High Performance and Selective Sequestration of Cd(II) from Water by Layered Thiophosphate

The extensive use of toxic cadmium (Cd) in energy conversion and industrial applications ranging from solar cells and battery appliances to paints and pigments contaminates water bodies. However, the upper limit of Cd contamination in drinking water is to be only 3 ppb by the WHO and 5 ppb by the USA-EPA, which underscores the need for cost-effective, efficient, and ppb level capture of Cd from contaminated water. Leveraging the selectivity due to Lewis's hard-soft acid-base (HSAB) theory, we have achieved swift and highly selective capture of Cd(II) ions from aqueous mediums using layered potassium manganese thiophosphate (K-MnPS3). K-MnPS3 effectively removes Cd(II) ions from extremely dilute aqueous solutions (ppb levels), achieving a maximum sorption capacity of 405.43 mg/g and a removal rate exceeding 97% within 20 min. Even in the presence of competing ions such as Na+, Mg2+, Ca2+, and Pb2+, K-MnPS3 remains selective. Additionally, it operates efficiently across a wide pH range (1.78-11.19) with a high distribution coefficient (∼104 mL/g). Breakthrough experiments using a 1 wt % K-MnPS3 and 99 wt % sand column showed complete breakthrough of Cd(II) after 62 h, leading K-MnPS3 as a promising candidate for Cd(II) removal from industrial effluents.

Wormhole Mesoporous Silica Framework with Enhanced Thiol Loading for Improved Hg2+ Sequestration

Thiol-functionalized mesoporous silica and materials potentially dedicated to diverse applications of composite materials, metal colloids, and metal catalysts, etc. Here, we developed a new synthesis route for 3-methacryloxypropyl trimethoxy silane (MPTMS) functionalized mesoporous silica (KIT-6), achieving a 71.5 % enhancement in thiol functionalization on KIT-6 surfaces. Characterization using XRD, TEM, BET, FTIR, Raman, 29Si NMR, XPS, and ICP-OES revealed structural and morphological features. XRD, TEM, and BET confirmed the three-dimensional structural stabilization of mesoporous silica with ~4 nm pore diameter and a surface area of 1451 m2 g-1. FTIR, Raman, and 29Si NMR studies established the mechanism of thiol functionalization, the formation of a new wormhole chain structural framework (WCSF), and stabilization through hydrogen bonding within the mesopores. The 29Si NMR spectra showed characteristic peaks (T3, T2, Q4, Q3) indicating self-condensed functionalized thiols with siloxane networks. XPS analysis validated enhanced thiol functionalization, indicating a structurally homogeneous WCSF suitable for mercury adsorption. ICP-OES measured a mercury adsorption capacity of 3199.6 mg g-1 for KIT-6, with an Hg2+/S ratio of 1.8, corroborated by molecular structure and mechanism analysis. This innovative thiol functionalization approach enhances the efficacy of applications such as extracting Hg2+ from contaminated sources.

Metal-sulfide/polysulfide functionalized layered double hydroxides - recent progress in the removal of heavy metal ions and oxoanionic species from aqueous solutions

Water constitutes an indispensable resource for global life but remains susceptible to pollution from diverse human activities. To mitigate this issue, researchers are committed to purifying water using a variety of materials to remove harmful chemicals, such as heavy metals. Layered double hydroxides (LDHs), with their intriguing, layered structure and chemical behavior, have attained substantial attention for their effectiveness in removing heavy metal cations and various inorganic oxoanions from water. To enhance the efficiency, considerable endeavors have focused on functionalizing LDHs with different chemical species. Intercalation with metal sulfides has proven to be particularly effective, facilitating heavy metal absorption through multiple mechanisms, including ion-exchange, reductive precipitation, and surface sorption. This review concentrates on the synthesis and performance of polysulfide (Sx, x = 2-5), Mo-S, and Sn-S anion intercalated LDHs for heavy metal cations and inorganic oxoanion sorption, along with their mechanisms. Furthermore, the discussion includes prospects for expanding the chemistry of metal sulfide intercalated LDHs, with existing challenges and future outlooks.

Stimuli-responsive biodegradable silica nanoparticles: From native structure designs to biological applications

Due to their inherent advantages, silica nanoparticles (SiNPs) have greatly potential applications as bioactive materials in biosensors/biomedicine. However, the long-term and nonspecific accumulation in healthy tissues may give rise to toxicity, thereby impeding their widespread clinical application. Hence, it is imperative and noteworthy to develop biodegradable and clearable SiNPs for biomedical purposes. Recently, the design of multi-stimuli responsive SiNPs to improve degradation efficiency under specific pathological conditions has increased their clinical trial potential as theranostic nanoplatform. This review comprehensively summaries the rational design and recent progress of biodegradable SiNPs under various internal and external stimuli for rapid in vivo degradation and clearance. In addition, the factors that affect the biodegradation of SiNPs are also discussed. We believe that this systematic review will offer profound stimulus and timely guide for further research in the field of SiNP-based nanosensors/nanomedicine.

Role of mesoporous silica nanoparticles in combating mercury-induced stress in Vigna radiata (mung bean) and Bacillus coagulans (soil bacteria)

The last few decades have witnessed a dramatic progress of human civilization via industrialization, which, in turn, is associated with a surge in pollution of the environment. Heavy metals being one of the most hazardous pollutants have posed a serious threat to life sustaining ecosystem. Among the various remediation techniques, presently, the use of nanoparticles as adsorbents and chelator of heavy metal ions has emerged being practical and cost effective. Mesoporous silica nanoparticles, due to its unique structural attributes, have found application in adsorption of heavy metals in solutions. This study encompasses elucidation of the role of mesoporous silica nanoparticles MCM 41 and MCM 48 in mitigating stress caused by toxic dose of heavy metal Hg2+ (25 ppm) on growing seedlings of Vigna radiata and probiotic soil bacteria Bacillus coagulans. The results revealed that application of the nanoparticles at specific concentration can stimulate an increase in growth of plantlets, decrease in the yield reactive oxygen species like superoxide anion and hydrogen peroxide, reduction of lipid peroxidation, increase in antioxidant enzyme activity in Vigna radiata, and enhancement of growth of Bacillus coagulans as compared to that of Hg2+ alone. Moreover, it was found that MCM 41 was effective at higher dosages compared to MCM 48, which indicates the structure to function relationship.

How Key Alterations of Mesoporous Silica Nanoparticles Affect Anti-Lung Cancer Therapy? A Comprehensive Review of the Literature

In 2020, there were 2.21 million new instances of lung cancer, making it the top cause of mortality globally, responsible for close to 10 million deaths. The physicochemical problems of chemotherapy drugs are the primary challenge that now causes a drug's low effectiveness. Solubility is a physicochemical factor that has a significant impact on a drug's biopharmaceutical properties, starting with the rate at which it dissolves and extending through how well it is absorbed and bioavailable. One of the most well-known methods for addressing a drug's solubility is mesoporous silica, which has undergone excellent development due to the conjugation of polymers and ligands that increase its effectiveness. However, there are still very few papers addressing the success of this discovery, particularly those addressing its molecular pharmaceutics and mechanism. Our study's objectives were to explore and summarize the effects of targeting mediator on drug development using mesoporous silica with and without functionalized polymer. We specifically focused on highlighting the molecular pharmaceutics and mechanism in this study's innovative findings. Journals from the Scopus, PubMed, and Google Scholar databases that were released during the last ten years were used to compile this review. According to inclusion and exclusion standards adjusted. This improved approach produced very impressive results, a very significant change in the characteristics of mesoporous silica that can affect effectiveness. Mesoporous silica approaches have the capacity to greatly enhance a drug's physicochemical issues, boost therapeutic efficacy, and acquire superb features.

Purification and water resource circulation utilization of Cd-containing wastewater during microbial remediation of Cd-polluted soil

The purification and water resource circulation utilization of cadmium-containing leachate is a key link in the field application of microbial remediation in Cd-polluted soil. In this study, through a simulation experiment of microbial remediation of Cd-polluted paddy soil, the feasibility of the purification and recycling process of wastewater derived from microbial remediation of Cd-polluted soil was explored. The results of the microbial mobilization and removal experiment showed that the concentrations of Cd, N, P, and K in the leachate were 88.51 μg/L, 38.06, 0.53, and 98.87 mg/L, respectively. The leachate also contained a large number of microbial resources, indicating that it had high recovery values. To recycle this wastewater, activated carbon (C), humic acid (H), and self-assembled monolayers on mesoporous supports (SAMMS; S) were used as adsorbents. The results showed that the co-existing cations in the leachate had a major influence on the adsorption of Cd. In the ternary system of Fe, Al, and Cd, the removal efficiency of Cd increased to 91.2% when the S dosage was increased to 5‰, and the sorption of Cd occurred after Fe and Al. However, C and H exhibited poor adsorption performances. The isotherm models further showed that the maximum adsorption capacities of S, H, and C were 13.96, 6.41 and 2.94 mg/g, respectively. The adsorption kinetics of S showed that adsorption was a rapid process, and the C-H and O-Si-O of S were the key functional groups. The pH of the leachate significantly affected the adsorption efficiency of Cd. Finally, the purified leachate was successfully applied to microbial cultivation and soil remediation. Overall, the reclamation of Cd-containing wastewater can not only dampen the impacts of water shortages, but also achieve the purposes of Cd removal and resource recovery to lower costs by approximately 1166-3499 yuan per mu.

Optical and quantitative detection of cobalt ion using graphitic carbon nitride-based chemosensor for hydrometallurgy of waste lithium-ion batteries

A hydrometallurgy is one of the most important techniques for recycling waste LIBs, where identifying the exact composition of the metal-leached solution is critical in controlling the metal extraction efficiency and the stoichiometry of the regenerated product. In this study, we report a simple and selective optical detection of high-concentrated Co²⁺ using a graphitic carbon nitride (g-CN)-based fluorescent chemosensor. g-CN is prepared by molten salt synthesis using dicyandiamide (DCDA) and LiI/KI. The mass ratio of LiI/KI to DCDA modifies the resulting g-CN (CNI) in terms of in-plane molecular distances of base sites including cyano functional groups (─CN) and fluorescent emission wavelength via nucleophilic substitution. The fluorescent sensing performance of CNIs is evaluated through photoluminescence (PL) emission spectroscopy in a broad Co²⁺ concentration range (10^-4-10⁰ M). The correlation between the surface exposure of hidden nitrogen pots (base sites) and PL intensity change is achieved where the linear relationship between the PL quenching and the logarithm of Co²⁺ concentration in the analyte solution is well established with the regression of 0.9959. This study will provide the design principle of the chemosensor suitable for the fast and accurate optical detection of Co²⁺ present in a broad concentration range for hydrometallurgy for the recycling of waste LIBs.

Preparation of Self-Assembled Nanoparticle-Polymer Hybrids from Modified Silica Nanoparticles and Polystyrene-Block-Polyacrylic Acid Vesicles via the Co-Precipitation Method

Nanoparticle-polymer hybrids are becoming increasingly important because seemingly contrasting properties, such as mechanical stability and high elasticity, can be combined into one material. In particular, hybrids made of self-assembled polymers are of growing interest since they exhibit high structural precision and diversity and the subsequent reorganization of the nanoparticles is possible. In this work, we show, for the first time, how hybrids of silica nanoparticles and self-assembled vesicles of polystyrene-block-polyacrylic acid can be prepared using the simple and inexpensive method of co-precipitation, highlighting in particular the challenges of using silica instead of other previously well-researched materials, such as gold. The aim was to investigate the influence of the type of modification and the particle size of the silica nanoparticles on the encapsulation and structure of the polymer vesicles. For this purpose, we first needed to adjust the surface properties of the nanoparticles, which we achieved with a two-step modification procedure using APTES and carboxylic acids of different chain lengths. We found that silica nanoparticles modified only with APTES could be successfully encapsulated, while those modified with APTES and decanoic acid resulted in vesicle agglomeration and poor encapsulation due to their strong hydrophobicity. In contrast, no negative effects were observed when different particle sizes (20 nm and 45 nm) were examined.

Squaramide-Immobilized Carbon Nanoparticles for Rapid and High-Efficiency Elimination of Anthropogenic Mercury Ions from Aquatic Systems

Water pollution due to environmental remediation and poor waste administration in certain areas of the globe signifies a serious problem in acquiring safe and clean drinking water. This problem is especially critical in rural areas, where advanced water purification techniques are deficient, and it remains a daunting task for ecosystem and public health protection. This critical task can be addressed herein by developing scalable poly squaramide-phenyl methacrylamide (PSQ)-functionalized carbon nanoparticles (CNPs) (PSQ-CNPs) with densely populated chelating sites with strong Hg²⁺-binding capacity. The PSQ-CNPs have shown high efficiency in removing Hg²⁺ from aqueous solution, providing a Hg²⁺ capacity of 2840 mg g^-1, surpassing all the amine and thiol-based adsorbents reported hitherto. More significantly, the adsorbent reveals the largest distribution coefficient value (K_d) of 9.09 × 10¹⁰ mL g^-1, which allows it to reduce Hg²⁺ content from 10 ppm to less than 0.011 ppb, well below the United States Environmental Protection Agency (EPA) limits for drinking water standards (2 ppb). The adsorption measurements of the adsorbent followed the Langmuir isotherm model and pseudo-second order. The practical applicability of PSQ-CNPs was verified with the real samples (the lake, river, and industrial wastewater) and has been proven to be excellent. The adsorbent could still retain its Hg²⁺ removal efficacy even after 12 sorption cycles. It is attributed that the remarkable performance of PSQ-CNPs arises from the high-density chelating sites and pores on the surface of CNPs. The present work shows a new benchmark for Hg²⁺-removal adsorbents and presents a novel practical approach for decontaminating Hg²⁺ and other heavy metal ions from wastewater.

Nanostructured Materials for Water Purification: Adsorption of Heavy Metal Ions and Organic Dyes

Chemical water pollution poses a threat to human beings and ecological systems. The purification of water to remove toxic organic and inorganic pollutants is essential for a safe society and a clean environment. Adsorption-based water treatment is considered one of the most effective and economic technologies designed to remove toxic substances. In this article, we review the recent progress in the field of nanostructured materials used for water purification, particularly those used for the adsorption of heavy metal ions and organic dyes. This review includes a range of nanostructured materials such as metal-based nanoparticles, polymer-based nanomaterials, carbon nanomaterials, bio-mass materials, and other types of nanostructured materials. Finally, the current challenges in the fields of adsorption of toxic materials using nanostructured materials are briefly discussed.

Mercapto-functionalized ordered mesoporous silica-modified PVDF membrane for efficiently scavenging Cd2+ from water

In this study, (3-mercaptopropyl) triethoxysilane (MPTMS)-modified ordered mesoporous silica (OMS) materials were prepared using a post-grifting method, with MPTMS as the organic functionalized reagent. The OMS materials were analyzed by FT-IR spectra, N₂ sorption, and small angle X-ray scattering to evaluate their potential for scavenging Cd²⁺ from water. Moreover, a (3-mercaptopropyl) triethoxysilane-functionalized ordered mesoporous silica modified polyvinylidene fluoride (MPTMS-OMS/PVDF) membrane was synthesized using the solvent phase inversion method to remediate wastewater containing heavy metal ions. The MPTMS-OMS was characterized by a maximum specific surface area of 422 m²/g, high surface hydrophilicity, and high pure water flux. The MPTMS-OMS/PVDF exhibited a dynamic adsorption capacity for Cd²⁺ in water. At an MPTMS-OMS content of 5 wt%, the Cd²⁺ removal efficiency was 90%, whereas the pure PVDF showed no Cd²⁺ adsorption capacity. These results highlight the potential of the MPTMS-OMS/PVDF membrane to eliminate Cd²⁺ during the decontamination of aqueous streams containing low-concentrations of contaminants.

Effect of Surface-Chelated Cu2+ on Amyloid-β Peptide Fibrillation

Abnormal interactions of copper (Cu) ions with amyloid-β (Aβ) peptides are believed to play an important role in the pathogenesis of Alzheimer's disease (AD). However, there is still debate as to the exact role of Cu ions in Aβ amyloidosis despite extensive studies on Aβ-Cu interactions. Unlike previously reported works, we herein study the effect of surface-chelated Cu²⁺, rather than the more usual solution-phase dissolved Cu²⁺, on Aβ aggregation. Through the combination of single molecule fluorescent tracking, atomic force microscopy imaging experiments, and all-atom molecular dynamic simulations, we show that the surface-chelated Cu²⁺ dynamically interacts with Aβ chains, restricts their 2D-diffusivity on the surface, and retards their fibrillation, while the designated surfaces without Cu²⁺ facilitate the 2D-diffusivity of Aβ chains for better interpeptide interaction and promote Aβ fibrillation. We offer a microscopic molecular insight into the retardation mechanism of surface-chelated Cu²⁺ on Aβ fibrillation, suggesting that the surface-bound pools of metal ions are critical in AD progression and drug design.

2D material based field effect transistors and nanoelectromechanical systems for sensing applications

Sensors are ubiquitous in modern society because of their wide applications in healthcare, security, forensic industries as well as environmental protection. Specifically, sensors which can be microfabricated employing very-large-scale-integration (VLSI) compatible microfabrication techniques are particularly desirable. This is because they can provide several advantages: small size, low cost, and possibility of mass fabrication. 2D materials are a promising building block for such sensors. Their atomically thin nature, flat surfaces and ability to form van der Waals hetero junctions opens up the pathway for versatile functionalities. Here, we review 2D material-based field-effect-transistors (FETs) and nano-electro-mechanical systems (NEMs) for applications in detecting different gases, chemicals, and biomolecules. We will provide insights into the unique advantages of these materials for these sensing applications and discuss the fabrication methods, detection schemes and performance pertaining to these technologies. Finally, we will discuss the current challenges and prospects for this field.

Enzymatic Production of Ecodiesel by Using a Commercial Lipase CALB, Immobilized by Physical Adsorption on Mesoporous Organosilica Materials

The synthesis of two biocatalysts based on a commercial Candida antarctica lipase B, CALB enzyme (E), physically immobilized on two silica supports, was carried out. The first support was a periodic mesoporous organosilica (PMO) and the second one was a commercial silica modified with octyl groups (octyl-MS3030). The maximum enzyme load was 122 mg enzyme/g support on PMO and 288 mg enzyme/g support on octyl-MS3030. In addition, the biocatalytic efficiency was corroborated by two reaction tests based on the hydrolysis of p-nitrophenylacetate (p-NPA) and tributyrin (TB). The transesterification of sunflower oil with ethanol was carried out over the biocatalysts synthesized at the following reaction conditions: 6 mL sunflower oil, 1.75 mL EtOH, 30 °C, 25 μL NaOH 10 N and 300 rpm, attaining conversion values over 80% after 3 h of reaction time. According to the results obtained, we can confirm that these biocatalytic systems are viable candidates to develop, optimize and improve a new methodology to achieve the integration of glycerol in different monoacylglycerol molecules together with fatty acid ethyl esters (FAEE) molecules to obtain Ecodiesel.

Functionalized silica nanoparticles: classification, synthetic approaches and recent advances in adsorption applications

Nanotechnology is rapidly sweeping through all the vital fields of science and technology such as electronics, aerospace, defense, medicine, and catalysis. It involves the design, synthesis, characterization, and applications of materials and devices on the nanometer scale. At the nanoscale, physical and chemical properties differ from the properties of the individual atoms and molecules of bulk matter. In particular, the design and development of silica nanomaterials have captivated the attention of several researchers worldwide. The applications of hybrid silicas are still limited by the lack of control on the morphology and particle size. The ability to control both the size and morphology of the materials and to obtain nano-sized silica particles has broadened the spectrum of applications of mesoporous organosilicas and/or has improved their performances. On the other hand, adsorption is a widely used technique for the separation and removal of pollutants (metal ions, dyes, organics,...) from wastewater. Silica nanoparticles have specific advantages over other materials for adsorption applications due to their unique structural characteristics: a stable structure, a high specific surface area, an adjustable pore structure, the presence of silanol groups on the surface which allow easy modification, less environmental harm, simple synthesis, low cost, etc. Silica nanoparticles are potential adsorbents for pollutants. We present herein an overview of the different types of silica nanoparticles going from the definitions to properties, synthetic approaches and the mention of potential applications. We focus mainly on the recent advances in the adsorption of different target substances (metal ions, dyes and other organics).

Eco-Friendly Ferrimagnetic-Humic Acid Nanocomposites as Superior Magnetic Adsorbents

Recyclable, cheap, eco-friendly, and efficient adsorbent materials are very important for the removal of pollution. In this work, we report the design and implementation of ferrimagnetic-humic acid nanocomposites as superior magnetic adsorbent for heavy metals. Ferrimagnetic and ferrimagnetic-humic acid nanocomposite particles with different morphologies were prepared using the coprecipitation method and hydrothermal synthesis method, respectively. The results show that the morphology of the nanoparticles prepared by the coprecipitation method is more uniform and the size is smaller than that by the hydrothermal synthesis method. Adsorption experiments show that the ferrimagnetic-humic acid nanoparticles prepared by the coprecipitation method has high sorption capacity for cadmium, and the maximum adsorption capacity is about 763 μg/g. At the same time, magnetic technology can be used to realize the recycling of ferrimagnetic-humic acid adsorbents.

A dual-channel colorimetric and ratiometric fluorescence chemosensor for detection of Hg2+ ion and its bioimaging applications

A new colorimetric and ratiometric fluorescence chemosensor 4-((3-(octadecylthio)-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)benzenesulfonamide (4DBS) was synthesized and investigated for the selective detection of Hg²⁺ in DMSO-H₂O (9:1, v/v) solution. The chemosensor was efficiently synthesized in two steps via Michael-like addition and nucleophilic substitution reactions. The ratiometric fluorescence turn-on response was obtained towards Hg²⁺, and its fluorescence emission peak was red-shifted by 140 nm with an associated color change from light maroon to pale yellow due to the intramolecular charge transfer effect. The formed coordination metal complex was further evaluated by FT-IR, ¹H NMR, and quantum chemical analyses to confirm the binding mechanism. The detection process was sensitive/reversible, and the calculated limit of detection for Hg²⁺ was 0.451 µM. Furthermore, 4DBS was effectively utilized as a bioimaging agent for detection of Hg²⁺ in live cells and zebrafish larvae. Additionally, 4DBS showed distinguishing detection of Hg²⁺ in cancer cells in comparison with normal cells. Thus, 4DBS could be employed as an efficient bioimaging probe for discriminative identification of human cancer cells.

Ion-capture electrodialysis using multifunctional adsorptive membranes

Technologies that can efficiently purify nontraditional water sources are needed to meet rising global demand for clean water. Water treatment plants typically require a series of costly separation units to achieve desalination and the removal of toxic trace contaminants such as heavy metals and boron. We report a series of robust, selective, and tunable adsorptive membranes that feature porous aromatic framework nanoparticles embedded within ion exchange polymers and demonstrate their use in an efficient, one-step separation strategy termed ion-capture electrodialysis. This process uses electrodialysis configurations with adsorptive membranes to simultaneously desalinate complex water sources and capture diverse target solutes with negligible capture of competing ions. Our methods are applicable to the development of efficient and selective multifunctional separations that use adsorptive membranes.

Amphiphilic Thiol Polymer Nanogel Removes Environmentally Relevant Mercury Species from Both Produced Water and Hydrocarbons

Technologies for removal of mercury from produced water and hydrocarbon phases are desired by oil and gas production facilities, oil refineries, and petrochemical plants. Herein, we synthesize and demonstrate the efficacy of an amphiphilic, thiol-abundant (11.8 wt % S, as thiol) polymer nanogel that can remove environmentally relevant mercury species from both produced water and the liquid hydrocarbon. The nanogel disperses in both aqueous and hydrocarbon phases. It has a high sorption affinity for dissolved Hg(II) complexes and Hg-dissolved organic matter complexes found in produced water and elemental (Hg⁰) and soluble Hg-alkyl thiol species found in hydrocarbons. X-ray absorption spectroscopy analysis indicates that the sorbed mercury is transformed to a surface-bound Hg(SR)₂ species in both water and hydrocarbon regardless of its initial speciation. The nanogel had high affinity to native mercury species present in real produced water (>99.5% removal) and in natural gas condensate (>85% removal) samples, removing majority of the mercury species using only a 50 mg L^-1 applied dose. This thiolated amphiphilic polymeric nanogel has significant potential to remove environmentally relevant mercury species from both water and hydrocarbon at low applied doses, outperforming reported sorbents like sulfur-impregnated activated carbons because of the mass of accessible thiol groups in the nanogel.

A Review of Composite Phase Change Materials Based on Porous Silica Nanomaterials for Latent Heat Storage Applications

Phase change materials (PCMs) can store thermal energy as latent heat through phase transitions. PCMs using the solid-liquid phase transition offer high 100-300 J g-1 enthalpy at constant temperature. However, pure compounds suffer from leakage, incongruent melting and crystallization, phase separation, and supercooling, which limit their heat storage capacity and reliability during multiple heating-cooling cycles. An appropriate approach to mitigating these drawbacks is the construction of composites as shape-stabilized phase change materials which retain their macroscopic solid shape even at temperatures above the melting point of the active heat storage compound. Shape-stabilized materials can be obtained by PCMs impregnation into porous matrices. Porous silica nanomaterials are promising matrices due to their high porosity and adsorption capacity, chemical and thermal stability and possibility of changing their structure through chemical synthesis. This review offers a first in-depth look at the various methods for obtaining composite PCMs using porous silica nanomaterials, their properties, and applications. The synthesis and properties of porous silica composites are presented based on the main classes of compounds which can act as heat storage materials (paraffins, fatty acids, polymers, small organic molecules, hydrated salts, molten salts and metals). The physico-chemical phenomena arising from the nanoconfinement of phase change materials into the silica pores are discussed from both theoretical and practical standpoints. The lessons learned so far in designing efficient composite PCMs using porous silica matrices are presented, as well as the future perspectives on improving the heat storage materials.

A dithizone-anchored silica gel surface, {SiO2}@DZ for the selective sample cleanup of Gd(iii) amidst Fe(iii), Th(iv), and Ce(iv) employing ion pair complexation

Sorption–desorption equilibration, {extractor-HOMO}:{H₃O}⁺ + {metal-species}ⁿ⁺ ⇄ {extractor-HOMO}:{metal-species}ⁿ⁺ + {H₃O}⁺, an eventual ion-pair complexation controlled by {H₃O}⁺.

Removal of heavy metals and radionuclides from water using nanomaterials: current scenario and future prospects

There is an increase in concern about the hazardous effects of radioactivity due to the presence of undesirable radioactive substances in our vicinity. Nuclear accidents such as Chernobyl (1986) and Fukushima (2011) have further raised concerns towards such incidents which have led to contamination of water bodies. Conventional methods of water purification are less efficient in decontamination of radioisotopes. They are usually neither cost-effective nor environmentally friendly. However, nanotechnology can play a vital role in providing practical solutions to this problem. Nano-engineered materials like metal oxides, metallic organic frameworks, and nanoparticle-impregnated membranes have proven to be highly efficient in treating contaminated water. Their unique characteristics such as high adsorption capacity, large specific surface area, high tensile strength, and excellent biocompatibility properties make them useful in the field of water purification. This review explores the present status and future prospects of nanomaterials as the next-generation water purification systems that can play an important role in the removal of heavy metals and radioactive contaminants from aqueous solutions.

Interactions between adsorbents and adsorbates in aqueous solutions

Adsorption is one of the most widely used processes in physicochemical operations. To design an adsorbent for a specific adsorbate, it is important to understand the interactions between adsorbents and adsorbates, which are very important for both adsorption capacity and selectivity. Electrostatic interactions, hydrogen bonding, hydrophobic interactions, complexation, and precipitation are comprehensively discussed. Adjusting solution pH and ionic strength is an effective method to improve the adsorption, especially when electrostatic and hydrophobic interactions are main interactions. With the increase in ionic strength, the hydrophobic interactions between adsorbents and adsorbates increase, while the electrostatic interactions decrease.

Structurally designed porous polymer monoliths as probe-anchoring templates as benign and fast responsive solid-state optical sensors for the sensing and recovery of copper ions

In this study, we report on the superior ion-capturing and sensing competence of a new breed of aqua-compatible solid-state ion-sensor using a structurally organized polymer monolith, for the ocular sensing of trace levels of divalent copper ions. The polymer monolithic template exhibits a single block framework with a uniform structural pattern and porous network that serves as an efficient host for the homogeneous probe anchoring, to constitute a renewable solid-state optical sensor. Here, a series of solid-state colorimetric Cu(II) sensors has been designed using three indigenously synthesized chelating probes (molecules) namely, 4-butyl-N-(2-(2,4-dinitrophenyl)hydrazine-1-carbonothioyl)benzamide (BNHCB), 2-(thiophen-2-ylmethylene)hydrazinen-1-carbothioamide (TMHCA), and 4-butylphenyl(diazenyl)-2-mercaptopyrimidine-4,6-diol (BDMPD). The polymer monoliths are characterized using various surface and structural analysis techniques such as HR-SEM, HR-TEM, XPS, XRD, FT-IR, EDAX, and BET surface area analysis. The fabricated solid-state sensors exhibit excellent selectivity and sensitivity for copper ions with unique color transitions that are reliable even at ultra-trace (ppb) levels. The impact of diverse sensing parameters such as solution pH, probe concentration, sensor quantity, target ion concentration, temperature, response kinetics, and matrix tolerances have been optimized. The fabricated sensor materials proffer maximum sensing efficiency in neutral pH conditions, with a limit of detection (L_D) and quantification (L_Q) values of 0.56 and 1.87μg l^-1, 0.30 and 1.0μg l^-1, and 0.12 and 0.42μg l^-1, for BNHCB-, BDMPD-, and TMHCA-anchored polymer sensors, respectively. The proposed reusable solid-state colorimetric sensors are environmentally benign, cost-effective and data reproducible, with superior analytical performance.

Immobilization of Cellulolytic Enzymes in Mesostructured Silica Materials

Mesostructured silica nanoparticles offer a unique opportunity in the field of biocatalysis thanks to their outstanding properties. The tunable pore size in the range of mesopores allows for immobilizing bulky enzyme molecules. The large surface area improves the catalytic efficiency by increasing enzyme loading and finely dispersing the biocatalyst molecules. The easily tunable pore morphology allows for creating a proper environment to host an enzyme. The confining effect of mesopores can improve the enzyme stability and its resistance to extreme pH and temperatures. Benefits also arise from other peculiarities of nanoparticles such as Brownian motion and easy dispersion. Fossil fuel depletion and environmental pollution have led to the need for alternative sustainable and renewable energy sources such as biofuels. In this context, lignocellulosic biomass has been considered as a strategic fuel source. Cellulases are a class of hydrolytic enzymes that convert cellulose into fermentable sugars. This review is intended to survey the immobilization of cellulolytic enzymes (cellulases and β-glucosidase) onto mesoporous silica nanoparticles and their catalytic performance, with the aim to give a contribution to the urgent action required against climate change and its impacts, by biorefineries’ development.

Covalently functionalized uniform amino-silica nanoparticles. Synthesis and validation of amine group accessibility and stability

This paper describes the synthesis and characterization of colloidally stable, 18 nm silica nanoparticles that are functionalized with amine groups. Electron microscopy, small-angle X-ray scattering (SAXS), and dynamic light scattering show the amine grafting does not impact particle size. SAXS and DLS confirm the particles do not aggregate at 10 mg mL^-1 and pH 2 for 30 days. Ninhydrin analysis, fluorescamine binding, and NMR studies of carboxylic acid binding show that the amines are present on the surface and accessible with maximum loading calculated to be 0.14 mmol g^-1. These materials should find a range of use in nanotechnology applications.

Tuning the amphiphilicity of terpyridine-based fluorescent probe in water: Assembly and disassembly-controlled H g2+ sensing, removal, and adsorption of H2S

A water-soluble terpyridine-based cationic fluorescent probe (SP-TPy) was synthesized, which emerged with pH-dependent amphiphilicity, resulting in self-assembly and disassembly in aqueous media with the aggregation-induced emission (AIE) property. In neutral water (pH 7.4), a moderate sensing response to Hg²⁺ ions was given by the self-assembly of SP-TPy. However, in acidic aqueous media, the monomer of SP-TPy not only appeared to be highly selective and sensitive for Hg²⁺ ions, but also displayed highly efficient removal of Hg²⁺ ions from solution by rapid precipitation, which was attributed to the coordination-triggered reassembly of SP-TPy. The removal efficiency of SP-TPy for Hg²⁺ was found to be over 99%. Further study indicated that the precipitates were composed of various polyhedral porous frameworks, a property that was further used to adsorb H₂S gas to form HgS complexes with higher uptake capacities. In addition, SP-TPy can be efficiently regenerated and recycled using a simple treatment with acidic water after adsorption of the H₂S gas.

Immobilization of Cr(VI) on engineered silicate nanoparticles: Microscopic mechanisms and site energy distribution

Engineered nanoparticles-mediated contaminant transport has been recognized as a significant process governing the mobility of metals and radionuclides in groundwater. Engineered silicate nanoparticles (ESNPs) are attractive materials for the sequestration or extraction of Cr(VI) and other metals and radionuclides from groundwater. While great efforts have been devoted toward the application of these materials for Cr(VI) sequestration, the underlying interface adsorption mechanism is not thoroughly elucidated. This study investigates the immobilization mechanisms of Cr(VI) on a representative ESNPs, NH₂-MCM-41, over a range of water chemistry conditions. By combining batch adsorption experiments with an array of complementary characterizations, we provided spectroscopic and microscopic evidence that the electrostatic interactions between the positively charged NH₂-MCM-41 surface derived from amino functionality and the negatively charged Cr(VI) species was the dominant mechanism responsible for Cr(VI) immobilization. In addition, the weak hydrogen bonding interactions may also contribute to adsorption to a degree. Furthermore, thermodynamic studies suggested a favorable, spontaneous, and exothermic adsorption process. Site energy analysis illustrated that the distribution of energy binding sites on NH₂-MCM-41 is Cr(VI) loading dependent. The new insights provided here can advance understanding of the transport of Cr(VI) associated NH₂-MCM-41 that benefits the application of ESNPs-based technologies for metals immobilization in groundwater.

Monolayers of an organosilane on magnetite nanoparticles for the fast removal of Cr(VI) from water

Monolayers of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane have been established on magnetite nanoparticles to develop a novel magnetic adsorbent for fast decontamination of hexavalent chromium (Cr(VI)) from water. Results indicated that monolayer adsorption of the silane from water took place at low concentrations (<300 mg/L) and around 100% surface coverage was obtained at temperatures ≥90°C. The hydrolysed silane was anchored to the magnetite surface through condensation reactions between its silanol groups and the surface hydroxyl groups of magnetite. The functional amine groups were protonated by acid treatment for adsorbing Cr(VI). The monolayer of the silane on magnetite (MSM) with approximately 100% surface coverage showed extremely rapid adsorption kinetics for Cr(VI), such that the process was complete within 1 min. This enables the treatment of large amounts of sewage per unit time. The adsorption capacity for Cr(VI) was 8.0 mg/g, as estimated from the Langmuir isotherm model. The saturation magnetization of the MSM reached 64.16 emu/g, allowing easy magnetic recovery from water. In the presence of up to 50-fold molar excesses of chloride and nitrate anions, little effect on Cr(VI) removal was seen, but moderate and large impacts were observed with sulphate and hydroxyl anions, respectively. Desorption of adsorbed Cr(VI) and regeneration of the MSM were successfully achieved by NaOH and HCl treatments to deprotonate and protonate the amine groups, respectively. By selecting a silane with suitable functional groups, the surface properties may be tailored for a particular pollutant.

Fabrication of soft-nanocomposites from functional molecules with diversified applications

With the increasing demand for new soft materials having excellent physical and biological characteristics and functionality, the design of hybrid materials offers a simple, yet versatile platform for the development of materials with specific and tunable properties. By definition a "soft-nanocomposite" is the combination of supramolecular self-assemblies with nanomaterials of different origins (inorganic/metallic nanoparticles and carbonaceous allotropes like carbon nanotubes and graphene) through covalent/non-covalent interactions. Dynamic supramolecular self-assemblies can serve as excellent hosts for the incorporation of these dimensionally different nanomaterials. Nanomaterials within the matrix of supramolecular self-assemblies can give rise to new characteristics due to the synergistic contribution of both materials. Although the very initial work intended to use molecular gels as media for the preparation and stabilization of nanoparticles, recent reports have suggested that amalgamation of different supramolecular self-assemblies with nanoparticles is advantageous for both constituents. These newly developed soft-nanocomposites have interesting properties including electrical conductivity, viscoelasticity, thermal robustness, magnetic, phase-selective, redox and near-infrared radiation sensitive properties and so on. This review will focus on some of the most recent advancements in the development of novel soft-nanocomposites. In particular, we intend to correlate various design strategies for synthesis as well as composite preparation from functional molecules with interesting applications in the area of supercapacitors, nanoelectronics, photovoltaic devices, chemical and biosensors, biomedicine and so on. We expect that this article will be a general and conceptual demonstration of various approaches to develop different soft-nanocomposites and will highlight their applications across disciplines.

Postsynthetic functionalization of covalent organic frameworks

Covalent organic frameworks (COFs) have been at the forefront of porous-material research in recent years. With predictable structural compositions and controllable functionalities, the structures and properties of COFs could be controlled to achieve targeted materials. On the other hand, the predesigned structure of COFs allows fruitful postsynthetic modifications to introduce new properties and functions. In this review, the postsynthetic functionalizations of COFs are discussed and their impacts towards structural qualities and performances are comparatively elaborated on. The functionalization involves the formation of specific interactions (covalent or coordination/ionic bonds) and chemical reactions (oxidation/reduction reaction) with pendant groups, skeleton and reactive linkages of COFs. The chemical stability and performance of COFs including catalytic activity, storage, sorption and opto-electronic properties might be enhanced by specific postsynthetic functionalization. The generality of these strategies in terms of chemical reactions and the range of suitable COFs places them as a pivotal role for the development of COF-based smart materials.

π-π stacking interactions: Non-negligible forces for stabilizing porous supramolecular frameworks

Revealing the contribution of π-π stacking interactions in supramolecular assembly is important for understanding the intrinsic nature of molecular assembly fundamentally. However, because they are much weaker than covalent bonds, π-π stacking interactions are usually ignored in the construction of porous materials. Obtaining stable porous materials that are only dependent on π-π stacking interactions, despite being very challenging, could address this concern. Here, we present a porous supramolecular framework (π-1) stabilized only by intermolecular π-π stacking interactions. π-1 shows good thermal and chemical stability not only in various organic solvents but also in aqueous solution in a broad pH range. Furthermore, featuring one-dimensional channels with dangling thiolate groups, π-1 exhibits excellent Hg2+ removal performance, with adsorption capacity as high as 786.67 mg g-1 and an adsorption ratio as high as 99.998%. In addition, π-1 also shows high adsorption selectivity to Hg2+ in the presence of a series of interfering ions.