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With the enhancement in biomimetic and bioinspired synthesis approaches, plant-derived nanostructures provide the most suitable synthesis alternatives in terms of being non-toxic, economical and eco-friendly. The present work focused on Cannabis sativa-derived carbon dots co-doped with nitrogen and sulphur (N–S@CsCD) as a nanosensor. N–S@CsCD exhibited size distribution in the range of 4–6 nm and showed an excitation-independent emission behaviour with an emission wavelength around 414 nm. The XPS spectra confirmed the presence of heteroatom doping by nitrogen and sulphur with the concentrations of 10.71% and 1.94%, respectively. N–S@CsCD showed excellent stability to pH, time and salt concentration. Interestingly, N–S@CsCD exhibited a reversible temperature-responsive fluorescence "turn-off" behaviour. Furthermore, N–S@CsCD showed a selective fluorescence "turn-off" behaviour in the presence of vitamin B12 (VB12), with a limit of detection of 7.87 μg mL−1. The fluorescence lifetimes of N–S@CsCD with and without VB12 were similar, which implied that the sensing behaviour was purely static in nature. Moreover, N–S@CsCD showed biocompatible and non-toxic behaviours with very high cell viability. The fluorescence nature of N–S@CsCD was further evaluated for intracellular imaging. [ABSTRACT FROM AUTHOR]

The photophysical properties of eight structurally diverse near-infrared cyanine dyes were investigated with respect to their structural features and potential use as light-harvesting sensitizers of dye sensitized solar cells. The absorption, emission, and lifetime characteristics of the dyes were assessed under a variety of conditions. The photophysical properties and sensitizing efficiency of three of the eight dyes, with an additional six-membered cyclic ring, were markedly different from the other five. The dyes absorbed light of wavelength within the range of 779–823 nm and emitted within the range of 832–876 nm.The dyes had fluorescence quantum yield in the range of 14–22%. The surface morphology and elemental analysis of the cyanine dye sensitized photoanodes were characterized via Field-Emission Scanning Microscopy Imaging (FESEM) and Transmission Electron Microscopy (TEM). The performance of the fabricated cyanine dye sensitized solar cells was assessed via current-voltage and electrochemical impedance spectroscopic measurements. The solar-to-electric power conversion efficiency ranged from 0.04% to 0.24%. [ABSTRACT FROM AUTHOR]

We present a simple method for size determination of nanoparticles using conventional optical microscopes. The method, called through-focus scanning optical microscopy, makes use of the four-dimensional optical information collected at different focus positions. Low partial coherence illumination combined with analysis of through-focus optical content enables nanoparticle size determination with nanometer scale sensitivity. We experimentally demonstrate this using fabricated Si nanodots and spherical gold nanoparticles. The method is economical, as no hardware modifications to conventional optical microscopes are needed. In addition, the method also has high throughput and potential for soft nanoparticle size determination without distortion. [ABSTRACT FROM AUTHOR]

We present a quantitative scheme for full-field polarization rotating fluorescence microscopy. A quarter-wave plate, in combination with a liquid crystal variable retarder, provides a tunable method to rotate polarization states of light prior to its being coupled into a fluorescence microscope. A calibration of the polarization properties of the incident light is performed in order to correct for elliptical polarization states. This calibration allows the response of the sample to linear polarization states of light to be recovered. Three known polarization states of light can be used to determine the average fluorescent dipole orientations in the presence of a spatially varying dc offset or background polarization-invariant fluorescence signal. To demonstrate the capabilities of this device, we measured a series of full-field fluorescence polarization images from fluorescent analogs incorporated in the lipid membrane of Burkitts lymphoma CA46 cells. The fluorescent lipid-like analogs used in this study are molecules that are labeled by either a DiI (1,1′-Dioctadecyl 3,3,3′,3′-Tetramethylindocarbocyanine) fluorophore in its head group or a Bodipy (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) molecule in its acyl chain. A spatially varying contrast in the normalized amplitude was observed on the cell surface, where the orientation of the DiI molecules is tangential to the cell membrane. The internally labeled cellular structures showed zero response to changes in linear polarization, and the net linear polarization amplitude for these regions was zero. This instrument provides a low cost calibrated method that may be coupled to existing fluorescence microscopes to perform investigations of cellular processes that involve a change in molecular orientations. [ABSTRACT FROM AUTHOR]

Blinking of zinc blende CdSe-based core/shell nanocrystals is studied as a function of shell materials and surface ligands. CdSe/ZnS, CdSe/ZnSe/ZnS and CdSe/CdS/ZnS core/shell nanocrystals are prepared by colloidal synthesis and six monolayers of larger bandgap shell materials are grown over the CdSe core. Organic-soluble nanocrystals covered with stearate are made water-soluble by ligand exchange with 3-mercaptopropionic acid. The light-emitting states of nanocrystals are characterized by absorption and emission spectroscopy as well as photoluminescence lifetime measurements in solution. The blinking time trace is recorded for single nanocrystals on a glass coverslip. Both on- and off-time distributions are fitted to the power law. The power-law exponents vary, depending on shell materials and surface ligands. The off-time exponents for organic and water-soluble nanocrystals are measured in the range of 1.36–1.55 and 1.25–1.37, respectively, while their on-time exponents are spread in the range of 1.53–1.86 and 1.85–2.17, respectively. Water-soluble surface passivation with thiolate prolongs the dark period regardless of shell materials and core/shell structures. Of the core/shell structures, CdSe/CdS/ZnS exhibits the longest bright state. The on/off-time exponents are inversely correlated, although the successive on/off events are not individually correlated. A two competing charge-tunneling model is presented to describe the variation of on- and off-time exponents with shell materials and surface ligands. [ABSTRACT FROM AUTHOR]

Abstract: The influence of surface modifications, including carboxyl-, amine-, and mercaptoundecanoicacid-functionalized chemistries, on the dynamic fluorescence properties of single quantum dots (QDs) are probed using a combined confocal fluorescence microscopy and spectroscopy system. Water-soluble QDs with carboxyl- or amine-functionalized surfaces prepared through a linker arm show significant fluorescence intermittency and appear statistically identical. In contrast, water-soluble QDs functionalized via mercaptoundecanoicacid, an electron-donating thiol group, demonstrate suppressed fluorescence intermittency suggesting the photostability of water-soluble QDs is strongly dependant upon the method of surface functionalization. In addition, the long-term photostability of the mercaptoundecanoicacid-functionalized QD demonstrates an excitation-time-dependent blue-shift in the fluorescence emission spectra. Our measurement and analysis techniques promise a wealth of insight in elucidating the photophysics of bio-conjugated QDs and assessing and designing bio-conjugated QDs for biomedical applications requiring long-term photostabililty. [Copyright &y& Elsevier]

The dyes extracted from pomegranate and berry fruits were successfully used in the fabrication of natural dye sensitized solar cells (NDSSC). The morphology, porosity, surface roughness, thickness, absorption and emission characteristics of the pomegranate dye sensitized photo-anode were studied using various analytical techniques including FESEM, EDS, TEM, AFM, FTIR, Raman, Fluorescence and Absorption Spectroscopy. Pomegranate dye extract has been shown to contain anthocyanin which is an excellent light harvesting pigment needed for the generation of charge carriers for the production of electricity. The solar cell's photovoltic performance in terms of efficiency, voltage, and current was tested with a standard illumination of air-mass 1.5 global (AM 1.5 G) having an irradiance of 100 mW/cm2. After optimization of the photo-anode and counter electrode, a photoelectric conversion efficiency (η) of 2%, an open-circuit voltage (Voc) of 0.39 mV, and a short-circuit current density (Isc) of 12.2 mA/cm2 were obtained. Impedance determination showed a relatively low charge-transfer resistance (17.44 Ω) and a long lifetime, signifying a reduction in recombination losses. The relatively enhanced efficiency is attributable in part to the use of a highly concentrated pomegranate dye, graphite counter electrode and TiCl4 treatment of the photo-anode. [ABSTRACT FROM AUTHOR]

Graphical abstract The photovoltaic performance of two ruthenium based dyes was measured and compared to assess the effect of anchoring groups on the current-voltage characteristics of dye sensitized solar cells. One of the two dyes, Di-tetrabutylammonium cis -bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II), (N719) had anchoring groups while the other, Tris(bipyridine)ruthenium(II) chloride (Ru-BPY) lacked anchoring groups. N719 showed a higher efficiency compared to Ru-BPY. The results were validated by density functional calculation. Abstract Two ruthenium-based dyes were used as sensitizers for dye sensitized solar cells: one with anchoring groups – Di-tetrabutylammonium cis -bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)Ruthenium(II), (N719) – and the other without any anchoring group, Tris(bipyridine)Ruthenium(II) chloride (Ru-BPY) were studied to assess the effect of anchoring groups on the performance of dye sensitized solar cells. N719 dye has carboxyl groups that bind to the surface of mesoporous TiO 2 whereas Ru-BPY contains no such anchoring groups capable of binding to the surface of TiO 2 nanoparticles. The dyes were characterized using absorption spectroscopy, emission measurements and lifetime measurements. The wavelength of maximum absorption for the N719 was 525 nm but this was blue shifted to 516 nm upon attachment to the titanium dioxide substrate. The wavelength of maximum absorption for the Ru-BPY was 450 nm before and after application of the dye to titanium dioxide indicating that the interaction of the anchoring groups with the TiO 2 nanoparticles had an effect on the absorption band of the N719. The N719 dye sensitized solar cell yielded a solar-to-electrical energy conversion efficiency of 1.35%, which was much higher than that of Ru-BPY (0.09%), thus indicating that anchoring groups on dye sensitizers greatly increase the efficiency of dye sensitized solar cell. [ABSTRACT FROM AUTHOR]

With the enhancement in biomimetic and bioinspired synthesis approaches, plant-derived nanostructures provide the most suitable synthesis alternatives in terms of being non-toxic, economical and eco-friendly. The present work focused on Cannabis sativa-derived carbon dots co-doped with nitrogen and sulphur (N–S@CsCD) as a nanosensor. N–S@CsCD exhibited size distribution in the range of 4–6 nm and showed an excitation-independent emission behaviour with an emission wavelength around 414 nm. The XPS spectra confirmed the presence of heteroatom doping by nitrogen and sulphur with the concentrations of 10.71% and 1.94%, respectively. N–S@CsCD showed excellent stability to pH, time and salt concentration. Interestingly, N–S@CsCD exhibited a reversible temperature-responsive fluorescence "turn-off" behaviour. Furthermore, N–S@CsCD showed a selective fluorescence "turn-off" behaviour in the presence of vitamin B12 (VB12), with a limit of detection of 7.87 μg mL−1. The fluorescence lifetimes of N–S@CsCD with and without VB12 were similar, which implied that the sensing behaviour was purely static in nature. Moreover, N–S@CsCD showed biocompatible and non-toxic behaviours with very high cell viability. The fluorescence nature of N–S@CsCD was further evaluated for intracellular imaging. [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron nanoparticles (nZVIs) are known to boost biomass production and lipid yield in Fremyella diplosiphon , a model biodiesel-producing cyanobacterium. However, the impact of nZVI-induced reactive oxygen species (ROS) in F. diplosiphon has not been evaluated. In the present study, ROS in F. diplosiphon strains (B481-WT and B481-SD) generated in response to nZVI-induced oxidative stress were quantified and the enzymatic response determined. Lipid peroxidation as a measure of oxidative stress revealed significantly higher malondialdehyde content ( p < 0.01) in both strains treated with 3.2, 12.8, and 51.2 mg L -1 nZVIs compared to untreated control. In addition, ROS in all nZVI-treated cultures treated with 1.6-25.6 mg L -1 nZVIs was significantly higher than the untreated control as determined by the 2',7'-dichlorodihydrofluorescein diacetate fluorometric probe. Immunodetection using densitometric analysis of iron superoxide dismutase (SOD) revealed significantly higher SOD levels in both strains treated with nZVIs at 51.2 mg L -1 . In addition, we observed significantly higher ( p < 0.001) SOD levels in the B481-SD strain treated with 6.4 mg L -1 nZVIs compared to 3.2 mg L -1 nZVIs. Validation using transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDS) revealed adsorption of nZVIs with a strong iron peak in both B481-WT and B481-SD strains. While the EDS spectra showed strong signals for iron at 4 and 12 days after treatment, a significant decrease in peak intensity was observed at 20 days. Future efforts will be aimed at studying transduction mechanisms that cause metabolic and epigenetic alterations in response to nZVIs in F. diplosiphon ., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The multiwalled carbon nanotubes has a myriad of applications due to its unique electrical and mechanical properties. The biomedical application of multiwalled carbon nanotubes that have been reported include drug delivery, medical imaging, gene delivery, tissue regeneration, and diagnostics. Proper characterization is required to enhance the potential application of the multiwalled carbon nanotubes. Terahertz technology is a relatively unfamiliar spectrometric technique that show promise in efficiently characterizing multiwalled carbon nanotubes. In this paper, terahertz imaging was used to characterize multiwalled carbon nanotube in comparison with other characterization techniques, including transmission electron microscopy and field emission scanning electron microscopy. The average diameter of the carbon nanotubes from the reconstructed terahertz images was 48.54 nm, while the average length of a fiber was found to be approximately 1.2 μm. The multiwalled carbon nanotubes were additionally characterized by FTIR, Raman spectroscopy, and Energy-dispersive X-ray spectroscopy.

A simple colorimetric method has been developed for the detection of lead (Pb 2+ ) in water samples using lipoic acid-functionalized gold nanoparticles. The lipoic acid-functionalized gold nanoparticles are induced to aggregate in the presence of the Pb 2+ which results in a change in the color of the functionalized gold nanoparticles. The change in color and the amount of Pb 2+ producing the change could be monitored via UV-visible spectrophotometry. A good correlation coefficient of 0.9927 was obtained for the calibration curve of the colorimetric method. The method was applied in the determination of Pb 2+ in water samples and the results compared to that of measurement carried out with Atomic Absorption Spectroscopy.

Low-cost, high-throughput and nondestructive metrology of truly three-dimensional (3-D) targets for process control/monitoring is a critically needed enabling technology for high-volume manufacturing (HVM) of nano/micro technologies in multi-disciplinary areas. In particular, a survey of the typically used metrology tools indicates the lack of a tool that truly satisfies the HVM metrology needs of 3-D targets, such as high aspect ratio (HAR) targets. Using HAR targets here we demonstrate that through-focus scanning optical microscopy (TSOM) is a strong contender to fill the gap for 3-D shape metrology. Differential TSOM (D-TSOM) images are extremely sensitive to small and/or dissimilar types of 3-D shape variations. Based on this here we propose a TSOM method that involves creating a database of cross-sectional profiles of the HAR targets along with their respective D-TSOM signals. Using the database, we present a simple-to-use, low-cost, high-throughput and nondestructive process-monitoring method suitable for HVM of truly 3-D targets, which also does not require optical simulations, making its use straightforward and automatable. Even though HAR targets are used for this demonstration, the similar process can be applied to any truly 3-D targets with dimensions ranging from micro-scale to nano-scale. The TSOM method couples the advantage of analyzing truly isolated targets with the ability to simultaneously analyze many targets present in the large field-of-view of a conventional optical microscope.

Dye sensitized solar cells were fabricated with DyLight680 (DL680) dye and its corresponding europium conjugated dendrimer, DL680-Eu-G5PAMAM, to study the effect of europium on the current and voltage characteristics of the DL680 dye sensitized solar cell. The dye samples were characterized by using Absorption Spectroscopy, Emission Spectroscopy, Fluorescence lifetime and Fourier Transform Infrared measurements. Transmission electron microscopy imaging was carried out on the DL680-Eu-G5PAMAM dye and DL680-Eu-G5PAMAM dye sensitized titanium dioxide nanoparticles to analyze the size of the dye molecules and examine the interaction of the dye with titanium dioxide nanoparticles. The DL680-Eu-G5PAMAM dye sensitized solar cells demonstrated an enhanced solar-to-electric energy conversion of 0.32% under full light illumination (100 mWcm -2 , AM 1.5 Global) in comparison with that of DL680 dye sensitized cells which recorded an average solar-to-electric energy conversion of only 0.19%. The improvement of the efficiency could be due to the presence of the europium that enhances the propensity of dye to absorb sunlight.

It is important to economically and non-destructively analyze three-dimensional (3-D) shapes of nanometer to micrometer scale objects with sub-nanometer measurement resolution for emerging high-volume nanomanufacturing, especially for process control. High-throughput through-focus scanning optical microscopy (TSOM) demonstrates promise for such applications. TSOM uses a conventional optical microscope for 3-D shape metrology by making use of the complete set of through-focus, four-dimensional optical data. However, a systematic study showing the effect of various parameters on the TSOM method is lacking. Here we present the optimization of the basic parameters such as illumination numerical aperture (NA), collection NA, focus step height, digital camera pixel size, illumination polarization, and illumination wavelength to achieve peak performance of the TSOM method.

Understanding the optical properties of clustered quantum dots (QDs) is essential to the design of QD-based optical phantoms for molecular imaging. Single and clustered core/shell colloidal QDs of dimers, trimers, and tetramers are self-assembled, separated, and preferentially collected using electrospray differential mobility analysis (ES-DMA) with electrostatic deposition. Multimodal optical characterization and analysis of their dynamical photoluminescence (PL) properties enables the long-term evaluation of the physicochemical and optical properties of QDs in a single or a clustered state. A multimodal time-correlated spectroscopic confocal microscope capable of simultaneously measuring the time evolution of PL intensity fluctuation, PL lifetime, and emission spectra reveals the long-term dynamic optical properties of interacting QDs in individual dimeric clusters of QDs. This new method will benefit research into the quantitative interpretation of fluorescence intensity and lifetime results in QD-based molecular imaging techniques. The process of photooxidation leads to coupling of the QDs in a dimer, leading to unique optical properties when compared to an isolated QD. These results guide the design and evaluation of QD-based phantom materials for the validation of the PL measurements for quantitative molecular imaging of biological samples labeled with QD probes.

A multimodality imaging technique integrating atomic force, polarized Raman, and fluorescence lifetime microscopies, together with 2D autocorrelation image analysis is applied to the study of a mesoscopic heterostructure of nanoscale materials. This approach enables simultaneous measurement of fluorescence emission and Raman shifts from a quantum dot (QD)-single-wall carbon nanotube (SWCNT) complex. Nanoscale physical and optoelectronic characteristics are observed including local QD concentrations, orientation-dependent polarization anisotropy of the SWCNT Raman intensities, and charge transfer from photoexcited QDs to covalently conjugated SWCNTs. Our measurement approach bridges the properties observed in bulk and single nanotube studies. This methodology provides fundamental understanding of the charge and energy transfer between nanoscale materials in an assembly.