Epitaxial Heterostructures of CsPbBr3 Perovskite Nanocrystals with Post-transition Metal Bismuth.

The facet chemistry of halide perovskite nanocrystals plays a key role in designing nanoscale epitaxial heterostructures. However, despite significant successes achieved in designing these nanocrystals, their heterostructures with several leading transition metals could not be established yet. Herein, the possible heterostructures of metals beyond transition metals are explored and the epitaxial combinations of soft CsPbBr3 nanocrystals with the post-transition metal Bi(0) are reported. These heterostructures are built with interfacing facets having hexagonal atomic configurations of both the rhombicuboctahedron CsPbBr3 and octahedral Bi(0). A high reaction temperature and the presence of alkylamine kept Bi(III) in reduced form and helped in sustaining these CsPbBr3-Bi(0) heteronanocrystals. Since understanding of and synthesis optimization of metal-halide perovskite heterostructures are limited, this finding adds a new fundamental insight in designing ionic and nonionic materials heterojunctions. Furthermore, oxidation and sulfidation of Bi(0) are studied, and the possible oxide/sulfide heterostructures with CsPbBr3 are discussed.

Facets-Directed Epitaxially Grown Lead Halide Perovskite-Sulfobromide Nanocrystal Heterostructures and Their Improved Photocatalytic Activity.

Lead halide perovskite nanocrystal heterostructures have been extensively studied in the recent past for improving their photogenerated charge carriers mobility. However, most of such heterostructures are formed with random connections without having strong evidence of epitaxial relation. Perovskite-chalcohalides are the first in this category, where all-inorganic heterostructures are formed with epitaxial growth. Going beyond one facet, herein, different polyhedral nanocrystals of CsPbBr3 are explored for facet-selective secondary epitaxial sulfobromide growths. Following a decoupled synthesis process, the heterojunctions are selectively established along {110} as well as {200} facets of 26-faceted rhombicuboctahedrons, the {110} facets of armed hexapods, and the {002} facets of 12-faceted dodecahedron nanocrystals of orthorhombic CsPbBr3. Lattice matching induced these epitaxial growths, and their heterojunctions have been extensively studied with electron microscopic imaging. Unfortunately, these heterostructures did not retain the intense host emission because of their indirect band structures, but such combinations are found to be ideal for promoting photocatalytic CO2 reduction. The pseudo-Type-II combination helped here in the successful movement of charge carriers and also improved the rate of catalysis. These results suggest that facet-selective all-inorganic perovskite heterostructures can be epitaxially grown and this could help in improving their catalytic activities.

Nucleophile-Controlled Halide Release from the Substitution Reaction of Haloketone for Facet Tuning and Manganese Doping in CsPbCl3 Nanocrystals.

Halide content of the reaction medium not only enhances the brightness of CsPbCl3 nanocrystals but also, control the shape modulations as well as doping Mn(II) in these host nanocrystals. Correlating both the shape effect and doping, herein, an in situ reaction of nucleophile-controlled halide release was explored for monitoring facets modulations and doping in CsPbCl3 nanocrystals. This was performed using alkyl amine as nucleophile which reacted with α-halo ketone, phenacyl chloride, to release chloride ions. Increase in amine concentration which released more Cl ions, reduced the possibility of shape transformation from perfect to truncated cubes during annealing. Similarly, for Mn(II) doping, the dopant photoluminescence intensity remained directly proportional to the amount of introduced amine nucleophiles. Quality of both doped and undoped nanocrystals obtained in this procedure remained unparallel and the method provided a strong correlation of rate of halide release with both facet modulations and doping in these nanocrystals.

Facets Directed Connecting Perovskite Nanocrystals.

Connecting nanocrystals with removal of interface ligand barriers is one of the key steps for efficient carrier transportation in optoelectronic device fabrication. Typically, ion migration for crystal deformation or connection with other nanocrystals needs a solvent as medium. However, on the contrary, this has been observed for CsPbBr3 perovskite nanocrystals in film where nanocrystals were swollen to get wider and fused with adjacent nanocrystals in self-assembly on film during solvent evaporation. Depending on precursor composition and exposed facets, again these connections could be programmed for tuning their connecting directions leading to different shapes. Aging further on solid substrate, these were also turned to continuous film of nanostructures eliminating all interparticle gaps on the film. This transformation could be ceased at any point of time, simply by heating or adding sufficient ligands. Analysis suggested that these unique and controlled connections were only observed with polyhedron shaped nanostructures with certain compositions and not with traditionally cubes. Details of this solid-surface transformation during solvent evaporation were analyzed, and an interparticle material transfer type mechanism was proposed. As these observations were not seen in chalcogenide and oxide nanocrystals and exclusively observed in perovskite nanocrystals, this would add new fundamentals to the insights of crystal growths of nanocrystals and would also help in obtaining films of connecting nanocrystals.

Molecular characterization of Myxoboluscatmrigalae (Myxosporea: Myxobolidae) infecting the gill lamellae of carp Cirrhinusmrigala (Hamilton).

The present study attempted sequencing the 18S rRNA gene of Myxoboluscatmrigalae infecting the gill lamellae of carp, Cirrhinusmrigala and compared its genetic homology and phylogenetic characteristics with 18S rRNA genes of other Myxobolus spp. The infected fish had up to 3 small, creamy white plasmodia per gill filament with 30-50 spores each. The spore size was 17.90 ± 0.70 × 7.40 ± 0.40 µm. The sporoplasm contained two large nuclei of size 0.57 ± 0.09 µm and no iodinophilous vacuole. The DNA sequence of M.catmrigalae was clustered phylogenetically with other Myxobolus spp. infecting the gills of cyprinids available in GenBank, which showed 77-87 % homogeneity. On the phylogenetic tree, M.catmrigalae (KC933944) was clustered with M.pavlovskii (HM991164) infecting the gill lamellae of silver carp, Hypophthalmichthysmolitrix. The species most closely related to M.catmrigalae in GenBank was M.pavlovskii (AF507973) infecting the gill lamellae of big head carp, Aristichthysnobilis with 87 % homogeneity. This is the first report on molecular characterization of gill lamellae infecting M. catmrigalae.

Detection of goldfish haematopoietic necrosis herpes virus (Cyprinid herpesvirus-2) with multi-drug resistant Aeromonas hydrophila infection in goldfish: First evidence of any viral disease outbreak in ornamental freshwater aquaculture farms in India.

This outbreak report details of a mortality event where Cyprinid herpes virus-2 (CyHV-2) was detected in association with multidrug-resistant Aeromonas hydrophila infection in goldfish, Carassius auratus, from commercial farms. The goldfish exhibited large scale haemorrhages on the body, fins and gills, lepidorthosis, necrosed gills, protruded anus and shrunken eyes. White nodular necrotic foci in spleen and kidneys were noticed, along with necrosis and fusion of gill lamellae. Transmission electron microscopy of affected tissues revealed the presence of mature virus particles. Involvement of CyHV-2 was confirmed by PCR, sequencing and observed cytopathic effect in koi carp fin cell line along with experimental infection study. A bacterium isolated from the internal organs of affected fish was found to be pathogenic Aeromonas hydrophila having resistance to more than 10 classes of antibiotics. We postulate that CyHV-2 was the primary etiological agent responsible for this outbreak with secondary infection by A. hydrophila. The experimental infection trials in Labeo rohita and koi carp by intraperitoneal challenge with CyHV-2 tissue homogenates failed to reproduce the disease in those co-cultured fish species. This is the first report of a viral disease outbreak in organised earthen ornamental fish farms in India and bears further investigation.

Molecular characterization of Argulus bengalensis and Argulus siamensis (Crustacea: Argulidae) infecting the cultured carps in West Bengal, India using 18S rRNA gene sequences.

The present study characterized Argulus spp. infecting the cultured carps using 18S rRNA gene sequences, estimated the genetic similarity among Argulus spp. and established their phylogenetic relationship. Of the 320 fish samples screened, 34 fish (10.6%) had Argulus infection. The parasitic frequency index (PFI) was observed to be high (20%) in Hypophthalmichthys molitrix and Labeo bata. The frequency of infection was high in September (PFI: 17%) and October (PFI: 12.9%). The 18S rRNA sequences of five A. bengalensis (KF583878, KF192316, KM016968, KM016969, and KM016970) and one A. siamensis (KF583879) of this study showed genetic heterogeneity and exhibited 77-99% homology among the 18S rRNA gene sequences of Argulus spp. of NCBI GenBank database. Among the Indian Argulus spp. the sequence homology was 87-100%. Evolutionary pair-wise distances between Indian Argulus spp. and other Argulus spp. ranged from 0 to 20.20%. In the phylogenetic tree, all the crustaceans were clustered together as a separate clade with two distinct lineages. The lineage-1 comprised exclusive of Branchiura (Argulus spp.). All Argulus bengalensis clustered together and A. siamensis (KF583879) was closely related to Argulus sp. JN558648. The results of the present study provided baseline data for future work on population structure analysis of Indian Argulus species.

Molecular phylogeny of Myxobolus orissae (Myxosporea: Myxobolidae) infecting the gill lamellae of mrigal carp Cirrhinus mrigala (Actinopterygii: Cyprinidae).

Myxosporeans are best known for the diseases they cause in commercially important fish species. Identification of myxosporeans at the species-level is mainly based on conventional methods. The 18S rRNA gene sequence of morphologically identified Myxobolus orissae infecting the gill lamellae of mrigal carp Cirrhinus mrigala was characterized in the present study. The plasmodia of M.orissae were small, elongated and white to pale in colour. Phylogenetically, the 18S rDNA nucleotide sequence of M.orissae was clustered with other gill-infecting Myxobolus spp. of cyprinids. The species closely related to M. orissae was M. koi (FJ841887) infecting the gill lamellae of Cyprinus carpio with 96% similarity. The carp fin-infecting Thelohanelluscaudatus (KC865607) from India exhibited only 78% DNA sequence similarity with M. orissae. Low level of M. orissae infection on gill caused thickening of epithelial cells surrounding the plasmodium. Under stressful conditions, it is likely that such infection can easily spread in confined fish and may cause serious disease outbreaks and economical losses.

Molecular and phylogenetic characterization of Thelohanellus qadrii (Myxozoa, Myxosporea, Bivalvulida) infecting the secondary gill epithelium of Indian major carp, Catla catla (Hamilton, 1822).

Myxosporean taxonomy which is traditionally based on the morphology of the myxospore stage, is in a state of flux given new insights provided by the expanding dataset of DNA sequences. To date, more than 40 species of Thelohanellus from India have been described according to morphometric characteristics. Nevertheless, molecular data on these histozoic myxosporean parasites of freshwater fish are scarce. In the present study, molecular characterizations of Thelohanellus qadrii infecting the secondary gill epithelium of Indian major carp Catla catla (Hamilton, 1822) and its phylogenetic relationship is reported. The sub-adult cultured catla were observed to have low to moderate gill myxosporean infections. The morphometry of mature spores was in compliance with original descriptions of T. qadrii. Based on the analysis of 18S rRNA gene, phylogenetic clusters which were established according to a consensus sequence, illustrated the taxonomic placement of a series of myxobolids. The DNA sequence homogeneity of T. qadrii (KF170928) with other Thelohanllus spp. ranged from 78% to 95% and formed a dichotomy with cyprinid gill lamellae infecting T. toyamai (HQ338729). Distance matrix results indicated a high genetic diversity among myxosporeans. The present report is the first on the molecular and phylogenetic characterizations of T. qadrii.

The phylogenetic position of Myxoboluscarnaticus (Myxozoa, Myxosporea, Bivalvulida) infecting gill lamellae of Cirrhinus mrigala (Hamilton, 1822) based on 18S rRNA sequence analysis.

Myxozoans are an economically important group of microscopic parasites best known for the diseases they cause in commercially important fish hosts. The classification of myxosporeans is generally based on the morphology of their myxospores. Without molecular data, it is very difficult to identify new or existing species. DNA sequence information is therefore, a prerequisite to taxonomic and phylogenic studies of myxosporeans. In the present study, a myxozoan parasite, Myxobolus carnaticus, infecting the gill lamellae of mrigal carp, Cirrhinus mrigala, was characterized by the 18S rRNA gene sequence. The DNA sequence of M. carnaticus clustered phylogenetically with other gill infecting Myxobolus spp. of freshwater clades, forming a dichotomy with closely related M. pavlovskii (HM991164) that infects the gill lamellae epithelium of silver carp, Hypophthalmichthys molitrix with 95% similarity. Evolutionary pair-wise distances among M. carnaticus and other species of myxosporeans indicated high genetic diversity among myxosporeans. The present study demonstrated that tissue tropism, host specificity and habitat play important roles in phylogenetic relationships among myxozoan species.

Molecular characterization of Myxobolus cuttacki (Myxozoa, Myxosporea, Bivalvulida) infecting gill lamellae of minor carp Labeo bata (Ham.).

As new pathogenic strains are emerging and threatening aquaculture development, myxosporeans (Myxozoa) are receiving much attention in recent years. Myxosporean taxonomy is traditionally based on morphology of the myxospore stage. Molecular data on Indian myxosporeans are rare. In this report, the 18S rRNA gene sequence of Myxobolus cuttacki infecting gill lamellae of minor carp Labeo bata (Ham.) and its phylogenetic relationship with other myxobolids are described for the first time. The plasmodia of M. cuttacki were 0.5-0.9 mm in size and whitish with a round to oval shape. The mean mature spore size was 16.10×7.05 µm. The 18S rRNA nucleotide sequence with 1703 bp of M. cuttacki (accession number KF465682) clustered phylogenetically with other Myxobolus spp. infecting cyprinid gills with 78-90% homogeneity. The gill lamellae infecting M. catmrigalae (KC933944) and M. orissae (KF448527) of Indian major carp Cirrhinus mrigala from India, exhibited 86% and 81% homogeneity with M. cuttacki, respectively. The infection rate was low to moderate on the gills which can have a negative impact on respiratory and physiological functions and subsequently on fish production.