Microbes and microbial strategies in carcinogenic polycyclic aromatic hydrocarbons remediation: a systematic review.

Degradation, detoxification, or removal of the omnipresent polycyclic aromatic hydrocarbons (PAHs) from the ecosphere as well as their prevention from entering into food chain has never appeared simple. In this context, cost-effective, eco-friendly, and sustainable solutions like microbe-mediated strategies have been adopted worldwide. With this connection, measures have been taken by multifarious modes of microbial remedial strategies, i.e., enzymatic degradation, biofilm and biosurfactant production, application of biochar-immobilized microbes, lactic acid bacteria, rhizospheric-phyllospheric-endophytic microorganisms, genetically engineered microorganisms, and bioelectrochemical techniques like microbial fuel cell. In this review, a nine-way directional approach which is based on the microbial resources reported over the last couple of decades has been described. Fungi were found to be the most dominant taxa among the CPAH-degrading microbial community constituting 52.2%, while bacteria, algae, and yeasts occupied 37.4%, 9.1%, and 1.3%, respectively. In addition to these, category-wise CPAH degrading efficiencies of each microbial taxon, consortium-based applications, CPAH degradation-related molecular tools, and factors affecting CPAH degradation are the other important aspects of this review in light of their appropriate selection and application in the PAH-contaminated environment for better human-health management in order to achieve a sustainable ecosystem.

Polycyclic aromatic hydrocarbon (PAH) remediation during vermicomposting and composting: Mechanistic insights through PAH-budgeting.

Knowledge on the mechanism of earthworm-induced removal of polycyclic aromatic hydrocarbons (PAH) in vermicomposting systems and interaction with nutrient mineralization and microbial growth is scarce in literature. Moreover, the PAH accumulation capacity of Eudrilus eugeniae has not been studied. This research, therefore, investigates the apportionment dynamics of 13 PAH compounds in aerobic composting and vermicomposting (Eisenia fetida and E. eugeniae) systems using novel budget equations. The PAH removal efficiency of vermicomposting was significantly higher (2-threefold) than composting with concurrent microbial augmentation (p < 0.01). However, the 4-6 ring compounds reduced more significantly (30-50%) than the 3-ring PAHs (p < 0.01), and E. eugeniae was an equally competitive PAH-accumulator compared to E. fetida. The budget equations revealed that although the bioaccumulation capabilities of earthworms were retarded due to PAH exposure, earthworms facilitated PAH-immobilization in decomposed feedstock. A marked increase in bacterial, fungal, and actinomycetes proliferation in PAH-spiked vermibeds with parallel removal of the PAHs indicated that earthworm-induced microbial enrichment plays a vital role in PAH detoxification during vermicomposting. Correlation analyses strongly implied that earthworm-driven mineralization-humification balancing and microbial enrichment could be the critical mechanism of PAH remediation under vermicomposting.

Eco-bioengineering tools in ecohydrological assessment of eutrophic water bodies.

Eutrophication of water bodies and deterioration of water quality are emerging environmental crises. The root causes and consequences of eutrophication are multidirectional. Thus, they provide a huge scope of risk-analysis and risk-assessment in the domain of remediation studies. However, recent restoration studies reveal a global trend of utilizing traditional restoration methods combined with advanced pioneer innovative techniques developed in the field of science and technology. This review introduces a novel approach to consider ecohydrological assessment of eutrophication by classical biomanipulation practices emphasising on their evolution into innovative 'eco-bioengineering' methods. The main objective of this study is to critically analyse and recognize the research gaps in classical biomanipulation and appreciate the reproducibility and efficacy of eco-bioengineering methods at micro- and macrolevel aquatic ecosystems. Comprehensive literature review was conducted on offline and online platforms. Our survey revealed (a) continuation of a historical trend in classical biomanipulation practices (61.64%) and (b) an ascending drift in eco-bioengineering research (38.36%) in the last decade (2010-2021). At a global scale, recent biomanipulation research has a skewed distribution in Europe (41.10%), East Asia (32.88%), North America (10.96%), South Africa (4.11%), South America (2.74%), Middle East (1.37%), Oceania (1.37%), and non-specific regions (5.48%). Finally, this review analysis revealed the comprehensiveness of eco-bioengineering methods and their strong ecological resilience to recurrence of eutrophication and fluctuating environmental flows in the future. Therefore, our review reinforces the supremacy of eco-bioengineering methods as cost-effective green technologies providing sustainable solutions to restore the eutrophic waters at a global scale.

Observation of Protonation-Induced Spin State Switching in a Cyanido-Bridged {Fe2Co2} Molecular Square.

The self-assembly of [Co(MeTPyA)(CH3COO)]PF6 (1) and [Fe(bbp)(CN)3]2- affords a cyanido-bridged square-shaped {Fe2Co2} tetranuclear complex, [{Co(MeTPyA)(µ2-NC)2Fe(bbp)(CN)}2]·3H2O (2; MeTPyA = tris((3,5-dimethylpyrazol-1-yl)methyl)amine and H2bbp = bis(2-benzimidazolyl)pyridine). The possibility of inducing an intramolecular electron transfer coupled spin transition in 2 by employing protonation as an external stimulant is explored. UV-visible spectrophotometric measurements, electrochemical and 1H NMR studies establish that a reversible intramolecular electron transfer coupled spin transition can be triggered in 2 upon addition of either acid or base.

Evidence of protonation induced intra-molecular metal-to-metal charge transfer in a highly symmetric cyanido bridged {Fe2Ni2} molecular square.

The possibility to induce intra-molecular metal-to-metal charge transfer in a cyanido bridged tetranuclear square shaped {Fe2Ni2} complex by employing protonation as an external stimulant is explored. Two cyanido bridged square shaped tetranuclear complexes, [{Ni(TPA)(µ2-NC)2Ni(CN)2}2]·4H2O (2) and [{Ni(TPA)(µ2-NC)2Fe(bbp)(CN)}2]·10H2O (3) [TPA = tris(3,5-dimethylpyrazol-1-ylmethyl)amine and H2bbp = bis(2-benzimidazolyl)pyridine], are synthesized and characterized. Low temperature magnetic measurements reveal that complex 3 has dominant ferromagnetic interactions between low-spin FeIII (S = 1/2) and high-spin NiII (S = 1) ions. UV-visible spectrophotometric measurements and electrochemical studies establish that reversible intra-molecular metal-to-metal electron transfer can be triggered in 3 upon the addition of either an acid or a base.

Primacy of ecological engineering tools for combating eutrophication: An ecohydrological assessment pathway.

Eutrophication of freshwater bodies causes loss of earth's biological resources and aggravates climate change, thus assuming major environmental concern. Both endogenous and exogenous nutrient enrichment are responsible for eutrophication. Numerous monitoring and management studies conducted worldwide have resulted high-level technological innovations. These studies cumulatively uphold the significance of ecohydrological and ecological engineering approaches. However, holistic and insightful reviews with feasible recommendations of such huge academic outputs are rather scanty. Therefore, our main objective was to introduce a new perspective of eutrophication as an ecohydrological component; to discover all possibilities of monitoring and restoration of eutrophic water bodies. Furthermore, the present study critically analyzes various methods of treatment of eutrophication (physical, biological, chemical, and eco-engineering). Comprehensive volume of literature has been surveyed using search engines like Scopus, Google Scholar, PubMed, ScienceDirect etc. Meaningful keywords were used to obtain reliable information on methods of ecohydrological assessment in relation to eutrophication of freshwater bodies. According to our survey, ecohydrological research is diversified into conceptual knowledge (37.2%), assessment (32.6%), climate change (9.3%), algae/cyanotoxins (7%), engineering and restoration (7%), modelling (4.6%) and biodiversity (2.3%), in the instant decade (2010-2020). We have identified a clear trend of transition of restoration methods from traditional towards modern techniques over time. Moreover, this review recognizes a pool of biophysicochemical and ecological engineering techniques, which are very effective in regard to time, cost, and labor and have immense scopes of modification for improved results. This work focuses on the importance of ecohydrology and eco-engineering tools for restoration of eutrophic water bodies for the first time. We have highlighted how these approaches have emerged as one of the best suitable and sustainable water resource conservation routes in the present era.

Accessing water processable cyanido bridged chiral heterobimetallic Co(ii)-Fe(iii) one dimensional network.

A water processable cyanido bridged extended chiral heterobimetallic Co(ii)-Fe(iii) network is assembled. The unusual water processability of the coordination polymer originates from dangling hydrophilic substituents. The present approach offers a simple route to impart solution processability to cyanido bridged molecular magnetic materials.

Deciphering the influence of structural distortions on the uniaxial magnetic anisotropy of pentagonal bipyramidal Ni(ii) complexes.

The effect of subtle structural distortions on single ion magnetic anisotropy of pentagonal bipyramidal Ni(ii) complexes was probed by magnetization measurements and theoretical calculations. Reducing structural distortion on the equatorial pentagonal plane and employing strong field ligands on axial coordination sites dramatically enhance the uniaxial magnetic anisotropy in pentagonal bipyramidal Ni(ii) complexes.

Enhanced catalytic activity and near room temperature gas sensing properties of SnO2 nanoclusters@mesoporous Sn(iv) organophosphonate composite.

A simple, facile and one-pot route for preparing SnO2 nanoclusters embedded on a mesoporous Sn(iv) organophosphonate (MSnP) framework is described. Reaction of SnCl4·5H2O with a flexible tris-phosphonic acid, mesityl-1,3,5-tris(methylenephosphonic acid), in the presence of a surfactant under hydrothermal conditions produced the desired nanocomposite, SnO2@MSnP. Analytical, spectroscopic and microscopic studies establish that SnO2@MSnP composite is comprised of SnO2 nanoparticles of an average size of 5 nm evenly and abundantly dispersed over the MSnP framework. The mesoporous metal organophosphonate support significantly augments the catalytic efficacy and vapor sensitivity of SnO2 nanoparticles. The catalytic efficiency of SnO2@MSnP was tested for two acid-catalyzed reactions: deoximation reaction and esterification of fatty acids. SnO2@MSnP exhibits remarkable sensitivity towards ammonia and acetone vapors at near room temperature and under open atmospheric conditions. The present method represents an important step towards preparation of mesoporous metal organophosphonate supported metal oxide nanoclusters and hence offers easy access to functional metal oxide based nanocomposites.

Pentagonal Bipyramid FeII Complexes: Robust Ising-Spin Units towards Heteropolynuclear Nanomagnets.

Pentagonal bipyramid FeII complexes have been investigated to evaluate their potential as Ising-spin building units for the preparation of heteropolynuclear complexes that are likely to behave as single-molecule magnets (SMMs). The considered monometallic complexes were prepared from the association of a divalent metal ion with pentadentate ligands that have a 2,6-diacetylpyridine bis(hydrazone) core (H2 LN3O2R ). Their magnetic anisotropy was established by magnetometry to reveal their zero-field splitting (ZFS) parameter D, which ranged between -4 and -13 cm-1 and was found to be modulated by the apical ligands (ROH versus Cl). The alteration of the D value by N-bound axial CN ligands, upon association with cyanometallates, was also assessed for heptacoordinated FeII as well as for related NiII and CoII derivatives. In all cases, N-coordinated cyanide ligands led to large magnetic anisotropy (i.e., -8 to -18 cm-1 for Fe and Ni, +33 cm-1 for Co). Ab initio calculations were performed on three FeII complexes, which enabled one to rationalize the role of the ligand on the nature and magnitude of the magnetic anisotropy. Starting from the pre-existing heptacoordinated complexes, a series of pentanuclear compounds were obtained by reactions with paramagnetic [W(CN)8 ]3- . Magnetic studies revealed the occurrence of ferromagnetic interactions between the spin carriers in all the heterometallic systems. Field-induced slow magnetic relaxation was observed for mononuclear FeII complexes (Ueff /kB up to 53 K (37 cm-1 ), τ0 =5×10-9  s), and SMM behavior was evidenced for a heteronuclear [Fe3 W2 ] derivative (Ueff /kB =35 K and τ0 =4.6 10-10  s), which confirmed that the parent complexes were robust Ising-type building units. High-field EPR spectroscopic investigation of the ZFS parameters for a Ni derivative is also reported.

Modulation of the coordination environment: a convenient approach to tailor magnetic anisotropy in seven coordinate Co(II) complexes.

The possibility of controlling magnetic anisotropy by tuning contribution of second order perturbation to spin-orbit coupling through modulation of the coordination environment is investigated. Subtle variation of the coordination environment triggers a remarkable deviation in the axial zero field splitting parameter of seven coordinate Co(II) complexes.

Single-ion magnet behaviour of heptacoordinated Fe(II) complexes: on the importance of supramolecular organization.

Supramolecular organization of a metal complex may significantly contribute to the magnetization dynamics of mononuclear SMMs. This is illustrated for a heptacoordinated Fe(II) complex with rather moderate Ising-type anisotropy for which a slow magnetization relaxation with significant energy barrier was reached when this complex was properly organized in the crystal lattice. Incidentally, it is the first example of single-ion magnet behaviour of Fe(II) in a pentagonal bipyramid surrounding.

Green synthesis and characterization of silver nanoparticles using alcoholic flower extract of Nyctanthes arbortristis and in vitro investigation of their antibacterial and cytotoxic activities.

Here we report the synthesis of silver nanoparticles using ethanolic flower extract of Nyctanthes arbortristis, UVvisible spectra and TEM indicated the successful formation of silver nanoparticles. Crystalline nature of the silver nanoparticles was confirmed by X-ray diffraction. Fourier Transform Infra-Red Spectroscopy analysis established the capping of the synthesized silver nanoparticles with phytochemicals naturally occurring in the ethanolic flower extract of N. arbortristis. The synthesized silver nanoparticles showed antibacterial activity against the pathogenic strain of Escherichia coli MTCC 443. Furthermore, cytotoxicity of the silver nanoparticles was tested on mouse fibroblastic cell line (L929) and found to be non-toxic, which thus proved their biocompatibility. Antibacterial activity and cytotoxicity assay carried out in this study open up an important perspective of the synthesized silver nanoparticles.

Ab initio chemical synthesis of designer metal phosphate frameworks at ambient conditions.

Stepwise hierarchical and rational synthesis of porous zinc phosphate frameworks by predictable and directed assembly of easily isolable tetrameric zinc phosphate [Zn(dipp)(solv)]4 (dippH2 = diisopropylphenyldihydrogen phosphate; solv = CH3OH or dimethyl sulfoxide) with D4R (double-4-ring) topology has been achieved. The preformed and highly robust D4R secondary building unit can be coordinatively interconnected through a varied choice of bipyridine-based ditopic spacers L1-L7 to isolate eight functional zinc phosphate frameworks, [Zn4(dipp)4(L1)1.5(DMSO)]·4H2O (2), [Zn4(dipp)4(L2)1.5(CH3OH)] (3), [Zn4(dipp)4(L1)2] (4), [Zn4(dipp)4(L3)2] (5), [Zn4(dipp)4(L4)2] (6), [Zn4(dipp)4(L5)2] (7), [Zn4(dipp)4(L6)2] (8), and [Zn4(dipp)4(L7)2] (9), in good yield. The preparative procedures are simple and do not require high pressure or temperature. Surface area measurements of these framework solids show that the guest accessibility of the frameworks can be tuned by suitable modification of bipyridine spacers.

Geometry-mediated enhancement of single-ion anisotropy: a route to single-molecule magnets with a high blocking temperature.

Not just any old iron ion: A linear, two-coordinate ionic Fe(I) complex with a S=3/2 ground state has a large energy barrier for magnetization reversal, Ueff =226 cm(-1) , and undergoes slow magnetic relaxation in the absence of an applied magnetic field. The preparation of complexes with these properties is a step towards the eventual practical application of single-molecule magnets.

Heptacoordinated nickel(II) as an Ising-type anisotropic building unit: illustration with a pentanuclear [(NiL)3{W(CN)8}2] complex.

Heptacoordinated nickel(II) complexes characterized by substantial Ising-type single-ion anisotropy have been involved in the construction of two pentanuclear [Ni3W2] compounds by association with [W(CN)8](3-). For one of them, slow relaxation of magnetization was observed to occur concomitantly with antiferromagnetic ordering.

Origin of the magnetic anisotropy in heptacoordinate Ni(II) and Co(II) complexes.

The nature and magnitude of the magnetic anisotropy of heptacoordinate mononuclear Ni(II) and Co(II) complexes were investigated by a combination of experiment and ab initio calculations. The zero-field splitting (ZFS) parameters D of [Ni(H(2)DAPBH)(H(2)O)(2)](NO(3))(2)⋅2 H(2)O (1) and [Co(H(2)DAPBH)(H(2)O)(NO(3))](NO(3)) [2; H(2)DAPBH = 2,6-diacetylpyridine bis- (benzoyl hydrazone)] were determined by means of magnetization measurements and high-field high-frequency EPR spectroscopy. The negative D value, and hence an easy axis of magnetization, found for the Ni(II) complex indicates stabilization of the highest M(S) value of the S = 1 ground spin state, while a large and positive D value, and hence an easy plane of magnetization, found for Co(II) indicates stabilization of the M(S) = ±1/2 sublevels of the S = 3/2 spin state. Ab initio calculations were performed to rationalize the magnitude and the sign of D, by elucidating the chemical parameters that govern the magnitude of the anisotropy in these complexes. The negative D value for the Ni(II) complex is due largely to a first excited triplet state that is close in energy to the ground state. This relatively small energy gap between the ground and the first excited state is the result of a small energy difference between the d(xy) and d(x(2)-y(2)) orbitals owing to the pseudo-pentagonal-bipyramidal symmetry of the complex. For Co(II), all of the excited states contribute to a positive D value, which accounts for the large magnitude of the anisotropy for this complex.

Green synthesis of gold nanoparticles using Nyctanthes arbortristis flower extract.

The present study explores the reducing and capping potentials of ethanolic flower extract of the plant Nyctanthes arbortristis for the synthesis of gold nanoparticles. The extract at different volume fractions were stirred with HAuCl4 aqueous solution at 80 °C for 30 min. The UV-Vis spectroscopic analysis of the reaction products confirmed successful reduction of Au(3+) ions to gold nanoparticles. Transmission electron microscope (TEM) revealed dominant spherical morphology of the gold nanoparticles with an average diameter of 19.8 ± 5.0 nm. X-ray diffraction (XRD) study confirmed crystalline nature of the synthesized particles. Fourier transform infra-red (FTIR) and nuclear magnetic resonance (NMR) analysis of the purified and lyophilized gold nanoparticles confirmed the surface adsorption of biomolecules during preparation and caused long-term (6 months) stability. Low reaction temperature (25 °C) favored anisotropy. The strong reducing power of the flower extract can also be tested in the green synthesis of other metallic nanoparticles.

Assembling discrete D4R zeolite SBUs through noncovalent interactions. 3. Mediation by butanols and 1,2-bis(dimethylamino)ethane.

The use of tetrameric zinc phosphate [Zn(dipp)(CH(3)OH)](4) (1; dipp = diisopropylphenylphosphate dianion) as a suitable building block for realizing new noncovalently linked extended structures, via facile replacement of coordinated methanol molecules by other alcohols, is reported herein. Compounds [Zn(dipp)(sec-butanol)](4) x 4 H(2)O (2) and [Zn(dipp)(tert-butanol)](4) x 4 H(2)O (3) have been synthesized by the addition of sec- or tert-butanol to 1 at room temperature. The reaction of zinc acetate or zinc sulfate with dippH(2) in the presence of N,N,N',N'-tetramethylethylenediamine (tmeda) under similar reaction conditions results in the formation of [H(2)tmeda][Zn(4)(dipp)(4)(MeOH)(2)(OAc)(2)] x (CH(3)OH) (4) or [H(2)tmeda][Zn(3)(dipp)(3)(dippH)(2)(CH(3)OH)] x (CH(3)OH)(3) (5), respectively. Analytically pure compounds 2-5 have been isolated in the form of single crystals directly from the respective reaction mixtures in very good yields and characterized with the aid of analytical and spectroscopic studies. Single-crystal X-ray diffraction studies reveal that compounds 2 and 3 are neutral tetranuclear zinc phosphates. Compound 4 is also a tetrameric phosphate but is anionic. The core structures of compounds 2-4 resemble the double-4-ring secondary building unit (D4R SBU) in zeolites. Compound 5 is a trinuclear ionic zinc phosphate built from three fused S4R SBUs. Compounds 4 and 5 represent the first examples of discrete anionic zinc organophosphates. The presence of coordinated sec- or tert-butanol molecules and a planar water tetramer cluster in 2 and 3, and the H(2)tmeda cations and methanol solvents in 4 and 5, leads to the formation of zigzag chainlike supramolecular assemblies in the solid state.

Noncovalent synthesis of hierarchical zinc phosphates from a single Zn(4)O(12)P(4) double-four-ring building block: dimensionality control through the choice of auxiliary ligands.

In contrast to the well-known reaction of phosphonic acids RP(O)(OH)(2) with divalent transition-metal ions that yields layered metal phosphonates [RPO(3)M(H(2)O)](n), the 2,6-diisopropylphenyl ester of phosphoric acid, dippH(2), reacts with zinc acetate in methanol under ambient conditions to afford tetrameric zinc phosphate [(ArO)PO(3)Zn(MeOH)](4) (1). The coordinated methanol in 1 can be readily exchanged by stronger Lewis basic ligands at room temperature. This strategy opens up a new avenue for building double-four-ring (D4R) cubane-based supramolecular assemblies through strong intercubane hydrogen-bonding interactions. Seventeen pyridinic ligands have been used to synthesize as many D4R cubanes [(ArO)PO(3)Zn(L)](4) (2-18) from 1. The ligands have been chosen in such a way that the majority of them contain an additional functional group that could be used for noncovalent synthesis of extended structures. When the ligand does not contain any other hydrogen-bonding donor-acceptor sites (e.g., 2,4,6-trimethylpyridine (collidine)), zero-dimensional D4R cubanes have been obtained. The use of pyridine, lutidine, 2-aminopyridine, and 2,6-diaminopyridine, however, results in the formation of linear or zigzag one-dimensional assemblies of D4R cubanes through strong intermolecular C-H...O or N-H...O interactions. Construction of two-dimensional assemblies of zinc phosphates has been achieved by employing 2-hydroxypyridine or 2-methylimidazole as the exo-cubane ligand on zinc centers. The introduction of an alcohol side chain on the pyridinic ligand in such a way that the -CH(2)OH group cannot participate in intracubane hydrogen bonding (e.g., pyridine-3-methanol, pyridine-4-methanol, and 3,5-dimethylpyrazole-N-ethanol) leads to the facile noncovalent synthesis of three-dimensional framework structures. Apart from being useful as building blocks for noncovalent synthesis of zeolite-like materials, compounds 1-18 can also be thermolyzed at approximately 500 degrees C to yield high-purity zinc pyrophosphate (Zn(2)P(2)O(7)) ceramic material.