Incorporation Of Metal Ions Research Articles

Design of Bifunctional Nanocatalysts Based on Zeolites for Biomass Processing.

Bifunctional catalysts consisting of metal-containing nanoparticles (NPs) and zeolite supports have received considerable attention due to their excellent catalytic properties in numerous reactions, including direct (biomass is a substrate) and indirect (platform chemical is a substrate) biomass processing. In this short review, we discuss major approaches to the preparation of NPs in zeolites, concentrating on methods that allow for the best interplay (synergy) between metal and acid sites, which is normally achieved for small NPs well-distributed through zeolite. We focus on the modification of zeolites to provide structural integrity and controlled acidity, which can be accomplished by the incorporation of certain metal ions or elements. The other modification avenue is the adjustment of zeolite morphology, including the creation of numerous defects for the NP entrapment and designed hierarchical porosity for improved mass transfer. In this review, we also provide examples of synergy between metal and acid sites and emphasize that without density functional theory calculations, many assumptions about the interactions between active sites remain unvalidated. Finally, we describe the most interesting examples of direct and indirect biomass (waste) processing for the last five years.

Structural and optical properties of sol-gel synthesized TiO2 nanocrystals: Effect of Ni and Cr (co)doping

Nickel and chromium metal ions have been utilized to dope and co-dope titanium dioxide nanocrystals, thereby broadening the light absorption range of titania into the visible light spectrum. The doped and co-doped TiO2 nanocrystals were prepared using sol-gel techniques, with a varied doping concentration that extended from 0.25 to 10.0 wt%.These modified materials underwent comprehensive analysis using standard analytical tools such as X-ray diffraction, Raman spectroscopy, BET surface area measurement, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, and fluorescence spectroscopy. Powder XRD technique reveals that the modified catalyst majorly contains the anatase polymorph with the transition metal ion either substituting Ti or located as interstitials in the lattice of TiO2. Raman and UV–Vis absorption spectra of the doped and codoped catalyst a show λmax shift towards longer wavelength when in the metal ion concentration is increased from 0.25 to 10 wt%. FTIR patterns show the stretching and vibration patterns of hydroxyl radicals present in the nanocrystals. The BET surface areas of the doped and codoped TiO2 nanocrystals have substantially higher surface areas compared with that of the undoped TiO2. Electronic structural studies of the TiO2, (Ti,Cr)O2, (Ti,Ni)O2, and (Ti,Ni,Cr)O2 crystals using density functional theory indicated a reduction in the band gap width (Eg) of pure TiO2 when doped with transition metals. Specifically, the indirect bandgap values for Ni(10%), Cr(10%) and NiCr(5% + 5%) doping were 2.96, 2.83, and 2.7 eV, respectively. Furthermore, the photoluminescence intensity substantially decreased with the incorporation of transition metal ions in the TiO2 nanocrystals.

Vanadyl as a Spectroscopic Probe of Tunable Ligand Donor Strength in Bimetallic Complexes.

Incorporation of secondary metal ions into heterobimetallic complexes has emerged as an attractive strategy for rational tuning of compounds' properties and reactivity, but direct solution-phase spectroscopic interrogation of tuning effects has received less attention than it deserves. Here, we report the assembly and study of a series of heterobimetallic complexes containing the vanadyl ion, [VO]2+, paired with monovalent cations (Cs+, Rb+, K+, Na+, and Li+) and a divalent cation (Ca2+). These complexes, which can be isolated in pure form or generated in situ from a common monometallic vanadyl-containing precursor, enable experimental spectroscopic and electrochemical quantification of the influence of the incorporated cations on the properties of the vanadyl moiety. The data reveal systematic shifts in the V-O stretching frequency, isotropic hyperfine coupling constant for the vanadium center, and V(V)/V(IV) reduction potential in the complexes. These shifts can be interpreted as charge density effects parametrized through the Lewis acidities of the cations, suggesting broad potential for the vanadyl ion to serve as a spectroscopic probe in multimetallic species.

Effect of Nanoparticle Interaction on Structural, Conducting and Sensing Properties of Mixed Metal Oxides

This review analyzes the studies published, mainly in the last 10–15 years, on the synthesis, structure, and sensor properties of semiconductor nanocomposites. Particular attention is paid to the interaction between nanoparticles of the sensitive layer, and its effect on the structure, sensitivity, and selectivity of semiconductor sensor systems. Various mechanisms of interaction between nanoparticles in metal oxide composites are considered, including the incorporation of metal ions of one component into the structure of another, heterocontacts between different nanoparticles, and core–shell systems, as well as their influence on the characteristics of gas sensors. The experimental data and studies on the modeling of charge distribution in semiconductor nanoparticles, which determine the conductivity and sensor effect in one- and two-component systems, are also discussed. It is shown that the model which considers the interactions of nanoparticles best describes the experimental results. Some mechanisms of detection selectivity are considered in the conclusion.

Effect of Ni and Mn dopant on thermoelectric power generation performance of ZnO nanostructures synthesized via hydrothermal method

In this article, we have presented a low-cost hydrothermal approach to enhance the thermoelectric performance of ZnO nanostructures via modulation doping. For this purpose, we have prepared a series of pure and X:ZnO (X = Ni & Mn) samples. The Seebeck value of the Mn-doped samples possesses the maximum Seebeck coefficient of −36 μV/°C compared to the pure and Ni-doped samples (−22 μV/°C & −27 μV/°C) at room temperature. The highest value of the Seebeck coefficient for the Mn-doped samples is related to the formation of mid-gap energy band states due to the substitution of Mn2+ with Zn2+. These mid-band states induce an imbalance in the DOS, by producing a spin polarization effect that leads to a high Seebeck value. In terms of electrical conductivity, the Ni-doped ZnO sample exhibits the highest electrical conductivity of about 122 S/cm, due to the incorporation of Ni metal ions inside the ZnO matrix (confirmed by XRD) and leads to a high carrier concentration. However, the highest Seebeck value for the Mn-doped sample results in the maximum thermoelectric power factor ∼1.12 × 10−5 Wm−1C−2 at room temperature.

Unveiling the novel interfacial anchoring effect of neodymium(III) for realization of blue-emitting InP/ZnS quantum dots

Colloidal indium phosphide (InP) quantum dots (QDs) have attracted worldwide attention due to their intrinsic environmental friendliness and excellent optical properties. The incorporation of metal ions has been a common way to modify the properties of InP QDs and some metal ions have been confirmed to be effective in preparation of blue-emitting InP QDs. Herein, the interfacial anchoring effect of rare earth metal ions neodymium(III) (Nd3+) is unveiled for the first time by analyzing the alteration of spectra, size, and composition of QDs after Nd doping. It is evidenced that Nd substitutes for In of InP during the process of nucleation. More crucially, Nd is anchored at the surface of InP and inhibits their further growth at the high temperature of shelling. This ensures that the size of InP QDs and the absorption peak position are almost maintained during shell growth. It is demonstrated that the emitting wavelength of InP/ZnS core/shell QDs is systematically tunable through varying Nd amounts. Finally, the optimized InP/ZnS QDs exhibiting an emission peak of 470 nm with a photoluminescence quantum yield of 44%, and a full width at half-maximum of 46 nm are prepared.

Metal and Nonmetal Ion Doping Effect on the Dielectric Relaxation of TiO2 Electrodes

TiO2-Based Materials The incorporation of both metallic and non-metallic ions into TiO2 has emerged as a promising area of research, as it has the potential to enhance the charge carrier kinetics. In article number 2200807 by Manish Kumar Vishwakarma, Monojit Bag, and Puneet Jain, the correlation analysis of impedance and modulus spectroscopy data paints a detailed picture of the charge carrier relaxation and conduction mechanism. It will help to optimize TiO2-based materials for practical applications.

Engineering of a Hybrid g-C3N4/ZnO-W/Cox Heterojunction Photocatalyst for the Removal of Methylene Blue Dye

Robust hybrid g-C3N4/ZnO-W/Cox heterojunction composites were synthesized using graphitic carbon nitride (g-C3N4) and ZnO-W nanoparticles (NPs) and different concentrations of Co dopant. The hybrid heterojunction composites were prepared by simple and low-cost coprecipitation methods. The fabricated catalyst was explored and investigated using various characterization techniques such as FTIR, XRD, FESEM and EDX. The surface morphology of the as-prepared hybrid nanocomposites with particle sizes in the range of 15–16 nm was validated by SEM analysis. The elemental composition of the synthesized composites was confirmed by EDS analysis. Photocatalysis using a photon as the sole energy source is considered a challenging approach for organic transformations under ambient conditions. The photocatalytic activity of the heterojunctions was tested by photodegrading methylene blue (MB) dye in the presence of sunlight. The reduced band gap of the heterojunction composite of 3.22–2.28 eV revealed that the incorporation of metal ions played an imperative role in modulating the light absorption range for photocatalytic applications. The as-synthesized g-C3N4/ZnO-W/Co0.010 composite suppressed the charge recombination ability during the photocatalytic degradation of methylene blue (MB) dye. The ternary heterojunction C3N4/ZnO-W/Co0.010 composite showed an impressive photocatalytic performance with 90% degradation of MB under visible light within 90 min of irradiation, compared to the outcomes achieved with the other compositions. Lastly, the synthesized composites showed good recyclability and mechanical stability over five cycles, confirming them as promising photocatalyst options in the future.

Design of high-performance ion-doped CoP systems for hydrogen evolution: From multi-level screening calculations to experiment

Rational design of high-performance electrocatalysts for hydrogen evolution reaction (HER) is vital for future renewable energy systems. The incorporation of foreign metal ions into catalysts can be an effective approach to optimize its performance. However, there is a lack of systematic theoretical studies to reveal the quantitative relationships at the electronic level. Here, we develop a multi-level screening methodology to search for highly stable and active dopants for CoP catalysts. The density functional theory (DFT) calculations and symbolic regression (SR) were performed to investigate the relationship between the adsorption free energy (ΔGH*) and 10 electronic parameters. The mathematic formulas derived from SR indicate that the difference of work function (ΔΦ) between doped metal and the acceptor plays the most important role in regulating ΔGH*, followed by the d-band center (d-BC) of doped system. The descriptor of HER can be expressed as ΔGH∗=1.59×0.188ΔΦ+dBC+0.120-0.166 with a high determination coefficient (R2 = 0.807). Consistent with the theoretical prediction, experimental results show that the Al-CoP delivers superior electrocatalytic HER activity with a low overpotential of 75 mV to drive a current density of 10 mA cm−2, while the overpotentials for undoped CoP, Mo-CoP, and V-CoP are 206, 134, and 83 mV, respectively. The current work proves that the ΔΦ is the most significant regulatory parameter of ΔGH* for ion-doped electrocatalysts. This finding can drive the discovery of high-performance ion-doped electrocatalysts, which is crucial for electrocatalytic water splitting.

Facile and Effective Band Gap Engineering of 2D Ruddlesden–Popper Perovskites with Improved Structural and Optoelectronic Properties

Incorporation of alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) into 3D metal-halide perovskite crystal structures has resulted in improved crystallinity and film morphology, reduced trap density, and enhanced charge carrier transport. However, due to intrinsic structural instability associated with 3D perovskites, their alkali metal ion-doped semiconductors are not a suitable option for real device optoelectronics. In recent years, Ruddlesden–Popper (RP)-phase quasi-two-dimensional (2D) metal halide perovskites have drawn considerable attention due to their tunable energy band gap, large electron and hole diffusion lengths (∼10 μm), and lower recombination rates compared to pristine 2D metal halide perovskites (n = 1). However, alkali metal ion-incorporated RP perovskite systems are not explored much; therefore, we demonstrate the incorporation of Rb+, using the RbI precursor, into the quasi-2D RP perovskite (BA)2(MA)Pb2Br7 (BA = C4H9NH3; MA = CH3NH3), which has also resulted in the successive replacement of Br– with I– in the PbBr6 network. Subsequent replacement of Br– with I– finely tuned the energy band gap from 2.92 to 2.43 eV, while keeping the phase of the pristine lead bromide RP perovskite intact, as confirmed by X-ray diffraction investigations. MA+ cations available at the outer edge sites got partially exchanged with Rb ions, which in turn has regulated the perovskite crystal growth, whereas the excess Rb+ alloyed with replaced Br– to form RbBr, which resulted in the formation of thinner grain boundaries and thus showed improved charge transport. Transient photocurrent measurements performed for RbI-doped perovskites (lateral configuration photodetector: fluorine-doped tin oxide (FTO)/RP-perovskite/FTO of channel width ∼150 μm), for 35 cycles under standard Xe-lamp (100 mW/cm2) illumination, have shown strong and fast photocurrent response with large photoresponsivity (3.92 × 10–4 A/W). Comparison of structural, optical, and optoelectronic properties of RbI-doped RP perovskites is carried out with the mixed RP perovskites and has further confirmed that Rb+ incorporation plays an important role in enhancing the crystal growth.

Ion-Selective Assembly of Supertetrahedral Selenido Germanate Clusters for Alkali Metal Ion Capture and Separation

Supertetrahedral chalcogenido (semi)metalate cluster-based frameworks possess high selectivity for alkali metal cations, matching the specific charge density of their inner surfaces, which enables their use as ion-exchange materials. Aggregates of the supertetrahedral chalcogenido metalate cluster offer even new perspectives for metal ion capture and separation. Herein, we report on ionothermal preparation of two corresponding model compounds, (C2C1Im)7[Cs@GeII4(GeIV4Se10)4] (1) and (C2C1Im)10[Na5(CN)6@Cu6(Ge4Se10)4(Cu)] (2). Their formation is reliant on one specific cation type each, Cs+ for 1 and Na+ for 2, thus providing promising separation potential during crystallization. Compound 1 is based on the largest discrete binary selenido germanate cluster reported to date and the first mixed-valent chalcogenido germanate(II/IV) supertetrahedron. Moreover, it adds to the few examples of chalcogenides capable of capturing Cs+ ions. Its high selectivity for Cs+ compared to that of Li+, Na+, K+, and Rb+ was confirmed by single-crystal X-ray diffraction, energy-dispersive X-ray spectroscopy, and electrospray ionization mass spectrometry. Quantum chemical studies indicate that smaller ions, K+ and Rb+, could also be embedded in an isolated cluster assembly, but as the cluster aggregate slightly distorts for crystallization, the selectivity for Cs+ becomes exclusive in the salt. The anionic substructure of compound 2 is based on a two-dimensional network of supramolecular assemblies and exhibits an exclusive preference for Na+. This work thus provides the first comprehensive insight into the selective incorporation of specific alkali metal ions into supramolecular aggregates of supertetrahedral chalcogenide clusters, as a promising basis for new ion trapping techniques─especially for heavy alkali metal ions that pose environmental challenges.

Metalated Nucleic Acid Nanostructures.

Nucleic acid nanotechnology takes advantage of the self-assembling property of nucleic acids to form a variety of shapes and structures. The incorporation of metal ions into these structures introduces functionality for sensor and molecular electronic applications. Here, we describe a protocol for the incorporation of silver ions into polygonal nanoshapes that self-assemble from RNA and DNA modules.

Solar light driven transition metal codoped ZnO (Ag, Ni- codoped ZnO) photocatalyst for environmental remediation

Visible light efficient Ag, Ni-codoped ZnO photocatalyst has been synthesised in the nano form by co-precipitation and sonochemical method using ZnSO4ꞏ7H2O as a precursor. The structural, morphological and elemental observations of synthesised photocatalyst have been characterized using X-ray diffraction (XRD), FTIR, UV-DRS, SEM with EDX and HRTEM analysis. Incorporation of metal ions into ZnO lattice caused a red shift in the absorption band thus extending its absorption towards visible region through inhibition of electron hole recombination reaction and through the property of surface plasmon resonance (SPR). However the addition of silver and nickel ions has modified the electronic and optical properties of the photocatalyst thus improving the photocatalytic performance of the sample. The photocatalytic performance of Ag, Ni-codoped ZnO nanoparticles have been tested for degradation of Direct Red 81 dye (DR-81), as pollutant in aqueous solution. Under the optimum conditions (20 ppm dye and 10 mg/L photocatalyst), complete mineralization of dye solution under study was achieved within 40min of time duration. The Ag, Ni-codoped ZnO photocatalyst is thermally stable and efficient for five successive consecutive runs thus retaining its efficiency towards degradation. The overall results thus obtained have suggested that a suitable method for the detoxification of environmental pollutants emerging from industries.

Alkaline earth metal ion doping to enhance the light emission from Er3+:SnO2 nanocrystal Co-doped silica films.

Alkaline earth metal ions (Mg2+, Ca2+, Sr2+) have been introduced into Er3+:SnO2 nanocrystal co-doped silica thin films fabricated by a sol-gel method combined with a spin-coating technique. It is found that the incorporation of alkaline earth metal ions can enhance the light emission from Er3+ at the wavelength around 1540 nm and the strongest enhancement is observed in samples doped with 5 mol% Sr2+ ions. Based on X-ray diffraction, X-ray photoelectron spectroscopy and other spectroscopic measurements, the improved light emission can be attributed to more oxygen vacancies, better crystallinity and a stronger cross-relaxation process with the introduction of alkaline earth metal ions.

Synthesis and characterization of nanostructured Ag- and In-doped vanadium pentoxide for ethanol-sensing application

Abstract This study presents a facile method for preparing low-temperature gas sensors based on nanostructured Ag-doped and In-doped vanadium pentoxide (V2O5). Pure, In-doped, and Ag-doped V2O5 samples were synthesized using the thermal decomposition method, and thermogravimetric analysis was used to determine the optimal calcination temperature. All the samples were characterized and analyzed using field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Both Ag- and In-doped V2O5 exhibited higher sensitivity toward ethanol compared to pure V2O5. Hence, incorporating metal ions into semiconducting metal oxides holds the potential to enhance the sensitivity of gas sensors.

Ionic Transistor – A New Generation Memory Device

We have come a long way since Alan Tuning first proposed the Artificial Intelligence (AI) in modern computers in 1950s enabling them to response like a human brain under certain conditions. But in order to perform various machine-learning operations such as image or speech recognition, huge datasets need to be processed leading to massive power consumption. Hence for the practical implementation and progress of AI with energy efficiency there is a pressing need of new class of memory devices which can mimic the performance of human brain at equivalent low energy. The focus of my PhD project is to develop such memory element by controlled incorporation of metal ions into the insulating layer in Metal Oxide Semiconductor (MOS) transistor which can be an innovative solution for muti-level (Analog; for reference, Binary system represents two levels), non-volatile (stored data retained even after power is off), Neuromorphic (mimics human brain response) memory device. Here I have reported controlled incorporation of lithium ions in an additional deposited insulating polymer layer in a metal-oxide-semiconductor capacitor and have shown that lithium ions motion in this layer can be controlled externally which enables it to modify the conductivity of the device, overall making it a promising candidate for the new generation memory element. Successfully integrating this with present silicon-based integrated circuits can lead to a breakthrough in AI in the future.

Computational investigation of functionalized carbenes on dinitrogen activation

Activation of the dinitrogen triple bond is a crucial step in the overall fixation of atmospheric nitrogen into usable forms for industrial and biological applications. Current synthetic catalysts incorporate metal ions to facilitate the activation and cleavage of dinitrogen. The high price of metal-based catalysts and the challenge of catalyst recovery during industrial catalytic processes has led to increasing interest in metal-free catalysts. One step toward metal-free catalysis is the use of frustrated Lewis pairs (FLPs). In this study, we have examined 18 functionalized carbenes as FLPs to elucidate the influence of steric and electronic effects on the activation of dinitrogen. To test the effects of functionalization on dinitrogen activation, we have performed density functional theory (DFT), multireference, non and extended transition state-natural orbital for chemical valence (ETS-NOCV) calculations. Our results suggest that functional groups which introduce strong electron-withdrawing effects and/or engage in extended π/π* systems lead to the lowering of the dissociation energy of the dinitrogen bond, which further contributes to greater nitrogen activation. We conjecture that these effects are due to enhanced back-bonding capability of the p orbital of the carbene carbon atoms to the adjacent nitrogen atoms (increasing Lewis basicity of the carbene carbon atom) and enhanced stability of dissociated products. Our concluding remarks include opportunities to extend this activation study to explore the entire catalytic cycle with promising functionalized carbenes for experimental evaluation.

Fluorimetric Recognition of Nerve Agent Mimic Diethylchlorophosphate Along with Cu2+/Hg2+ Ions Using Imidazole Possessing Sensor.

An imidazole possessing sensor (1) has been designed and developed by simple one step reaction and characterization was done by using common spectroscopic methods. The fluorimetric sensing of nerve agent mimic, DCP, was carried out by observing blue shift in spectra accompanied with quenching in semi-aqueous solvent. The sensor was found proficient for the detection of DCP amongst other phosphates with detection limit of 69nM. Furthermore, upon incorporation of various metal ions to CH3CN:H2O (4:1, v/v) solution of 1 (λex 340nm), the fluorescent probe turned non-fluorescent only in presence of Cu2+/Hg2+ ions. This was accompanied by fluorescent color change from light blue to yellow in case of Hg2+ and colorless in case of Cu2+ ions. Moreover, practical applications of sensor 1 were investigated for recognition of Cu2+ and Hg2+ ions in real water samples along with the detection of DCP in soil samples from different areas. Differential emission changes observed with addition of Hg2+ ions and DCP led to observation of "NOR" and an "INHIBIT" molecular photonic logic operations at 446 and 385nm, respectively.

Substituting Chromium in Iron-Based Catalysts for the High-Temperature Water-Gas Shift Reaction.

A set of doped iron oxides (chromium, aluminum, gallium, indium, manganese, zinc, niobium) were prepared by a one-step coprecipitation/calcination approach evaluated for their WGS activity under industrially relevant conditions and characterized in detail. The WGS activity after ageing the doped catalyst for 4 days at 25 bar follows the order chromium ≈ aluminum > gallium > indium > manganese > zinc > niobium for copper-codoped catalysts. The activated catalysts predominantly consist of magnetite, irrespective of the dopant. Mössbauer spectra of aged catalysts showed that aluminum and zinc occupy both tetrahedral and octahedral sites of magnetite, while chromium, gallium, indium, manganese, and niobium preferentially substitute octahedral iron. The incorporation of trivalent metal ions of similar size to octahedral Fe3+ (i.e., chromium, aluminum, gallium) results in moderate to high CO conversion, irrespective of incorporation in tetrahedral or octahedral sites. The substitution of Fe2+ with Mn2+ results in an increased Fe3+/Fe2+ ratio. Incorporation of Zn2+ in tetrahedral sites (replacing Fe3+ ions) leads to a complex structure where the charge balance is compensated from the octahedral sites. Separate dopant metal oxide phases were observed in indium- and niobium-doped catalysts. XPS shows that copper is present as a separate phase in activated copper-codoped catalysts. Aluminum is identified as the most promising promoter for substituting chromium in commercial high-temperature WGS catalysts on the basis of their similar high CO conversion although incorporation of these dopants into the magnetite structure differed substantially.

Linearly potentiated synaptic weight modulation at nanoscale in a highly stable two-terminal memristor

The fabrication of nanoscale electronic synapses is an essential step towards the development of neuromorphic devices having a high integration density. Excellent learning abilities of such electronic synapses are crucial for the emulation of human brain potentialities. In order to achieve the same, linearly potentiated synaptic weight modulation (having negligible variability at nanoscale) is a primary and essential requirement. Here, we investigate solid-state memristor-based nanoscale synaptic emulators that exhibit linearly potentiated synaptic weight entries irrespective of amplitude, width, and frequency of the input voltage pulses. The memristive synapses under consideration replicate all the essential synaptic functions including potentiation and depression, spike-rate dependent plasticity, paired-pulse facilitation, and both excitatory-inhibitory responses and therefore, fulfil the requirements to build neuromorphic devices which can emulate brain-like functionalities. The incorporation of metallic ions in an amorphous oxide thin film leads to both distinctly linear weight adjustability and highly stable resistive switching operation which depend on the amplitude of the driving bias voltage. This study will help to understand and optimize the linearity in performances of oxide memristor-based synapses for neuromorphic applications.