Unconventional ratiometric-enhanced optical sensing of oxygen by mixed-phase TiO2

We show that mixed-phase titanium dioxide (TiO2) can be effectively employed as an unconventional, inorganic, dual-emitting and ratiometric optical sensor of O2. Simultaneous availability of rutile and anatase TiO2 PL and their peculiar anti-correlated PL responses to O2 allow using their ratio as measurement parameter associated to O2 concentration, leading to an experimental responsivity being by construction larger than the one obtainable for single-phase PL detection. A proof of this concept in given, showing a two-fold enhancement of the optical responsivity provided by the ratiometric approach. Besides the peculiar ratiometric-enhanced responsivity, other characteristics of mixed phase TiO2 can be envisaged as favorable for O2 optical probing, namely: a) low production costs, b) absence of heterogeneous components, c) self-supporting properties. These characteristics encourage experimenting its use for applications requiring high indicator quantities at competitive price, possibly also tackling the need to develop supporting matrixes that carry the luminescent probes and avoiding issues related to the use of different components for ratiometric sensing.Comment: 12 pages, 5 figure

Time-resolved energy transfer from single chloride terminated nanocrystals to graphene

We examine the time-resolved resonance energy transfer of excitons from single n-butyl amine-bound, chloride-terminated nanocrystals to two-dimensional graphene through time-correlated single photon counting. The radiative biexponential lifetime kinetics and blinking statistics of the individual surface-modified nanocrystal elucidate the non-radiative decay channels. Blinking modification as well as a 4 times reduction in spontaneous emission were observed with the short chloride and n-butylamine ligands, probing the energy transfer pathways for the development of graphene-nanocrystal nanophotonic devices

Tuning the Coupling in Single-Molecule Heterostructures: DNA-Programmed and Reconfigurable Carbon Nanotube-Based Nanohybrids

Herein a strategy is presented for the assembly of both static and stimuli‐responsive single‐molecule heterostructures, where the distance and electronic coupling between an individual functional nanomoiety and a carbon nanostructure are tuned via the use of DNA linkers. As proof of concept, the formation of 1:1 nanohybrids is controlled, where single quantum dots (QDs) are tethered to the ends of individual carbon nanotubes (CNTs) in solution with DNA interconnects of different lengths. Photoluminescence investigations—both in solution and at the single‐hybrid level—demonstrate the electronic coupling between the two nanostructures; notably this is observed to progressively scale, with charge transfer becoming the dominant process as the linkers length is reduced. Additionally, stimuli‐responsive CNT‐QD nanohybrids are assembled, where the distance and hence the electronic coupling between an individual CNT and a single QD are dynamically modulated via the addition and removal of potassium (K+) cations; the system is further found to be sensitive to K+ concentrations from 1 pM to 25 × 10−3m. The level of control demonstrated here in modulating the electronic coupling of reconfigurable single‐molecule heterostructures, comprising an individual functional nanomoiety and a carbon nanoelectrode, is of importance for the development of tunable molecular optoelectronic systems and devices

Ultrafast supercontinuum spectroscopy of carrier multiplication and biexcitonic effects in excited states of PbS quantum dots

We examine the multiple exciton population dynamics in PbS quantum dots by ultrafast spectrally-resolved supercontinuum transient absorption (SC-TA). We simultaneously probe the first three excitonic transitions over a broad spectral range. Transient spectra show the presence of first order bleach of absorption for the 1S_h-1S_e transition and second order bleach along with photoinduced absorption band for 1P_h-1P_e transition. We also report evidence of the one-photon forbidden 1S_{h,e}-1P_{h,e} transition. We examine signatures of carrier multiplication (multiexcitons for the single absorbed photon) from analysis of the first and second order bleaches, in the limit of low absorbed photon numbers (~ 10^-2), at pump energies from two to four times the semiconductor band gap. The multiexciton generation efficiency is discussed both in terms of a broadband global fit and the ratio between early- to long-time transient absorption signals.. Analysis of population dynamics shows that the bleach peak due to the biexciton population is red-shifted respect the single exciton one, indicating a positive binding energy.Comment: 16 pages, 5 figure

The relationship between childhood parental loss and metabolic syndrome in obese subjects

The increasing global trend of obesity is a fundamental contributor to the growing prevalence of metabolic syndrome, a cluster of medical abnormalities including impaired glucose and lipid metabolism, obesity and hypertension. Results from animal and human investigations have shown that early life stress can result in weight gain and metabolic changes. Our aim is to investigate whether a particular type of an early adverse event, i.e. parental loss during childhood, is associated with the development of metabolic syndrome in severely obese subjects. One hundred thirty-five consecutive obese patients who were seeking bariatric surgery were assessed for metabolic syndrome according to the Adult Treatment Panel (ATP) III criteria. Information regarding the experience of parental separation or bereavement before the age of 17 was collected with the use of a semi-structured interview. In our population, 31.1% of the subjects met the criteria for metabolic syndrome. No significant differences in demographic factors, health habits or psychiatric diagnosis were found between patients with and without coexisting metabolic syndrome. After adjusting for age and gender, multivariate logistic regression analysis revealed that both childhood loss of a parent and a body mass index (BMI) value greater than 50 were significant predictors of metabolic syndrome. This study provides preliminary evidence linking childhood parental loss to risk factors for the development of metabolic syndrome

Thickness identification of 2D materials by machine learning assisted optical microscopy

We report a rapid and cost-effective method for the identification of the thickness of twodimensional materials such as transition metal dichalcogenides. Our technique is based on the analysis of the optical contrast by means of machine learning algorithms and it is well suited for accurate characterization of 2D materials over large areas

Childhood parental loss and bipolar spectrum in obese bariatric surgery candidates

Background: Early adverse experiences such as sexual, verbal, or physical abuse and parental neglect have been associated with a higher risk of weight or eating problems in adulthood, and death or prolonged separation from parents during childhood has been implicated as a correlate of adult psychiatric disorders that are widely represented in obese subjects seeking bariatric surgery. Objective: The aim of this study was to examine the rate of childhood parental loss in obese bariatric surgery candidates and explore its association with a psychiatric diagnosis and clinical and weight/eating-related characteristics. Methods: The current and lifetime psychiatric diagnoses of 120 consecutive bariatric patients undergoing pre-surgical psychiatric consultation were assessed using a modified version of the Structured Clinical Interview for DSM-IV (SCID-CV), and information relating to parental death or separation before the age of 17 years was collected using a semi-structured interview. The rate of childhood parental loss was compared with that of an always slender population sharing the same psychiatric diagnosis. Results: 91.7% of the obese subjects were diagnosed as having a bipolar spectrum disorder. Overall, 28% of the patients reported a childhood parental death or separation. Early parental loss was not equally distributed in the different diagnostic subgroups, being more frequent in those with bipolar II disorders; the always slender subjects with bipolar II disorders showed a lower rate of early parental loss. Conclusions: The study findings confirm the association between obesity and bipolar disorders and suggest that early parental loss may play a role in the development of obesity in bipolar II subjects

Bacillus amyloliquefaciens ANT1 activity against Pennicillum spp. as bread spoliage mould

Moulds are main responsible for bread spoilage even because of its low water activity (wa). In the course of six months, we analized different kind of breads, with the aim to evaluate their content in moulds. Penicillum decumbens, Penicillum crysogenum and Pennicillum spp. were isolated from all breads sample. A modified susceptibility test was carried out to ascertain mould isolates sensitivity to Bacillus amyloliquefaciens ANT1 antimicrobials. ANT1 antimicrobial activity against potentially pathogenic bacteria and moulds was proved and the results reported elsewhere [3][4] Bread samples were artificially contaminated with the moulds isolates and ANT1. The moulds content in samples was measured after 24 h. Aspergillus niger ATCC9642 was used as positive control microorganism in test susceptibility because of its sensitivity to ANT1 antimicrobials [1][2]. ANT1 production of NRPS, PKS was also ascertained [5]. The results of our survey proved the antimicrobial activity of ANT1 against moulds responsible for bread spoilage. A possible utilization of ANT1 as bread preservative is hypothesized