Deposition of Pd, Pt, and PdPt Nanoparticles on TiO2 Powder Using Supercritical Fluid Reactive Deposition: Application in the Direct Synthesis of H2O2.

In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.

Sol-Gel Synthesis of Ceria-Zirconia-Based High-Entropy Oxides as High-Promotion Catalysts for the Synthesis of 1,2-Diketones from Aldehyde.

Efficient Lewis-acid-catalyzed direct conversion of aldehydes to 1,2-diketones in the liquid phase was enabled by using newly designed and developed ceria-zirconia-based high-entropy oxides (HEOs) as the actual catalysts. The synergistic effect of various cations incorporated in the same oxide structure (framework) was partially responsible for the efficiency of multicationic materials compared to the corresponding single-cation oxide forms. Furthermore, a clear, linear relationship between the Lewis acidity and the catalytic activity of the HEOs was observed. Due to the developed strategy, exclusively diketone-selective, recyclable, versatile heterogeneous catalytic transformation of aldehydes can be realized under mild reaction conditions.

A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite.

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.

Methods for Hydroxamic Acid Synthesis.

Substituted hydroxamic acid is one of the most extensively studied pharmacophores because of their ability to chelate biologically important metal ions to modulate various enzymes, such as HDACs, urease, metallopeptidase, and carbonic anhydrase. Syntheses and biological studies of various classes of hydroxamic acid derivatives have been reported in numerous research articles in recent years but this is the first review article dedicated to their synthetic methods and their application for the synthesis of these novel molecules. In this review article, commercially available reagents and preparation of hydroxylamine donating reagents have also been described.

Direct Synthesis of Heavy Grignard Reagents: Challenges, Limitations, and Derivatization.

The direct synthesis of organocalcium compounds (heavy Grignard reagents) by the reduction of organyl halides with activated calcium powder succeeded in a straightforward manner for organic bromides and iodides that are bound at sp2 -hybridized carbon atoms. Extension of this strategy to alkyl halides was very limited, and only the reduction of trialkylsilylmethyl bromides and iodides with activated calcium allowed the isolation of the corresponding heavy Grignard reagents. Substitution of only one hydrogen atom of the methylene moiety by a phenyl or methyl group directed this reduction toward the Wurtz-type coupling and the formation of calcium halide and the corresponding C-C coupling product. The stability of the methylcalcium and benzylcalcium derivatives in ethereal solvents suggests an unexpected reaction behavior of the intermediate organyl halide radical anions. Quantum chemical calculations verify a dependency between the ease of preparative access to organocalcium complexes and the C-I bond lengths of the organyl iodides. The bulkiness of the trialkylsilyl group is of minor importance. Chloromethyltrimethylsilane did not react with activated calcium; however, halogen-exchange reactions allowed the isolation of [Ca(CH2 SiMe3 )(thf)3 (µ-Cl)]2 . Furthermore, the metathetical approach of reacting [Ca(CH2 SiMe3 )I(thf)4 ] with KN(SiMe3 )2 and the addition of N,N,N',N'',N''-pentamethyldiethylenetriamine (pmdeta) allowed the isolation of heteroleptic [CaCH2 SiMe3 {N(SiMe3 )2 }(pmdeta)]. In the reaction of this derivative with phenylsilane, the trimethylsilylmethyl group proved to be more reactive than the bis(trimethylsilyl)amido substituent.

Highly cysteine-selective fluorescent nanoprobes based on ultrabright and directly synthesized carbon quantum dots.

Strongly green fluorescent carbon dots (CQDs) have been directly synthesized from 2,4-diaminophenylhydrazine and 2-hydroxy-5-methylisophthalaldehyde through a facile solvothermal method. The novel CQDs exhibit high fluorescence quantum yield and excellent water solubility due to the abundant amino and hydroxy groups on their surface. The use of the as-prepared CQDs combined with Cu2+ constructed a "turn-on" switch cysteine-responsive nanoprobe. In the CQDs-Cu2+ assemblies, the binding of Cu2+ to CQDs results in the fluorescence quenching of CQDs by electron transfer mechanism, while the addition of cysteine leads to the fluorescence recovery because of the competitive binding between cysteine and CQDs to Cu2+. The nanoprobes showed high sensitivity to cysteine with the detection limit of 2.6 nmol L-1. The selectivity investigation results demonstrated that the Cu2+-integrated nanoparticles were highly selective toward cysteine over the other amino acids and biologically related metal ions. The proposed nanoprobe was then employed for detecting the recovery of cysteine in rabbit serum and plasma samples and imaging the cysteine in cancer cells, and the recovery was found to be 98.2-104.0%. This "synthesis-modification integration" strategy for the fabrication of CQDs may offer a new sight for the preparation of multifunctional nanostructures and broadening the application of CQDs in bioimaging. Graphical abstract Fluorescent carbon dots (CQDs) were directly synthesized from 2,4-diaminophenylhydrazine and 2-hydroxy-5-methylisophthalaldehyde. CQDs exhibit high fluorescence quantum yield and excellent water solubility due to the abundant amino and hydroxy groups on their surface. The use of CQDs combined with Cu2+ constructed a cysteine-responsive nanoprobe, which showed high sensitivity to cysteine with the detection limit of 2.6 nM.

Facile Synthesis of Catalytic AuPd Nanoparticles within Capillary Microreactors Using Polyelectrolyte Multilayers for the Direct Synthesis of H2O2.

Microreactors present innovative solutions for problems pertaining to conventional reactors and therefore have seen successful application in several industrial processes. Yet, its application in heterogeneously catalyzed gas-liquid reactions has been challenging, mainly due to the lack of an easy and flexible methodology for catalyst incorporation inside these reactors. Herein, we report a facile technique for obtaining small (<2 nm) and well-distributed catalytic nanoparticles on the walls of silica-coated capillaries, that act as micro(channel) reactors. These particles are formed in situ on the reactor walls using polyelectrolyte multilayers (PEMs), built by layer-by-layer self-assembly. Manipulating the PEMs' synthesis condition gives easy control over metal loading, without compromising on particle size. Both monometallic (Au and Pd) and bimetallic (AuPd) nanoparticles were successfully obtained using this technique. Finally, these catalytic microreactors were found to exhibit exceptional activity for the direct synthesis of hydrogen peroxide from H2 and O2.

Heavy Grignard Reagents: Synthesis, Physical and Structural Properties, Chemical Behavior, and Reactivity.

The Grignard reaction offers a straight forward atom-economic synthesis of organomagnesium halides, which undergo redistribution reactions (Schlenk equilibrium) yielding diorganylmagnesium and magnesium dihalides. The homologous organocalcium complexes (heavy Grignard reagents) gained interest only quite recently owing to several reasons. The discrepancy between the inertness of this heavy alkaline earth metal and the enormous reactivity of its organometallics hampered a vast and timely development after the first investigation more than 100 years ago. In this overview the synthesis of organocalcium reagents is described as is the durability in ethereal solvents. Aryl-, alkenyl-, and alkylcalcium halides are prepared by direct synthesis. Characteristic structural features and NMR parameters are discussed. Ligand redistribution reactions can be performed by addition of potassium tert-butanolate to ethereal solutions of arylcalcium iodides yielding soluble diarylcalcium, whereas sparingly soluble potassium iodide and calcium bis(tert-butanolate) precipitate. Furthermore, reactivity studies with respect to metalation and addition to unsaturated organic compounds and metal-based Lewis acids, leading to the formation of heterobimetallic complexes, are presented.

Direct Synthesis of Highly Conductive tert-Butylthiol-Capped CuInS2 Nanocrystals.

tert-butylthiol (tBuSH) is used as the sulfur source, surface ligand and co-solvent in the synthesis of CuInS2 nanocrystals (NCs). The presented method gives direct access to short-ligand-capped NCs without post-synthetic ligand exchange. The obtained 5 nm CuInS2 NCs crystallize in the cubic sphalerite phase with space group F-43m and a lattice parameter a=5.65 Å. Their comparably large optical and electrochemical band gap of 2.6-2.7 eV is attributed to iodine incorporation into the crystal structure as reflected by the composition Cu1.04 In0.96 S1.84 I0.62 determined by EDX. Conductivity measurements on thin films of the tBuSH-capped NCs result in a value of 2.5(.) 10(-2)  S m(-1) , which represents an increase by a factor of 400 compared to established dodecanethiol-capped CuInS2 NCs.

Halide-free diarylcalcium complexes--syntheses, structures, and stability.

A general procedure was developed for the synthesis of diarylcalcium complexes by addition of KOtBu to arylcalcium iodides in THF. Intermediate arylcalcium tert-butanolate dismutates immediately leading to insoluble tert-butanolate precipitates of calcium. Depending on the steric demand and denticity of additional neutral aliphatic azabases, mononuclear or dinuclear complexes trans-[Ca(α-Naph)2(thf)4] (1), [Ca(ß-Naph)2(thf)4] (2), [Ca(Tol)2(tmeda)]2 (3), [Ca(Ph)2 (tmeda)]2 (4), [Ca(Ph)2(pmdta)(thf)] (5), [Ca(hmteta)(Ph)2] (6), and [Ca([18]C-6)(Ph)2] (7) were isolated (Naph=naphthyl; meda=N,N,N',N'-tetramethylethylenediamine; pmdta= N,N,N',N'',N''-pentamethyldiethylenetriamine; hmteta=N,N,N',N'',N''',N'''-hexamethyltriethylenetetramine). The Ca-C bond lengths vary between 250.8 and 263.5 pm, the ipso-carbon atoms show low-field-shifted resonances in the (13) C NMR spectra.

1-Alkenylcalcium iodide: synthesis and stability.

To enhance the scope of heavy calcium-based Grignard reagents, 1,2-dihydro-4-iodonaphthalene (1) was reduced with calcium in THF giving tetrakis(thf) (1,2-dihydronaphth-4-yl)calcium iodide (2). This derivative represents a 1-alkenylcalcium complex based on X-ray structure determination and NMR data. The stability of this compound is significantly reduced compared with the aromatic naphthylcalcium iodide.

Tailored Synthesis of Heterogenous 2D TMDs and Their Spectroscopic Characterization.

Two-dimensional (2D) vertical van der Waals heterostructures (vdWHs) show great potential across various applications. However, synthesizing large-scale structures poses challenges owing to the intricate growth parameters, forming unexpected hybrid film structures. Thus, precision in synthesis and thorough structural analysis are essential aspects. In this study, we successfully synthesized large-scale structured 2D transition metal dichalcogenides (TMDs) via chemical vapor deposition using metal oxide (WO3 and MoO3) thin films and a diluted H2S precursor, individual MoS2, WS2 films and various MoS2/WS2 hybrid films (Type I: MoxW1-xS2 alloy; Type II: MoS2/WS2 vdWH; Type III: MoS2 dots/WS2). Structural analyses, including optical microscopy, Raman spectroscopy, transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy, and cross-sectional imaging revealed that the A1g and E2g modes of WS2 and MoS2 were sensitive to structural variations, enabling hybrid structure differentiation. Type II showed minimal changes in the MoS2's A1g mode, while Types I and III exhibited a ~2.8 cm-1 blue shift. Furthermore, the A1g mode of WS2 in Type I displayed a 1.4 cm-1 red shift. These variations agreed with the TEM-observed microstructural features, demonstrating strain effects on the MoS2-WS2 interfaces. Our study provides insights into the structural features of diverse hybrid TMD materials, facilitating their differentiation through Raman spectroscopy.

Enhancing Pd Catalytic Activity by Amine Group Modification for Efficient Direct Synthesis of H2O2.

A great deal of research has been carried out on the design of Pd-based catalysts in the direct synthesis of H2O2, mainly for the purpose of improving the H2O2 selectivity by weakening the activation energy on the Pd active site and thus inhibiting the dissociation of the O-O bonds in O2*, OOH*, and HOOH*. However, this often results in insufficient activation energy for the reaction between H2 and O2 on Pd, leading to difficulties in improving both the selectivity and productivity of H2O2 simultaneously. Based on this, this study reports an efficient catalyst composed of amine-functionalized SBA-15-supported Pd. The strong metal-support interaction not only makes the PdNPs highly dispersed with more Pd active sites but also improves the stability of the catalyst. The amine group modification increases the proportion of Pd0, further enhancing Pd activity and promoting the adsorption and conversion of H2 and O2 on Pd, thereby significantly increasing H2O2 productivity. Additionally, the density-functional theory simulation results showed that due to the hydrogen-bonding force between the amine group and H2O2, this particular anchoring effect would make the hydrogenation and decomposition of H2O2 effectively suppressed. Ultimately, both the selectivity and productivity of H2O2 are improved simultaneously.

Progress in Development of Magadiite to Produce Multifunctional Lamellar Materials.

The attractive properties of magadiite, a lamellar and crystalline material, could give rise to new industrial processes due to its unique and modulating intrinsic properties. In this context, the high degree of expansion of its lamellae, a key factor for its potential use in several areas of scientific research, has attracted the attention of several researchers. The aim of this review is to provide a historical overview of the hypothetical models developed to explain the magadiite crystalline structure. Furthermore, different synthesis strategies for the preparation of magadiites as sodic, protonic, and hybrid (inorganic-inorganic and inorganic-organic) materials are discussed along with several routes for obtaining modified magadiites. Also, the use of magadiite in catalytic reactions, notably in ethanol dehydration and fructose conversion reactions, is a growing area of research. Other potential applications include the adsorption and absorption of environmental pollutants (e.g., phenol and methylene blue in wastewater), use as a photocatalyst in the oxidation of toluene, and use in medicine (e.g., as a drug delivery or antibacterial/antifungal agent). This highlights the many opportunities for the development of new synthesis methods to obtain multifunctional materials in the search for new applications.

Direct Synthesis of Metal-Organic Framework Sols: Advances and Perspectives.

The intrinsic lack of processability in the conventional nano/microcrystalline powder form of metal-organic frameworks (MOFs) greatly limits their application in various fields. Synthesis of MOFs with certain flowability make them promising for multitudinous applications. The direct synthesis strategy represents one of the simplest and efficient method for synthesizing solution processable MOF sols/suspensions, compared with other approaches, for instance, the post-synthesis surface modification, the direct dispersion of MOFs in hindered ionic liquids, as well as the calcination method toward a few MOFs with melting behavior. This article reviews the recent direct synthesis strategies of solution processable MOF sols and their typical applications in different fields. The direct synthesis strategies of MOF sols can be classified into two categories: particle size reduction strategy, and selective coordination strategy. The synthesis mechanism of different strategies and the factors affecting the formation of sols are summarized. The application of solution processable MOF sols in different fields are introduced, showing great application potentials. Furthermore, the challenges faced by the direct synthesis of MOF sols and the main methods to deal with the challenges are emphasized, and the future development trend is prospected.

Improved Dimethyl Ether Production from Syngas over Aerogel Sulfated Zirconia and Cu-ZnO(Al) Bifunctional Composite Catalysts.

This work is dedicated to the study of the effect of the synthesis conditions (drying and calcination) of sulfated zirconia on the final catalytic behavior of bifunctional composite catalysts prepared by the physical mixing of the sulfated zirconia (methanol dehydration catalyst) with Cu/ZnO/Al2O3 (CZA; methanol synthesis catalyst). The main objective was to optimize the CZA-ZrO2/SO42- composite catalyst for its use in the direct production of dimethyl ether (DME) from syngas. Sulfated zirconia aerogel (AZS) and xerogel (XZS) were prepared using the sol-gel method using different solvent evacuation conditions and calcination temperatures, while the Cu-ZnO(Al) catalyst was synthesized using the coprecipitation procedure. The effectivity of CZA-ZrO2/SO42- composite catalysts for the direct production of dimethyl ether (DME) from syngas was evaluated in a flow reactor at 250 °C and 30 bar total pressure. The characterization of the sulfated zirconia aerogels and xerogels using different techniques showed that the mesoporous aerogel (AZS0.5300) exhibited the best textural and acidic properties due to the gel drying under supercritical conditions and calcination at 300 °C. As a result, the composite catalyst CZA-AZS0.5300 exhibited seven times higher DME production than its xerogel-containing counterpart (364 vs. 52 µmolDME·min-1·gcat-1). This was attributed to its well-matched metal surface, mesoporous structure, optimal crystallite size and, most importantly, its higher acidity.

Pd-Sn Alloy Catalysts for Direct Synthesis of Hydrogen Peroxide from H2 and O2 in a Microchannel Reactor.

Direct synthesis of hydrogen peroxide (DSHP) from H2 and O2 offers a promising alternative to the present commercial anthraquinone method, but it still faces the challenges of low H2O2 productivity, low stability of catalysts, and high risk of explosion. Herein, by loading in a microchannel reactor, the as-synthesized Pd-Sn alloy materials exhibit high catalytic activity for H2O2 production, presenting a H2O2 productivity of 3124 g kgPd-1 h-1. The doped Sn atoms on the surface of Pd not only facilitate the release of H2O2 but also effectively slow down the deactivation of catalysts. Theoretical calculations demonstrate that the Pd-Sn alloy surface has the property of antihydrogen poisoning, showing higher activity and stability than pure Pd catalysts. The deactivation mechanism of the catalyst was elucidated, and the online reactivation method was developed. In addition, we show that the long-life Pd-Sn alloy catalyst can be achieved by supplying an intermittent flow of hydrogen gas. This work provides guidance on how to prepare high performance and stable Pd-Sn alloy catalysts for the continuous and direct synthesis of H2O2.

Biosensor Based on Graphene Directly Grown by MW-PECVD for Detection of COVID-19 Spike (S) Protein and Its Entry Receptor ACE2.

Biosensors based on graphene field-effect transistors (G-FET) for detecting COVID-19 spike S protein and its receptor ACE2 were reported. The graphene, directly synthesized on SiO2/Si substrate by microwave plasma-enhanced chemical vapor deposition (MW-PECVD), was used for FET biosensor fabrication. The commercial graphene, CVD-grown on a copper substrate and subsequently transferred onto a glass substrate, was applied for comparison purposes. The graphene structure and surface morphology were studied by Raman scattering spectroscopy and atomic force microscope. Graphene surfaces were functionalized by an aromatic molecule PBASE (1-pyrenebutanoic acid succinimidyl ester), and subsequent immobilization of the receptor angiotensin-converting enzyme 2 (ACE2) was performed. A microfluidic system was developed, and transfer curves of liquid-gated FET were measured after each graphene surface modification procedure to investigate ACE2 immobilization by varying its concentration and subsequent spike S protein detection. The directly synthesized graphene FET sensitivity to the receptor ACE2, evaluated in terms of the Dirac voltage shift, exceeded the sensitivity of the transferred commercial graphene-based FET. The concentration of the spike S protein was detected in the range of 10 ag/mL up to 10 µg/mL by using a developed microfluidic system and measuring the transfer characteristics of the liquid-gated G-FETs. It was found that the shift of the Dirac voltage depends on the spike S concentration and was 27 mV with saturation at 10 pg/mL for directly synthesized G-FET biosensor, while for transferred G-FET, the maximal shift of 70 mV was obtained at 10 µg/mL with a tendency of saturation at 10 ng/mL. The detection limit as low as 10 ag/mL was achieved for both G-FETs. The sensitivity of the biosensors at spike S concentration of 10 pg/mL measured as relative current change at a constant gate voltage corresponding to the highest transconductance of the G-FETs was found at 5.6% and 8.8% for directly synthesized and transferred graphene biosensors, respectively. Thus, MW-PECVD-synthesized graphene-based biosensor demonstrating high sensitivity and low detection limit has excellent potential for applications in COVID-19 diagnostics.

Heteroatom-Doped Flash Graphene.

Heteroatom doping can effectively tailor the local structures and electronic states of intrinsic two-dimensional materials, and endow them with modified optical, electrical, and mechanical properties. Recent studies have shown the feasibility of preparing doped graphene from graphene oxide and its derivatives via some post-treatments, including solid-state and solvothermal methods, but they require reactive and harsh reagents. However, direct synthesis of various heteroatom-doped graphene in larger quantities and high purity through bottom-up methods remains challenging. Here, we report catalyst-free and solvent-free direct synthesis of graphene doped with various heteroatoms in bulk via flash Joule heating (FJH). Seven types of heteroatom-doped flash graphene (FG) are synthesized through millisecond flashing, including single-element-doped FG (boron, nitrogen, oxygen, phosphorus, sulfur), two-element-co-doped FG (boron and nitrogen), as well as three-element-co-doped FG (boron, nitrogen, and sulfur). A variety of low-cost dopants, such as elements, oxides, and organic compounds are used. The graphene quality of heteroatom-doped FG is high, and similar to intrinsic FG, the material exhibits turbostraticity, increased interlayer spacing, and superior dispersibility. Electrochemical oxygen reduction reaction of different heteroatom-doped FG is tested, and sulfur-doped FG shows the best performance. Lithium metal battery tests demonstrate that nitrogen-doped FG exhibits a smaller nucleation overpotential compared to Cu or undoped FG. The electrical energy cost for the synthesis of heteroatom-doped FG synthesis is only 1.2 to 10.7 kJ g-1, which could render the FJH method suitable for low-cost mass production of heteroatom-doped graphene.

catena-Poly[[tetra-kis-(3,5-dimethyl-1H-pyrazole-κN 2)copper(II)]-µ2-sulfato-κ2 O:O']: crystal structure and Hirshfeld surface analysis of a CuII coordination polymer.

The title coordination polymer, [Cu(SO4)(C5H8N2)4] n , was synthesized using a one-pot reaction of copper powder, anhydrous copper(II) sulfate and 3,5-dimethyl-1H-pyrazole (Hdmpz) in aceto-nitrile under ambient conditions. The asymmetric unit can be described as a chain consisting of four [Cu(SO4)(Hdmpz)4] formula units that are connected to each other by a µ2-sulfato-bridged ligand. The octa-hedral coordination geometry (O2N4) of all copper atoms is realized by coordination of four pyrazole ligands and two sulfate ligands. Four pyridine-like N atoms of the pyrazole ligands occupy the equatorial positions, while two oxygen atoms of two sulfate ligands are in axial positions. As a result of the sulfate ligand rotation, there is a pairwise alternation of terminal O atoms (which are not involved in coordination to the copper atom) of the SO4 tetra-hedra. The Cu⋯Cu distances within one asymmetric unit are in the range 7.0842 (12)-7.1554 (12) Å. The crystal structure is built up from polymeric chains packed in a parallel manner along the b-axis direction. Hirshfeld surface analysis suggests that the most important contributions to the surface contacts are from H⋯H (74.7%), H⋯O/O⋯H (14.8%) and H⋯C/C⋯H (8.2%) inter-actions.