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Environmental contextReleases to the aquatic environment from radiological dispersal devices, accidents or leaking waste disposal sites require close monitoring for radionuclide identification. A novel in situ gamma spectrometer deployable on platforms in coastal waters can provide detailed radioisotopic, however, only after the radionuclides are pre-concentrated on efficient sorbents. Here, we report results of particle–water distribution coefficients, KD, on three novel MnO2 sorbents using a set of artificial and natural radionuclides in small batch experiments. AbstractAfter nuclear disasters, there is a need to monitor released radionuclides in aquatic systems. A novel in situ gamma spectrometer deployable on mobile and stationary platforms can detect individual radionuclides, provided concentrations are high enough. Owing to rapid dilution effects, efficient sorbents are needed for preconcentration of radionuclides. Here, we report results of particle–water distribution coefficients, KD, on three novel MnO2 sorbents mounted in high-capacity cartridges using a set of artificial (57Co, 106Ru, 125Sb, 133Ba, 137Cs) and natural (7Be, 210Pb, 233Pa, 234Th) radionuclides in small batch experiments. Compared with conventionally impregnated MnO2 sorbents, novel nanostructured MnO2 sorbents displayed superior sorption for some artificial radionuclides, displaying up to one order of magnitude greater KD values than traditionally impregnated MnO2. In particular, the log KD value of 210Pb was highest (4.48±0.23) compared with all values using the other MnO2 sorbents, whereas that of 233Pa was among the lowest (3.24±0.16). These results promise some improvements for capturing not only artificially produced radionuclides, but also naturally produced 7Be from seawater using nanostructured MnO2. We also show that colloidal forms of selected radionuclides are not captured by MnO2 phases. If they could be sorbed by another sorbent, KD values could be considerably higher for Th, Po and other radionuclides. Finally, our results might add further complexities to the discussion of the potential of Th/Pa fractionation by MnO2 phases in seawater.

We have developed a thiol-modified nanoporous silica material (SH-SAMMS) as an oral therapy for the prevention and treatment of heavy metal poisoning. SH-SAMMS has been reported to be highly efficient at capturing heavy metals in biological fluids and water. Herein, SH-SAMMS was examined for efficacy and safety in both in vitro and in vivo animal models for the oral detoxification of heavy metals. In simulated gastrointestinal fluids, SH-SAMMS had a very high affinity (Kd) for methyl mercury (MeHg(I)), inorganic mercury (Hg(II)), lead (Pb(II)), and cadmium (Cd(II)) and was superior to other SAMMS with carboxylic acid or phosphonic acid ligands or commercially available metal chelating sorbents. SH-SAMMS also effectively removed Hg from biologically digested fish tissue with no effect on most nutritional minerals found in fish. SH-SAMMS could hold Hg(II) and MeHg(I) tightly inside the nanosize pores, thus preventing bacteria from converting them to more absorbable forms. Rats fed a diet containing MeHg(I), Cd(II), and Pb(II) and SH-SAMMS for 2 weeks had blood Hg levels significantly lower than rats fed the metal-rich diet only. Upon cessation of the metal-rich diet, continued administration of SH-SAMMS for 2 weeks facilitated faster and more extensive clearance of Hg than in animals not continued on oral SH-SAMMS. Rats receiving SH-SAMMS also suffered less weight loss as a result of the metal exposure. Retention of Hg and Cd in major organs was lowest in rats fed with SH-SAMMS throughout the entire four weeks. The reduction of blood Pb by SH-SAMMS was significant. SH-SAMMS was safe to intestinal epithelium model (Caco-2) and common intestinal bacteria (Escherichia coli). Altogether, it has great potential as a new oral drug for the treatment of heavy metal poisoning. This new application is enabled by the installation of tailored interfacial chemistry upon nontoxic nanoporous materials.

Surface-functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS), has previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems, suggesting that they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials’ biocompatibility, and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e., blood, urine, etc.) Consequentially, thiol-functionalized SAMMS was further analyzed to assess the material’s performance under a number of different biologically relevant conditions (i.e., variable pH and ionic strength) to gauge any potentially negative effects resulting from interaction with the sorbent, such as cellular toxicity or the removal of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus nontoxic. The results show that organic ligand functionalized nanoporous silica could be a valuable material for a range of detoxification therapies and potentially other biomedical applications.

Mercury-free sensors for europium (Eu3+) assay based on the chemical modification of screen-printed carbon electrodes (SPCEs) with self-assembled salicylamide on mesoporous silica (Sal-SAMMS) have been developed. The preconcentration of Eu3+ at SAMMS-based sensors utilizes the binding affinity of the salicylamide and Eu3+, accomplished at open circuit potential without electrolyte and solution de-gassing. Optimal Eu detection was obtained after 3–5 min preconcentration in Eu solution (pH 2–6), electrolysis at −0.9 V for 60 s in a new medium (0.1–0.2 M NH4Cl, pH 3.5), followed by a square-wave voltammetric detection of Eu in the same electrolyte. Attributed to the strong covalent bonding of the functional groups on mesoporous silica and silane cross-linking, the SAMMS-modified SPCEs with a built-in 3-electrode system can be re-used for tens of measurements with minimal degradation, enabling the establishment of the calibration curve and lowering the costs. A linear calibration curve was found in the range of 75 to at least 500 ppb Eu3+ after 5 min preconcentration. The experimental detection limit was 10 ppb after 10 min preconcentration, which can be improved with increased preconcentration time. Reproducibility (% RSD) of 100 ppb Eu2+ was 10% for a single sensor and 10% for 5 sensors, which can be improved through the precision of sensor manufacturing, in which SAMMS modification can be made in-situ.

This study reports a new approach for developing a uranium electrochemical sensor that is mercury-free, solid-state, and has less chance for ligand depletion than existing sensors. A carbon-paste electrode modified with carbamoylphosphonic acid self-assembled monolayer on mesoporous silica was developed for uranium detection based on an adsorptive square-wave stripping votammetry technique. Voltammetric responses for uranium detection are reported as a function of pH, preconcentration time, and aqueous phase uranium concentration. The uranium detection limit is 25 ppb after 5 minutes preconcentration and improved to 1 ppb after 20 minutes preconcentration. The relative standard deviations are normally less than 5%.

This study reports a new approach for developing a uranium electrochemical sensor that is mercury‐free, solid‐state, and has less chance for ligand depletion than existing sensors. A carbon‐paste electrode modified with carbamoylphosphonic acid self‐assembled monolayer on mesoporous silica was developed for uranium detection based on an adsorptive square‐wave stripping votammetry technique. Voltammetric responses for uranium detection are reported as a function of pH, preconcentration time, and aqueous phase uranium concentration. The uranium detection limit is 25 ppb after 5 minutes preconcentration and improved to 1 ppb after 20 minutes preconcentration. The relative standard deviations are normally less than 5%.

Through the marriage of mesoporous ceramics with self-assembled monolayer chemistry, the genesis of a powerful new class of environmental sorbent materials has been realized. By coating the mesoporous ceramic backbone with a monolayer terminated with a lanthanide-selective ligand, it is possible to couple high lanthanide binding affinity with the high loading capacity (resulting from the extremely high surface area of the support). This lanthanide-selective ligand field is created by pairing a “hard” anionic Lewis base with a suitable synergistic ligand, in a favorable chelating geometry. Details of the synthesis, characterization, lanthanide binding studies, binding kinetics, competition experiments and sorbent regeneration studies are summarized.

Through the marriage of mesoporous ceramics with self-assembled monolayer chemistry, the genesis of a powerful new class of environmental sorbent materials has been realized. By coating the mesoporous ceramic backbone with a monolayer terminated with a lanthanide-selective ligand, it is possible to couple high lanthanide binding affinity with the high loading capacity (resulting from the extremely high surface area of the support). This lanthanide-selective ligand field is created by pairing a “hard” anionic Lewis base with a suitable synergistic ligand, in a favorable chelating geometry. Details of the synthesis, characterization, lanthanide binding studies, binding kinetics, competition experiments and sorbent regeneration studies are summarized.

A mesoporous silica thin film was synthesized via a surfactant-templating process, where a silica sol gel is spin-coated onto the surface of a microchip-based gold microelectrode. Within the film was a cubic lattice of pores having a primary size of 77 Å. Thiol (-SH) functional groups were subsequently immobilized onto the mesoporous silica thin film through a self-assembly process. The thiol-functionalized mesoporous silica (SH-FMS) thin film was used as the electrode sensing layer for detection of lead(ii) in aqueous solutions by employing a square wave adsorptive stripping voltammetry technique. The electrode modified with the SH-FMS thin-film utilized the binding affinity of lead(ii) to the thiol ligands to perform the preconcentration step under an open circuit, with no additional electrolytes. The voltammetric responses for lead(ii) increased linearly with the preconcentration time from 1 to 30 min. The responses also increased linearly with lead(ii) concentrations ranging from 250 to 5000 ppb after 5 min preconcentration and from 25–100 ppb after 30 min preconcentration.

The anodic stripping voltammetry at a carbon paste electrode modified with thiol terminated self-assembled monolayer on mesoporous silica (SH-SAMMS) provides a new sensor for simultaneous detection of lead (Pb2+) and mercury (Hg2+) in aqueous solutions. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the stripping analysis. Factors affecting the performance of the SH-SAMMS modified electrodes were investigated, including electrode activation and regeneration, electrode composition, preconcentration time, electrolysis time, and composition of electrolysis and stripping media. The most sensitive and reliable electrode contained 20% SH-SAMMS and 80% carbon paste. The optimal operating conditions were a sequence with a 2 min preconcentration period, then a 60 s electrolysis period of the preconcentrated species in 0.2 M nitric acid, followed by square wave anodic stripping voltammetry from −1.0 V to 0.6 V in 0.2 M nitric acid. The areas of the peak responses were linear with respect to metal ion concentrations in the ranges of 10–1500 ppb Pb2+ and 20–1600 ppb Hg2+. The detection limits for Pb2+ and Hg2+ were 0.5 ppb Pb2+ and 3 ppb Hg2+ after a 20 min preconcentration period.

A mesoporous silica thin film was synthesized viaa surfactant-templating process, where a silica sol gel is spin-coated onto the surface of a microchip-based gold microelectrode. Within the film was a cubic lattice of pores having a primary size of 77 . Thiol -SH functional groups were subsequently immobilized onto the mesoporous silica thin film through a self-assembly process. The thiol-functionalized mesoporous silica SH-FMS thin film was used as the electrode sensing layer for detection of leadii in aqueous solutions by employing a square wave adsorptive stripping voltammetry technique. The electrode modified with the SH-FMS thin-film utilized the binding affinity of leadii to the thiol ligands to perform the preconcentration step under an open circuit, with no additional electrolytes. The voltammetric responses for leadii increased linearly with the preconcentration time from 1 to 30 min. The responses also increased linearly with leadii concentrations ranging from 250 to 5000 ppb after 5 min preconcentration and from 25–100 ppb after 30 min preconcentration.

The anodic stripping voltammetry at a carbon paste electrode modified with thiol terminated self-assembled monolayer on mesoporous silica SH-SAMMS provides a new sensor for simultaneous detection of lead Pb2 and mercury Hg2 in aqueous solutions. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the stripping analysis. Factors affecting the performance of the SH-SAMMS modified electrodes were investigated, including electrode activation and regeneration, electrode composition, preconcentration time, electrolysis time, and composition of electrolysis and stripping media. The most sensitive and reliable electrode contained 20 SH-SAMMS and 80 carbon paste. The optimal operating conditions were a sequence with a 2 min preconcentration period, then a 60 s electrolysis period of the preconcentrated species in 0.2 M nitric acid, followed by square wave anodic stripping voltammetry from −1.0 V to 0.6 V in 0.2 M nitric acid. The areas of the peak responses were linear with respect to metal ion concentrations in the ranges of 10–1500 ppb Pb2and 20–1600 ppb Hg2. The detection limits for Pb2and Hg2were 0.5 ppb Pb2and 3 ppb Hg2after a 20 min preconcentration period.

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This paper discusses the interfacial chemistry encountered in the self-assembly of ordered nanoscale materials based on surfactant liquid crystalline structures. The paper contains three sections. The first section gives a brief introduction to the interfacial chemistry in the co-assembly of surfactants and inorganic materials. The second section discusses the formation of inorganic–inorganic nanocomposites, the properties of such materials, and the interfacial atomic structures. The last section discusses hybrid nanoscale materials with functional monolayers, their interfacial chemistry, and their potential applications.

Mesoporous materials have great potential for environmental and industrial processes, but many applications require the materials to exhibit specific surface chemistry and binding sites. A new approach has been developed so that organized functional monolayers are covalently bound to mesoporous supports. The functionalized hybrid materials show exceptional selectivity and capacity for removing heavy metals from waste streams. Tailored hybrid materials have also shown potential to

Mesoporous materials have great potential for environmental and industrial processes, but many applications require the materials to exhibit specific surface chemistry and binding sites. A new approach has been developed so that organized functional monolayers are covalently bound to mesoporous supports. The functionalized hybrid materials show exceptional selectivity and capacity for removing heavy metals from waste streams. Tailored hybrid materials have also shown potential to

The beneficial effects humidity treatments have on molecularly templated mesoporous silica films with respect to elastic modulus, with minimal detrimental effects on porosity and dielectric constant, were identified.

The beneficial effects that alkali metal and alkylammonium salt additions to molecularly templated silica sols have on the resulting mesoporous silica films formed from evaporative-coating methods with respect to porosity, elastic modulus, dielectric constant, and film surface uniformity were investigated and identified.

The beneficial effects that alkali metal and alkylammonium salt additions to molecularly templated silica sols have on the resulting mesoporous silica films formed from evaporative-coating methods with respect to porosity, elastic modulus, dielectric constant, and film surface uniformity were investigated and identified.

The beneficial effects humidity treatments have on molecularly templated mesoporous silica films with respect to elastic modulus, with minimal detrimental effects on porosity and dielectric constant, were identified.

The synthesis of carbamoylphosphonate silanes (CMPO analogs) designed for sequestering actinide cations in self-assembled monolayers on mesoporous supports (SAMMS) is described.

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