Biocompatible Carbon Dot Decorated α-FeOOH Nanohybrid for an Effective Fluorometric Sensing of Cr (VI) in Wastewater and Living Cells.

This article reports the fluorometric detection of toxic hexavalent chromium Cr (VI)) in wastewater and Cr (VI) contaminated living cells using in-situ grown carbon quantum dots into the goethite (α-FeOOH) nano-matrix. The synthesized nano-hybrid shows enormous potential in determining the chromium contamination levels in various types of water samples. This selective fluorometric probe is enormously sensitive (LOD 81 nM) toward hexavalent chromium, which makes it a dedicated chromium sensor. Moreover, the sensing mechanism has been assessed using Stern-Volmer's equation and fluorescence lifetime experiments showing the simultaneous occurrence of photoinduced electron transfer and the inner filter effect. This chromium sensor has also been employed to assess the contamination level in real-life industrial wastewater. The performance of this probe in a real-life wastewater sample is quite commendable. Further, this biocompatible fluorometric probe has been used to demonstrate the in-vitro sensing of Cr (VI) in HeLa cells. The rapid detection mechanism of hexavalent chromium in living cells has been validated using theoretical docking simulations. Henceforth, this fluorometric sensor material could open new avenues not only in wastewater monitoring but also in biomedical applications.

Synthesis and Property of Copper-Impregnated α-MnO2 Semiconductor Quantum Dots.

Because of the superior optical and electrical properties, copper-impregnated size tuneable high-temperature stable manganese dioxide semiconductor quantum dots (SQDs) have been successfully synthesized by a modified chemical synthesis technique. Their size-dependent dielectric properties, semiconducting properties, and current-voltage ( I- V) characteristics have been investigated. X-ray diffraction pattern and Raman spectra confirmed that the required phase is present. Because of the different sintering temperature tuneable size of SQDs has been found and confirmed by high-resolution transmission electron microscopy. The band gap energy of the material is found to be 1.25-1.67 eV, measured from Tauc plot using UV-vis absorbance spectrum and their semiconducting properties have been confirmed by the non linear current-voltage ( I- V) behavior. Most intense green emission peak of photoluminescence (PL) spectroscopy confirms the oxygen vacancy defect state. The stoke shifting of Raman spectra, UV absorption, and PL emission are the footprint of quantum confinement effect. Incorporation of a little amount of Cu in tetragonal hollandite structure of α-MnO2 generates strain within that structure. This leads to create sufficient crystal defect state as well as rise in dielectric constant accompanied with low dielectric loss and higher ac conductivity. All these highly desirable properties make the SQDs a potential candidate for developing multifunctional photo-electronic devices. Owing to the tuneable band gap and electronic transport of the SQDs, we realized that the controllable size paves the way for designing SQDs possessing unique properties for optical and electronic device applications. Using this material as a high dielectric separator, a high-performance supercapacitor has been successfully fabricated which can light up 15 light-emitting diodes for 47 min 23 s after charging them only for 30 s.

High-Performance Broadband Self-Driven Photodetector Based on MoS2/Cs2CuBr4 Heterojunction.

Few-layer transition metal dichalcogenides and perovskites are both promising materials in high-performance optoelectronic devices. Here, we developed a self-driven photodetector by creating a heterojunction between few-layer MoS2 and lead-free perovskite Cs2CuBr4. The detector shows a unique property of very high sensitivity in a broad spectral range of 400 to 800 nm with response speed in a millisecond order. Current-voltage characteristics of the heterojunction device show rectifying behavior, in contrast to the ohmic behavior of the MoS2-based device. The rectifying behavior is attributed to the type II band alignment of the MoS2/Cs2CuBr4 heterojunction. The device shows a broadband (400 to 800 nm) photodetection with very high responsivity reaching up to 2.8 × 104 A/W and detectivity of 1.6 × 1011 Jones at a bias voltage of 3 V. The detector can also operate in self-bias mode with sufficient response. The photocurrent, photoresponsivity, detectivity, and external quantum efficiency of the device are found to be dependent on the illumination power density. The response time of the device is found to be ∼32 and ∼79 ms during the rise and fall of the photocurrent. The work proposes a MoS2/Cs2CuBr4 heterostructure to be a promising candidate for cost-effective, high-performance photodetector.

Monolayer Graphene-MoSSe van der Waals Heterostructure for Highly Responsive Gate-Tunable Near-Infrared-Sensitive Broadband Fast Photodetector.

Transition metal dichalcogenides (TMDCs) are potential two-dimentional materials as natural partners of graphene for highly responsive van der Waals (vdW) heterostructure photodetectors. However, the spectral detection range of the detectors is limited by the optical bandgap of the TMDC, which acts as a light-absorbing medium. Bandgap engineering by making alloy TMDC has evolved as a suitable approach for the development of wide-band photodetectors. Here, broadband (visible to near-infrared) photodetection with high sensitivity in the near-infrared region is demonstrated in a MoSSe/graphene heterostructure. In the ambient environment, the photodetector exhibits high responsivity of 0.6 × 102 A/W and detectivity of 7.9 × 1011 Jones at 800 nm excitation with a power density of 17 fW/µm2 and 10 mV source-drain bias. The photodetector shows appreciable responsivity in self-bias mode due to nonuniform distribution of MoSSe flakes on the graphene layer between the source and drain end and the asymmetry between the two electrodes. Time-dependent photocurrent measurements show fast rise/decay times of ∼38 ms/∼48 ms. A significant gate tunability on the efficiency of the detector has been demonstrated. The device is capable of low power detection and exhibits high operational frequency, gain, and bandwidth. Thus, the MoSSe/graphene heterostructure can be a promising candidate as a high-speed and highly sensitive near-infrared photodetector capable of operating at ambient conditions with low energy consumption.

Förster resonance energy transfer in a nanoscopic system on a dielectric interface.

We investigate picosecond-resolved energy transfer between a quantum dot (donor) and an organic molecule (acceptor) in the proximity of a reflecting metallic/non-metallic surface. We demonstrate experimentally that the Förster resonance energy transfer (FRET) is significantly influenced by the proximity of the mirror. Locating a cadmium selenide quantum dot (donor: D) attached to an organic dye merocyanine (acceptor: A) at well-defined positions from the reflecting silver/silicon surface allows the transfer rate to be determined as a function of distance from the surface. An attempt to fit the experimental data to a model relying upon the change of the apparent energy transfer rate due to interference of direct and reflected light waves reveals reasonably good results. The results show that the observed FRET rate in a D-A pair on the mirror surface is oscillating in nature, providing information for the measured energy transfer, which could be potentially different from that of the actual transfer due to optical interference.

NIR femtosecond laser induced hyper-Rayleigh scattering and luminescence from silver nanoprisms.

The nonlinear response of silver nanoprisms (edge length 40 +/- 5 nm and thickness 4.5 +/- 0.5 nm) was studied by exciting with NIR femtosecond pulses (780-880 nm). These nanostructures were observed to generate hyper-Rayleigh scattering (HRS) and broadband luminescence. While HRS showed the expected second order power dependence, the luminescence was observed to follow a third order excitation power dependence. Both HRS and luminescence were observed to be dipolar in nature. The first hyperpolarizability of the nanoprisms was found to be an order of magnitude higher than approximately 15 nm sized nanospheres.

Essential oil impregnated luminescent hydroxyapatite: Antibacterial and cytotoxicity studies.

In this study, porous fluorescent nanocrystalline erbium doped hydroxyapatite (eHAp) was synthesized via hydrothermal assisted co-precipitation method. Eucalyptus oil (EU), frankincense oil (FO), Tea tree oil (TTO), wintergreen oil (WO) were successfully absorbed into eHAp pellet by vacuum filtration technique using Buckner funnel. Phase crystallization, fluorescence property and microstructure of eHAp were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Photoluminiscence spectroscopy (PL) and Field emission scanning electron microscopy (FESEM). Strong antimicrobial activity was observed for EU, TTO and WO on both E. coli and S. aureus mediated by cell membrane damage and leakage of cytoplasmic components. The oil absorbed eHAp nanocomposites were found to be moderately biocompatible with normal WI-38 cells up to MIC concentration various time scale. The nanocomposites showed significant cytotoxic activity on breast cancer cell line MDA-MB 468 and the fluorescent property of the eHAp was utilized to visualize internalization of particles in the cells. The release profile of the oils from the eHAp matrix showed pH dependent release indicated that the porous matrix can be used as a suitable carrier for modulated and sustained release of bioactive components. Thus, given the multifunctional attributes these natural essential oil-based nanocomposites show great promise as an alternative to conventional therapeutic treatments.

Spectroscopic investigations on the binding of the photosensitizer Chlorin p6 with amine-modified silica nanoparticles in aqueous media.

Absorption and emission properties of the amphiphilic photosensitizer Chlorin p6 were investigated in aqueous medium in the presence of silica nanoparticles (SiNPs) having positively charged amino groups. The results of these studies reveal that the acid-base ionization equilibrium of Chlorin p6 in aqueous medium is significantly affected as a result of strong electrostatic binding between the negatively charged drug and SiNP. The spectroscopic signature of the drug bound to SiNPs suggests that the tri-anionic form of the drug remains bound to the positively charged SiNPs at pH 8.0. As the pH is progressively decreased the formation of hydrophobic aggregates is disrupted significantly due to the presence of electrostatic binding force, which competes with intermolecular hydrophobic forces. The interplay of hydrophobic and electrostatic forces in the drug-nanoparticle binding process might affect the relative uptake and photodynamic efficacy of the free drug and the drug-nanoparticle complex in cancer cells.

FTIR of touch imprint cytology: a novel tissue diagnostic technique.

Fourier transform infrared spectroscopic (FTIR) interrogation of biological tissues in real time has largely been a challenging proposition because of the strong absorption of mid-infrared light in water filled tissues. To enable sampling of tissues they must be sectioned and dried, which has time and resource implications. FTIR of touch imprint cytology (TIC) has been proposed to circumvent this problem. TIC is a well known histopathological method of rapidly analysing biological tissues. In this article we demonstrate the ability of FTIR of TIC to provide detailed spectra which can be used to differentiate various tissue pathologies. FTIR spectral profiles of TIC of lymph node and thyroid tissues differ visually when compared with TIC spectra of parathyroid tissue. The lymph node showed strong lipid spectral peaks at 1166cm(-1) and 1380cm(-1) including a very strong carbonyl-ester band at 1748cm(-1), and a strong methylene bending band (scissoring, at 1464cm(-1)). Smaller intensity protein peaks at 1547cm(-1) and 1659cm(-1) were also seen. The thyroid spectra, in addition to evident strong protein peaks at 1547cm(-1) and 1659cm(-1), also demonstrated possible nucleic acid signals at 1079cm(-1) and 1244cm(-1). The C-OH peak at 1037cm(-1) was attributed to carbohydrate signals. Parathyroid adenoma showed a marginal shift to lower wavenumbers with decreased amide I and II peak intensities when compared to hyperplasia. Nucleic acid peak positions at 1079cm(-1) and 1244cm(-1) were of higher intensity in adenomas compared to hyperplastic glands possibly demonstrating an increase in cell proliferation and growth. This study demonstrates the feasibility of cytoimprint FTIR for the intraoperative diagnosis of tissue during surgical neck exploration for the management of hyperparathyroidism. There is potential for the application of the technique in sentinel lymph node biopsy diagnosis and tumour margin evaluation.

Au nanoparticles functionalized 3D-MoS2 nanoflower: An efficient SERS matrix for biomolecule sensing.

Fabrication of Molybdenum disulfide (MoS2) nanostructures and surface functionalization with noble metal nano particles is an emerging field of research as it has potential applications in electronic devices and chemical sensing. Here we report application of gold nanoparticles (AuNPs) decorated MoS2 nanoflowers (Au-MoS2 NFs) as an efficient bio-sensor. MoS2 NFs, synthesized using green synthesis process, are further functionalized with AuNPs to tune their physical properties and make them more appropriate for biological applications. The abundant 'hot-spots' created by AuNPs through localization of electromagnetic field endows the Au-MoS2 hybrid structure as an excellent substrate for biochemical sensing through surface enhanced Raman scattering (SERS). The sensing efficiency of the SERS substrate is examined using Rh6G as probe molecule with concentration as low as 10-12 M. Main emphasis is given in detecting free bilirubin, an important component of human blood, using SERS technique. Au-MoS2 NF SERS substrate exhibits high sensitivity, stability and excellent reproducibility in sensing bilirubin from high level (10-3 M) to picomolar level. The concentration (C) dependent SERS intensity (I) is found to follow the general relationship I = Cα, with α ranging from 0.09 to 0.12. The substrate shows excellent selectivity and reliability while sensing of free bilirubin performed in human serum in the presence of crucial interferences such as dextrose, cholesterol and phosphate. In the present study, this Au-MoS2 hybrid offers a new potential biosensing technology for free bilirubin detection and is anticipated to be applied for clinic diagnosis.

Is a deep subfascial approach better than the subfascial apporach to temporo-mandibular joint in terms of facial nerve injury and quality of life?

PURPOSE: The objective of the study was to compare the deep subfascial approach to subfascial approach in terms of facial nerve injury and quality of life. MATERIALS AND METHODS: A randomized study was performed from August 2013 to March 2017 on 24 patients with unilateral TMJ ankylosis. The subjects were randomly allotted to either Group I (12, Deep Subfascial) or Group II (12, Subfascial). All patients were evaluated objectively for facial nerve injury post-operatively and subjectively for quality of life in the form of a questionnaire post-operatively for 6 months. The data were analyzed using simple descriptive statistics, mean standard deviation, Wilcoxon paired t test, Friedman's test, and Mann Whitney U test. RESULTS: The comparison of the difference between the groups for postoperative facial nerve function at various time intervals did not give any significant differences (p > 0.05). In terms of quality of life there was a significant difference at 1 month post-operatively (p < 0.05) amidst the two approaches, however, 6-month follow-up revealed that there is no significant difference between the two approaches (p > 0.05). CONCLUSION: The study reveals that both the approaches are safe in terms of facial nerve injury and quality of life long term.

Antimicrobial and biocompatible fluorescent hydroxyapatite-chitosan nanocomposite films for biomedical applications.

Development of fluorescent erbium doped hydroxyapatite (eHAp)-chitosan nanocomposite film is reported. Nanocrystalline eHAp has been synthesized by hydrothermal assisted precipitation method using erbium (III) ions as dopant. Physico-chemical characterization by UV/Visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminiscence spectroscopy (PL) and Field emission scanning electron microscopy(FESEM) confirmed incorporation and uniform distribution of eHAp in the chitosan films. Strong antimicrobial activity was observed using eHAp incorporated chitosan films against E. coli and S. aureus by contact inhibition on agar plates. On the other hand, excellent biocompatibility was observed with human lung fibroblast cells (WI-38) which showed strong attachment and proliferation on the chitosan films with minimal cytotoxicity. Moreover, the doped films showed good biodegradation and mineralization behavior after 2 weeks in simulated body fluid. Thus the doped fluorescent chitosan films with multifunctional attributes can be a strong candidate for diverse applications like in antimicrobial treatments, wound healing, tissue scaffolds and bioimaging.

Role of Fourier transform infrared spectroscopy (FTIR) in the diagnosis of parathyroid pathology.

BACKGROUND: With the advent of minimally invasive parathyroid surgery (MIPS) accurate pathological diagnosis to differentiate parathyroid adenomas from hyperplasia has become difficult for the pathologist. This is because now single glands are excised, guided by better preoperative localisation scans, while for an accurate pathological diagnosis, at least a two-gland biopsy is required. Ultimately, an accurate pathological diagnosis to establish the aetiology is essential for the management of hyperparathyroidism. To resolve this issue we evaluated the ability of FTIR to accurately differentiate between parathyroid adenoma and hyperplasia using their biochemical signatures. METHODS: Samples of diseased glands were collected intraoperatively from consenting patients over a 1-year period. Sixteen glands were analysed - eight hyperplasias and eight adenomas. Samples were analysed using an infrared spectroscope and reflected the biochemical nature of the sample tissue. Spectra collected were subjected to both empirical and multivariate analytical techniques. RESULTS: Empirical analysis highlighted differences in spectral protein peaks, with possibly additional subtle differences in nucleic acid spectra between the pathologies. A multivariate statistical predictive model demonstrated the sensitivity of FTIR for adenomas to be 93% and hyperplasia 93%, (88% on cross validation testing). CONCLUSIONS: Thus, infrared spectroscopy is potentially an excellent tool to differentiate the two pathologies and could be a useful adjunct to the pathological diagnosis of single glands.

Photoresponse of a Single Y-Junction Carbon Nanotube.

We report investigation of optical response in a single strand of a branched carbon nanotube (CNT), a Y-junction CNT composed of multiwalled CNTs. The experiment was performed by connecting a pair of branches while grounding the remaining one. Of the three branch combinations, only one combination is optically active which also shows a nonlinear semiconductor-like I-V curve, while the other two branch combinations are optically inactive and show linear ohmic I-V curves. The photoresponse includes a zero-bias photocurrent from the active branch combination. Responsivity of ≈1.6 mA/W has been observed from a single Y-CNT at a moderate bias of 150 mV with an illumination of wavelength 488 nm. The photoresponse experiment allows us to understand the nature of internal connections in the Y-CNT. Analysis of data locates the region of photoactivity at the junction of only two branches and only the combination of these two branches (and not individual branches) exhibits photoresponse upon illumination. A model calculation based on back-to-back Schottky-type junctions at the branch connection explains the I-V data in the dark and shows that under illumination the barriers at the contacts become lowered due to the presence of photogenerated carriers.

Nile Blue in Triton-X 100/benzene-hexane reverse micelles: a fluorescence spectroscopic study.

We report the observation of ground state prototropic equilibrium of the dye Nile Blue in Triton-X 100/benzene-hexane reverse micellar system. In the absence of water, the deprotonated form of the dye is predominant. Addition of water produces the protonated form. At highest water loading, the equilibrium is still shifted towards the deprotonated form as revealed by the absorption spectrum. In neat Triton-X 100 also, the dye is present almost predominantly in the deprotonated form as revealed by the absorption spectrum. The average fluorescence lifetime of the dye is greater in neat Triton-X 100 than in Triton-X 100 reverse micelles, when no water is added. Addition of water to the reverse micelles increases the average lifetime of the deprotonated species. We offer possible explanations to the above observations by discussing the structure and properties of the Triton-X 100/benzene-hexane reverse micelles.

Low-frequency flicker noise in a MSM device made with single Si nanowire (diameter ≈ 50 nm).

: Low-frequency flicker noise has been measured in a metal-semiconductor-metal (MSM) device made from a single strand of a single crystalline Si nanowire (diameter approximately 50 nm). Measurement was done with an alternating current (ac) excitation for the noise measurement superimposed with direct current (dc) bias that can be controlled independently. The observed noise has a spectral power density ∝1/fα. Application of the superimposed dc bias (retaining the ac bias unchanged) with a value more than the Schottky barrier height at the junction leads to a large suppression of the noise amplitude along with a change of α from 2 to ≈ 1. The dc bias-dependent part of the noise has been interpreted as arising from the interface region. The residual dc bias-independent flicker noise is suggested to arise from the single strand of Si nanowire, which has the conventional 1/f spectral power density.

Optically induced tunable magnetization dynamics in nanoscale co antidot lattices.

We report the time-domain measurements of optically induced precessional dynamics in a series of Co antidot lattices with fixed antidot diameter of 100 nm and with varying lattice constants (S) between 200 and 500 nm. For the sparsest lattice, we observe two bands of precessional modes with a band gap, which increases substantially with the decrease in S down to 300 nm. At S = 200 nm, four distinct bands with significant band gaps appear. The numerically calculated mode profiles show various localized and extended modes with the propagation direction perpendicular to the bias magnetic field. We numerically demonstrate some composite antidot structures with very rich magnonic spectra spreading between 3 and 27 GHz based upon the above experimental observation.

Photodynamic action of Rose Bengal silica nanoparticle complex on breast and oral cancer cell lines.

Rose Bengal, an anionic photosensitizer was conjugated to organically modified silica nanoparticles having 3-amino propyl groups by electrostatic or covalent interaction. The drug-nanoparticle complexes were characterized by FTIR, light scattering and zeta potential measurements. Significant changes were observed in the spectroscopic properties of the drug when it is conjugated with nanoparticles. The toxicity of the free drug and drug-nanoparticle complex was studied against oral (4451) and breast (MCF-7) cancer cell lines. Both complexes with nanoparticles were more phototoxic than free Rose Bengal, with the covalent complex being the more effective. Studies carried out on cellular uptake, photostability and singlet oxygen generation suggest that enhanced phototoxicity is primarily due to the enhanced uptake of the drug-nanoparticle complex.

Improved infrared photoluminescence characteristics from circularly ordered self-assembled Ge islands.

The formation of circularly ordered Ge-islands on Si(001) has been achieved because of nonuniform strain field around the periphery of the holes patterned by focused ion beam in combination with a self-assembled growth using molecular beam epitaxy. The photoluminescence (PL) spectra obtained from patterned areas (i.e., ordered islands) show a significant signal enhancement, which sustained till 200 K, without any vertical stacking of islands. The origin of two activation energies in temperature-dependent PL spectra of the ordered islands has been explained in detail.

Raman spectroscopy of parathyroid tissue pathology.

Primary hyperparathyroidism (HPT) in 80% of patients is due to a solitary parathyroid adenoma, while in 20% multigland pathology exists, usually hyperplasia [Scott-Coombes, Surgery, 21(12):309-312, 2003]. Despite recent advances in minimally invasive parathyroidectomy, better preoperative localisation techniques and intraoperative parathyroid hormone (PTH) monitoring, a 4% failure rate [Grant CS, Thompson G, Farley D, Arch Surg, 140:47-479, 2005] persists making accurate differentiation between adenomas and hyperplasia of prime importance. We investigated the ability of Raman spectroscopy to accurately differentiate between parathyroid adenomas and hyperplasia. Raman spectra were measured at defined points on the parathyroid tissue sections using a bench-top microscopy system. Multivariate analysis of the spectra was carried out to construct a diagnostic algorithm correlating spectral results with the histopathological diagnosis. A total of 698 spectra were analysed. Principal-component (PCA)-fed linear discriminant analysis (LDA) used to construct a diagnostic algorithm. Detection sensitivity for parathyroid adenomas was 95% and hyperplasia was 93%. These preliminary results indicate that Raman spectroscopy is potentially an excellent tool to differentiate between parathyroid adenomas and hyperplasia.