Mass Sensing for the Advanced Fabrication of Nanomechanical Resonators

We report on a nanomechanical engineering method to monitor matter growth in real time via e-beam electromechanical coupling. This method relies on the exceptional mass sensing capabilities of nanomechanical resonators. Focused electron beam-induced deposition (FEBID) is employed to selectively grow platinum particles at the free end of singly clamped nanotube cantilevers. The electron beam has two functions: it allows both to grow material on the nanotube and to track in real time the deposited mass by probing the noise-driven mechanical resonance of the nanotube. On the one hand, this detection method is highly effective as it can resolve mass deposition with a resolution in the zeptogram range; on the other hand, this method is simple to use and readily available to a wide range of potential users because it can be operated in existing commercial FEBID systems without making any modification. The presented method allows one to engineer hybrid nanomechanical resonators with precisely tailored functionalities. It also appears as a new tool for studying the growth dynamics of ultrathin nanostructures, opening new opportunities for investigating so far out-of-reach physics of FEBID and related methods

Optomechanics with a hybrid carbon nanotube resonator

© 2018 The Author(s). In just 20 years of history, the field of optomechanics has achieved impressive progress, stepping into the quantum regime just 5 years ago. Such remarkable advance relies on the technological revolution of nano-optomechanical systems, whose sensitivity towards thermal decoherence is strongly limited due to their ultra-low mass. Here we report a hybrid approach pushing nano-optomechanics to even lower scales. The concept relies on synthesising an efficient optical scatterer at the tip of singly clamped carbon nanotube resonators. We demonstrate high signal-to-noise motion readout and record force sensitivity, two orders of magnitude below the state of the art. Our work opens the perspective to extend quantum experiments and applications at room temperature

High Efficiency Colloidal Quantum Dot Infrared Light Emitting Diodes via Engineering at the Supra-Nanocrystalline Level

Colloidal quantum dot (CQD) light-emitting diodes (LEDs) deliver a compelling performance in the visible, yet infrared CQD LEDs underperform their visible-emitting counterparts, largely due to their low photoluminescence quantum efficiency. Here we employ a ternary blend of CQD thin film that comprises a binary host matrix that serves to electronically passivate as well as to cater for an efficient and balanced carrier supply to the emitting quantum dot species. In doing so, we report infrared PbS CQD LEDs with an external quantum efficiency of ~7.9% and a power conversion efficiency of ~9.3%, thanks to their very low density of trap states, on the order of 1014 cm−3, and very high photoluminescence quantum efficiency in electrically conductive quantum dot solids of more than 60%. When these blend devices operate as solar cells they deliver an open circuit voltage that approaches their radiative limit thanks to the synergistic effect of the reduced trap-state density and the density of state modification in the nanocomposite.Peer ReviewedPostprint (author's final draft

Lead-sulphide quantum-dot sensitization of tin oxide based hybrid solar cells

We have fabricated infrared active hybrid solar cells composed of mesoporous SnO 2 sensitized with PbS nanoparticles and infiltrated with organic hole-transporters, 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene(spiro-OMeTAD) or poly(3-hexylthiophene). We observe photo-action to 1100nm, peak quantum-efficiency over 20%, open-circuit voltages up to 0.5V and power conversion efficiencies of over 0.5% under simulated sun light. As compared to solar cells composed of mesoporous TiO 2 sensitized with the same PbS nanoparticles, the SnO 2 based devices generate 4 times the photocurrent density under simulated sun light. © 2011

Optomechanics with a hybrid carbon nanotube resonator

In just 20 years of history, the field of optomechanics has achieved impressive progress, stepping into the quantum regime just 5 years ago. Such remarkable advance relies on the technological revolution of nano-optomechanical systems, whose sensitivity towards thermal decoherence is strongly limited due to their ultra-low mass. Here we report a hybrid approach pushing nano-optomechanics to even lower scales. The concept relies on synthesising an efficient optical scatterer at the tip of singly clamped carbon nanotube resonators. We demonstrate high signal-to-noise motion readout and record force sensitivity, two orders of magnitude below the state of the art. Our work opens the perspective to extend quantum experiments and applications at room temperature.Peer Reviewe

Direct formation of PbS nanorods in a conjugated polymer

A study was carried out to demonstrate that PbS nanorods can be directly assembled in a conducting polymer. The controlled assembly of the nanorods has been reported through oriented attachment of PbS nanocrystals using a post-synthesis treatment of PbS nanocrystal/poly(2-methoxy-5-(2'-ethyl-hexyloxy) -p-phenylene vinylene) (MEH-PPV) composites synthesized by a low-temperature and surfactant-free method. The composite has broad optical absorption and the results of the experimentation have also shown that the nanorods formation is governed by the polarity of alcohol used for precipitation. This formation also appears to arise from dipole-induced oriented attachment of PbS nanocrystals. The results of the study also have found that the extension of the composite absorption beyond the main polymer exciton peak at ca. 520 nm is due to the presence of nanocrystals

SnS/PbS nanocrystal heterojunction photovoltaics.

We report advances in the growth, characterization and photovoltaic properties of SnS nanocrystals, with controlled < 10 nm size, and their inclusion into a lead chalcogenide solar cell. The SnS/PbS nanocrystalline film heterojunction is shown to display a type II band alignment, in which the direction of flow of the photocurrent depends on the order of the layers and not the relative work functions of the contacts. On placing the SnS layer next to the indium tin oxide (ITO) cathode we observe a dramatic increase in V(oc) to as much as 0.45 V. Our results suggest that SnS nanocrystal films can be used in multi-junction solar cells, that a SnS/PbS heterojunction on its own shows photovoltaic behaviour, and that a SnS layer in an ITO/SnS/PbS/Al device is acting to suppress the flow of an electron injection current

Optomechanics with a hybrid carbon nanotube resonator

In just 20 years of history, the field of optomechanics has achieved impressive progress, stepping into the quantum regime just 5 years ago. Such remarkable advance relies on the technological revolution of nano-optomechanical systems, whose sensitivity towards thermal decoherence is strongly limited due to their ultra-low mass. Here we report a hybrid approach pushing nano-optomechanics to even lower scales. The concept relies on synthesising an efficient optical scatterer at the tip of singly clamped carbon nanotube resonators. We demonstrate high signal-to-noise motion readout and record force sensitivity, two orders of magnitude below the state of the art. Our work opens the perspective to extend quantum experiments and applications at room temperature.Peer Reviewe

Epidemiology, clinical course and impact on hospitalization costs of acute diarrhea among hospitalized children in Athens, Greece

The aim of this study was to describe the etiology, morbidity and hospitalization costs associated with acute diarrhea among hospitalized children in Greece. During 1999, 294 hospitalized children (median age 1 y) with acute diarrhea were prospectively studied. Bacterial and viral enteropathogens were detected in 100 (34%) and 37 (12.5%) patients, respectively; 17 (6%) patients had mixed infections. Isolated agents included Salmonella spp. (43 patients; 15%), rotavirus (32; 11%), Campylobacter spp. (26; 9%), enteropathogenic Escherichia coli (16; 5.5%), Shigella spp. (11; 4%), Aeromonas spp. (7; 2.5%), adenovirus (6; 2%), Yersinia enterocolitica (6; 2%), enterohemorrhagic Escherichia coli (2; 0.5%) and Giardia lamblia (1; 0.5%). Of the patients with bacterial infection, 70% were admitted between April and September 1999. A rotavirus-associated peak was noted in March. Patients with a bacterial infection were hospitalized for longer periods than those with viral infections. It is concluded that bacterial enteropathogens account for one-third of admissions due to acute diarrhea among children in Greece and are associated with significant hospitalization costs. Rotavirus is also a frequent cause of acute diarrhea necessitating hospitalization