Precursor Complex Research Articles

Block Copolymer-Templated, Single-Step Synthesis of Transition Metal Oxide Nanostructures for Sensing Applications.

The synthesis of transition metal oxide nanostructures, thanks to their high surface-to-volume ratio and the resulting large fraction of surface atoms with high catalytic activity, is of prime importance for the development of new sensors and catalytic materials. Here, we report an economical, time-efficient, and easily scalable method of fabricating nanowires composed of vanadium, chromium, manganese, iron, and cobalt oxides by employing simultaneous block copolymer (BCP) self-assembly and selective sequestration of metal-organic acetylacetonate complexes within one of the BCP blocks. We discuss the mechanism and the primary factors that are responsible for the sequestration and conformal replication of the BCP template by the inorganic material that is obtained after the polymer template is removed. X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) studies indicate that the metal oxidation state in the nanowires produced by plasma ashing the BCP template closely matches that of the precursor complex and that their structure is amorphous, thus requiring high-temperature annealing in order to sinter them into a crystalline form. Finally, we demonstrate how the developed nanowire array fabrication scheme can be used to rapidly pattern a multilayered iron oxide nanomesh, which we then used to construct a prototype volatile organic compound sensor.

Structural stability and magnetic properties of Ni nanoparticles with an in situ formed surface stabilization layer of graphitic-carbon

Finely dispersed spherical-shaped Ni nanoparticles, surface stabilized by a thin layer of in situ formed graphitic-carbon, were synthesized by a simple process involving heat-treatment of a complex precursor of Ni2+-poly-vinyl alcohol (PVA)-sucrose in Ar atmosphere at selected temperatures in the range of 400–600°C. The structural and compositional properties of the Ni nanoparticles were analyzed with X-ray diffraction (XRD), thermal analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). All the samples showed stable face-centered cubic (fcc) structure of Ni (Fm3m space group). Microstructural analysis disclosed the narrow size distribution of the Ni nanoparticles. The surface structure of the nanoparticles was evaluated by Raman and XPS techniques. The surface layer of graphitic-carbon ensures the structural stability of the nanoparticles even at a high temperature of 1200°C. The magnetic properties of the samples were analyzed at room-temperature with a vibrating sample magnetometer (VSM).

Spin-orbit charge transfer from guanine and 9-methylguanine radical cations to nitric oxide radicals and the induced triplet-to-singlet intersystem crossing.

Nitric oxide (●NO) participates in many biological activities, including enhancing DNA radiosensitivity in ionizing radiation-based radiotherapy. To help understand the radiosensitization of ●NO, we report reaction dynamics between ●NO and the radical cations of guanine (a 9HG●+ conformer) and 9-methylguanine (9MG●+). On the basis of the formation of 9HG●+ and 9MG●+ in the gas phase and the collisions of the radical cations with ●NO in a guided-ion beam mass spectrometer, the charge transfer reactions of 9HG●+ and 9MG●+ with ●NO were examined. For both reactions, the kinetic energy-dependent product ion cross sections revealed a threshold energy that is 0.24 (or 0.37) eV above the 0K product 9HG (or 9MG) + NO+ asymptote. To interrogate this abnormal threshold behavior, the reaction potential energy surface for [9MG + NO]+ was mapped out at closed-shell singlet, open-shell singlet, and triplet states using density functional and coupled cluster theories. The results showed that the charge transfer reaction requires the interaction of a triplet-state surface originating from a reactant-like precursor complex 3[9MG●+(↑)⋅(↑)●NO] with a closed-shell singlet-state surface evolving from a charge-transferred complex 1[9MG⋅NO+]. During the reaction, an electron is transferred from π∗(NO) to perpendicular π∗(9MG), which introduces a change in orbital angular momentum. The latter offsets the change in electron spin angular momentum and facilitates intersystem crossing. The reaction threshold in excess of the 0K thermochemistry and the low charge-transfer efficiency are rationalized by the vibrational excitation in the product ion NO+ and the kinetic shift arising from a long-lived triplet intermediate.

Magnetic properties of an oxo-bridged dinuclear iron(III) complex resulting from the oxidation of mononuclear iron metallacycles with a flexible ethylenediphenylenebis(oxamate) ligand

Transition metal ions such as copper(II), nickel(II), cobalt(II), and manganese(II) are widely used in the formation of mono- or oligonuclear metallacyclic complexes with the flexible N,N’-2,2′-ethylenediphenylenebis(oxamate) ligand (H4edpba); however similar supramolecular complexes with iron(II) and iron(III) are rarely obtained. In this work, we synthesized for the first time a new air-stable oxo-bridged diiron(III) complex of formula {[Fe(H2edpba)(dmso)]2(μ-O)}·dmso·H2O (2) from dioxygen oxidation of the putative mononuclear iron(II) complex precursor of formula [Fe(H2edpba)(H2O)2]Cl (1) in dimethylsulfoxide (dmso). Compound 2 crystallizes in the monoclinic system and contains one oxo group bridging two cationic mononuclear metallacyclic moieties, [Fe(H2edpba)(dmso)]+. The iron(III) ions are also coordinated to four oxygen atoms from the dianionic H2edpba2− ligands in a tetradentate fashion, while an oxygen atom from the coordinated dmso molecules. Mössbauer spectroscopy confirms the presence of high-spin (HS) Fe3+ ions (2). The magnetic properties of 2 reveal a strong antiferromagnetic interaction between the two HS Fe3+ ions (J = −226.46 cm−1), in agreement with the DFT calculations (J = −207.99 cm−1).

Green valorization of PET waste into functionalized Cu-MOF tailored to catalytic reduction of 4-nitrophenol

Metal-organic frameworks (MOFs) are attractive functional materials due to their high surface area, high porosity, and flexible compositions. However, the high precursor cost and complex synthetic processes hinder their large-scale applications. Herein, a novel green approach has been developed toward the synthesis of Cu-based MOF by a solvent-free mechano-synthesis method and utilizing consumed polyethylene terephthalate (PET)-derived benzenedicarboxylate (BDC) as the linker. The as-prepared CuBDC and aminated CuBDC (CuBDC-NH2) act as green catalysts for the reduction of deleterious 4-nitrophenol (4-NP) into the value-added 4-aminophenol (4-AP). Compared with CuBDC, CuBDC-NH2 shows increased adsorption capability and reduction efficiency. The mechanism and thermodynamic studies suggest that the adsorption of 4-NP on CuBDC-NH2 is an endothermic, spontaneous, favorable, and physical adsorption process. Furthermore, CuBDC-NH2 can expedite the reduction of 4-NP by participating in an adsorptive catalytic process. With the CuBDC-NH2 catalyst, the catalytic normalized kinetic rate of 4-NP was achieved 11.28 mol/min. mg, outperforming state-of-the-art catalysts, and a complete reduction occur in 5 min for a concentrated effluent (200-ppm 4-NP). The plastic waste-derived MOF-mediated catalytic valorization of organic pollutants demonstrated here opens an avenue for the green recycling/utilization of plastic waste, providing meaningful insights into the sustainable management of organic pollutants in wastewater.

Supported gold nanoparticles prepared from NHC-Au complex precursors as reusable heterogeneous catalysts

Gold nanoparticles supported on SiO2, Al2O3, TiO2, and carbon (Maxsorb, Ketjen black and Shirasagi New Gold) were prepared by impregnation and solid grinding methods using N-heterocyclic carbene (NHC)-Au complexes as precursors. A total of nine NHC-Au complex precursors were tested by impregnation and solid grinding method, and [Au(OH)(IPr)] (IPr = 1,3-bis(2,6-diisopropylphenyl)1,3-dihydro-2H-imidazol-2-ylidene) complex led to (1–2 nm) particle sizes by both methods. The prepared catalysts were characterized by XRD (X-ray diffraction), HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy), in situ XAFS (X-ray absorption fine structure), etc. In addition, [Au(OH)(IPr)] and its impregnated [Au(OH)(IPr)]/SiO2 were subjected to TG-DTA (thermogravimetry analysis-differential thermal analysis) and in situ XAFS analysis under calcination conditions, respectively. Moreover, the obtained supported Au nanoparticles (NPs) were effective as catalysts for low-temperature CO oxidation, intramolecular cyclization of alkynyl carboxylic acids, and isomerization of allylic esters. Their results suggested that the reduction of [Au(OH)(IPr)] proceeds rapidly from around 300°C, and the residual ligands should be attached to the surface of the Au NPs and protect them from drastic agglutination. These results reveal that properly designed NHC-Au complexes can facilitate the preparation of supported Au NP catalysts with small particle sizes and high activities.

Photocatalytic and Antibacterial Activities of a Nickel(II)-Bipyridine Complex-Modified Graphene Oxide Nanocomposite: Synthesis and Characterization

In this study, we aimed to synthesize and characterize a nickel(II) complex-modified graphene oxide (Ni-GO) nanocomposite with enhanced photocatalytic and antimicrobial properties. The nanocomposite was prepared through a modified Hummer’s method, followed by an adsorption technique using the precursor complex [Ni(bipy)3]Cl2·5H2O, which was preferentially adsorbed onto the graphene oxide (GO) surface. The surface interaction between the nickel complex ions and GO was characterized using various analytical techniques, including FTIR, XRD, SEM-EDX, DRS, and XPS analyses. Photoluminescence analysis demonstrated the fluorescence property of the prepared composite. The DRS spectra indicated that the adsorption of composite particles extended to the visible region, making it excitable by visible light. The photocatalytic activity of the Ni-GO nanocomposite was tested by studying the degradation of an organic model pollutant, Rhodamine B dye, under real sunlight irradiation. The introduction of the Ni(II) complex onto the GO surface matrix intensified the photocatalytic property, making it more efficient under direct sunlight exposure. Comparisons with pristine graphite and GO revealed that Ni-GO exhibited enhanced photocatalytic potential. Additionally, we have evaluated the antimicrobial property of the Ni(II) complex-modified GO against Klebsiella pneumoniae. The results demonstrated that both the Ni(II) precursor complex and Ni-GO nanocomposite possessed an excellent antimicrobial efficacy, suggesting their potential use in antimicrobial applications. The synthesis and characterization of the Ni(II) complex-modified GO nanocomposite presented in this study showed promising results for both ameliorative photocatalytic and antimicrobial activities. These findings indicated the potential utility of Ni-GO as an efficient photocatalyst and antimicrobial agent, surpassing the performance of pristine graphite and GO. This research opens up new avenues for the development of advanced nanocomposites with diverse applications in environmental remediation and biomedical fields.

Ni(II)-Salophen-Comprehensive Analysis on Electrochemical and Spectral Characterization and Biological Studies.

New aspects of the Ni(II)-salophen complex and salophen ligand precursor were found during deep electrochemical and optical characterization, as well as biological studies for new pharmacological applications. Physicochemical and spectroscopic methods (1H- and 13C-NMR, FT-IR and UV-Vis, electrospray ionization mass spectroscopy, thermogravimetric analysis, and molar conductance measurements) were also used to prove that the salophen ligand acts as a tetradentate and coordinates to the central metal through nitrogen and oxygen atoms. The electrochemical behavior of the free Schiff salophen ligand (H2L) and its Ni(II) complex (Ni(II)L) was deeply studied in tetrabutylammonium perchlorate solutions in acetonitrile via CV, DPV, and RDE. Blue films on the surfaces of the electrodes as a result of the electropolymerization processes were put in evidence and characterized via CV and DPV. (H2L) and Ni(II)L complexes were tested for their antimicrobial, antifungal, and antioxidant activity, showing good antimicrobial and antifungal activity against several bacteria and fungi.

Location-selective immobilisation of single-atom catalysts on the surface or within the interior of ionic nanocrystals using coordination chemistry

Single-atom catalysts dispersed on support materials show excellent heterogeneous catalytic properties that can be tuned using the interactions between the single atoms and the support. Such interactions depend on whether the single atoms are located on the surface or within the interior of the support. However, little is known about immobilising single atoms on the surface or within the interior of supports deliberately and selectively. Herein, such location-selective placement of single atoms is achieved through the choice of metal complex precursor, solvent, and workup procedure. Using CdSe nanoplatelets as a support, a cis-[PtCl2(SO(CH3)2)2] precursor in an aprotic solvent exclusively attaches single Pt atoms on the surface of the support. In contrast, a [PtCl4]2− precursor in a protic solvent followed by amine treatment places 60% of the single Pt atoms inside the support by cation substitution. The surface-adsorbed single Pt atoms show higher stability in photocatalytic hydrogen evolution than the substituted ones, and the preclusion of substitution as internal Pt maximises the activity. Thus, this study provides a viable strategy for the structurally precise synthesis and design of single-atom catalysts.

Synthesis, characterization and exploration of the NIR luminescent properties in HfO2: Er, HfO2:Tm and HfO2:Er/Tm films photochemically prepared

The photolysis of the Hf(dbm)4, Er(dbm)3 and Tm(dbm)3 complexes on silicon substrates results in the production of pure HfO2, HfO2/Er, HfO2/Tm, and HfO2/Er/Tm films. The photochemistry of these complex precursors was monitored using UV–Visible and FT-IR spectroscopy. Under 254-nm light photolysis, the ligands were detached from the complexes, leading to the release of metal ions. These ions gradually oxidized and formed the respective oxide. Subsequently, the resulting films were calcined at 600 °C for 2 h to achieve complete oxidation and crystallinity. To characterize selected samples, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM-EDX) were employed.NIR luminescent studies revealed that when excited at 980 nm, the HfO2/Er samples exhibited emissions corresponding to the 4I13/2 → 4I15/2 transitions of the Er3+ ions. Conversely, the HfO2/Tm samples displayed emissions attributed to the 3H4 → 3F4 and 3F4 → 3H6 transitions of the Tm ions. In the case of HfO2 co-doped with Er/Tm, some of these emissions overlapped, resulting in a broadband centered at 590 nm. To explain the observed emissions, a mechanism based on energy transfer processes between both activators (Tm ↔ Er) has been proposed.

Key role of Fe(VI)-activated Bi2WO6 in the photocatalytic oxidation of sulfonamides: Mediated electron transfer mechanism

The widespread use of sulfonamides (SAs) in animals and human infections has raised significant concerns regarding their presence in ambient waterways and potential for inducing antimicrobial resistance. Herein, we report on the capacity of ferrate (VI) (FeVIO42-, Fe(VI)) to facilitate the photocatalytic degradation of sulfamethazine (SMT) via bismuth tungstate (Bi2WO6, BWO) under blue LED light (Vis/BWO/Fe(VI)) exposure, at rates that were 45-fold faster than BWO photocatalysis. Both the stepwise and time-series addition of Fe(VI) contributed to the degradation. Multiple lines of evidence confirmed that the common reactive species (RSs) in BWO-based photocatalytic systems and Fe(VI)-involved systems (e.g., •OH/h+, O2•−, 1O2 and Fe(V)/Fe(IV)) played subtle roles in our study system. Herein, for the first time, it was discovered that the precursor complex (BWO-Fe(V)/Fe(IV)* )) was the main contributor to induce electron transfer of SAs through the "conductive bridge" effect of BWO. The studied system was able to effectively degrade SMT in synthetic hydrolyzed urine (SHU) with low interference from background substances in water. This work not only offers a novel facilitation strategy for BWO, but also holds a great application prospect for contamination remediation in urine.

Precursor Solution Aging: A Universal Strategy Modulating Crystallization of Two-Dimensional Tin Halide Perovskite Films

Two-dimensional (2D) tin (Sn2+)-based perovskites have achieved remarkable advancements in (opto)electronic devices. However, fabricating high-quality and reproducible Sn halide perovskite thin films remains challenging due to uncontrollably fast crystallization. To overcome this issue, dimethyl sulfoxide has been incorporated as an indispensable strategy to form Lewis acid–base adducts but also has been proven to induce an irreversible Sn2+ oxidization effect. As the crystalline films grow directly from solution, a better understanding of precursor colloidal chemistry and the film formation process is critical. In this study, we report a universal solution aging approach to fabricate high-quality and reliable 2D Ruddlesden–Popper and Dion–Jacobson Sn2+ perovskite films and devices. The proper solution aging stabilizes the precursor colloids by eliminating aggregated complex and unreacted precursor clusters in the fresh precursor, leading to homogeneous nucleation/crystallization and film growth. The precursor aging reduced film defect density by nearly 2 orders of magnitude and improved charge transport mobility by over 5 times. This study can inspire the community to understand the deposition mechanism for high-quality Sn2+ perovskite thin films and promote the development of high-performance and reproducible Sn2+ perovskite based (opto)electronic devices.

Aminodiphosphine substituted 2Fe2Se complex as new precursor to single and double butterfly Fe/Se models related to FeFe hydrogenase models

A convenient way to synthesize the aminediphosphine (PNP) substituted Fe/Se models with [Fe2(µ-Se2)(CO)4(μ-PNP)] as a new precursor was described. Firstly, treatment of [Fe2(µ-SeR)2(CO)6] (R = C6H5 and CH2C6H5) with (Ph2P)2NBui in refluxing xylene gave [Fe2(μ-SeR)2(CO)4(μ-Ph2P)2NBui] (R = C6H51 and CH2C6H52). Further debenzylation reaction was found in complex 2 after long-time heating, and precursor complex [Fe2(μ-Se2)(CO)4(μ-Ph2P)2NBui] (3) was isolated with satisfactory yield. GC–MS analysis showed that the reaction involved the formation of (C6H5CH2)2. Further, the “open” single butterfly complex 2 and “closed” butterfly complex [Fe2(µ-pdSe)(CO)4(μ-Ph2P)2NBui] (pdSe = Se(CH2)3Se) (4) were conveniently prepared via a new synthetic route involving the reaction of 3 with 2 equiv of Et3BHLi, followed by treatment of the resulting [Fe2(μ-SeLi)2(CO)4(μ-Ph2P)2NBui] with BzBr (Bz = CH2C6H5) and Br(CH2)3Br, respectively. On the other hand, to obtain a double butterfly complex [{Fe2(μ-SeEt)(CO)4(μ-Ph2P)2NBui}2(μ-Se2)] (5), the first Fe4Se4 carbonyl model containing two PNP substituents, successive reactions were performed, including treating precursor complex 3 with EtMgBr, protonation with CF3CO2H (TFA), and air-direct oxidation. All the complexes were well characterized by various spectral techniques and particularly by X-ray crystallography. Moreover, a comparison of the electrochemical and electrocatalytic properties of single and double clusters 4 and 5 is also presented.

Progression of the dealloying front in bilayer Cu–Al and Cu–Zn nanoporous foams

The role of interfaces and the controlling synthesis parameters of graded dealloyed nanoporous metallic materials are investigated, focusing on the dealloying front progression in complex precursor materials with multiple alloy compositions. Specifically, the effects of relative density and chemical potential on the dealloying front in sputtered bilayer copper alloy films are explored with two case studies: Cu–Al/Cu–Al and Cu–Al/Cu–Zn. Cross-sectional scanning electron (SEM) micrographs and energy-dispersive X-ray spectroscopy mapping trace the dealloying front across three time intervals, while top-surface and cross-sectional SEM probes the final dealloyed foam morphology. Final ligament sizes were found to be independent of the synthesis parameters (21–28 nm), due to a combination of fast reaction times and phosphate-inhibited surface diffusion of Cu atoms. The chemical potential gradient yielded faster reaction times, whereas slower reaction times and a higher at.% of Cu in the top layer of precursor material produced a more uniform morphology.Graphical abstract

Silver-zinc oxide heterojunction-induced electrical and charge transfer property

The solution combustion synthesis approach successfully synthesized the porous silver-zinc oxide nanocomposites (Ag-ZnO NCs). The pore generation and silver metal reduction occurred due to the evolution of gaseous byproducts during the combustion of poly(vinyl alcohol)-precursor complex. The low-resolution SEM and TEM images confirmed the porous nature of the synthesized NPs ad NCs. The nanoscale crystallite size (30 – 70 nm), crystallinity, and Ag-ZnO NCs heterojunction were confirmed from the XRD pattern and TEM/HRTEM/SAED analysis. The absence of a bandgap change between ZnO and NCs confirmed from the DRS-UV-vis analysis, indicating the non-inclusion of Ag in the ZnO lattice. The photoluminescence spectrum of doped NCs has less intensity than pure ZnO NPs, confirming the presence of charge transfer within the Ag-ZnO NCs, which prevents electron-hole recombination. The Mott–Schottky analysis confirmed the n– and p–type characters of the NCs, unlike that of ZnO NPs, which have only n-type characters. Thus, synthesizing nanomaterials by the solution combustion synthesis approach is a novel method for producing pure and electrical properties improved catalyst, which is beneficial in several applications such as catalysis and sensor.

Accessing Lanthanide Metallocene Two-Electron Reduction Chemistry Using 2,2′-Bipyridine

The feasibility of using redox-active 2,2′-bipyridine (bipy) as a synthetically convenient electron carrier to enable lanthanide metallocenes to effect two-electron reduction chemistry has been examined. The Ln(III) precursor complexes, Cp*2LnCl(bipy), 1-Ln (Ln = Nd, Gd; Cp* = C5Me5), were readily synthesized in 75–81% yield in one pot from LnCl3, KCp*, and bipy and were identified by X-ray crystallography. Treatment of the 1-Ln compounds with K/KI (4.3 wt %) afforded in 74–77% yield the products, Cp*2Ln(bipy), 2-Ln, which contain (bipy)1– ligands based on their spectroscopic characteristics and X-ray crystal structures. The molecular structure of the previously reported 2-Eu was also determined, which showed structural features consistent with a neutral bipy ligand. Further reduction of 2-Nd or 2-Gd, or the previously reported 2-Sm, 2-Eu, and 2-Yb with K/KI (4.3 wt %) in the presence of 2.2.2-cryptand (crypt) afforded in 58–88% yield the salts, [K(crypt)][Cp*2Ln(bipy)], 3-Ln, which show metrical parameters identified by X-ray crystallography that are consistent with a (bipy)1– ligand for 3-Eu and 3-Yb and a (bipy)2– ligand for 3-Nd, 3-Sm, and 3-Gd. The two-electron reduction of azobenzene (PhN=NPh) to (PhN−NPh)2– using the 3-Ln complexes was examined as a proof of concept. The 1:1 reactions of 3-Nd, 3-Sm, and 3-Yb with azobenzene afforded in 36–79% yield the [K(crypt)][Cp*2Ln(N2Ph2)], 4-Ln (Ln = Nd, Sm, Yb) complexes, each of which were crystallographically characterized. In another example of two-electron reduction by 3-Ln, treatment of 3-Nd or 3-Sm with elemental sulfur afforded in 70–75% yield [K(crypt)][Cp*2Ln(S5)], 5-Ln (Ln = Nd, Sm), which were shown by crystallography to be rare examples of f-element organometallic complexes that contain the (S5)2– ligand.

Ecological Interdependence of Pollution, Fish Parasites, and Fish in Freshwater Ecosystems of Turkey

Records of mass fish deaths were found in different data sources for this study. A map of mass fish deaths in Turkey was also realized for the first time. We aimed to present a review of the distribution of mass fish deaths in the freshwater ecosystems of Turkey, mostly present in the Marmara Region and Aegean Sea Region, where there are intensive industrial and agricultural activities. Fish parasites generally occur in equilibrium with their hosts in natural environments. In the freshwater ecosystems of Turkey, which are highly affected by human activities and have extremely rich natural ichthyofauna, the negative effects of pollution on environmental parameters, which can directly affect the fish, and the emergence and overextension of fish parasites can cause a supplementary synergic direct negative effect transposition in mass fish deaths due to the deterioration of host immunity and to the wounds induced in fish where bacterial, viral, and fungal pathogens can be effective. Finally, these factors can influence the fish rate of survival and skew the structure of fish populations. Mass fish deaths have been frequently reported in Turkey, but are usually only explained by pollution as a single accepted anthropogenic stressor. Together with pollution, a supplementary induced bioecological stressor, the qualitative and quantitative characteristics of the fish parasites’ association variations should be assessed and monitored as potential complex precursor indicators of fish communities’ structural degradation and freshwater ecosystems’ dreadful conditions. Fish parasites as biomonitor species should be used to identify the effects of pollution in Turkish ecosystems, and not only in freshwater ecosystems, in the future. An optimum management plan for freshwater ecosystems should include all the physico-chemical factors, fish parasites, and fish elements involved in permanent assessment and monitoring activities.

Thermodynamics of Azo Dye Adsorption on a Newly Synthesized Titania-Doped Silica Aerogel by Cogelation: A Comparative Investigation with Silica Aerogels and Activated Charcoal.

The adsorption isotherms of azo dyes on a newly synthesized titania-doped silica (TdS) aerogel compared to silica aerogels and activated charcoal (AC) are systematically investigated. Monolithic TdS aerogels were synthesized by the cogelation process followed by supercritical drying of tetraethyl orthosilicate (TEOS) as a gel precursor and titanium(IV) isopropoxide (TTIP) as a metal complex precursor for co-polymerization in ethanol solvent. An acid-base catalyst was used for the hydrolysis and condensation of TEOS and TTIP. The effect of Ti4+ doping in a silica aerogel on the mesoporous structure and the adsorption capacity of methylene blue (MB) and crystal violet (CV) dyes were evaluated from the UV-vis absorption spectra. In order to compare the adsorption isotherms, the surface areas of silica and TdS aerogels were first normalized with respect to AC, as adsorption is a surface phenomenon. The azo dye equilibrium adsorption data were analyzed using different isotherm equations and found to follow the Langmuir adsorption isotherm. The maximum monolayer adsorption capacities for the adsorbent TdS aerogel normalized with the AC of the Langmuir isotherm are 131.58 and 159.89 mg/g for MB and CV dyes, respectively. From the Langmuir curve fitting, the Q max value of the TdS aerogel was found to increase by 1.22-fold compared to AC, while it increased 1.25-1.53-fold compared to the silica aerogel. After four cycles, regeneration efficiency values for MB and CV dyes are about 84 and 80%, respectively. The study demonstrates the excellent potential and recovery rate of silica and TdS aerogel adsorbents in removing dyes from wastewater. The pore volume and average pore size of the new aerogel, TdS, were found to be lower than those of the silica aerogel. Thus, a new TdS aerogel with a high capacity of adsorption of azo dyes is successfully achieved.

Effect of Redox Potential on Diiron-Mediated Disproportionation of Hydrogen Peroxide.

Heme and nonheme dimanganese catalases are widely distributed in living organisms to participate in antioxidant defenses that protect biological systems from oxidative stress. The key step in these processes is the disproportionation of H2O2 to O2 and water, which can be interpreted via two different mechanisms, namely via the formation of high-valent oxoiron(IV) and peroxodimanganese(III) or diiron(III) intermediates. In order to better understand the mechanism of this important process, we have chosen such synthetic model compounds that can be used to map the nature of the catalytically active species and the factors influencing their activities. Our previously reported μ-1,2-peroxo-diiron(III)-containing biomimics are good candidates, as both proposed reactive intermediates (FeIVO and FeIII2(μ-O2)) can be derived from them. Based on this, we have investigated and compared five heterobidentate-ligand-containing model systems including the previously reported and fully characterized [FeII(L1-4)3]2+ (L1 = 2-(2'-pyridyl)-1H-benzimidazole, L2 = 2-(2'-pyridyl)-N-methyl-benzimidazole, L3 = 2-(4-thiazolyl)-1H-benzimidazole and L4 = 2-(4'-methyl-2'-pyridyl)-1H-benzimidazole) and the novel [FeII(L5)3]2+ (L5 = 2-(1H-1,2,4-triazol-3-yl)-pyridine) precursor complexes with their spectroscopically characterized μ-1,2-peroxo-diiron(III) intermediates. Based on the reaction kinetic measurements and previous computational studies, it can be said that the disproportionation reaction of H2O2 can be interpreted through the formation of an electrophilic oxoiron(IV) intermediate that can be derived from the homolysis of the O-O bond of the forming μ-1,2-peroxo-diiron(III) complexes. We also found that the disproportionation rate of the H2O2 shows a linear correlation with the FeIII/FeII redox potential (in the range of 804 mV-1039 mV vs. SCE) of the catalysts controlled by the modification of the ligand environment. Furthermore, it is important to note that the two most active catalysts with L3 and L5 ligands have a high-spin electronic configuration.

Supercritical millifluidic reactor for the synthesis of efficient GaN nanophotocatalysts

Here, we demonstrate the continuous synthesis of gallium nitride (GaN) nanophotocatalysts exhibiting high quantum confinement using a preheated supercritical millireactor. The GaN quantum dots (QDs) are obtained from the direct thermolysis of a single source amido complex precursor (tris(dimethyl)amido gallium(III) dimer), in anhydrous supercritical cyclohexane. The quality of the synthesized QDs is highly dependent on the chemical pathways for the single source precursor thermolysis. Through the use of numerical modeling, we designed a millifluidic reactor allowing a sufficiently high heating rate for a direct precursor thermolysis towards efficient GaN nanoparticles. The as-designed preheated supercritical flow reactor yields highly reproducible GaN QDs (optical properties, crystallite phase and morphology) at high throughput, enabling gram scale production. Eventually, the photocatalytic properties of the GaN QDs were evaluated in a direct photochemical reaction through the degradation of a dye molecule (Methyl Orange). The obtained results demonstrate the higher photocatalytic activity of such photocatalysts compared to the commercially and reference available Degussa P25.