Nonlinear optical measurements of BF2–aza dipyrromethene fluorophores

Nonlinear absorption coefficient and the nonlinear refractive index of a series of BF2 aza dipyrromethene chromophores in tetrahydrofuran (THF) solutions were measured using the Z-scan technique with a low power continuous wave laser at 633 nm. Acquired data illustrated that the process involved in nonlinear absorption is reverse saturation absorption. The excited state absorption cross sections for all complexes were calculated and a pump and probe technique was used to record the triplet absorption spectrum. The band gap of the triplet state was estimated from this spectral data and the optical limiting behavior was demonstrated for each derivative. Keyword: BF2-azadipyrromethene fluorophore propertie

Comparative nonlinear optics and optical limiting properties of metallophthalocyanines

Biyiklioglu, Zekeriya/0000-0001-5138-214XWOS: 000454151300043In this study, peripherally tetra-{2-[[4-((E)-{[4-dimethylamino)phenyl]imino}methyl)phenyl](methyl)amino]ethoxy} substituted cobalt(II), manganese(III), copper(II) phthalocyanines 2a-2c and axially di-{2-[[4-((E)-{[4-(dimethylamino)phenyl]imino}methyl)phenyl](methyl)amino]ethoxy} substituted silicon phthalocyanine 3 were synthesized for the first time. These compounds were characterized by standard spectroscopy methods. Their nonlinear optical properties are evaluated with the help of z-scan technique. Both open and closed aperture configurations show clear z-scan signal in the four samples. The refractive nonlinear index n(2) is found to be ranging between -4.9 and -28.1 x 10(-8) cm(2)/W, and the nonlinear absorptive coefficient varied between 0.2 and 5.4 x 10(-3) cm/W. The optical limiting measurements showed low threshold levels, 645 W/cm(2) in 2c and 680 W/cm(2) in 2a in full agreement with Z-scan measurements.Research Fund of Karadeniz Technical University, Trabzon, TurkeyKaradeniz Teknik UniversityThis study was supported by The Research Fund of Karadeniz Technical University, Trabzon, Turkey

Visible and near-infrared absorption properties of blood from sickle cell patients and normal individuals.

Sickle cell disease (SCD) is a genetic blood disorder characterised by red blood cells that assume an abnormal and rigid shape. A point mutation in the beta globin chain of haemoglobin results in glutamic acid to be replaced with valine at the sixth position. The abnormal haemoglobin (HbS) leads to the distortion of red blood cells in certain conditions, such as low oxygen tension, and leads to sickling. Sickling decreases the flexibility of red blood cells and causes microvascular occlusion, which may manifest as stroke, acute chest syndrome, pulmonary hypertension or organ damage. SCD occurs primarily among people of sub-Saharan African, Mediterranean, Middle Eastern and Indian descent. Of note, sickle cell anaemia refers to people who are homozygous for the mutation causing HbS, while sickle cell trait refers to heterozygotes who have one normal haemoglobin gene and one sickle cell gene. Approximately 250,000 children worldwide are born each year with sickle cell anaemia. According to the Gulf Genetic Center (GGC), abnormal haemoglobin was detected in 44.35% of neonatal samples in Bahrain. Of those, 18.1% had sickle cell trait and 2.1% had SCD. Additionally, the GGC reported that in the non-neonatal cases, the overall frequency of SCD was found to be 10.44%. Several techniques are used to screen for sickle cell trait or SCD, such as high-performance liquid chromatography (HPLC), haemoglobin electrophoresis and DNA sequencing. HPLC uses ultraviolet rays to detect the difference in shape and surface area between the normal blood cells and the sickle cells. Haemoglobin electrophoresis differentiates between the haemoglobin forms based on charge, while DNA sequencing of the haemoglobin gene can detect the presence of the single amino acid substitution implicated in SCD. First reported in 1942, five different formsof haemoglobin (oxyhaemoglobin, carbomyl haemoglobin, methaemoglobin, reduced haemoglobin and metcyanhaemoglobin) were detected based on marked differences in the absorption spectra in the visible (380nm-760nm) and near-infrared (760nm-2,500nm) region of the electromagnetic spectrum. No such investigation comparing the absorption spectra of normal adult haemoglobin (HbA) and sickle cell haemoglobin (HbS) has been conducted in the visible and near-infrared region. Such is the aim of this brief study.</p

An Exploration of Nanoparticle-Based Diagnostic Approaches for Coronaviruses: SARS-CoV-2, SARS-CoV and MERS-CoV

The wildfire-like spread of COVID-19, caused by severe acute respiratory syndrome-associated coronavirus-2, has resulted in a pandemic that has put unprecedented stress on the world&rsquo;s healthcare systems and caused varying severities of socio-economic damage. As there are no specific treatments to combat the virus, current approaches to overcome the crisis have mainly revolved around vaccination efforts, preventing human-to-human transmission through enforcement of lockdowns and repurposing of drugs. To efficiently facilitate the measures implemented by governments, rapid and accurate diagnosis of the disease is vital. Reverse-transcription polymerase chain reaction and computed tomography have been the standard procedures to diagnose and evaluate COVID-19. However, disadvantages, including the necessity of specialized equipment and trained personnel, the high financial cost of operation and the emergence of false negatives, have hindered their application in high-demand and resource-limited sites. Nanoparticle-based methods of diagnosis have been previously reported to provide precise results within short periods of time. Such methods have been studied in previous outbreaks of coronaviruses, including severe acute respiratory syndrome-associated coronavirus and middle east respiratory syndrome coronavirus. Given the need for rapid diagnostic techniques, this review discusses nanoparticle use in detecting the aforementioned coronaviruses and the recent severe acute respiratory syndrome-associated coronavirus-2 to highlight approaches that could potentially be used during the COVID-19 pandemic

An exploration of nanoparticle-based diagnostic approaches for coronaviruses: SARS-CoV-2, SARS-CoV and MERS-CoV

The wildfire-like spread of COVID-19, caused by severe acute respiratory syndrome-associated coronavirus-2, has resulted in a pandemic that has put unprecedented stress on the world's healthcare systems and caused varying severities of socio-economic damage. As there are no specific treatments to combat the virus, current approaches to overcome the crisis have mainly revolved around vaccination efforts, preventing human-to-human transmission through enforcement of lockdowns and repurposing of drugs. To efficiently facilitate the measures implemented by governments, rapid and accurate diagnosis of the disease is vital. Reverse-transcription polymerase chain reaction and computed tomography have been the standard procedures to diagnose and evaluate COVID-19. However, disadvantages, including the necessity of specialized equipment and trained personnel, the high financial cost of operation and the emergence of false negatives, have hindered their application in high-demand and resource-limited sites. Nanoparticle-based methods of diagnosis have been previously reported to provide precise results within short periods of time. Such methods have been studied in previous outbreaks of coronaviruses, including severe acute respiratory syndrome-associated coronavirus and middle east respiratory syndrome coronavirus. Given the need for rapid diagnostic techniques, this review discusses nanoparticle use in detecting the aforementioned coronaviruses and the recent severe acute respiratory syndrome-associated coronavirus-2 to highlight approaches that could potentially be used during the COVID-19 pandemic. </p