Iodine Molecules Research Articles

Positional Isomerism: A Novel Paradigm for Enhancing Iodine Adsorption in Functionalized Metal-Organic Frameworks.

Porous metal-organic frameworks (MOFs) have shown great potential as adsorbents for capturing radioiodine, a major fission product generated during the reprocessing of nuclear fuel. However, studies exploring the correlation between the structure of MOFs and iodine uptake capacity remain notably rare. In this study, we introduce a new strategy for enhancing the iodine adsorption efficiency of MOFs by strategically varying the position of functional groups on the organic linkers. Employing ligand-functionalized UiO-67 MOFs, our findings reveal that ortho-amino substitution of UiO-67-o-NH2, proximal to the node of the dicarboxylate linker, markedly accelerates adsorption kinetics of iodine vapor in comparison to meta-amino substitution of UiO-67-m-NH2, where the amino groups are oriented away from the node. In contrast, UiO-67-m-NH2 exhibits a higher adsorption capacity of 2.19 g/g, compared to 1.91 g/g for UiO-67-o-NH2, attributable to its higher porosity. Furthermore, a competitive I2/H2O vapor adsorption study demonstrated that UiO-67-o-NH2 exhibits faster adsorption kinetics and higher selectivity for iodine in the presence of water vapor compared to UiO-67-m-NH2. Additionally, the crucial influence of positional isomerism on enhancing iodine adsorption has been corroborated through Raman spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. These analyses reveal that the nitrogen atom positioned at the ortho site demonstrates a stronger affinity for iodine molecules compared to the nitrogen atom at the meta site, thereby improving adsorption kinetics.

Nitrogen-doped hierarchically porous carbon derived from biomass for efficient capture of iodine

Effectively capturing radioactive iodine formed during nuclear energy utilization is crucial for environment protection and human health. Herein, we present a facile and effective strategy to synthesize a nitrogen-doped hierarchically porous carbon from corn stalks for iodine capture in gaseous and liquid environment. The as-prepared carbon material possesses a hierarchically micro/mesopore structure with highly developed mesopores, a large specific surface area (1892.99 m2 g−1), and suitable nitrogen-doping (2.32 at.%). As a result, the carbon material exhibits efficient iodine capture performance, showing a large capture capacity of 3.14 g g−1 at 80 °C for iodine vapor and a fast removal rate of ∼97 % within 5 min for iodine aqueous solution, outperforming most of carbon-based materials for iodine capture reported in literatures. Thermodynamic and kinetic analyses reveal that the adsorption of iodine vapor conforms to the Langmuir model and pseudo-second-order model, respectively. Density functional theory calculation results indicate that the doped-nitrogen heteroatoms strengthen the interaction between iodine molecules and carbon, which can enhance the affinity for iodine molecules by forming a donor–acceptor complex through the donation of lone-pair electrons, thereby facilitating effective capture of iodine. This work develops a biomass-based porous carbon with potential to efficiently capture radioactive iodine.

A Supramolecular‐Nanocage‐Based Framework Stabilized by π‐π Stacking Interactions with Enhanced Photocatalysis

Abstractπ frameworks, defined as a type of porous supramolecular materials weaved from conjugated molecular units by π‐π stacking interactions, provide a new direction in photocatalysis. However, such examples are rarely reported. Herein, we report a supramolecular‐nanocage‐based π framework constructed from a photoactive Cu(I) complex unit. Structurally, 24 Cu(I) complex units stack together through π‐π stacking interactions, forming a truncated octahedral nanocage with sodalite topology. The inner diameter of the nanocage is 2.8 nm. By sharing four open faces, each nanocage connects with four equivalent ones, forming a 3D porous π framework (π‐2). π‐2 shows good thermal and chemical stability, which can adsorb CO2, iodine, and methyl orange molecules. More importantly, π‐2 can serve as a photocatalyst for hydrogen evolution reaction. With ultrafine Pt subnanometer particles (0.9±0.1 nm) incorporated into the nanocages as a co‐catalyst, the hydrogen evolution rate reaches a record‐high value of 524012 μmol/gPt/h in the absence of any additional photosensitizers. The high photocatalytic activity can be ascribed to the ultrafine size of the Pt particles, as well as the fast electron transfer from π‐2 to the highly active Pt upon illumination. π‐2 represents the unique stable supramolecular‐cage‐based π framework with excellent photocatalytic activity.

A Supramolecular-Nanocage-Based Framework Stabilized by π-π Stacking Interactions with Enhanced Photocatalysis.

π frameworks, defined as a type of porous supramolecular materials weaved from conjugated molecular units by π-π stacking interactions, provide a new direction in photocatalysis. However, such examples are rarely reported. Herein, we report a supramolecular-nanocage-based π framework constructed from a photoactive Cu(I) complex unit. Structurally, 24 Cu(I) complex units stack together through π-π stacking interactions, forming a truncated octahedral nanocage with sodalite topology. The inner diameter of the nanocage is 2.8 nm. By sharing four open faces, each nanocage connects with four equivalent ones, forming a 3D porous π framework (π-2). π-2 shows good thermal and chemical stability, which can adsorb CO2, iodine, and methyl orange molecules. More importantly, π-2 can serve as a photocatalyst for hydrogen evolution reaction. With ultrafine Pt subnanometer particles (0.9±0.1 nm) incorporated into the nanocages as a co-catalyst, the hydrogen evolution rate reaches a record-high value of 524012 μmol/gPt/h in the absence of any additional photosensitizers. The high photocatalytic activity can be ascribed to the ultrafine size of the Pt particles, as well as the fast electron transfer from π-2 to the highly active Pt upon illumination. π-2 represents the unique stable supramolecular-cage-based π framework with excellent photocatalytic activity.

Synthesis of a Novel Zwitterionic Hypercrosslinked Polymer for Highly Efficient Iodine Capture from Water.

Cationic porous organic polymers have a unique advantage in removing radioactive iodine from the aqueous phase because iodine molecules exist mainly in the form of iodine-containing anions. However, halogen anions will inevitably be released into water during the ion-exchange process. Herein, we reported a novel and easy-to-construct zwitterionic hypercrosslinked polymer (7AIn-PiP)-containing cationic pyridinium-type group, uncharged pyridine-type group, pyrrole-type group, and even an electron-rich phenyl group, which in synergy effectively removed 94.2% (456 nm) of I2 from saturated I2 aqueous solution within 30 min, surpassing many reported iodine adsorbents. Moreover, an I2 adsorption efficiency of ~95% can still be achieved after three cyclic evaluations, indicating a good recycling performance. More importantly, a unique dual 1,3-dipole was obtained and characterized by 1H/13C NMR, HRMS, and FTIR, correlating with the structure of 7AIn-PiP. In addition, the analysis of adsorption kinetics and the characterization of I2@7AIn-PiP indicate that the multiple binding sites simultaneously contribute to the high affinity towards iodine species by both physisorption and chemisorption. Furthermore, an interesting phenomenon of inducing the formation of HIO2 in unsaturated I2 aqueous solution was discovered and explained. Overall, this work is of great significance for both material and radiation protection science.

Two-Dimensional Biodegradable l-Cysteine-Iodine Nanosheets for Computed Tomography-Guided Cancer Synergistic Sonodynamic Therapy and Chemotherapy.

Biodegradable versatile inorganic nanomaterials are highly desirable in the field of nanomedicine. Here, for the first time, we report a kind of novel two-dimensional biodegradable l-cysteine-iodine (l-Cys-I) nanosheet with high computed tomography (CT) imaging ability and sonosensitization efficacy. Such l-Cys-I nanosheets consist of iodine molecules and l-Cys, where the iodine molecules are coordinated and stabilized by l-Cys and cross-linked to form nanosheets through disulfide bonds. The large and convenient functional surface is further modified with targeting moieties DSPE-PEG-RGD and cancer drug doxorubicin (DOX) to construct a nanotheranostic nanoplatform (CIRD). Under ultrasound irradiation, the CIRD nanosheets assist in tremendous reactive oxygen species generation and controllable DOX release, leading to remarkable anticancer performance both in vitro and in vivo due to the synergistic sonodynamic therapy (SDT) and chemotherapy. Our results validate that the CIRD nanosheets enable effective body excretion and negligible systemic toxicity owing to the biodegradation properties. The CIRD nanosheets, with biodegradability, biocompatibility, and versatility, hold great promise in nanotheranostics.

Persistent Ground-State Planar Alignment of Iodine Molecule through Resonant Excitation.

We demonstrate the generation of a persistent planar molecular alignment by subjecting a relatively warm gas sample to a resonant femtosecond laser pulse. By optically probing I_{2} molecules in their vibronic ground states, we observe a persistent delocalization of their axes near the plane orthogonal to the field direction. This phenomenon is attributed to the one-photon resonant excitation, primarily removing molecules from the thermal ground-state distribution that are initially aligned along the field, i.e., those with small projection of their rotational angular momentum along the field.

Tunable sulfur vacancies in amorphous-crystalline AC-Bi2S3-x@C derived from CAU-17 for efficient capture of radioiodine: Comparison of sulfur vacancies in amorphous and crystalline structures

Solid-phase adsorption has been recognized as an effective method for the control of volatile radioactive iodine in spent fuel reprocessing plant off-gases. However, it is still a challenge to develop efficient and stable iodine capture adsorbents. In this work, sulfur-vacancy-rich amorphous-crystalline AC-Bi2S3-x@C was prepared by solvothermal vulcanization using CAU-17 as a precursor. Based on the synergistic effect of the amorphous structure and sulfur vacancy defects, AC-Bi2S3-x@C exhibited fast adsorption equilibrium time (15 min), distinguished iodine adsorption capacity (1763.9 mg g−1), high percentage of chemical adsorption (93.4 %) as well as favorable thermal and irradiation stability. Adsorption experiments and theoretical calculations verified that the amorphous structure not only enhance the charge transfer between sulfur vacancy defects and iodine molecules, but also offers rapid diffusion channels for iodine molecules to the interior of the adsorbent and sufficient internal binding sites to promote iodine molecule adsorption in its interior. The used adsorbent showed high iodine retention (92.3 %) and excellent chemical durability (normalized iodine leaching rate of 4.63 × 10-5 g m−2 d-1) in glass solidification. In general, this work presented a new concept in the design and synthesis of efficient radioactive iodine capture materials.

Construction of nitrogen-rich groups @ zirconium-based metal-organic frameworks for efficient iodine capture

Efficient capture of radioactive iodine serves as an inevitable demand for secure utilization of nuclear energy, environmental conservation, and human health. In this contribution, a series of iodine adsorbent materials Im@UiO-66 were fabricated by encapsulating imidazole (Im) molecules into the pore of a classical zirconium-based metal–organic frameworks UiO-66, employing a simple and feasible vapor-diffusion strategy. Compared with original UiO-66, the resulting composites achieved a significant enhancement in iodine capture performance. Particularly, Im@UiO-66-3 demonstrated outstanding iodine adsorption performance with capacities of 4.66 g g−1 for vapor and 915 mg g−1 for solution, which were 3.5 and 9.2 times of the original UiO-66, respectively. Moreover, the introduction of nitrogen through ligand encapsulation provided additional sites for iodine immobilization. The primary mechanism underlying this remarkable performance was identified as charge transfer between iodine and imidazole (Im) molecules. The research offers valuable insights for the design of high-efficiency iodine adsorbents.

Copper nanoparticles embedded flexible graphene aerogel for effective capture of iodine vapor

Development of highly efficient and low-cost adsorbents for radioactive iodine vapor is significant but still challenged now. In this work, we reported a novel graphene aerogel (GA-Cu-ED) decorated by zero-valence copper and nitrogen active sites, prepared via a two-step route of hydrothermal reaction and freeze-drying processes. The combination of X-ray photoelectron spectroscopy (XPS) valence imaging and high-resolution transmission electron microscope (TEM) confirms the formation of Cu0 and its uniform distribution. Besides, the good elasticity and ultra-low density of this aerogel were proved. Adsorption experiments indicate that GA-Cu-ED has a high adsorption capacity of 3.76 g/g for gaseous iodine and short adsorption equilibrium time of 90 min. Even after three cycles, this aerogel still shows an almost unchanged adsorption capacity of 3.74 g/g. Meanwhile, this aerogel can be long-term stored under air atmosphere with only slight loss in adsorption performance. In addition, the captured iodine molecules can be tightly bound in this aerogel even after being exposed in air for three days. Mechanism analysis indicates the I-benzene conjugation, I–N charge transfer, and I2–Cu0 chemisorption contribute together to the capture of gaseous iodine. Therefore, our work provides a highly efficient and reliable adsorbent for radioactive iodine vapor, which may be worthy in large-scale application in future.

Recyclable β-CD-crosslinked porous polymer networks for iodine capture

Developing a green and safe reversible iodine capture material is key for nuclear waste treatment. Herein, we report a readily obtainable β-CD-based polymer network (CDPN) that can reversibly capture iodine. This white CDPN material is able to capture both gaseous iodine and liquid iodine, with a good iodine uptake capacity of 2.73 g/g. The I2 can be easily released from I2@CDPN by soaking it in methanol, achieving nearly complete release within 1 min. The CDPN powder exhibits good recyclability in its iodine capture performance. The efficient iodine capture ability of CDPN is ascribed to the cyclodextrin cavity and the crosslinked polymer network, which enhance the interactions between the host (CDPN) and guest (iodine) molecules, both intermolecularly and intramolecularly.

Halogen-doped 2D reduced graphene oxide with TiO2 nanocomposite for water remediation application

Water contamination by organic and inorganic pollutants has been a challenging problem impacting living organisms. The current study explores the photocatalytic property of nanocomposite based on iodine-doped reduced graphene oxide with titanium dioxide nanoparticles (TNPs) for methyl orange (MO) dye degradation. A nanocomposite of TNPs with iodine-doped reduced graphene oxide (TIR) is prepared using the hydrothermal technique. The physicochemical properties of nanocomposite were explored by various techniques such as an X-diffractometer (XRD), Raman spectroscopy, Fourier transforms the infrared spectrum, energy-dispersive X-ray spectroscopy spectrum (EDX), and high-resolution transmission electron microscopy (HRTEM). The XRD reveals the crystalline structure of the TIR nanocomposite. The anatase TNPs with an average particle size of 9.68 ± 2.1 nm are confirmed by HRTEM. The Raman spectrum confirms the presence of iodine molecules with a peak at 101 cm−1, and the EDX spectrum confirms the presence of iodine molecules with 15.31 % elements in the TIR nanocomposite. The MO dye degradation efficiency of 96.12 % with 120 min UV exposure for TIR suggests that the iodine-doped nanocomposite is a promising photocatalyst for water remediation.

Introgression of Lone Electron Pairs into π-Conjugated Structures Resulting in Giant Electron-Rich Clusters with High Trapping Capacity for Iodine Molecules

Introgression of Lone Electron Pairs into π-Conjugated Structures Resulting in Giant Electron-Rich Clusters with High Trapping Capacity for Iodine Molecules

Fabrication of amidoxime grafted polyacrylonitrile for iodine vapor capture from off-gas

The exploration of effective gaseous iodine adsorbents is an interesting and challenging task in the field of radwaste disposal. In this study, amidoxime groups (AO) were successfully grafted onto polyacrylonitrile to obtain amidoxime grafted polyacrylonitrile (PAN-AO) for capturing gaseous iodine. The results of the combined characterization analysis have confirmed that the introduction of AO greatly improved its thermostability, porosity and available functional groups of PAN. The impacts of reaction time, iodine concentration and reaction heat on the uptake capacity for gaseous iodine were systematically studied. The PAN-AO exhibited higher iodine capture capacity (1534.4 mg/g) than PAN (72.1 mg/g) at 80 °C and 600 min, which was ascribed to the chemical reaction between electron-rich AO groups and electron-deficient iodine molecules. The studies of kinetic fitting and activation energy (Ea = 44.11 kJ/mol) further confirmed that chemical adsorption was the major fashion during the whole uptake process of PAN-AO for iodine. Besides, PAN-AO still had an iodine uptake capacity of 704.4 mg/g after five recycling, manifesting the remarkable cycle performance of PAN-AO. In brief, this study offered a new reference for radioactive iodine uptake and the synthesized PAN-AO was able to serve as an efficient iodine capture material.

Solvent-Responsive Nonporous Adaptive Crystals Derived from Pyridinium Hydrochloride and the Application in Iodine Adsorption.

Nonporous adaptive crystals (NACs) are crystalline nonporous materials that can undergo a structural adaptive phase transformation to accommodate specific guest via porous cavity or lattice voids. Most of the NACs are based on pillararenes because of their flexible backbone and intrinsic porous structure. Here a readily prepared organic hydrochloride of 4-(4-(diphenylamino)phenyl)pyridin-1-ium chloride (TPAPyH), exhibiting the solvent dimension-dependent adaptive crystallinity is reported. Wherein it forms a nonporous α crystal in a solvent with larger dimensions, while forming two porous β and γ crystals capable of accommodating solvent molecules in solvent with small size. Furthermore, the thermal-induced single-crystal-to-single-crystal (SCSC) transition from the β to α phase can be initiated. Upon exposure to iodine vapor or immersion in aqueous solution, the nonporous α phase transforms to porous β phase by adsorbing iodine molecules. Owing to the formation of trihalide anion I2Cl- within the crystal cavity, TPAPyH exhibits remarkable performance in iodine storage, with a high uptaking capacity of 1.27 g g-1 and elevated iodine desorption temperature of up to 110 and 82°C following the first and second adsorption stage. The unexpected adaptivity of TPAPyH inspires the design of NACs for selective adsorption and separation of volatile compound from organic small molecules.

Adsorption induced bipolar excitation at semiconductor surface

Adsorption on metal surfaces has been shown to lead to chemisorption induced electronic excitation but direct experimental evidence of chemisorption induced excitation on semiconductor surfaces is still missing. Here, we design and use high-quality Silicon (Si) p-n diodes to in-situ probe the charge transfer process taking place during vapor and liquid phase chemisorption of iodine molecules on H-Si (100) surface. We find that the diodes can generate electricity and feed an external circuit during the chemisorption process, demonstrating chemisorption-induced electron and hole generation and the means to electrically monitor the process. A bipolar semiconductor electrochemical model where a single semiconductor surface hosts the spontaneous oxidation (electron injection) and reduction (hole injection) reactions simultaneously on its conduction and valence bands without any electrolytes is proposed to explain the observations. Our work provides new insight on the energy relaxation processes of chemisorption and also calls for further studies on the observed chemovoltaic effect. Overall, the results indicate a possibility for developing electrolyte-free vapor phase chemical energy-to-electricity converters and detectors.

Iodine-doped reduced graphene oxide and titanium dioxide nanocomposite as effective amperometric glucose biosensor

The current study fabricated a non-enzymatic glucose sensor based on iodine-doped reduced graphene oxide with titanium dioxide (I-rGO@TiO2) nanocomposite. Initially, the sol-gel and thermal reduction methods synthesized titanium dioxide (TiO2) nanoparticles and reduced graphene oxide (rGO). Then, the hydrothermal technique was utilized to synthesize a composite of I-rGO@TiO2 by combining I-rGO and TiO2 in a 1:4 ratio. The XRD spectrum and TEM images revealed that in the I-rGO@TiO2 nanocomposite, nanocrystalline anatase titanium is randomly distributed on the I-rGO sheets. Fourier transforms the infrared spectrum of nanocomposite shows the presence of titanium and oxygen bond characteristics peak between 400 and 850 cm−1. Iodine molecules peak at 100 cm−1 were obtained in Raman spectra. The AC conductivity and dielectric properties of the nanocomposite were analyzed. For the sensor fabrication, the indium tin oxide electrode surface is modified by I-rGO@TiO2, and the electrochemical performance was examined. At room temperature, the sensor demonstrated a wider linear detection range (0.5−10 mM). The lower detection limit of the sensor was 0.23 μM (S/N = 3), and the sensitivity was 221.69 μA mM−1 cm−2. The I-rGO@TiO2 nanocomposite shows a positive temperature coefficient via the thermal activation of charge carriers and a conductivity of 3.82 × 10−5 Ω−1m−1 at 200 °C. Additionally, the antibacterial properties was evaluated, and dose-dependent properties were observed towards E. coli and Bacillus subtilis bacterium.

Humic acid-based polyphenol-functionalized collagen fiber for efficient recognition capture of iodine vapor

Effective capture of radioactive iodine vapor is a crucial part of the spent fuel reprocessing process. In this study, humic acid (HA), which has excellent recognition capture of iodine vapor, is introduced as the active site construction center, functionalizing and modifying alkali-activated collagen fiber (ACF), to prepare the biomass composite functional materials (HA@ACF). The results demonstrate that HA@ACF exhibits exceptional recognition ability and a strong affinity for iodine vapor, with an adsorption capacity of 2811.8 mg/g (ACF is only 1068.6 mg/g). Simultaneously, under relative humidity of 27 % and strong acid conditions, the iodine vapor capture capacity of HA@ACF only decreased by 17.2 %, indicating that the material exhibits excellent iodine capture performance under complex conditions. The excellent adsorption performance is attributed to the synergistic effect of abundant −NHR, C = O, and phenolic hydroxyl active sites in HA@ACF, which recognize and induce iodine vapor, resulting in the capture of iodine molecules as I3-. Meanwhile, DFT calculations reveal the excellent adsorption energy (−0.51 eV) of iodine vapor on the phenolic hydroxyl groups on HA. Therefore, the HA@ACF biomass composite functional material can be an ideal candidate adsorbent for the efficient recognition capture of radioactive iodine vapor in airborne effluent.

Analytical determination of enthalpy, heat capacity and Gibbs free energy for nitrogen and iodine

The analytical solutions for the modified shifted Morse potential model have been obtained for some molecules. Despite the importance of this potential in molecular systems, this model hasn’t gained extensive attention. This research delves into predicting thermodynamic functions, specifically examining molar enthalpy, molar heat capacity, and molar Gibbs free energy for nitrogen and iodine molecules using this modified shifted Morse potential. The predicted result aligned with the experimental data, with iodine exhibiting a closer match.

Theoretical prediction of molar entropy of modified shifted Morse potential for gaseous molecules

The modified shifted Morse potential is a molecular potential that describes the molecular vibration and atomic interaction. This potential has not received much report as one of the useful potential function. In this study, the molar entropy of a modified shifted Morse is obtained via the vibrational partition function, rotational partition function and translational partition function. Numerical results are obtained for iodine molecule (I2), silicon carbide (SiC), carbon phosphide (CP) and fluorine molecule (F2) for temperatures of 200 K to 6000 K. The predicted results are compared with the experimental results obtained from the National Institute of Standards and Technology (NIST) data base. The predicted values aligned with the experimental results for the four molecules. The average absolute percentage deviation obtained for each molecule is less than one, which shows a good representation of the modified shifted Morse potential for thermodynamic functions.