Biogenic Synthesis of Antifungal Silver Nanoparticles Using Aqueous Stem Extract of Banana

The present study reports the synthesis of silver nanoparticles (AgNPs) from silver precursor using banana stem extract (BSE) as a plant biomaterial. Biologically synthesized AgNPs were observed at 425 nm with particle size ranges from 75.50 nm to 1.22 μm of truncated octahedron, rhombdodecahedron, cubic, octahedron and octagon structures. The presence of water-soluble organic compounds such as flavanones, polyphenols etc. in the BSE was identified by FTIR which were found to be responsible for the reduction of Ag+ ions to AgNPs. The EDX analysis of the nanoparticles dispersion, using a range of 2–4 keV, confirmed the presence of elemental silver, with no other impurity peaks detected. In addition, the characterised AgNPs have the potential for various medical and industrial applications. The results showed that fungal susceptibility to AgNPs is different for each fungus

Exploration of Wedelia chinensis leaf-assisted silver nanoparticles for antioxidant, antibacterial and in vitro cytotoxic applications

Green synthetic route of silver nanoparticles (AgNPs) has already been proved to be an advantageous over other physico-chemical approaches due to its simplicity, cost effectiveness, ecofriendly and nontoxicity. In this finding, aqueous Wedelia chinensis leaf extract (WLE) mediated synthesis of AgNPs was approached. Surface plasmon resonance (SPR) band at 408 nm preliminary indicated the formation of AgNPs, while TEM and XRD characterization confirmed the formation of spherically shaped and crystalline AgNPs with an average size of 31.68 nm, respectively. The plausible biomolecules in the aqueous leaf extract responsible for the reduction and stabilization of AgNPs were identified by FTIR analysis and found to be polyphenolic groups in flavonoid. Further, synthesized AgNPs was explored for different biological applications. Biosynthesized AgNPs showed significant free radical scavenging activity as compared to Wedelia leaf extract and antibacterial activity against clinically isolated test pathogens where Gram-negative bacteria were found more susceptible to AgNPs than Gram-positive one. In addition, in vitro cytotoxic response was also evaluated on hepatocellular carcinoma Hep G2 cell lines and showed a dose-dependent cytotoxic response with an IC50 value of 25 μg/mL. Keywords: Wedelia chinensis, AgNPs, Antioxidant, Antibacterial, Cytotoxicit

Fault Diagnosis in Scan-Based BIST Using Both Time and Space Information

A new technique for diagnosis in a scan-based BIST environment is presented. It allows non-adaptive identification of both the scan cells that capture errors (space information) as well as a subset of the failing test vectors (time information). Having both space and time information allows a faster and more precise diagnosis. Previous techniques for identifying the failing test vectors during BIST have been limited in the multiplicity of errors that can be handled and/or require a very large hardware overhead. The proposed approach, however, uses only two cycling registers at the output of the scan chain to accurately identify a subset of the failing BIST test vectors. This is accomplished using some novel pruning techniques that efficiently extract information from the signatures of the cycling registers. While not all the failing BIST test vectors can be identified, results indicate that a significant number of them can be. This additional information can save a lot of time in failu..

Pd-Catalyzed Dual-γ-1,1-C(sp³)–H Activation of Free Aliphatic Acids with Allyl–O Moieties

Allyl alcohols represent a unique class of coupling partners in C–H functionalization reactions. In this work, we report a simple strategy that involves dual-1,1-C(sp3)–H activation of free aliphatic acids, leading to the direct synthesis of γ-lactones that contain α,β-unsaturated groups at the γ-position. Various allyl alcohols including primary, secondary, tertiary, etc., have been used as suitable coupling partners to generate a diverse range of γ-lactones. A number of aliphatic acids including the long-chain ones have been used as substrates in the protocol. A mechanistic investigation has been carried out and suggests C–H activation to be the rate-determining step and a subsequent allylic C–H activation in the reaction. The synthesized lactones having α,β-unsaturated fragments attached are expected to be useful in the synthesis of complex molecules via further synthetic manipulation

Electropotential-Inspired Star-Shaped Gold Nanoconfined Multiwalled Carbon Nanotubes: A Proof-of-Concept Electrosensoring Interface for Lung Metastasis Biomarkers

Herein, an innovative way of designing a star-shaped gold nanoconfined multiwalled carbon nanotube-engineered sensoring interface (AuNS@MWCNT//GCE) is demonstrated for quantification of methionine (MTH); a proof of concept for lung metastasis. The customization of the AuNS@MWCNT is assisted by surface electrochemistry and thoroughly discussed using state-of-the-art analytical advances. Micrograph analysis proves the protrusion of nanotips on the surface of potentiostatically synthesized AuNPs and validates the hypothesis of Turkevich seed (AuNP)-mediated formation of AuNSs. In addition, a facile synthesis of electropotential-assisted transformation of MWCNTs to luminescent nitrogen-doped graphene quantum dots (Nd-GQDs avg. ∼4.3 nm) is unveiled. The sensor elucidates two dynamic responses as a function of CMTH ranging from 2 to 250 μM and from 250 to 3000 μM with a detection limit (DL) of ∼0.20 μM, and is robust to interferents except for tiny response of a similar −SH group bearing Cys (–1·cm–2) and selectivity of the sensor can be attributed to the strong hybridization of the Au nanoparticle with the sp2 C atom of the MWCNTs, which makes them a powerful electron acceptor for Au–SH–MTH interaction as evidenced by density functional theory (DFT) calculations. The validation of the acceptable recovery of MTH in real serum and pharma samples by standard McCarthy–Sullivan assay reveals the holding of great promise to provide valuable information for early diagnosis as well as assessing the therapeutic consequence of lung metastasis

Pd-Catalyzed Dual-γ-1,1-C(sp³)–H Activation of Free Aliphatic Acids with Allyl–O Moieties

Allyl alcohols represent a unique class of coupling partners in C–H functionalization reactions. In this work, we report a simple strategy that involves dual-1,1-C(sp3)–H activation of free aliphatic acids, leading to the direct synthesis of γ-lactones that contain α,β-unsaturated groups at the γ-position. Various allyl alcohols including primary, secondary, tertiary, etc., have been used as suitable coupling partners to generate a diverse range of γ-lactones. A number of aliphatic acids including the long-chain ones have been used as substrates in the protocol. A mechanistic investigation has been carried out and suggests C–H activation to be the rate-determining step and a subsequent allylic C–H activation in the reaction. The synthesized lactones having α,β-unsaturated fragments attached are expected to be useful in the synthesis of complex molecules via further synthetic manipulation

A Prodigious Behavior of Cycloalkyl Carboxylic Acid to Access 2D Space from 3D Space via Multifold C-H Activation

The dehydrogenation chemistry has long prevailed in the paradigm of organic synthesis. More common with carbonyl compounds, many classical reactions evolved around it. The emergence of the transition metal catalysis redefined the dehydrogenation chemistry with strategies such as transfer dehydrogenation, C-H activation and single electron transfer processes. These strategies have been extended to enable multiple dehydrogenations that had led to aromatization depending on the substrate class. On a contrary, dehydrogenative transformations of aliphatic carboxylic acids offers substantial challenges. Engineered ligands in conjunction with metal catalysis can effectuate the dehydrogenation in carboxylic acids initiated by C-H activation with subsequent functionalization or vice versa; however, the reactivity and product formation vary with the substrate structure. Herein, we have developed a catalytic system that enables cyclohexane carboxylic acid to undergo multifold C-H activation to furnish olefinated arenes implying 3D to 2D conversion and thus, completely bypassing the lactone formation, showcasing a display of the change in reactivity of aliphatic carboxylic acids. The reaction occurs via a tandem dehydrogenation-olefination-decarboxylation-aromatization sequence which has been proved by various control experiments and isolation of key intermediates. For cyclopentane carboxylic acid which are reluctant to aromatization, the same catalytic system allows controlled dehydrogenation to provide difunctionalized cyclopentene derivatives via a tandem dehydrogenation-olefination-decarboxylation-allylic acyloxylation reaction sequence. The transformation is amenable to diversify carboxylic acids to be transformed to molecules of new identity having applications in different fields thus underscoring the im-portance

Access to Unsaturated Bicyclic Lactones by Overriding Conventional C(sp3)-H Site Selectivity

Selective transformation of unactivated CH bonds is one of the notable advances in synthetic chemistry in last 20 years to streamline the synthesis of complex organic molecules. Transition metal catalysis has become a powerful tool to convert unreactive aliphatic CH bonds into an array of useful functionalities.1-3 Nonetheless, selective transformation of distal aliphatic CH bonds still presents a significant challenge, more so in absence of an exogenous directing group.4-5 In this context, aliphatic acids have been identified as the choice of substrates that could be functionalized without utilizing any extra directing group. However, the weak coordination of carboxylate group has been shown to activate mostly the methyl group at or position, limiting the scope and applicability of aliphatic acids.6-8 Herein, we have developed a ligand enabled palladium catalyzed protocol that activates the challenging methylene CH bond of aliphatic acids in presence of methyl CH bonds to form bicyclic lactones in an intramolecular manner (mid to large size). The reported protocol allows the reversal of the general selectivity in aliphatic CH bond activation. Computational mechanistic studies suggest that the CH activation in the cycloalkane ring of the starting material is followed by -hydride elimination to give Pd-coordinated cycloalkene, C-O cyclization, and another -hydride elimination to provide bicyclic unsaturated lactones. The scope of this previously unfamiliar reaction mode has been highlighted via dehydrogenative lactonization of mid to macro ring containing acids along with CH olefination reaction with olefin and allyl alcohol. Furthermore, synthesis of a variety of complex molecules via formal synthesis of natural products underscore the generality and significance of this reaction and suggestive of a new mode of CH activation reactions in aliphatic acids that could simplify the synthesis of bicyclic lactones, that are important features of numerous natural products as well as pharmacoactive molecules