Inorganic nanoparticles for photothermal treatment of cancer

In recent years, inorganic nanoparticles (NPs) have attracted increasing attention as potential theranostic agents in the field of oncology. Photothermal therapy (PTT) is a minimally invasive technique that uses nanoparticles to produce heat from light to kill cancer cells. PTT requires two essential elements: a photothermal agent (PTA) and near-infrared (NIR) radiation. The role of PTAs is to absorb NIR, which subsequently triggers hyperthermia within cancer cells. By raising the temperature in the tumor microenvironment (TME), PTT causes damage to the cancer cells. Nanoparticles (NPs) are instrumental in PTT given that they facilitate the passive and active targeting of the PTA to the TME, making them crucial for the effectiveness of the treatment. In addition, specific targeting can be achieved through their enhanced permeation and retention effect. Thus, owing to their significant advantages, such as altering the morphology and surface characteristics of nanocarriers comprised of PTA, NPs have been exploited to facilitate tumor regression significantly. This review highlights the properties of PTAs, the mechanism of PTT, and the results obtained from the improved curative efficacy of PTT by utilizing NPs platforms.

Heterostructures coupling ultrathin metal carbides and chalcogenides

Non-layered transition metal carbides (TMCs) and layered transition metal dichalcogenides (TMDs) are two well-studied material families that have individually received considerable attention over the past century. In recent years, with the shift towards two-dimensional materials and heterostructures, a field has emerged that is focused on the structure and properties of TMC/TMD heterostructures, which through chemical conversion exhibit diverse types of heterostructure configuration that host coupled 2D-3D interfaces, giving rise to exotic properties. In this Review, we highlight experimental and computational efforts to understand the routes to fabricate TMC/TMD heterostructures. Furthermore, we showcase how controlling these heterostructures can lead to emergent electronic transport, optical properties and improved catalytic properties.

Toward the Rational Design of More Efficient Mo2C Catalysts for Hydrodeoxygenation-Mechanism and Descriptor Identification

Viable alternatives to scarce and expensive noble-metal-based catalysts are transition-metal carbides such as Mo and W carbides. It has been shown that these are active and selective catalysts in the hydrodeoxygenation of renewable lipid-based feedstocks. However, the reaction mechanism and the structure-activity relationship of these transition-metal carbides have not yet been fully clarified. In this work, the reaction mechanism of butyric acid hydrodeoxygenation (HDO) over molybdenum carbide (Mo2C) has been studied comprehensively by means of density functional theory coupled with microkinetic modeling. We identified the rate-determining step to be butanol dissociation: C4H9*OH + * → C4H9* + *OH. Then we further explored the possibility to facilitate this step upon heteroatom doping and found that Zr- and Nb-doped Mo2C are the most promising catalysts with enhanced HDO catalytic activity. Linear-scaling relationships were established between the electronic and geometrical descriptors of the dopants and the catalytic performance of various doped Mo2C catalysts. It was demonstrated that descriptors such as dopants' d-band filling and atomic radius play key roles in governing the catalytic activity. This fundamental understanding delivers practical strategies for the rational design of Mo2C-based transition-metal carbide catalysts with improved HDO performance.

Synthesis and Characterization of Supported Mixed MoW Carbide Catalysts

For mixed MoW carbide catalysts, the relationship between synthesis conditions, evolution of (mixed) phases, extent of mixing, and catalytic performance of supported Mo/W carbides remains unclear. In this study, we prepared a series of carbon nanofiber-supported mixed Mo/W-carbide catalysts with varying Mo and W compositions using either temperature-programmed reduction (TPR) or carbothermal reduction (CR). Regardless of the synthesis method, all bimetallic catalysts (Mo:W bulk ratios of 1:3, 1:1, and 3:1) were mixed at the nanoscale, although the Mo/W ratio in individual nanoparticles varied from the expected bulk values. Moreover, the crystal structures of the produced phases and nanoparticle sizes differed depending on the synthesis method. When using the TPR method, a cubic carbide (MeC_1-x ) phase with 3-4 nm nanoparticles was obtained, while a hexagonal phase (Me₂C) with 4-5 nm nanoparticles was found when using the CR method. The TPR-synthesized carbides exhibited higher activity for the hydrodeoxygenation of fatty acids, tentatively attributed to a combination of crystal structure and particle size.

Mo2C as Pre-Catalyst for the C-H Allylic Oxygenation of Alkenes and Terpenoids in the Presence of H2O2

In this study, commercially available molybdenum carbide (Mo2C) was used, in the presence of H2O2, as an efficient pre-catalyst for the selective C-H allylic oxygenation of several unsaturated molecules into the corresponding allylic alcohols. Under these basic conditions, an air-stable, molybdenum-based polyoxometalate cluster (Mo-POM) was formed in situ, leading to the generation of singlet oxygen (1O2), which is responsible for the oxygenation reactions. X-ray diffraction, SEM/EDX and HRMS analyses support the formation mainly of the Mo6O192− cluster. Following the proposed procedure, a series of cycloalkenes, styrenes, terpenoids and methyl oleate were successfully transformed into hydroperoxides. After subsequent reduction, the corresponding allylic alcohols were produced with good yields and in lab-scale quantities. A mechanistic study excluded a hydrogen atom transfer pathway and supported the twix-selective oxygenation of cycloalkenes on the more sterically hindered side via the 1O2 generation.

Preparation of Aluminum-Molybdenum Alloy Thin Film Oxide and Study of Molecular CO + NO Conversion on Its Surface

Adsorption and interaction of carbon monoxide (CO) and nitric oxide (NO) molecules on the surface of bare Al-Mo(110) system and on that obtained by its in situ oxidation have been studied in ultra-high vacuum (base pressure: ca. 10⁻⁸ Pa) by means of Auger and X-ray photoelectron spectroscopy (AES, XPS), low energy electron diffraction (LEED), reflection–absorption infrared and thermal desorption spectroscopy (RAIRS, TDS), and by the work function measurements. In order to achieve the Al-Mo(110) alloy the thin aluminum film of a few monolayers thick was in situ deposited onto the Mo(110) crystal and then annealed at 800 K. As a result of Al atoms diffusion into the Mo(110) subsurface region and the chemical reaction, the surface alloy of a hexagonal atomic symmetry corresponding to Al₂Mo alloy is formed. The feature of thus formed surface alloy regarding molecular adsorption is that, unlike the bare Mo(110) and Al(111) substrates, on which both CO and NO dissociate, adsorption on the alloy surface is non-dissociative. Moreover, adsorption of carbon monoxide dramatically changes the state of pre-adsorbed NO molecules, displacing them to higher-coordinated adsorption sites and simultaneously tilting their molecular axis closer to the surface plane. After annealing of this coadsorbed system up to 320 K the (CO + NO → CO₂ + N) reaction takes place resulting in carbon dioxide desorption into the gas phase and nitriding of the substrate. Such an enhancement of catalytic activity of Mo(110) upon alloying with Al is attributed to surface reconstruction resulting in appearance of new adsorption/reaction centers at the Al/Mo interface (steric effect), as well as to the Mo d-band filling upon alloying (electronic effect). Catalytic activity mounts further when the Al-Mo(110) is in situ oxidized. The obtained Al-Mo(110)-O ternary system is a prototype of a metal/oxide model catalysts featuring the metal oxides and the metal/oxide perimeter interfaces as a the most active reaction sites. As such, this type of low-cost metal alloy oxide models precious metal containing catalysts and can be viewed as a potential substitute to them.

Thermal Stability and Decomposition Pathways in Volatile Molybdenum(VI) Bis-imides

The vapor deposition of many molybdenum-containing films relies on the delivery of volatile compounds with the general bis(tert-butylimido)molybdenum(VI) framework, both in atomic layer deposition and chemical vapor deposition. We have prepared a series of (^tBuN)₂MoCl₂ adducts using neutral N,N'-chelates and investigated their volatility, thermal stability, and decomposition pathways. Volatility has been determined by thermogravimetric analysis, with the 1,4-di-tert-butyl-1,3-diazabutadiene adduct (5) found to be the most volatile (1 Torr of vapor pressure at 135 °C). Thermal stability was measured primarily using differential scanning calorimetry, and the 1,10-phenanthroline adduct (4) was found to be the most stable with an onset of decomposition of 303 °C. We have also investigated molybdenum compounds with other alkyl-substituted imido groups: these compounds all follow a similar decomposition pathway, γ-H activation, with varying reaction barriers. The tert-pentyl, 1-adamantyl, and a cyclic imido (from 2,5-dimethylhexane-2,5-diamine) were systematically studied to probe the kinetics of this pathway. All of these compounds have been fully characterized, including via single-crystal X-ray diffraction, and a total of 19 new structures are reported.

Recent advances in nanoparticles mediated photothermal therapy induced tumor regression

Photothermal therapy (PTT) is a minimally invasive procedure for treating cancer. The two significant prerequisites of PTT are the photothermal therapeutic agent (PTA) and near-infrared radiation (NIR). The PTA absorbs NIR, causing hyperthermia in the malignant cells. This increased temperature at the tumor microenvironment finally results in tumor cell damage. Nanoparticles play a crucial role in PTT, aiding in the passive and active targeting of the PTA to the tumor microenvironment. Through enhanced permeation and retention effect and surface-engineering, specific targeting could be achieved. This novel delivery tool provides the advantages of changing the shape, size, and surface attributes of the carriers containing PTAs, which might facilitate tumor regression significantly. Further, inclusion of surface engineering of nanoparticles is facilitated through ligating ligands specific to overexpressed receptors on the cancer cell surface. Thus, transforming nanoparticles grants the ability to combine different treatment strategies with PTT to enhance cancer treatment. This review emphasizes properties of PTAs, conjugated biomolecules of PTAs, and the combinatorial techniques for a better therapeutic effect of PTT using the nanoparticle platform.

Carbon nitride used as a reactive template to prepare mesoporous molybdenum sulfide and nitride

Carbon nitride C₃N₄ has been used as a sacrificial template to prepare inorganic materials with hierarchical pore structure. C₃N₄ impregnated with ammonium heptamolybdate was treated in reactive gas mixtures (H₂S/H₂ or NH₃/H₂). This approach allowed mesoporous molybdenum sulfide and molybdenum nitride materials to be obtained that replicate the morphology of the C₃N₄ template. Advantageous catalytic properties have been demonstrated in the thiophene hydrodesulfurization (HDS) and electrochemical hydrogen evolution reaction (HER). The highest rates in both reactions were observed for partially sulfidized Mo₂N solid.

Mo single atoms in the Cu(111) surface as improved catalytic active centers for deoxygenation reactions

The surface Mo-doped Cu(111) catalyst feature improved performance towards deoxygenation reactions, acting as a single-atom alloy capable of breaking Brønsted–Evans–Polanyi relations for carbonyl bond scissions.

A Review of Preparation Strategies for α-MoC1-x Catalysts

Transition metal carbides are attracting growing attention as robust and affordable alternative heterogeneous catalysts to platinum group metals, for a host of contemporary and established hydrogenation, dehydrogenation, and isomerisation reactions. In particular, the metastable α-MoC1-x phase has been shown to exhibit interesting catalytic properties for low temperature processes reliant on O-H and C-H bond activation. While demonstrating exciting catalytic properties, a significant challenge exists in the application of metastable carbides, namely the challenging procedure for their preparation. In this review we will briefly discuss the properties and catalytic applications of α-MoC1-x, followed by a more detailed discussion on available synthesis methods and important parameters that influence carbide properties. Techniques are contrasted with properties of phase, surface area, morphology and Mo:C being considered. Further, we briefly relate these observations to experimental and theoretical studies of α-MoC1-x in catalytic applications. Synthetic strategies discussed are, the original temperature programmed ammonolysis followed by carburisation, alternative oxycarbide or hydrogen bronze precursor phases, heat treatment of moybdate-amide compounds and other low temperature synthetic routes. The importance of carbon removal and catalyst passivation in relation to surface and bulk properties are also discussed. Novel techniques that by-pass the apparent bottle neck of ammonolysis are reported, however a clear understanding of intermediate phases is required to be able to fully apply these techniques. Pragmatically, the scaled application of these techniques requires the pre-pyrolysis wet chemistry to be simple and scalable. Further, there is a clear opportunity to correlate observed morphologies/phases and catalytic properties with findings from computational theoretical studies. Detailed characterisation throughout the synthetic process is essential and will undoubtedly provide fundamental insights that can be used for the controllable and scalable synthesis of metastable α-MoC1-x.