DFT Study of Gold Surfaces–Ligand Interactions: Alkanethiols versus Halides

The variation in the surface reactivity of gold nanorods (GNR) is explored by density functional theory (DFT) simulations of the different facets. The physical and chemical properties of Au310 and Au520 surfaces, recently detected on the GNR tips, were compared with conventional Au100 and Au111 surfaces. Due to the tight gold packing, the sloped Au111 surfaces have the highest binding energy with rigid ligands, whereas the Au310 have the lowest. The observed correspondence between the ligand binding energies and the surface moduli of elasticity demonstrates that the overall monolayer structure, stability and reactivity is a balance between the ligand induced surface strain and the interligand strain. The GNR tips are able to distribute the ligand induced strain with minimal surface reorganization due to a high modulus of elasticity combined with extra free volume within the ligand shell. A simulation of the halide-surface interaction, consisting of multiple bond breaking and forming points, showed that the halides will induce the same surface strain but halides with reduced ligand-to-ligand interaction can move freely around the gold surface. More importantly, the charge transfer between halide to gold depends mainly on this mobility and is a factor in the role of halides as shape directing agents in gold nanoparticle synthesis. These simulations reveal some of the key factors that must be considered to effectively functionalize GNRs for specific applications

Mechanistic Aspects of deNO_<i>x</i> Processing over TiO₂ Supported Co–Mn Oxide Catalysts: Structure–Activity Relationships and In Situ DRIFTs Analysis

Anatase TiO₂-supported manganese and cobalt oxide catalysts with different Co/Mn molar ratios were synthesized by a conventional impregnation method and used for selective catalytic reduction (SCR) of NO_<i>x</i> with NH₃. The catalysts were characterized by N₂ adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption with NH₃ and NO_<i>x</i>. Characterization of the catalyst confirmed that by using Co₃O₄ over Mn/TiO₂, we enhanced NO oxidation ability. From in situ diffuse reflectance infrared transform spectroscopy (DRIFTs) analysis of desorption and the transient reaction, we concluded that the addition of Co could remarkably lower the activation energy of NO_<i>x</i> chemisorption on the catalyst surface. In addition, low-temperature SCR activity mainly results from a “fast SCR” reaction. We observed four NO_<i>x</i> species (bidentate nitrates, gaseous NO₂, linear nitrites, and monodentate nitrites) on the surface of Mn/TiO₂ and Co–Mn/TiO₂ catalysts that all participated in the SCR reaction in the high temperature range. Doping of cobalt greatly improved the reactivity of gaseous NO₂, linear nitrites, and monodentate nitrites, which makes Co–Mn/TiO₂ a highly effective NH₃–SCR catalyst

In Situ DRIFTs Investigation of the Low-Temperature Reaction Mechanism over Mn-Doped Co₃O₄ for the Selective Catalytic Reduction of NO_<i>x</i> with NH₃

The Co₃O₄ and Mn-doped Co₃O₄ nanoparticle were synthesized by a co-precipitation method and used as selective catalytic reduction of NO with NH₃ (NH₃-SCR) catalysts. After the doping of manganese oxides, the NH₃-SCR activity of Mn_0.05Co_0.95O_<i>x</i> catalyst is greatly enhanced. The NO oxidation ability of two catalysts is compared, and the X-ray diffraction results demonstrate that Mn has been successfully doped into the lattice of Co₃O₄. The X-ray photoelectron spectroscopy and temperature-programmed reduction with H₂ results confirmed that there is a strong interaction between Mn and Co in the Mn_0.05Co_0.95O_<i>x</i> catalyst. Their adsorption and desorption properties were characterized by temperature-programmed desorption with NH₃ or NO + O₂ and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs). These results indicated that the doping of manganese could provide more acid sites on the catalysts, and bidentate nitrates species originated from NO_<i>x</i> adsorption are obviously activated on the Mn_0.05Co_0.95O_<i>x</i> catalyst surface. Moreover, the transient reaction studied by in situ DRIFTs found that the “fast SCR” reaction participated by gaseous NO₂ and the standard SCR reaction participated by bidentate nitrates contribute to the low-temperature SCR activity

In Situ DRIFTs Investigation of Promotional Effects of Tungsten on MnO_<i>x</i>‑CeO₂/meso-TiO₂ Catalysts for NO_<i>x</i> Reduction

In this work, mesoporous TiO₂ spheres supported MnCeW mixed oxide catalysts (MnCeW/m-TiO₂) for selective catalytic reduction of NO_<i>x</i> with NH₃ were prepared by a wet impregnation method. It is interesting that the MnCeW/m-TiO₂ catalysts exhibited excellent SCR activity and N₂ selectivity in a wide temperature range, even under the high gas hourly space velocity. From in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) studies of desorption, it could be concluded that the addition of tungsten brought about more Brønsted acid sites and reduced the energy barrier of NO_<i>x</i> species adsorbed on the surface. At high temperature range, there were still some Brønsted acid sites and NO_<i>x</i> species including bidentate nitrate and nitro compounds in MnCeW/m-TiO₂, therefore more intermediates could take part in the SCR reactions as well as better catalytic performance. Besides, the in situ DRIFTs of transient reactions indicated that the formed NH₃ species and NO_<i>x</i> species of MnCeW/m-TiO₂ were more reactive due to the promotional effects of tungsten. A series of traditional characterizations also revealed the promotional effects of tungsten for surface active elements, catalytic redox properties, and acid sites of NH₃ adsorption. In a word, all the results confirmed that the introduction of W could enhance active NH₃ and NO_<i>x</i> species as well as surface active elements, thus contributing to the catalytic performance. The present investigations may open a path for design and application of catalysts with outstanding catalytic activity and selectivity

Nanospray Desorption Electrospray Ionization (Nano-DESI) Mass Spectrometry Imaging with High Ion Mobility Resolution

Untargeted separation of isomeric and isobaric species in mass spectrometry imaging (MSI) is challenging. The combination of ion mobility spectrometry (IMS) with MSI has emerged as an effective strategy for differentiating isomeric and isobaric species, which substantially enhances the molecular coverage and specificity of MSI experiments. In this study, we have implemented nanospray desorption electrospray ionization (nano-DESI) MSI on a trapped ion mobility spectrometry (TIMS) mass spectrometer. A new nano-DESI source was constructed, and a specially designed inlet extension was fabricated to accommodate the new source. The nano-DESI-TIMS-MSI platform was evaluated by imaging mouse brain tissue sections. We achieved high ion mobility resolution by utilizing three narrow mobility scan windows that covered the majority of the lipid molecules. Notably, the mobility resolution reaching up to 300 in this study is much higher than the resolution obtained in our previous study using drift tube IMS. High-resolution TIMS successfully separated lipid isomers and isobars, revealing their distinct localizations in tissue samples. Our results further demonstrate the power of high-mobility-resolution IMS for unraveling the complexity of biomolecular mixtures analyzed in MSI experiments

Teflon: A Decisive Additive in Directly Fabricating Hierarchical Porous Carbon with Network Structure from Natural Leaf

Hierarchically porous carbons are of increasing importance due to their special physicochemical properties. The state-of-the-art approaches for synthesizing hierarchical porous carbon with network structure normally suffer from specific chemistries, rigid reaction conditions, high cost, and multiple tedious steps that limit their large scale production. Herein, we present an interesting insight into the important role of Teflon additive in fabrication of hierarchical porous carbon derived from biomass and, thus, use natural Indicalamus leaves for the first time to successfully synthesize hierarchical porous carbon with a three-dimensional morphology of interconnected nanoparticle units by using a facile and post-treatment-free carbonization technique. It is surprisingly found that the addition of Teflon not only reduces the synthesis procedure by combining post-removal of silica and carbonization in a single step but also plays a decisive role in generating the hierarchical carbonaceous network structure with a specific surface area as high as 1609 m²/g without any extra activation procedures. Benefiting from the combination of well-developed porosity and valuable hierarchical porous morphology, this type of hierarchical porous carbon has demonstrated attractive liquid-phase adsorption properties toward organic molecules

Enhancing Doxorubicin Delivery toward Tumor by Hydroxyethyl Starch‑<i>g</i>‑Polylactide Partner Nanocarriers

Doxorubicin (DOX), a kind of wide-spectrum chemotherapeutic drug, can cause severe side effects in clinical use. To enhance its antitumor efficacy while reducing the side effects, two kinds of nanoparticles with desirable compositions and properties were assembled using optimally synthesized hydroxyethyl starch-grafted-polylactide (HES-<i>g</i>-PLA) copolymers and utilized as partner nanocarriers. The large empty HES-<i>g</i>-PLA nanoparticles (mean size, <i>ca.</i> 700 nm), at an optimized dose of 400 mg/kg, were used to block up the reticuloendothelial system in tumor-bearing mice 1.5 h in advance, and the small DOX-loaded HES-<i>g</i>-PLA nanoparticles (mean size, <i>ca.</i> 130 nm) were subsequently applied to the mice. When these partner nanocarriers were administered in this sequential mode, the released DOX had a significantly prolonged plasma half-life time and much slower clearance rate as well as a largely enhanced intratumoral accumulation as compared to free DOX. <i>In vivo</i> antitumor studies demonstrated that the DOX-loaded HES-<i>g</i>-PLA nanoparticles working together with their partner exhibited remarkably enhanced antitumor efficacy in comparison to free DOX. In addition, these HES-<i>g</i>-PLA partner nanocarriers showed negligible damage to the normal organs of the treated mice. Considering safe and efficient antitumor performance of DOX-loaded HES-<i>g</i>-PLA nanoparticles, the newly developed partner nanocarriers in combination with their administration mode have promising potential in clinical cancer chemotherapy

Facile Synthesis of Highly Porous Carbon from Rice Husk

Highly porous carbon materials have attracted great interest for a wide range of important applications. Many examples for their synthesis exist, but these synthetic processes can be quite complex and also very time-consuming. There is still a major challenge to develop a facile yet versatile conceptual approach to produce them. Here, we present an efficient, activation-free, post-treatment-free strategy for the synthesis of highly porous carbon by a simple carbonization of a mixture of rice husk and polytetrafluoroethylene (PTFE) powder. PTFE employed here can <i>in situ</i> generate HF to etch out natural silica during the carbonization treatment of rice husk. This strategy not only reduces the synthesis procedure by combining carbonization and post-removal of silica into a single step but also eliminates completely the usage of hazardous HF or corrosive NaOH or KOH. The as-synthesized carbon materials exhibit a BET surface area as high as 2051 m²/g without any activation treatment, which is about 20 times enhanced in porosity compared to that of the traditional carbon material from rice husk. With the combination of the high porosity and the valuable hierarchical porous structure, the as-prepared porous carbon materials serve well as electrodes for supercapacitive energy storage, including a large capacitance of 317 F/g, good rate performance, and high capacitances per surface area. These findings could provide a new avenue for the facile production of high-performance porous carbon materials with promising applications in various areas

Nanocolloidosomes with Selective Drug Release for Active Tumor-Targeted Imaging-Guided Photothermal/Chemo Combination Therapy

Selective drug release is highly desirable for photothermal/chemo combination therapy when two or even more theranostic agents are encapsulated together within the same nanocarrier. A conventional nanocarrier can hardly achieve this goal. Herein, doxorubicin and indocyanine green (DOX/ICG)-loaded nanocolloidosomes (NCs), with selective drug release, were fabricated as a novel multifunctional theranostic nanoplatform for photothermal/chemo combination therapy. Templating from galactose-functionalized hydroxyethyl starch-polycaprolactone (Gal-HES-PCL) nanoparticles-stabilized Pickering emulsions, the resultant DOX/ICG@Gal-HES-PCL NCs had a diameter of around 140 nm and showed an outstanding tumor-targeting ability, preferable tumor penetration capability, and promotion of photothermal effect. Moreover, these NCs can be used for NIR fluorescence imaging and thus render real-time imaging of solid tumors with high contrast. Collectively, such NCs achieved the best in vivo antitumor efficacy combined with laser irradiation compared with DOX/ICG@HES-PCL NCs and DOX/ICG mixture. These NCs are valuable for active tumor-targeted imaging-guided combination therapy against liver cancer and potentially other diseases

Redox-Sensitive Hydroxyethyl Starch–Doxorubicin Conjugate for Tumor Targeted Drug Delivery

Doxorubicin (DOX) is one of the most potent anticancer agents in cancer chemotherapy, but the clinical use of DOX is restricted by its severe side effects caused by nonspecific delivery. To alleviate the side effects and improve the antitumor efficacy of DOX, a novel redox-sensitive hydroxyethyl starch–doxorubicin conjugate, HES-SS-DOX, with diameter of 19.9 ± 0.4 nm was successfully prepared for tumor targeted drug delivery and GSH-mediated intracellular drug release. HES-SS-DOX was relatively stable under extracellular GSH level (∼2 μM) but released DOX quickly under intracellular GSH level (2–10 mM). In vitro cell study confirmed the GSH-mediated cytotoxicity of HES-SS-DOX. HES-SS-DOX exhibited prolonged plasma half-life time and enhanced tumor accumulation in comparison to free DOX. As a consequence, HES-SS-DOX exhibited better antitumor efficacy and reduced toxicity as compared to free DOX in the in vivo antitumor activity study. The redox-sensitive HES-SS-DOX was proved to be a promising prodrug of DOX, with clinical potentials, to achieve tumor targeted drug delivery and timely intracellular drug release for effective and safe cancer chemotherapy