Ultrabright single-photon emission from germanium-vacancy zero-phonon lines: deterministic emitter-waveguide interfacing at plasmonic hot spots

Striving for nanometer-sized solid-state single-photon sources, we investigate atom-like quantum emitters based on single germanium-vacancy (GeV) centers isolated in crystalline nanodiamonds (NDs). Cryogenic characterization indicated symmetry-protected and bright (>106 counts/s with off-resonance excitation) zero-phonon optical transitions with up to 6-fold enhancement in energy splitting of their ground states as compared to that found for GeV centers in bulk diamonds (i.e. up to 870 GHz in highly strained NDs vs. 150 GHz in bulk). Utilizing lithographic alignment techniques, we demonstrate an integrated nanophotonic platform for deterministic interfacing plasmonic waveguides with isolated GeV centers in NDs, which enables 10-fold enhancement of single-photon decay rates along with the emission direction control by judiciously designing and positioning a Bragg reflector. This approach allows one to realize the unidirectional emission from single-photon dipolar sources, thereby opening new perspectives for the realization of quantum optical integrated circuits

Gold nanostructure-enhanced immunosensing: ultra-sensitive detection of VEGF tumor marker for early disease diagnosis

Abstract We present an advanced electrochemical immunosensor designed to detect the vascular endothelial growth factor (VEGF) precisely. The sensor is constructed on a modified porous gold electrode through a fabrication process involving the deposition of silver and gold on an FTO substrate. Employing thermal annealing and a de-alloying process, the silver is eliminated from the electrode, producing a reproducible porous gold substrate. Utilizing a well-defined protocol, we immobilize the heavy-chain (VHH) antibody against VEGF on the gold substrate, facilitating VEGF detection through various electrochemical methods. Remarkably, this immunosensor performs well, featuring an impressive detection limit of 0.05 pg/mL and an extensive linear range from 0.1 pg/mL to 0.1 µg/mL. This emphasizes it’s to measure biomarkers across a wide concentration spectrum precisely. The robust fabrication methodology in this research underscores its potential for widespread application, offering enhanced precision, reproducibility, and remarkable detection capabilities for the developed immunosensor

Genetic diversity of ‘Candidatus Phytoplasma phoenicium’ strain populations associated with almond witches’ broom in Lebanon and Iran

Candidatus Phytoplasma phoenicium\u2019 (subgroup 16SrIX-B) strains associated with almond witches\u2019 broom disease in Lebanon and Iran were typed by PCR-based amplification and sequence analyses of rplV-rpsC and secY genes. Results showed that Iranian and Lebanese AlmWB-associated phytoplasma strain populations constitute at least two distinct genetic lineages, supporting previous evidence obtained through 16S rDNA analysis. Such genetic diversity reflects differences in biological features (i.e. insect vectors and plant hosts) of \u2018Ca. P. phoenicium\u2019 in Lebanon and Iran. Molecular markers identified within rplVrpsC and secY genes should be employed to improve the knowledge about \u2018Ca. P. phoenicium\u2019 ecology and almond witches\u2019 broom epidemiology in the Middle East

Phytoplasmas: an update

A summary of the research carried out on phytoplasma-associated diseases 50 years after their discovery is presented. The great majority of the research was devoted to classification and differentiation of these prokaryotes by molecular and bioinformatic tools applied to specific phytoplasma genes. The availability of a robust classification system has greatly facilitated phytoplasma identification leading to an increased knowledge of plant diseases worldwide. Scientific knowledge on phytoplasma biology still needs to be improved to allow better management solutions to reduce the impact of these diseases in agricultural and natural environments

The Family Acholeplasmataceae (Including Phytoplasmas)The Prokaryotes

The family Acholeplasmataceae was originally established to accommodate the genus Acholeplasma, comprising the mollicutes that could be cultivated without the supplement of cholesterol and that use UGA as a stop codon instead of coding for tryptophan. It was later shown that the phytoplasmas, a large group of uncultivable, wall-less, non-helical mollicutes that are associated with plants and insects, shared taxonomically relevant properties with members of the genus Acholeplasma. Being not cultivable in vitro in axenic culture, the phytoplasmas could not be classified using the standards used for other mollicutes and are named using the category of Candidatus, as “Ca. Phytoplasma.” Although phytoplasmas are associated with habitats and ecology different from acholeplasmas, the two genera Acholeplasma and “Candidatus Phytoplasma” are phylogenetically related and form a distinct clade within the Mollicutes. The persisting inability to grow the phytoplasmas in vitro hinders the identification of their distinctive phenotypic traits, important criteria for mollicute classification. Until supplemental phenotypic traits become available, the genus “Candidatus Phytoplasma” is designated, on the basis of phylogeny, as a tentative member in the family Acholeplasmataceae. Phylogenetic analysis based on gene sequences, in particular, ribosomal sequences, has provided the major supporting evidence for the composition and taxonomic subdivision of this group of organisms with diverse habitats and ecology and has become the mainstream for the Acholeplasmataceae systematics. However, without the ability to determine phenotypic properties, the circumscription of related species among the non culturable members of the family remains a major issue. The genus Acholeplasma comprises 14 species predominantly associated with animals and isolated from mammalian fluids but regarded as not normally pathogenic. Conversely, the genus “Ca. Phytoplasma” includes plant pathogens of major economic relevance worldwide. To date, 36 “Ca. Phytoplasma species” have been described