with a detection limit of 0.44 and 0.53 ppb and a quantification limit of 1.39 and 2.22 ppb for DPPE-loaded PPM and Al-MOF sensors, respectively. The practical utility of the sensor materials with industrial/environmental water samples reveals excellent data reliability/reproducibility (recovery ≥99.1 %; RSD ≤2.5 %) for real-time monitoring.

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

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.

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.

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.

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.

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.

Porous-polymer monolith decorated with dithizone for greener visual and spectrophotometric sensing of Hg(II)

This paper describes a hydrophobic porous polymer monolith for visual and spectrophotometric determination of Hg(II). The monolith was synthesized in the coffins of 2.0 mm i.d. transparent polypropylene ink-pen tubes using stearyl methacrylate (SMA) as the functional monomer and ethylene glycol dimethacrylate (EDMA) as the crosslinker by fast UV-mediated polymerization. The poly(SMA-co-EDMA) monolith retained dithizone, an anchor for the Hg(II) and colorimetric reagent. Besides the monolith's fast preparation, the polypropylene transparency enabled the naked-eye visualization of all color changes occurring in the solid phase extraction steps (conditioning, loading, washing and elution). This feature also enabled the unprecedented use of a simple ruler for detection since the distance occupied by Hg(II) inside the column was linearly related to Hg(II) concentration. Loading the column with 12.0 mL of sample and elution with 1.0 mL of ethanol contributed to the green analytical chemistry and provided a detection limit of 7.9 µg L−1, which was enough to determine Hg(II) in certified estuarine sediment (ERM-CC580) and urine samples. A sample volume of 45 mL provides a detection limit of 0.59 μg L−1, allowing the detection of trace Hg(II) levels in the Billings reservoir waters, an anthropized water reservoir located in the São Paulo Metropolitan Area of São Paulo State (Brazil), thus attending the maximum concentration levels preconized by the United States Environmental Protection Agency (1.0 µg L−1) and World Health Organization (6.0 µg L−1). The proposed method is simple, cheap and can be easily implemented in field measurements for sample trials.