Indolo[3,2-a]carbazoles as Engineered Materials for Optoelectronic Applications: Synthesis, Structural Insights, and Computational Screening.

The biological and medicinal importance of indolocarbazoles has been known for the past several decades. However, in recent times, these compounds have been emerging as potential candidates for optoelectronic applications, although several challenges are associated with their synthesis. We report here a Pd(II)-catalyzed process for the synthesis of indolo[3,2-a]carbazoles. The reaction proceeded under neat conditions and in the presence of aqueous nonmetallic oxidant TBHP, and the products were purified directly after the completion of the reaction. Also, the possibility of employing the present method for reaction with gram-scale feed was investigated. A detailed single-crystal analysis of several indolo[3,2-a]carbazoles revealed how the molecular arrangement can be tuned by altering the functionalization. Finally, the developed molecules were screened computationally to assess their potential for possible use as hole transport materials (HTMs) for organic light-emitting diodes (OLEDs).

Self-assembled molecular network with waterwheel-like architecture: experimental and theoretical evaluation toward electron transport capabilities for optoelectronic devices.

In recent times, self-assembled electron transport materials for optoelectronic devices, both solar cells and organic light-emitting diodes (OLEDs), have been gaining much interest as they help in fabricating high-efficiency devices. However, designing organic small molecular materials with star-shaped self-assembled networks is a challenge. To achieve this sort of target, we chose triazine and benzene-1,3,5-tricarbonyl cores for developing such architecture, and we developed four molecular systems, vizTCpCN, TCmCN, TmCN, and TpCN. Successful isolation of single crystals followed by structural analysis of TmCN revealed interesting molecular arrangements in the solid state resulting in the formation of a waterwheel type architecture with an extended network bearing characteristic voids. Theoretical calculations was carried out to check their electron transportability. The natural transition orbital calculation helped in understanding the locally excited and charge transfer excited states. The low electron reorganization energies of these molecules indicated that these materials may have potential to be used in electron transport layers of optoelectronic devices, particularly in OLEDs. Moreover, the assembled networks have a relatively wide surface area and linked structures, which are advantageous for the conduction of carriers with poor electron recombination inside the ETL, and these may offer a straightforward channel for electron conduction to the emissive layer. Finally, the fabricated electron-only device indicated that the synthesized materials may be used as ETMs in the electron transport layer of optoelectronic devices.

Sterically Crowded Donor-Rich Imidazole Systems as Hole Transport Materials for Solution-Processed OLEDs.

Imidazole, being an interesting dinitrogenic five-membered heterocyclic core, has been widely explored during the last several decades for developing various fascinating materials. Among the different domains where imidazole-based materials find wide applications, the area of optoelectronics has seen an overwhelming growth of functional imidazole derivatives developed through remarkable design and synthesis strategies. The present work reports a design approach for integrating bulky donor units at the four terminals of an imidazole core, leading to the development of sterically populated imidazole-based molecular platforms with interesting structural features. Rationally chosen starting substrates led to the incorporation of a bulky donor at the four terminals of the imidazole core. In addition, homo- and cofunctional molecular systems were synthesized through a suitable combination of initial ingredients. Our approach was extended to develop a series of four molecular systems, i.e., Cz3PhI, Cz4I, Cz3PzI, and TPA3CzI, containing carbazole, phenothiazine, and triphenylamine as known efficient donors at the periphery. Given their interesting structural features, three sterically crowded molecules (Cz4I, Cz3PzI, and TPA3CzI) were screened by using DFT and TD-DFT calculations to investigate their potential as hole transport materials (HTMs) for optoelectronic devices. The theoretical studies on several aspects including hole reorganization and exciton binding energies, ionization potential, etc., revealed their potential as possible candidates for the hole transport layer of OLEDs. Single-crystal analysis of Cz3PhI and Cz3PzI established interesting structural features including twisted geometries, which may help attain high triplet energy. Finally, the importance of theoretical predictions was established by fabricating two solution-process green phosphorescent OLED devices using TPA3CzI and Cz3PzI as HTMs. The fabricated devices exhibited good EQE/PE and CE of ∼15%/56 lm/W/58 cd/A and ∼13%/47 lm/W/50 cd/A, respectively, at 100 cd/m2.

Bicarbazole-Benzophenone-Based Twisted Donor-Acceptor-Donor Derivatives as Blue Emitters for Highly Efficient Fluorescent Organic Light-Emitting Diodes.

This paper delves into the development of a group of twisted donor-acceptor-donor (D-A-D) derivatives incorporating bicarbazole as electron donor and benzophenone as electron acceptor for potential use as blue emitters in OLEDs. The derivatives were synthesized in a reaction of 4,4'-difluorobenzophenone with various 9-alkyl-9'H-3,3'-bicarbazoles. The materials, namely, DB14, DB23, and DB29, were designed with different alkyl side chains to enhance their solubility and film-forming properties of layers formed using the spin-coating from solution method. The new materials demonstrate high thermal stabilities with decomposition temperatures >383 °C, glass transition temperatures in the range of 95-145 °C, high blue photoluminescence quantum yields (>52%), and short decay times, which range in nanoseconds. Due to their characteristics, the derivatives were used as blue emitters in OLED devices. Some of the OLEDs incorporating the DB23 emitter demonstrated a high external quantum efficiency (EQEmax) of 5.3%, which is very similar to the theoretical limit of the first-generation devices.

Recent Advances in Bimetallic Nanoporous Gold Electrodes for Electrochemical Sensing.

Bimetallic nanocomposites and nanoparticles have received tremendous interest recently because they often exhibit better properties than single-component materials. Improved electron transfer rates and the synergistic interactions between individual metals are two of the most beneficial attributes of these materials. In this review, we focus on bimetallic nanoporous gold (NPG) because of its importance in the field of electrochemical sensing coupled with the ease with which it can be made. NPG is a particularly important scaffold because of its unique properties, including biofouling resistance and ease of modification. In this review, several different methods to synthesize NPG, along with varying modification approaches are described. These include the use of ternary alloys, immersion-reduction (chemical, electrochemical, hybrid), co-electrodeposition-annealing, and under-potential deposition coupled with surface-limited redox replacement of NPG with different metal nanoparticles (e.g., Pt, Cu, Pd, Ni, Co, Fe, etc.). The review also describes the importance of fully characterizing these bimetallic nanocomposites and critically analyzing their structure, surface morphology, surface composition, and application in electrochemical sensing of chemical and biochemical species. The authors attempt to highlight the most recent and advanced techniques for designing non-enzymatic bimetallic electrochemical nanosensors. The review opens up a window for readers to obtain detailed knowledge about the formation and structure of bimetallic electrodes and their applications in electrochemical sensing.

Rationally heteroarylated pyridines as hole transport materials for OLEDs.

The advancement in developing highly efficient hole transport materials for OLED devices has been a challenge over the past several years. For an efficient OLED device, there should be an efficient promotion of charge carriers from each electrode and effective confinement of triplet excitons in the emissive layer of the phosphorescent OLED (PhOLED). Thus, the development of stable and high triplet energy hole transport materials is in urgent demand for high-performing PhOLED devices. The present work demonstrates the development of two hetero-arylated pyridines as high triplet energy (2.74-2.92 eV) multifunctional hole transport materials to reduce the exciton quenching and to enhance the extent of charge carrier recombination in the emissive layer. In this regard, we report the design, synthesis, and theoretical modeling with electro-optical properties of two molecules, namely PrPzPy and MePzCzPy, with suitable HOMO/LUMO energy levels and high triplet energy, by incorporating phenothiazine as well as other donating units into a pyridine scaffold, and finally developing a hybrid phenothiazine-carbazole-pyridine based molecular architecture. The natural transition orbital (NTO) calculations were done to analyze the excited state sensation in these molecules. The long-range charge transfer characteristics between the higher singlet and triplet states were also analyzed. The reorganization energy of each molecule was calculated to examine their hole transportability. The theoretical calculations for PrPzPy and MePzCzPy revealed that these two molecular systems could be promising materials for the hole transport layer of OLED devices. As a proof of concept, a solution-processed hole-only device (HOD) of PrPzPy was fabricated. The increase in current density with an increase in operating voltage in the range of ∼3-10 V supported that the suitable HOMO energy of PrPzPy can facilitate the hole transportation from the hole injection layer (HIL) to the emissive layer (EML). These results indicated the promising hole transportability of the present molecular materials.

An approximation to the vibrational coupled-cluster method for CH-stretching of large molecules: application to naphthalene and anthracene.

We propose an approximation to the vibrational coupled-cluster method (VCCM) to describe the CH-stretching region of the vibrational spectrum of large molecules. The vibrational modes of a molecule are divided into two sets: the target set and the bath set. The target set includes the CH stretches and the modes that are strongly coupled with the CH stretches and/or involve strong Fermi resonances with a CH stretch fundamental. The rest of the modes are in the bath set. First, the effective harmonic oscillator (EHO) approximation is invoked for the whole system to obtain the zeroth-order frequencies and modified potentials. The effects of interaction between the bath set and the target sets are included in the modified potential from the EHO calculation. The VCCM equations are constructed with the modified potential from the EHO calculations and for the target set only. The transition energies and intensities are calculated using such a truncated VCCM approximation. The proposed method is applied to calculate the IR spectra of naphthalene and anthracene. The results with three different criteria for selecting the modes in the target set are compared with the experimental IR spectra.

In Search of Hosts for Blue OLEDs: Computational Design and Experimental Validation.

Considering the difficulties associated with the conventional 'trial and error' method for a complete analysis of a giant molecular space, we took the aid of computational pathway (DFT) in screening a large space search of 780 (12×13×5) molecules to search for a host for the blue emitter. The selection process was completed in three Tiers with the conditions of highest theoretical triplet energy (>2.81 eV), aligned HOMO/LUMO levels w.r.t blue dopant (FIrpic), and position of substituents to meet the optimal requirements as host materials. Tier 1 screened twelve different imidazole heterocycle derivatives as base space groups which resulted in the selection of 4,5-diphenyl-1H-imidazole. Tier 2 process converged the search to mCN-CZ having the highest triplet energy and appropriate HOMO/LUMO level relative to FIrpic and ETL. Further, the carbazole of mCN-CZ was replaced with different aromatic hydrocarbons to find the other best compound in terms of triplet energy and HOMO/LUMO. Tier 3 resulted in another promising candidate (mCN-FL) as possible host materials. The band alignment with guest predicted mCN-FL and mCN-CZ to have optimal device performances compared to CZ-CZ and the experimentally observed device performance was in accordance with virtual screening results when TAPC was utilized as the hole transporter. The device results of mCN-CZ and mCN-FL were better than the reference host TCTA. The obtained results thus proved that a virtual screening process will be a useful tool for synthetic chemists in designing task-specific materials.

Investigation of the Failure of the MP2 Method to Describe the Out-of-Plane Bending Motions of Carbon-Carbon Double-Bonded Molecules: The Role of Atomic Orbitals.

We present a detailed study on the role of atomic orbitals in the unphysical description of the out-of-plane bending (OOPB) vibrations with the MP2 method. The anharmonicities of the OOPB vibrations are found to be unphysically large for several basis sets with the MP2 method. We find that the inclusion of additional valence s and p orbitals to the basis set leads to the lowering of π* orbitals' energies along with the generation of several spurious low-energy virtual molecular orbitals (VMOs). Such erroneous VMOs create a disbalance between the σ and π correlations for the planar structure of the molecules. Since the OOPB vibrations distort the π* orbitals, the disbalance in the σ and π correlations leads to errors in the derivatives of the correlation energy with respect to the displacement along with OOPB modes. The diffuse functions in the basis set enhance the unphysical anharmonicities of the OOPB modes since these functions are of s- and p-type atomic orbitals. The polarization atomic orbitals of higher angular momentum improve the description of the π* orbitals and thereby reduce the disbalance between the σ and π correlations in the MP2 calculations. We find that the unphysical frequencies for the OOPB modes are significantly eliminated with the d and f orbitals on the C atoms in the basis set.

Designing an effective therapeutic siRNA to silence RdRp gene of SARS-CoV-2.

The devastating outbreak of COVID-19 has spread all over the world and has become a global health concern. There is no specific therapeutics to encounter the COVID-19. Small interfering RNA (siRNA)-based therapy is an efficient strategy to control human viral infections employing post-transcriptional gene silencing (PTGS) through neutralizing target complementary mRNA. RNA-dependent RNA polymerase (RdRp) encoded by the viral RdRp gene as a part of the replication-transcription complex can be adopted as an acceptable target for controlling SARS-CoV-2 mediated infection. Therefore, in the current study, accessible siRNA designing tools, including significant algorithms and parameters, were rationally used to design the candidate siRNAs against SARS-COV-2 encoded RdRp. The designed siRNA molecules possessed adequate nucleotide-based and other features for potent gene silencing. The targets of the designed siRNAs revealed no significant matches within the whole human genome, ruling out any possibilities for off-target silencing by the siRNAs. Characterization with different potential parameters of efficacy allowed selecting the finest siRNA among all the designed siRNA molecules. Further, validation assessment and target site accessibility prediction also rationalized the suitability of this siRNA molecule. Molecular docking study between the selected siRNA molecule and component of RNA interference (RNAi) pathway gave an excellent outcome. Molecular dynamics of two complexes: siRNA and argonaute complex, guide RNA, and target protein complex, have shown structural stability of these proteins. Therefore, the designed siRNA molecule might act as an effective therapeutic agent against the SARS-CoV-2 at the genome level and can prevent further outbreaks of COVID-19 in humans.

Functional Pyrene-Pyridine-Integrated Hole-Transporting Materials for Solution-Processed OLEDs with Reduced Efficiency Roll-Off.

A series of new functional pyridine-appended pyrene derivatives, viz., 2,6-diphenyl-4-(pyren-1-yl)pyridine (Py-03), 2,6-bis(4-methoxyphenyl)-4-(pyren-1-yl)pyridine (Py-MeO), 4-(pyren-1-yl)-2,6-di-p-tolylpyridine (Py-Me), and 2,6-bis(4-bromophenyl)-4-(pyren-1-yl)pyridine (Py-Br) were designed, developed, and studied as the hole-transporting materials (HTMs) for organic light-emitting diode (OLED) application. The crystal structures of two molecules revealed to have a large dihedral angle between the pyrene and pyridine units, indicating poor π-electronic communication between them due to ineffective orbital overlap across the pyrene-pyridine systems as the two p-orbitals of pivotal atoms are twisted at 66.80° and 68.75° angles to each other in Py-03 and Py-Me, respectively. The influence of variedly functionalized pyridine units on the electro-optical properties and device performance of the present integrated system for OLED application was investigated. All of the materials have suitable HOMO values (5.6 eV) for hole injection by closely matching the HOMOs of indium tin oxide (ITO) and the light-emitting layer. All of the synthesized molecules have suitable triplet energies, glass transition temperatures, and melting temperatures, which are highly desirable for good HTMs. The pyrene-pyridine-based devices demonstrated stable performance with low-efficiency roll-off. The device with Py-Br as HTM showed a maximum luminance of 17300 cd/m2 with a maximum current efficiency of 22.4 cd/A and an EQE of 9% at 3500 cd/m2 with 7% roll-off from 1000 to 10 000 cd/m2. Also, the devices with Py-Me and Py-03 showed performance roll-up while moving from 1000 to 10 000 cd/m2.

Understanding of the C-H stretch region of infra-red spectroscopy: an analysis of the final state wavefunctions.

The nature of the wavefunctions associated with the final states in the CH stretching region of several medium sized molecules is analysed. The number of optically bright transitions is much larger than the number of CH oscillators present in the molecule, and they are spread over a range of about 300 cm-1. Several of them are clustered together within about 5 cm-1 with near equal intensities. The final states of all these transitions are superpositions of multiple zeroth order states. In almost all of such superpositions, no single zeroth order state has more than 50% weight. Several multiquantum states, with three to four quanta of excitation dominate the final states, with the CH chromophore contributing only a small weightage. Thus the band structure of the CH stretch region is due to several optically bright transitions whose final states are superpositions of low frequency multiquantum states with the CH chromophore contributing only a small weight to make them spectroscopically active.

Current Therapeutic Strategies of Xeroderma Pigmentosum.

Xeroderma pigmentosum (XP) is an autosomal recessive genetic disease caused by a defect in the DNA repair system, exhibiting skin cancer on sun exposure. As it is an incurable disease, therapeutic strategies of this disease are critical. This review article takes an attempt to explore the current therapeutic advancements in XP. Different approaches including sun avoidance; surgical removal of cancerous lesions; laser and photodynamic therapy; use of retinoid, 5-fluorouracil, imiquimod, photolyase, and antioxidant; interferon therapy and gene therapy are chosen by doctors and patients to lessen the adverse effects of this disease. Among these options, sun avoidance, use of 5-fluorouracil and imiquimod, and interferon therapy are effective. However, some approaches including laser and photodynamic therapy, and the use of retinoids are effective against skin cancer having severe side effects. Furthermore, surgical removal of cancerous lesions and use of antioxidants are considered to be effective against this disease; however, efficacies of these are not experimentally determined. In addition, some approaches including oral vismodegib, immunotherapy, nicotinamide, acetohexamide, glimepiride-restricted diet are found to be effective to minimize the complications secondary to defects in the nucleotide excision repair (NER) system and also enhance the NER, which are under experimental level yet. Besides these, gene therapy, including the introduction of missing genes and genome edition, may be a promising approach to combat this disease, which is also not well established now. In the near future, these approaches may be effective tools to manage XP.

Green Synthesized Silver Nanoparticles-Mediated Cytotoxic Effect in Colorectal Cancer Cells: NF-κB Signal Induced Apoptosis Through Autophagy.

Green synthesized silver nanoparticles (Ag-NPs) have demonstrated promising effects, including cytotoxicity and anticancer potential, in different cell lines. Therefore, in our previous study, Ag-NPs were synthesized from the reduction of AgNO3 using Brassica rapa var. japonica (Bj) leaf extract as a reducing and stabilizing agent. The synthesized Ag-NPs were spherical in shape, with a size range of 15-30 nm. They had phase-centered cubic structure with strong growth inhibition potential against some bacteria. In continuation with our previous study, in the present study, we aimed to investigate the autophagy-regulated cytotoxic effect of Ag-NPs against human epithelial colorectal adenocarcinoma cells (Caco-2 cells). We found that the Bj leaf aqueous extract facilitated Brassica silver nanoparticles (Brassica Ag-NPs)-induced NF-κB mediated autophagy in Caco-2 cells. Results showed that Ag-NPs reduced cell viability of Caco-2 cells by inducing oxidative stress and DNA damage. Therefore, to understand the mechanism underlying the death-promoting activity of Ag-NPs in Caco-2 cells, western blotting was performed. Western blot analysis showed decreased expression of NFκB and increased expression of IκB, which is a sign of autophagy initiation. In addition, autophagosome formation was accelerated by the activity of p53 and light chain 3 (LC3) II. In addition, inhibition of Akt and mTOR also played a pivotal role in autophagy formation. Finally, excessive expansion of autophagy promoted apoptosis, which subsequently resulted in necrosis. These findings support a novel cell death-promoting function of autophagy by Ag-NPs in Caco-2 cells.

Curcumin alleviates arsenic-induced toxicity in PC12 cells via modulating autophagy/apoptosis.

Arsenic is a recognized highly toxic contaminant, responsible for numerous human diseases and affecting many millions of people in different parts of the world. Contrarily, curcumin is a natural dietary polyphenolic compound and the main active ingredient in turmeric. Recently it has drawn great attention due to its diverse biological activities, strong antioxidant properties and therapeutic potential against many human ailments. In this study, we aimed to explore the protective effects and the regulatory role of curcumin on arsenic-induced toxicity and gain insights into biomolecular mechanism/s. Arsenic (10 µM) treatment in PC12 cells for 24 h induced cytotoxicity by decreasing cell viability and intracellular glutathione level and increasing lactate dehydrogenase activity and DNA fragmentation. In addition, arsenic caused apoptotic cell death in PC12 cells, which were confirmed from flow cytometry results. Moreover, arsenic (10 µM) treatment significantly down-regulated the inhibition factors of autophagy/apoptosis; mTOR, Akt, Nrf2, ERK1, Bcl-x, Xiap protein expressions, up-regulated the enhanced factors of autophagy/apoptosis; ULK, LC3, p53, Bax, cytochrome c, caspase 9, cleaved caspase 3 proteins and eventually caused autophagic and apoptotic cell death. However, curcumin (2.5 µM) pretreatment with arsenic (10 µM) effectively saves PC12 cells against arsenic-induced cytotoxicity through increasing cell viability, intracellular GSH level and boosting the antioxidant defense system, and limiting the LDH activity and DNA damage. Furthermore, pretreatment of curcumin with arsenic expressively alleviated arsenic-induced toxicity and cell death by reversing the expressions of proteins; mTOR, Akt, Nrf2, ERK1, Bcl-x, Xiap, ULK, LC3, p53, Bax, cytochrome c, caspase 9 and cleaved caspase 3. Our findings indicated that curcumin showed antioxidant properties through the Nrf2 antioxidant signaling pathway and alleviates arsenic-triggered toxicity in PC12 cells by regulating autophagy/apoptosis.

Carvacrol inhibits cadmium toxicity through combating against caspase dependent/independent apoptosis in PC12 cells.

Carvacrol is a monoterpenic phenol found in essential oils, is considered a safe food additive, and possesses various therapeutic properties. Numerous studies have also deciphered the protective role of carvacrol on various cytotoxicities. We clarify the effects of carvacrol on cadmium-induced apoptosis in PC12 cells. Carvacrol while co-exposed with cadmium for 48 h raised PC12 cell viability in comparison to only cadmium exposed group. The co-exposure increased the cellular glutathione levels and promoted the expression of glutathione reductase. The magnitude of DNA fragmentation caused by cadmium was also ameliorated by carvacrol. Flow cytometry exhibited the apoptosis rate augmented by cadmium was reduced by carvacrol. Western blotting revealed that cadmium and carvacrol co-exposure alleviated the cadmium-induced down-regulations of mammalian target of rapamycin (mTOR), protein kinase B (Akt), nuclear factor kappa-light-chain-enhancer of activated B cells (NFКB), extracellular signal-regulated kinase-1 (ERK-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) expressions. The co-exposure also reversed action of cadmium by suppressing the cleavage of caspase 3 and reducing the cytosolic levels of cytochrome c and apoptosis inducing factor (AIF). Moreover, carvacrol upon co-exposure significantly increased the intracellular metallothionein content. In conclusion, carvacrol strongly reduced cadmium-triggered oxidative stress and caspase-dependent and caspase-independent apoptosis in PC12 cells.

Direct Access to 9-Chloro-1H-benzo[b]furo[3,4-e]azepin-1-ones via Palladium(II)-Catalyzed Intramolecular syn-Oxypalladation/Olefin Insertion/sp2-C-H Bond Activation Cascade.

An efficient Pd(II)-catalyzed cascade approach was established for the synthesis of 9-chloro-1H-benzo[b]furo[3,4-e]azepin-1-ones starting from N-propargyl arylamines having a pendant α,ß-unsaturated ester scaffold. The mechanism of this sequential process involved intramolecular syn-oxypalladation followed by olefin insertion and ortho sp2-C-Cl bond formation reactions. This high atom- and step-economical cascade sequence generated two heterocycle rings and three new bonds in a single synthetic operation.

Selenium and zinc protections against metal-(loids)-induced toxicity and disease manifestations: A review.

Metals are ubiquitous in the environment due to huge industrial applications in the form of different chemicals and from extensive mining activities. The frequent exposures to metals and metalloids are crucial for the human health. Trace metals are beneficial for health whereas non-essential metals are dangerous for the health and some are proven etiological factors for diseases including cancers and neurological disorders. The interactions of essential trace metals such as selenium (Se) and zinc (Zn) with non-essential metals viz. lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in biological system are very critical and complex. A huge number of studies report the protective role of Se and Zn against metal toxicity, both in animal and cellular levels, and also explain the numerous mechanisms involved. However, it has been considered that a tiny dyshomeostasis in the metals/trace metals status in biological system could induce severe deleterious effects that can manifest to numerous diseases. Thus, in this particular review, we have demonstrated the critical protection mechanism/s of Se and Zn against Cd, Pb, As and Hg toxicity in a one by one manner to clarify the up-to-date findings and perspectives. Furthermore, biomolecular consequences are comprehensively presented in light of particular cellular/biomolecular events which are somehow linked to a subsequent disease. The analyzed reports support significant protection potential of Se and Zn, either alone or in combination with other agents, against each of the abovementioned non-essential metals. However, Se and Zn are still not being used as detoxifying agents due to some unexplained reasons. We hypothesized that Se could be a potential candidate for detoxifying As and Hg regardless of their chemical speciations, but requires intensive clinical trials. However, particularly Zn-Hg interaction warrants more investigations both in animal and cellular level.

Anomalous description of the anharmonicity of bending motions of carbon-carbon double bonded molecules with the MP2 method: ethylene as a case study.

In this work, we report anomalous descriptions of bending modes of the smallest carbon-carbon double bonded molecule ethylene with the MP2 method. The harmonic frequencies of the out-of-plane modes are found to be extremely low and the anharmonicities are found to be very large. Although the problem of harmonic frequencies of these out-of-plane vibrations disappears with larger basis sets, the anharmonicity of these modes is still found to be extremely large. Such anomalous anharmonicity with the MP2 method is not limited to out-of-plane modes and smaller basis sets. The anharmonic frequency of in-plane vibration CH2 rocking with a large basis set 6-311G(3d,3p) is much higher than the experimental value. The errors are not restricted to the MP2 method, but propagate to highly accurate ab initio methods like CCSD and CCSD(T). We found that such anomalous behavior of the post-Hartree Fock method for the bending motions of ethylene originates from the erroneous descriptions of the virtual molecular orbitals, especially with diffused basis sets.

A systematic review on silver nanoparticles-induced cytotoxicity: Physicochemical properties and perspectives.

With the development of nanotechnology, silver nanoparticles (Ag-NPs) have become one of the most in-demand nanoparticles owing to their exponential number of uses in various sectors. The increased use of Ag-NPs-enhanced products may result in an increased level of toxicity affecting both the environment and living organisms. Several studies have used different model cell lines to exhibit the cytotoxicity of Ag-NPs, and their underlying molecular mechanisms. This review aimed to elucidate different properties of Ag-NPs that are responsible for the induction of cellular toxicity along with the critical mechanism of action and subsequent defense mechanisms observed in vitro. Our results show that the properties of Ag-NPs largely vary based on the diversified synthesis processes. The physiochemical properties of Ag-NPs (e.g., size, shape, concentration, agglomeration, or aggregation interaction with a biological system) can cause impairment of mitochondrial function prior to their penetration and accumulation in the mitochondrial membrane. Thus, Ag-NPs exhibit properties that play a central role in their use as biocides along with their applicability in environmental cleaning. We herein report a current review of the synthesis, applicability, and toxicity of Ag-NPs in relation to their detailed characteristics.