Cellulose nanofiber backboned Prussian blue nanoparticles as powerful adsorbents for the selective elimination of radioactive cesium

Cellulose from dinoflagellates as a versatile and environmentally friendly platform for the production of functionalised cellulose nanofibres

Cellulose nanofibres (CNFs), also known as nano-fibrillated cellulose, have emerged as highly promising sustainable biomaterials owing to their numerous advantages, including high accessibility, long-term sustainability, low toxicity, and mechanical properties. Recently, marine organisms have been explored as novel and environmentally friendly sources of cellulose fibers (CFs) due to their easy cultivation, extraction and biocompatibility. Dinoflagellates, a group of marine phytoplankton, have gained particular attention due to their unique cellulosic morphology and lignin-free biomass. Previously, we showed that the unique amorphous nature of dinoflagellate-derived cellulose offers various benefits. This study further explores the potential of dinoflagellate-derived CFs as a sustainable and versatile CNF source. Extracted dinoflagellate cellulose is effectively converted into CNFs via one-step TEMPO oxidation without significant polymer degradation. In addition, the biological compatibility of the CNFs is improved by amine-grafting using putrescine and folic acid. The products are characterised by conductometric titration, zeta potential measurements, TGA, GPC, FTIR, SEM/TEM, XRD, and XPS. Finally, in a proof-of-principle study, the application of the functionalised CNFs in drug delivery is tested using methylene blue as a drug model. Our findings suggest that dinoflagellate-derived CNFs provide an eco-friendly platform that can be easily functionalised for various applications, including drug delivery.

Detecting possible pairs of materials for composites using a material word co-occurrence network

Composite materials are popular because of their high performance capabilities, but new material development is time-consuming. To accelerate this process, researchers studying material informatics, an academic discipline combining computational science and material science, have developed less time-consuming approaches for predicting possible material combinations. However, these processes remain problematic because some materials are not suited for them. The limitations of specific candidates for new composites may cause potential new material pairs to be overlooked. To solve this problem, we developed a new method to predict possible composite material pairs by considering more materials than previous techniques. We predicted possible material pairs by conducting link predictions of material word co-occurrence networks while assuming that co-occurring material word pairs in scientific papers on composites were reported as composite materials. As a result, we succeeded in predicting the co-occurrence of material words with high specificity. Nodes tended to link to many other words, generating new links in the created co-occurrence material word network; notably, the number of material words co-occurring with graphene increased rapidly. This phenomenon confirmed that graphene is an attractive composite component. We expect our method to contribute to the accelerated development of new composite materials.

Metal Recovery from Natural Saline Brines with an Electrochemical Ion Pumping Method Using Hexacyanoferrate Materials as Electrodes

The electrochemical ion pumping device is a promising alternative for the development of the industry of recovering metals from natural sources-such as seawater, geothermal water, well brine, or reverse osmosis brine-using electrochemical systems, which is considered a non-evaporative process. This technology is potentially used for metals like Li, Cu, Ca, Mg, Na, K, Sr, and others that are mostly obtained from natural brine sources through a combination of pumping, solar evaporation, and solvent extraction steps. As the future demand for metals for the electronic industry increases, new forms of marine mining processing alternatives are being implemented. Unfortunately, both land and marine mining, such as off-shore and deep sea types, have great potential for severe environmental disruption. In this context, a green alternative is the mixing entropy battery, which is a promising technique whereby the ions are captured from a saline natural source and released into a recovery solution with low ionic force using intercalation materials such as Prussian Blue Analogue (PBA) to store cations inside its crystal structure. This new technique, called "electrochemical ion pumping", has been proposed for water desalination, lithium concentration, and blue energy recovery using the difference in salt concentration. The raw material for this technology is a saline solution containing ions of interest, such as seawater, natural brines, or industrial waste. In particular, six main ions of interest-Na+, K+, Mg2+, Ca2+, Cl-, and SO42--are found in seawater, and they constitute 99.5% of the world's total dissolved salts. This manuscript provides relevant information about this new non-evaporative process for recovering metals from aqueous salty solutions using hexacianometals such as CuHCF, NiHCF, and CoHCF as electrodes, among others, for selective ion removal.

Green remediation of cadmium-contaminated soil by cellulose nanocrystals

Cellulose nanocrystals (CNC) were used as a novel, green eluent to remediate Cd-contaminated soil in this study. The influence of washing conditions on the removal of Cd, including CNC concentration, pH value, liquid/solid (L/S) ratio, contact time and temperature were investigated. The effect of CNC remediation of Cd-contaminated soil on soil health and the possible remediation mechanism were also explored. The results showed that CNC concentration, pH value and contact time had a significant effect on the removal efficiency of Cd. CNC rapidly removed heavy metals in soil within 30 min. When the pH value of the eluent was 9.0, the removal efficiency of Cd could reach 86.3 %. The eluent mainly removed exchangeable and reducible fractions of Cd, which could effectively reduce the bioavailability of heavy metals. CNC washing had no negative effects on seed growth, species abundance and Shannon index. C-O, -COO^- groups on CNC played an important role in the reaction between CNC and soil Cd, and other oxygen-containing functional groups on CNC could also assist in adsorption, ion exchange and chemical complexation processes. Therefore, cellulose nanocrystals had the potential to remediate heavy metal-contaminated soils in a green and efficient manner.

Tannic acid-assisted in-situ interfacial formation of Prussian blue-assembled adsorptive membranes for radioactive cesium removal

There is a growing interest in advanced materials that can effectively treat wastewater contaminated with radioactive cesium (¹³⁷Cs), which is an extremely hazardous material. Here, we report a new class of Cs-adsorptive membranes compactly assembled with Cs-adsorptive Prussian blue (PB) particles. The PB particle assembly was formed via an in-situ interfacial reaction between two PB precursors in the presence of tannic acid (TA) as a binder on a porous support. While the interfacial reaction enabled the formation of a defect-less PB network, TA enhanced the PB-PB and PB-support compatibilities, consequently producing a uniform, densely packed PB assembly near the support surface. The fabricated TA-assisted PB membrane (PB/TA-M) synergistically rejected Cs via a combination of adsorption and membrane filtration, although adsorption predominantly determined Cs rejection initially. Hence, the PB/TA-M membrane showed considerably higher Cs removal performance than commercial nanofiltration (NF) and reverse osmosis (RO) polyamide (PA) membranes for a sufficiently long operation time. Furthermore, the PB/TA-M membrane displayed excellent radioactive ¹³⁷Cs removal performance, significantly exceeding those of commercial NF and RO PA membranes due to its higher radiation stability, indicating its viability for application in treating actual radioactive wastewater.

Patent mining on soil pollution remediation technology from the perspective of technological trajectory

Recent years have seen a marked growth in soil environmental problems, however, the research & development (R&D) direction of soil pollution remediation technology (SPRT) for addressing related challenges to the global ecosystem is still unclear. Patent is the most effective carrier of technological information. Therefore, this study investigates the status and future direction of SPRT through the analysis and mining of 14,475 patents from 1971 to 2020. In 2006-2020, 14,435 SPRT patents (79% of the total) were published, which is in the development stage. By measuring the proportion of high-value patents, determined by the ratio of the number of patent families containing two or more patents (PF2) to that containing at least one patent (PF1), we found that United States (PF2/PF1 = 0.711), Japan (PF2/PF1 = 0.500), and South Korea (PF2/PF1 = 0.431) hold a monopoly. International patent organizations serve as a bridge for technology transfer. Patent CN101947539-A measured by structural hole index (Effective size = 98.194, Efficiency = 0.926) has the most significant technological influence. Therefore, in order to accomplish the technological transition and improve the soil remediation capacity, more attention should be paid to the microbial-assisted phytoremediation technology related to inorganic pollutants, hyperaccumulators and stabilizers. Additionally, patents CN102834190-A (Effective size = 23.930, Efficiency = 0.855, Constraint = 0.141, Hierarchy = 0.089) and CN105855289 (Effective size = 21.453, Efficiency = 0.795 Constraint = 0.149, Hierarchy = 0.086) are both at the location of structural holes. So, more research should be carried out on green and cost-effective solutions for reducing organic pollutants in soil remediation. The current study identifies opportunities for innovations and breakthroughs in SPRT and offers relevant information on technological development prospects.

Size-Controllable Prussian Blue Nanoparticles Using Pluronic Series for Improved Antioxidant Activity and Anti-Inflammatory Efficacy

Prussian blue (PB) is a metal cluster nanoparticle (NP) of cyanide-bridged iron(II)-iron(III) and exhibits a characteristic blue color. Its peroxidase-, catalase-, and superoxide-dismutase-like activities effectively remove excess reactive oxygen species that induce inflammation and tumorigenesis. However, the dispersion of PB NPs is not sufficiently stable for their application in the biomedical field. In this study, we developed Pluronic-stabilized Prussian blue nanoparticles (PB/Plu NPs) using a series of Pluronic triblock copolymers as a template material for PB NPs. Considering the hydrophilic-lipophilic balance (HLB) values of the Pluronic series, including F68, F127, L35, P123, and L81, the diameters of the PB/Plu NPs decreased from 294 to 112 nm with decreasing HLB values. The smallest PB NP stabilized with Pluronic P123 (PB/PP123 NP) showed the strongest antioxidant and anti-inflammatory activities and wound-healing efficacy because of its large surface area. These results indicated that the spatial distribution of PB NPs in the micelles of Pluronic greatly improved the stability and reactive oxygen species scavenging activity of these NPs. Therefore, PB/Plu NPs using U.S.-FDA-approved Pluronic polymers show potential as biocompatible materials for various biomedical applications, including the treatment of inflammatory diseases in the clinic.

Recent Advances in Designing Fibrous Biomaterials for the Domain of Biomedical, Clinical, and Environmental Applications

Unique properties and potential applications of nanofibers have emerged as innovative approaches and opportunities in the biomedical, healthcare, environmental, and biosensor fields. Electrospinning and centrifugal spinning strategies have gained considerable attention among all kinds of strategies to produce nanofibers. These techniques produce nanofibers with high porosity and surface area, adequate pore architecture, and diverse chemical compositions. The extraordinary characteristics of nanofibers have unveiled new gates in nanomedicine to establish innovative fiber-based formulations for biomedical use, healthcare, and a wide range of other applications. The present review aims to provide a comprehensive overview of nanofibers and their broad range of applications, including drug delivery, biomedical scaffolds, tissue/bone-tissue engineering, dental applications, and environmental remediation in a single place. The review begins with a brief introduction followed by potential applications of nanofibers. Finally, the future perspectives and current challenges of nanofibers are demonstrated. This review will help researchers to engineer more efficient multifunctional nanofibers with improved characteristics for their effective use in broad areas. We strongly believe this review is a reader's delight and will help in dealing with the fundamental principles and applications of nanofiber-based scaffolds. This review will assist students and a broad range of scientific communities to understand the significance of nanofibers in several domains of nanotechnology, nanomedicine, biotechnology, and environmental remediation, which will set a benchmark for further research.

Biofibrous nanomaterials for extracting strategic metal ions from water

Strategic metals play an indispensable role in the related industries. Their extraction and recovery from water are of great significance due to both their rapid consumption and environmental concern. Biofibrous nanomaterials have shown great advantages in capturing metal ions from water. Recent progress in extraction of typical strategic metal ions such as noble metal ions, nuclear metal ions, and Li-battery related metal ions is reviewed here using typical biological nanofibrils like cellulose nanofibrils, chitin nanofibrils, and protein nanofibrils, as well as their assembly forms like fibers, aerogels/hydrogels, and membranes. An overview of advances in material design and preparation, extraction mechanism, dynamics/thermodynamics, and performance improvement in the last decade is provided. And at last, we propose the current challenges and future perspectives for promoting biological nanofibrous materials toward extracting strategic metal ions in practical conditions of natural seawater, brine, and wastewater.

Sodium to cesium ions: a general ladder mechanism of ion diffusion in prussian blue analogs

Prussian blue analogs (PBAs) form crystals with large lattice voids that are suitable for the capture, transport and storage of various interstitial ions. Recently, we introduced the concept of a ladder mechanism to describe how sodium ions inside a PBA crystal structure diffuse by climbing the frames formed by aligned cyanide groups in the host structure. The current work uses semi-empirical tight-binding density functional theory (DFTB) in a multiscale approach to investigate how differences in the size of the monovalent cation affect the qualitative and quantitative aspects of the diffusion process. The results show that the ladder mechanism represents a unified framework, from which both similarities and differences between cation types can be understood. Fundamental Coulombic interactions make all positive cations avoid the open vacant areas in the structure, while cavities surrounded by partially negatively charged cyanide groups form diffusion bottlenecks and traps for larger cations. These results provide a new and quantitative way of understanding the suppression of cesium adsorption that has previously been reported for PBAs characterized by a low vacancy density. In conclusion, this work provides a unified picture of the cation adsorption in PBAs based on the newly formulated ladder mechanism.

Functionalization of Tailored Porous Carbon Monolith for Decontamination of Radioactive Substances

As the control over radioactive species becomes critical for the contemporary human life, the development of functional materials for decontamination of radioactive substances has also become important. In this work, a three-dimensional (3D) porous carbon monolith functionalized with Prussian blue particles was prepared through removal of colloidal silica particles from exfoliated graphene/silica composite precursors. The colloidal silica particles with a narrow size distribution were used to act a role of hard template and provide a sufficient surface area that could accommodate potentially hazardous radioactive substances by adsorption. The unique surface and pore structure of the functionalized porous carbon monolith was examined using electron microscopy and energy-dispersive X-ray analysis (EDS). The effective incorporation of PB nanoparticles was confirmed using diverse instrumentations such as X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). A nitrogen adsorption/desorption study showed that surface area and pore volume increased significantly compared with the starting precursor. Adsorption tests were performed with ¹³³Cs ions to examine adsorption isotherms using both Langmuir and Freundlich isotherms. In addition, adsorption kinetics were also investigated and parameters were calculated. The functionalized porous carbon monolith showed a relatively higher adsorption capacity than that of pristine porous carbon monolith and the bulk PB to most radioactive ions such as ¹³³Cs, ⁸⁵Rb, ¹³⁸Ba, ⁸⁸Sr, ¹⁴⁰Ce, and ²⁰⁵Tl. This material can be used for decontamination in expanded application fields.

The uptake characteristics of Prussian-blue nanoparticles for rare metal ions for recycling of precious metals from nuclear and electronic wastes

We have examined the uptake mechanisms of platinum-group-metals (PGMs) and molybdenum (Mo) ions into Prussian blue nanoparticles (PBNPs) in a nitric acid solution for 24-h sorption test, using inductively coupled plasma atomic emission spectroscopy, powder XRD, and UV–Vis-NIR spectroscopy in combination with first-principles calculations, and revealed that the Ru⁴⁺ and Pd²⁺ ions are incorporated into PBNPs by substitution with Fe³⁺ and Fe²⁺ ions of the PB framework, respectively, whereas the Rh³⁺ ion is incorporated into PBNPs by substitution mainly with Fe³⁺ and minorly with Fe²⁺ ion, and Mo⁶⁺ ion is incorporated into PBNPs by substitution with both Fe²⁺ and Fe³⁺ ions, with maintaining the crystal structure before and after the sorption test. Assuming that the amount of Fe elusion is equal to that of PGMs/Mo substitution, the substitution efficiency is estimated to be 39.0% for Ru, 47.8% for Rh, 87% for Pd, and 17.1% for Mo⁶⁺. This implies that 0.13 g of Ru, 0.16 g of Rh, 0.30 g of Pd, and 0.107 g of Mo can be recovered by using 1 g PBNPs with a chemical form of KFe(III)[Fe(II)(CN)₆].

Cesium ion adsorption and desorption on electrospun mesoporous silica nanofibers immobilized with Prussian blue

To fabricate an efficient Cs ion adsorbent and prevent unexpected loss of Prussian blue (PB) colloidal particles during use, PB was immobilized on the surface of electrospun mesoporous silica nanofibers (MSFs) via a newly developed method of double exposure to Fe (III) ions. To introduce PB on MSFs, the MSFs were functionalized with ethylenediamine moiety to bind to Fe (III) ions, which would firmly anchor PB. MSFs were pretreated with Fe (III) ions and exposed to K₄ [Fe(II) (CN)₆] to form PB. We found that this process did not provide a sufficient PB amount on the MSFs. To increase the PB amount, after initial PB formation, the MSFs were treated with Fe (III) ions again so that the unreacted K₄ [Fe(II) (CN)₆] remaining on the MSFs could become PB. An investigation of the adsorption isotherms and kinetics of the nanofibrous adsorbent indicated that monolayer chemisorption had occurred. The maximum Cs ion adsorption capacity using the method of double exposure to Fe (III) ions was determined to be 14.66 mg/g, which was higher by a factor of 2.24 than the case that was not prepared by this method. Cs ions were selectively adsorbed over other cations and could be removed in both acidic and basic conditions, presumably because of the robust MSFs.

One-pot synthesis of magnetic Prussian blue for the highly selective removal of thallium(I) from wastewater: Mechanism and implications

Thallium (Tl) often enters the environment via mineral exploitation and utilization. The main restriction of Tl removal is the interference of high concentrations of coexisting ions in wastewater, therefore, enhancing the selectivity for Tl is essential to its treatment. Magnetic Prussian blue particles (Fe₃O₄@PB), an ion-sieving material with an open structure, were synthesized through a "one-pot" method at room temperature for the highly selective removal of Tl⁺. The removal percentage of Tl⁺ was over 92% even when the concentration of coexisting ions (e.g. Zn²⁺, Cd²⁺, Cu²⁺, and Pb²⁺) were 10,000 times higher than the initial concentration of Tl⁺. The maximal experimental removal capacity was 528 mg Tl/g Fe₃O₄@PB, and the removal percentage remained steady at pH 3-10. The high selectivity of Fe₃O₄@PB for Tl⁺ is attributed to the fact that hydrated Tl⁺ has a smaller hydrated diameter and a lower hydration free energy than other coexisting ions, while the rapid adsorption kinetics of Tl⁺ results from the negative surface charge and the network of nanocapillaries of the Fe₃O₄@PB. Overall, a new low-cost material that is easy to synthesize and has superior Tl⁺ removal capacity with extremely high selectivity for Tl⁺ was obtained for effective magnetic removal of thallium from wastewater.

Mechanochemically Synthesized Prussian Blue for Efficient Removal of Cesium Ions from Aqueous Solutions

The adsorptive removal of radioactive cesium [Cs(I)] is important for ensuring a clean aquatic environment. In this work, the adsorption of Cs(I) was carried out using Prussian blue (PB) prepared by mechanochemical synthesis. X-ray diffraction, Fourier-transform infrared spectroscopy, and field-emission scanning electron microscopy results indicated that PB had been successfully synthesized by mechanochemical synthesis. Thermogravimetric analysis, contact angle analysis, inductively coupled plasma atomic emission spectrometry, elemental analysis, and electrophoretic light scattering spectrophotometry confirmed that several defects were formed, explaining the principal mechanism for the efficient adsorption over PB prepared by mechanochemical synthesis. The superior adsorption properties toward Cs(I) make PB prepared by mechanochemical synthesis an attractive candidate material for the efficient, economical, and eco-friendly processes for purifying radioactive wastewater.

Post-synthetic modification of Prussian blue type nanoparticles: tailoring the chemical and physical properties

This review focuses on recent advances in the post-synthetic modification of nano-sized Prussian blue and its analogues and compares them with the current strategies used in metal–organic frameworks to give future outlooks in this field.

Electrostatic interactions and physisorption: mechanisms of passive cesium adsorption on Prussian blue

The study finds atomic-level physisorption interactions that leads to electrostatic Langmuir adsorption.

Perspective on Nanofiber Electrochemical Sensors: Design of Relative Selectivity Experiments

The use of nanofibers creates the ability for non-enzymatic sensing in various applications and greatly improves the sensitivity, speed, and accuracy of electrochemical sensors for a wide variety of analytes. The high surface area to volume ratio of the fibers as well as their high porosity, even when compared to other common nanostructures, allows for enhanced electrocatalytic, adsorptive, and analyte-specific recognition mechanisms. Nanofibers have the potential to rival and replace materials used in electrochemical sensing. As more types of nanofibers are developed and tested for new applications, more consistent and refined selectivity experiments are needed. We applied this idea in a review of interferant control experiments and real sample analyses. The goal of this review is to provide guidelines for acceptable nanofiber sensor selectivity experiments with considerations for electrocatalytic, adsorptive, and analyte-specific recognition mechanisms. The intended presented review and guidelines will be of particular use to junior researchers designing their first control experiments, but could be used as a reference for anyone designing selectivity experiments for non-enzymatic sensors including nanofibers. We indicate the importance of testing both interferants in complex media and mechanistic interferants in the selectivity analysis of newly developed nanofiber sensor surfaces.

Mechanically Strong, Liquid-Resistant Photothermal Bioplastic Constructed from Cellulose and Metal-Organic Framework for Light-Driven Mechanical Motion

The development of photothermal materials with a high light-to-heat conversion capability is essential for the utilization of clean solar energy. In this work, we demonstrate the use of a novel and sustainable concept involving cellulose liquefaction, rapid gelation, in situ synthesis and hot-press drying to convert cellulose and metal-organic framework (Prussian blue) into a stable photothermal bioplastic that can harvest sunlight and convert it into mechanical motion. As expected, the obtained Prussian blue@cellulose bioplastic (PCBP) can effectively absorb sunlight and the surface can be heated up to 70.3 °C under one sun irradiation (100 mW cm-2). As a demonstration of the practicality of PCBP, it was successfully used to drive a Stirling engine motion. Meanwhile, hot-pressing promotes the densification of the structure of PCBP and, therefore, improves the resistance to the penetration of water/non-aqueous liquids. Moreover, PCBP shows good mechanical properties and thermal stability. Given the excellent photothermal performance and environmentally friendly features of photothermal conversion bioplastic, we envisage this sustainable plastic film could play important roles toward diversified applications: a photothermal layer for thermoelectric generator, agricultural films for soil mulching and photothermal antibacterial activity, among others.

Emerging Nanocellulose Technologies: Recent Developments

Nanocelluloses have unique morphologies, characteristics, and surface nanostructures, and are prepared from abundant and renewable plant biomass resources. Therefore, expansion of the use of CO₂ -accumulating nanocelluloses is expected to partly contribute to the establishment of a sustainable society and help overcome current global environmental issues. Nanocelluloses can be categorized into cellulose nanonetworks, cellulose nanofibrils, and cellulose nanocrystals, depending on their morphologies. All of these materials are first obtained as aqueous dispersions. In particular, cellulose nanofibrils have homogeneous ≈3 nm widths and average lengths of >500 nm, and significant amounts of charged groups are present on their surfaces. Such charged groups are formed by carboxymethylation, C6-carboxylation, phosphorylation, phosphite esterification, xanthation, sulfate esterification, and C2/C3 dicarboxylation during the pretreatment of plant cellulose fibers before their conversion into cellulose nanofibrils via mechanical disintegration in water. These surface-charged groups in nanocelluloses can be stoichiometrically counterion-exchanged into diverse metal and alkylammonium ions, resulting in surface-modified nanocelluloses with various new functions including hydrophobic, water-resistant, catalytic, superdeodorant, and gas-separation properties. However, many fundamental and application-related issues facing nanocelluloses must first be overcome to enable their further expansion.

The uptake mechanism of palladium ions into Prussian-blue nanoparticles in a nitric acid solution toward application for the recycling of precious metals from electronic and nuclear wastes

We have investigated the uptake mechanism of palladium (Pd: one of the most important elements in industry used as a catalyst) ions into Prussian-blue nanoparticles (PBNPs) in a nitric acid solution via high-resolution electron transmission microscopy, inductively coupled plasma atomic emission spectroscopy, powder X-ray diffraction, and ultraviolet-visible-near infrared spectroscopy in combination with first principles calculations. Comparison of the structural and electronic properties of PBNPs between before and after a 24 h sorption test reveals that the Pd²⁺ ions incorporated into PBNPs by the substitution of Fe²⁺ ions of the PB framework while maintaining the crystal structure, and the substitution efficiency is estimated to be 87% per PB unit cell. This implies that 0.30 g of Pd can be recovered by using 1 g of PB having the chemical formula KFe(iii)[Fe(ii)(CN)₆]. The present finding suggests that PB (or its analogues) can be applied to recycle noble and rare metals from electronic and nuclear wastes.

The uptake mechanism of palladium ions into Prussian-blue nanoparticles in a nitric acid solution was investigated via high-resolution TEM, ICP-AES, powder XRD, and UV-Vis-NIR spectroscopy in combination with first principles calculations.

Development of the Functionalized Nanocomposite Materials for Adsorption/Decontamination of Radioactive Pollutants

A polymer-based nanofiber membrane with a high specific surface area, high porosity and abundant adsorption sites is demonstrated for selective trapping of radionuclides. The Prussian blue (PB)/poly(methyl methacrylate) (PMMA) nanofiber composites were successfully prepared through a one-step, single-nozzle electrospinning method. Various analytical techniques were used to examine the physical and chemical properties of PB nanoparticles and electrospun nanofibers. It is possible to enhance binding affinity and selectivity to radionuclide targets by incorporation of the PB nanoparticles into the polymer matrix. It is noteworthy that the maximum 133Cs adsorption capacity of hte PB/PMMA nanofiber filter is approximately 28 times higher than that of bulk PB, and the removal efficiency is measured to be 95% at 1 ppm of 133Cs. In addition, adsorption kinetics shows that the PB/PMMA nanofiber has a homogenous surface for adsorption, and all sites on the surface have equal adsorption energies in terms of ion-exchange between cyano groups of the introduced PB nanoparticles and radionuclides.

Recent Advances in pH- or/and Photo-Responsive Nanovehicles

The combination of nanotechnology and chemotherapy has resulted in more effective drug design via the development of nanomaterial-based drug delivery systems (DDSs) for tumor targeting. Stimulus-responsive DDSs in response to internal or external signals can offer precisely controlled delivery of preloaded therapeutics. Among the various DDSs, the photo-triggered system improves the efficacy and safety of treatment through spatiotemporal manipulation of light. Additionally, pH-induced delivery is one of the most widely studied strategies for targeting the acidic micro-environment of solid tumors. Accordingly, in this review, we discuss representative strategies for designing DDSs using light as an exogenous signal or pH as an endogenous trigger.

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.

Aerogels from copper (II)-cellulose nanofibers and carbon nanotubes as absorbents for the elimination of toxic gases from air

A novel deodorizer that is capable of selectively eliminating the odorous chemicals, such as ammonia, trimethylamine, hydrogen sulfide and methyl mercaptan, is described. The deodorizer is a nanostructured aerogel by nature, consisting of 2,2-6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose nanofibrils (CNF), transition metal divalent cations (M²⁺), and multi-walled carbon nanotubes (CNT) as the constitutive elements. CNF are firstly mixed with M²⁺ (M²⁺, in this paper, typifies Ni²⁺, Co²⁺ and Cu²⁺) to form CNF-M²⁺ complexes, monodispersed CNT is then mixed to prepare CNT/CNF-M²⁺ waterborne slurries; CNT/CNF-M²⁺ hybridized aerogels are finally obtained via freezing-drying of the CNT/CNF-M²⁺ waterborne slurries. The CNT/CNF-M²⁺ aerogels are a foam-like structure consisting of CNF and CNT as backbones and M²⁺ as linkers. The aerogels show higher capabilities (in comparison with activated carbon) for selectively adsorbing ammonia, trimethylamine, hydrogen sulfide and methyl mercaptan. Computing simulations suggest a theoretical conclusion that the odorous chemicals are absorbed in a preferring manner of bimolecular absorptions via the M²⁺ moieties. The CNT/CNF-M²⁺ hybridized aerogels are lightweight, eco-friendly, and easy to produce in industrial scales. Our new finding, as is described in this paper, demonstrates potential applications of the TEMPO-oxidized CNF to the field of deodorizations.

More Efficient Prussian Blue Nanoparticles for an Improved Caesium Decontamination from Aqueous Solutions and Biological Fluids

Any release of radioactive cesium-137, due to unintentional accidents in nuclear plants, represents a dangerous threat for human health and the environment. Prussian blue has been widely studied and used as an antidote for humans exposed to acute internal contamination by Cs-137, due to its ability to act as a selective adsorption agent and to its negligible toxicity. In the present work, the synthesis protocol has been revisited avoiding the use of organic solvents to obtain Prussian blue nanoparticles with morphological and textural properties, which positively influence its Cs⁺ binding capacity compared to a commercially available Prussian blue sample. The reduction of the particle size and the increase in the specific surface area and pore volume values compared to the commercial Prussian blue reference led to a more rapid uptake of caesium in simulated enteric fluid solution (+35% after 1 h of contact). Then, after 24 h of contact, both solids were able to remove >98% of the initial Cs⁺ content. The Prussian blue nanoparticles showed a weak inhibition of the bacterial luminescence in the aqueous phase and no chronic detrimental toxic effects.

Cesium ion-exchange resin using sodium dodecylbenzenesulfonate for binding to Prussian blue

Radioactive Cs ions are extremely harmful to the human body, causing cancers and other diseases. Treatments were performed on radioactive Cs present in wastewater after use in industrial or medical fields. Prussian blue (PB) has been widely used for the removal of Cs ions from water but its colloidal structure hinders reuse, making it problematic for practical use. To solve this problem, we used a commercial macroporous polymer resin as a PB matrix. To provide an efficient anchor for PB, the surface of the polymer resin was decorated with sodium dodecylbenzenesulfonate to produce a negatively charged surface. The successful chemical binding between the polymer resin and PB prevented leakage of the latter during adsorption and crosslinked structure of the matrix provided regeneration of the adsorbent. The adsorbent maintained its removal efficiency after five repeats of the regeneration process. The PB-based, Cs ion-exchange resin showed excellent selectivity toward Cs ions and good reusability, maintaining its high adsorption capacity.

Stabilization of Prussian blue using copper sulfate for eliminating radioactive cesium from a high pH solution and seawater

Prussian blue (PB), an adsorbent for the selective elimination of radioactive cesium from water, is highly versatile due to its unique crystal structure. However, PB crystals quickly decompose in an alkaline solution, generating hazardous cyanide contamination. In this research, the alkaline susceptibility of PB was remedied by incorporating copper sulfate as a protector. A stability assessment was conducted at several environmental conditions, such as high pH and temperatures from 10 °C to 50 °C, in seawater, artificial seawater, and river water. The crystalline and chemical stability of PB in the new class of composite was extremely high, even at a pH value of 11.2, as confirmed using XRD and total cyanide analysis. A comprehensive mechanism study revealed that, at high pH, the copper ions that cover the PB react with hydroxide ions to form copper hydroxide and shielding inner crystals. To decontaminate radioactive cesium, the first step was to immobilize nano PB on a cellulose nanofiber, followed by copper sulfate stabilization. Then, a spongiform adsorbent was made using polyurethane as the precursor. The new stabilized PB showed promising adsorption efficiency. Thus, this research will open a new range of applications for all existing and emerging PB-based adsorbents.

Eu-metal organic framework@TEMPO-oxidized cellulose nanofibrils photoluminescence film for detecting copper ions

Metal-organic frameworks (MOFs) are emerging highly crystallized three-dimensional network complex formed by self-assembling metal ions and organic ligands. However, all MOFs are nanoscale and micro scale powder materials, which greatly impedes their further applications. In this study, a transparent Eu-MOF@TEMPO-oxidized cellulose nanofibrils (Eu-MOF@TOCNF) photoluminescence material for specifically detecting copper ions was fabricated via in-situ synthesis in hydroalcoholic medium. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Fluorescence spectrometer and other equipment were applied to characterize functionalized TOCNF film samples, and the results confirmed the successful fabrication of the functionalized TOCNF film with stable fluorescence properties. The film performed a high selectivity toward copper ion in the presence of other interfering metal ions. The fluorescence intensity of the film decreased gradually with the increase of copper ion concentration, and I₀/I-1 developed a good linear relationship with [Cu²⁺], which made the film a promising material for detecting Cu²⁺ in water body.

Prussian blue-embedded carboxymethyl cellulose nanofibril membranes for removing radioactive cesium from aqueous solution

In this study, we synthesized a Prussian blue (PB)-embedded macroporous carboxymethyl cellulose nanofibril (CMCNF) membrane for facile cesium (Cs) removal. The PB was formed in situ at Fe³⁺ sites on a CMCNF framework cross-linked using FeCl₃ as a cross-linking agent. Cubic PB particles of size 5-20 nm were observed on the macroporous CMCNF membrane surface. The PB-CMCNF membrane showed 2.5-fold greater Cs adsorption capacity (130 mg/g_PB-CMCNF) than commercial PB nanoparticles, even though the PB loading of the PB-CMCNF membrane was less than 100 mg/g_PB-CMCNF. The macroporous structure of the CMCNF membrane led to improved diffusion in the solution, thereby increasing the Cs adsorption capacity. The Cs adsorption behavior was systematically investigated in different solution chemistry. Finally, ¹³⁷Cs removal using a semicontinuous adsorption module was demonstrated in real seawater. The results showed that the PB-CMCNF membrane is a highly effective, practical material for the removal of ¹³⁷Cs from aqueous environments.

Fe-doped copper sulfide nanoparticles for in vivo magnetic resonance imaging and simultaneous photothermal therapy

Multifunctional theranostic agents are widely applied in cancer diagnosis and treatment. These agents can significantly improve therapeutic outcomes and reduce adverse effects in current cancer therapy. Here, we have designed and synthesized iron-doped copper sulfide nanoparticles with polyvinylpyrollidone (FCS@PVP NPs) for magnetic resonance imaging (MRI) guided photothermal therapy. The biocompatible FCS@PVP NPs with strong near-infrared absorption could be used as the photothermal agent and the magnetic characteristic of Fe³⁺ ions could be applied to T ₁-weighted magnetic resonance imaging (MRI). The T ₁-weighted MRI, high photothermal performance, and the biodistribution of FCS@PVP NPs were investigated in mice after intravenous administration. The data showed that there was a high accumulation of FCS@PVP NPs in the tumor sites because of the enhanced permeability and retention (EPR) effect. This result also indicated that the tumors in tumor-bearing mice were effectively suppressed after FCS@PVP NPs treatment under 808 nm laser irradiation. More importantly, FCS@PVP NPs show low cytotoxicity and few side effects because of the quick and safe elimination through the hepatobiliary/fecal route. This work provided a foundation for the clinical application of FCS@PVP NPs as a promising multifunctional theranostic agent for the MRI guided photothermal therapy of cancer.

Activated Carbon/Transition Metal (Ni, In, Cu) Hexacyanoferrate Nanocomposites for Cesium Adsorption

Transition metal hexacyanoferrate/microporous activated carbon composites were obtained using a simple successive impregnation approach. The effect of metal type (nickel, indium, or copper), and the carbon oxidation on the composite characteristics (porosity, metal structure, and particle size), as well as on the removal efficiency of cesium from aqueous solution was investigated. Successful formation of the desired metal hexacyanoferrate phase was achieved and the size of the metallic nanoparticles and their dispersion in the carbon network was found to depend on the metal type, with the indium and nickel-based materials exhibiting the smallest particle size distribution (< 10 nm). Adsorption tests performed under batch conditions demonstrate that the copper hexacyanoferrate/activated carbon composite present the highest cesium removal capacity from aqueous solution (74.7 mg·g⁻¹) among the three studied metal-based nanocomposites. The carbon oxidation treatment leads to the increase in the number of functional groups to the detriment of the porosity but allows for an improvement in the Cs adsorption capacity. This indicates that the Cs adsorption process is governed by the carbon surface chemistry and not its porosity. Moreover, combining oxidized carbon support with copper hexacyanoferrate induces the highest cesium adsorption capacity (101.5 mg·g⁻¹). This could be related to synergistic effects through two absorption mechanisms, i.e., a cation exchange mechanism of Cs with the metallic hexacyanoferrate phase and Cs adsorption via carbon oxygen surface groups, as demonstrated using X-ray photoelectron spectroscopy (XPS) analyses.

Two-dimensional transition metal carbide (Ti3C2Tx) as an efficient adsorbent to remove cesium (Cs+)

Industrial utilization of nuclear resources greatly depends on the effective treatment of nuclear waste.

Chemically bound Prussian blue in sodium alginate hydrogel for enhanced removal of Cs ions

A new approach for efficient removal of radioactive ¹³⁷Cs was developed using a sodium alginate hydrogel beads-based adsorbent containing chemically bound Prussian blue (PB). Sodium alginate was crosslinked with Fe (III) ions to form hydrogel beads, in which Fe (III) had a dual function; it served as a crosslinking agent and also led to PB formation via reaction with hexacyanoferrate. Fe (III) ions, an unusual crosslinking agent for sodium alginate gel, led to stable, homogeneous distribution of PB inside the beads. The amount of embedded PB in the composite beads was more than two times larger than in the conventional sodium alginate-PB composite beads, resulting in an adsorption capacity for Cs ions that was two to five times higher, mainly because of a higher PB contents and because of the microporosity of the sodium alginate hydrogel.

Photoresponsive Drug/Gene Delivery Systems

Light as an external stimulus can be precisely manipulated in terms of irradiation time, site, wavelength, and density. As such, photoresponsive drug/gene delivery systems have been increasingly pursued and utilized for the spatiotemporal control of drug/gene delivery to enhance their therapeutic efficacy and safety. In this review, we summarized the recent research progress on photoresponsive drug/gene delivery, and two major categories of delivery systems were discussed. The first category is the direct responsive systems that experience photoreactions on the vehicle or drug themselves, and different materials as well as chemical structures responsive to UV, visible, and NIR light are summarized. The second category is the indirect responsive systems that require a light-generated mediator signal, such as heat, ROS, hypoxia, and gas molecules, to cascadingly trigger the structural transformation. The future outlook and challenges are also discussed at the end.

A Highly Efficient Adsorbent Cu-Perusian Blue@Nanodiamond for Cesium in Diluted Artificial Seawater and Soil-Treated Wastewater

A new adsorbent Cu-Perussian blue@Nanodiamond (Cu-PB@DND) for Cs⁺ removal was prepared and characterized with IR, SEM, X-ray diffraction, particle size analysis, and zeta-potential. The adsorbent consists of a core of aggregated detonation nanodiamond (DND) particles with the surface treated with Cu-PB. Cesium adsorption was studied in two modes; a co-precipitation mode and a batch mode. In the co-precipitation mode, DND, CuCl₂, and K₄[Fe(CN)₆] were added sequentially to a Cs⁺ solution in diluted artificial seawater. In the batch mode, adsorbent Cu-PB@DND was dispersed into a Cs⁺ solution with stirring. The distribution coefficient (K_d) of the co-precipitation mode was 8.8 × 10⁷ (mL/g) at Cs⁺ 6.6 ppm in 0.07% seawater. The K_d value of the batch mode was 1.3 × 10⁶ (mL/g). Precipitation of Cs⁺-incorporated particles was complete, and post filtration was not necessary. Excess copper and iron ions were completely removed and were not detected in the supernatant. The adsorption data for Cu-PB@DND were analyzed by assuming Langmuir isotherm and a good fit was obtained with a maximum adsorption capacity Q_max of 759 mg/g. The co-precipitation method was also applied to soil-treated wastewater.

Porous 3D Prussian blue/cellulose aerogel as a decorporation agent for removal of ingested cesium from the gastrointestinal tract

In the present study, we successfully synthesized a porous three-dimensional Prussian blue-cellulose aerogel (PB-CA) composite and used it as a decorporation agent for the selective removal of ingested cesium ions (Cs⁺) from the gastrointestinal (GI) tract. The safety of the PB-CA composite was evaluated through an in vitro cytotoxicity study using macrophage-like THP-1 cells and Caco-2 intestinal epithelial cells. The results revealed that the PB-CA composite was not cytotoxic. An adsorption study to examine the efficiency of the decorporation agent was conducted using a simulated intestinal fluid (SIF). The adsorption isotherm was fitted to the Langmuir model with a maximum Cs⁺ adsorption capacity of 13.70 mg/g in SIF that followed pseudo-second-order kinetics. The PB-CA composite showed excellent stability in SIF with a maximum Cs⁺ removal efficiency of 99.43%. The promising safety toxicology profile, remarkable Cs⁺ adsorption efficacy, and excellent stability of the composite demonstrated its great potential for use as an orally administered drug for the decorporation of Cs⁺ from the GI tract.