Gut Microbiome and Polycystic Ovary Syndrome: Interplay of Associated Microbial-Metabolite Pathways and Therapeutic Strategies

Polycystic ovary syndrome (PCOS) is a multifaceted disease with an intricate etiology affecting reproductive-aged women. Despite attempts to unravel the pathophysiology, the molecular mechanism of PCOS remains unknown. There are no effective or suitable therapeutic strategies available to ameliorate PCOS; however, the symptoms can be managed. In recent years, a strong association has been found between the gut microbiome and PCOS, leading to the formulation of novel ideas on the genesis and pathological processes of PCOS. Further, gut microbiome dysbiosis involving microbial metabolites may trigger PCOS symptoms via many mechanistic pathways including those associated with carbohydrates, short-chain fatty acids, lipopolysaccharides, bile acids, and gut-brain axis. We present the mechanistic pathways of PCOS-related microbial metabolites and therapeutic opportunities available to treat PCOS, such as prebiotics, probiotics, and fecal microbiota therapy. In addition, the current review highlights the emerging treatment strategies available to alleviate the symptoms of PCOS.

Clinical and CT Scan Evaluation of Outcomes of Modified SARPE Using a Bone-Borne Hyrax Appliance in Unilateral Posterior Crossbite

Objective

The objective of this study was to evaluate, using clinical and computed tomography, outcomes of unilateral SARPE with a bone-borne hyrax appliance in case of unilateral crossbite and to assess the correlations between hyrax appliance opening and post-SARPE skeletal changes.

Materials and Methods

Two patients of unilateral crossbite underwent Unilateral SARPE and post-surgical expansion of maxilla using a bone-borne hyrax appliance. Computed tomography was used to make comparative linear and angular measurements of the anterior, intermediate, and posterior portions of the maxilla. The correlation between maxillary expansion and appliance opening was also investigated.

Results

Significant overall expansion was observed with maximum expansion in the anterior and inferior portions of the maxilla. The degree of appliance opening was significantly greater than that of the skeletal expansion. Comparative CAD measurements showed maximum increase in interdental width at the second premolar level.

Conclusion

The transverse expansion of the maxilla obtained with a bone-borne hyrax is less than uniform. The lack of linear correlation between appliance opening and skeletal expansion is attributable to multiple factors, including those related to the device, the surgical technique, and the craniofacial deformity itself.

Novel Nanoarchitectured Cu2Te as a Photocathodes for Photoelectrochemical Water Splitting Applications

Designing photocathodes with nanostructures has been considered a promising way to improve the photoelectrochemical (PEC) water splitting activity. Cu₂Te is one of the promising semiconducting materials for photoelectrochemical water splitting, the performance of Cu₂Te photocathodes remains poor. In this work, we report the preparation of Cu₂Te nanorods (NRs) and vertical nanosheets (NSs) assembled film on Cu foil through a vapor phase epitaxy (VPE) technique. The obtained nano architectures as photocathodes toward photoelectrochemical (PEC) performance was tested afterwards for the first time. Optimized Cu₂Te NRs and NSs photocathodes showed significant photocurrent density up to 0.53 mA cm^-2 and excellent stability under illumination. Electrochemical impedance spectroscopy and Mott-Schottky analysis were used to analyze in more detail the performance of Cu₂Te NRs and NSs photocathodes. From these analyses, we propose that Cu₂Te NRs and NSs photocathodes are potential candidate materials for use in solar water splitting.

Hollow spheres of iron oxide as an “enzyme-mimic”: preparation, characterization and application as biosensors

Nanostructured hollow spheres of iron oxide are demonstrated as “nanozymes” for the dual mode (spectrophotometric and electrochemical) detection of hydrogen peroxide & cholesterol biomarkers and a novel electrochemical sensing mechanism is proposed.

Tuning optical properties of nitrogen-doped carbon dots through fluorescence resonance energy transfer using Rhodamine B for the ratiometric sensing of mercury ions

Carbon dots (CDs) that exhibit fluorescence properties are generally derived from carbonaceous materials, and possess ultrasmall sizes with various exciting physical, chemical and photo-properties, which have been used in many different fields in recent time. Here, we have focused on the preparation of nitrogen-doped CDs (N-CDs) that emit a bright blue fluorescence upon exposure to UV excitation. Furthermore, by employing Rhodamine B (RhB) as a donor molecule, the emission color of N-CDs is altered from blue to red. Interestingly, the optical tuning based upon emission from one particular color to various other colors has been achieved by varying the doping ratio of the donor molecule, RhB. The reason is mainly attributed to the non-radiative energy transfer of the exciton energy from an excited donor to an acceptor through fluorescence resonance energy transfer (FRET). Furthermore, this emission behavior is explored for the ratiometric sensing of mercury ion (Hg2+) in aqueous medium. Among different color emissions, we chose one particular emission color, namely violet, for the detection of the Hg2+ ion. The photoluminescence properties of N-CDs are effectively and systematically quenched with the addition of different mercury ion concentrations, leading to efficient energy transformation arising from the synergetic effect of the electrostatic interaction and metal - ligand coordination between the surface functional groups of N-CDs and Hg2+ ion. On the other hand, RhB has no interaction with Hg2+ ions. These findings provide a way for developing a cheap, selective and suitable sensing matrix for the detection of toxic metal ions, such as mercury (Hg2+) at a low concentration level.

Electron transfer studies of a conventional redox probe in human sweat and saliva bio-mimicking conditions

Modern day hospital treatments aim at developing electrochemical biosensors for early diagnosis of diseases using unconventional human bio-fluids like sweat and saliva by monitoring the electron transfer reactions of target analytes. Such kinds of health care diagnostics primarily avoid the usage of human blood and urine samples. In this context, here we have investigated the electron transfer reaction of a well-known and commonly used redox probe namely, potassium ferro/ferri cyanide by employing artificially simulated bio-mimics of human sweat and saliva as unconventional electrolytes. Typically, electron transfer characteristics of the redox couple, [Fe(CN)₆]^3−/4− are investigated using electrochemical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. Many different kinetic parameters are determined and compared with the conventional system. In addition, such electron transfer reactions have also been studied using a lyotropic liquid crystalline phase comprising of Triton X-100 and water in which the aqueous phase is replaced with either human sweat or saliva bio-mimics. From these studies, we find out the electron transfer reaction of [Fe(CN)₆]^3−/4− redox couple is completely diffusion controlled on both Au and Pt disc shaped electrodes in presence of sweat and saliva bio-mimic solutions. Moreover, the reaction is partially blocked by the presence of lyotropic liquid crystalline phase consisting of sweat and saliva bio-mimics indicating the predominant charge transfer controlled process for the redox probe. However, the rate constant values associated with the electron transfer reaction are drastically reduced in presence of liquid crystalline phase. These studies are essentially carried out to assess the effect of sweat and saliva on the electrochemistry of Fe^2+/3+ redox couple.

Bio-assisted preparation of efficiently architectured nanostructures of γ-Fe2O3 as a molecular recognition platform for simultaneous detection of biomarkers

Magnetic nanoparticles of iron oxide (γ-Fe2O3) have been prepared using bio-assisted method and their application in the field of biosensors is demonstrated. Particularly in this work, different nanostructures of γ-Fe2O3 namely nanospheres (NS), nanograsses (NG) and nanowires (NW) are prepared using a bio-surfactant namely Furostanol Saponin (FS) present in Fenugreek seeds extract through co-precipitation method by following "green" route. Three distinct morphologies of iron oxide nanostructures possessing the same crystal structure, magnetic properties, and varied size distribution are prepared and characterized. The resultant materials are analyzed using field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometer and Fourier transform infrared spectroscopy. Moreover, the effect of reaction time and concentration of FS on the resultant morphologies of γ-Fe2O3 nanostructures are systematically investigated. Among different shapes, NWs and NSs of γ-Fe2O3 are found to exhibit better sensing behaviour for both the individual and simultaneous electrochemical detection of most popular biomarkers namely dopamine (DA) and uric acid (UA). Electrochemical studies reveal that γ-Fe2O3 NWs showed better sensing characteristics than γ-Fe2O3 NSs and NGs in terms of distinguishable voltammetric signals for DA and UA with enhanced oxidation current values. Differential pulse voltammetric studies exhibit linear dependence on DA and UA concentrations in the range of 0.15-75 µM and 5 μM - 0.15 mM respectively. The detection limit values for DA and UA are determined to be 150 nM and 5 µM. In addition γ-Fe2O3 NWs modified electrode showed higher sensitivity, reduced overpotential along with good selectivity towards the determination of DA and UA even in the presence of other common interferents. Thus the proposed biosensor electrode is very easy to fabricate, eco-friendly, cheaper and possesses higher surface area suggesting the unique structural patterns of γ-Fe2O3 nanostructures to be a promising candidate for electrochemical bio-sensing and biomedical applications.

Colour Doppler evaluation of uterine and ovarian blood flow in patients of polycystic ovarian disease and post-treatment changes

AIM

To assess the morphology and colour Doppler parameters in patients with polycystic ovarian syndrome (PCOS) and also to assess the changes in Doppler parameters in follow-up patients, who underwent treatment.

MATERIALS AND METHODS

The study was conducted on 50 women of reproductive age who had clinical and biochemical findings suggestive of PCOS. Clinico-hormonal parameters were recorded. Ultrasound and colour Doppler flow measurements of bilateral ovaries were performed in the early proliferative phase of the menstrual cycle. After assessment of the bilateral ovaries, colour Doppler ultrasound was used to evaluate the main uterine artery at the cervico-uterine junction. Follow-up imaging after 3 months was undertaken in patients who underwent treatment (metformin) and changes in the imaging and hormonal parameters were correlated.

RESULTS

The mean value of luteinising hormone (LH) and the ratio of LH: follicle-stimulating hormone (FSH) was significantly higher in PCOS patients. Ultrasound parameters were significantly higher in PCOS patients. Ovarian stromal vessels in PCOS patients had a significantly higher peak systolic velocity (PSV), low resistance index (RI), and pulsatility index (PI). The PSV of uterine arteries were significantly decreased and the RI and PI were significantly increased. On follow-up patients revealed changes in hormonal parameters.

CONCLUSION

PCOS is a heterogeneous disorder and is a convergence of multisystem endocrine derangements. Ultrasound is good diagnostic tool for PCOS and the use of Doppler aids in the evaluation of haemodynamic changes in small vessels of utero-ovarian circulation and in response assessment.

MnFe₂O₄ Nanoparticles as an Efficient Electrode for Energy Storage Applications

In this study, solvothermal method was used for the synthesis of MnFe₂O₄ nanoparticles at different processing period of 7, 14, and 21 h. X-ray diffraction (XRD) pattern study confirms that MnFe₂O₄ nanoparticles correspond to the face-centered cubic spinel structure and belong to the Fd3m [227] space group. From Raman spectra analysis, two major peaks were observed at 476 and 616 cm^-1, which correspond to the vibration modes of MnFe₂O₄ nanoparticles; especially, the broad peak at 620 cm^-1 (A1g) corresponds to the symmetric stretching vibration of oxygen atoms at tetrahedral site. Infrared spectra (FTIR) analysis at 490 and 572 cm^-1 can be attributed to the stretching vibration of tetrahedral groups of FeO₄, and the vibration of octahedral groups of FeO₆ belongs to the intrinsic vibrations of manganese ferrites. The uniformly distributed MnFe₂O₄ nanospheres (RT2) can be affirmed by field emission scanning electron microscopy images and confirmed by the high-resolution transmission electron microscopic studies. The electrochemical properties of synthesized MnFe₂O₄ nanoparticles investigated by cyclic voltammetry, impedance spectroscopy and galvanstatic charging and discharging (GCD) studies clearly predict the reversible faradaic reactions of MnFe₂O₄ nanospheres. Further, the MnFe₂O₄ nanospheres (RT2) exhibit high specific capacitance of 697 F g^-1 at 0.5 A g^-1 current density in galvanostatic charging and discharging profile and after 1000 cycles exhibits 79% retain ability of initial specific capacitance and hence can be considered as the efficient electrode for supercapacitor applications.

Zirconia nanocomposites with carbon and iron(iii) oxide for voltammetric detection of sub-nanomolar levels of methyl parathion

This study reports the synthesis of zirconia nanoparticles loaded on various carbon substrates, namely, reduced graphene oxide (Zr-r-GO), carbon nanotubes (Zr-CNT), and activated carbon (Zr-AC). In addition, a composite of zirconia-iron mixed oxide loaded on activated carbon (FeZr-AC) was also synthesized. The materials were characterized using SEM-EDX, HRTEM, FTIR, Raman spectroscopy, TGA and XRD. The FeZr-AC sample was found to have a nanorod like morphology. The samples were evaluated for their sensing potential towards methyl parathion (MP) using differential pulse voltammetry in a range of 0.0 V to -0.9 V (vs. Ag/AgCl) by drop casting on a glassy carbon electrode (GCE). All the modified GCEs best operated at a working potential of 0.4-0.9 V vs. Ag/AgCl/Cl-. FeZr-AC was found have the best limit of detection followed by Zr-AC, Zr-CNT and Zr-r-GO with their detection limits being 1.7 × 10-9 M, 17.2 ×10-9 M, 243.3 × 10-9 M and 534.0 × 10-9 M respectively. These materials were then used to detect MP in spiked sewage samples and showed good recoveries.

Nanostructured Diatom-ZrO2 composite as a selective and highly sensitive enzyme free electrochemical sensor for detection of methyl parathion

In the current work we report a simple and scalable technique for synthesis of ordered nanoporous Si-ZrO₂ composite derived from the diatom Phaeodactylum tricornutum. The composite was well characterized using SEM, TEM-EDX, FTIR, TGA, BET and DLS. The diatom-ZrO₂ was found to have a specific surface area of 140 m²/g, Si:Zr ratio of 1:4 and a particle size of 80 ± 2 nm. This composite was evaluated as an enzyme free electrochemical sensor towards the detection of methyl parathion (MP) and showed excellent sensing ability at extremely low detection limits of 54.3 pM and a linear concentration range of 3.4 nM to 64 μM. The diatom-ZrO₂ composite was also found to be highly selective towards MP as shown by its response even in the presence of high concentrations of other interfering molecules and ions.

Low Surface Energy and pH Effect on SnO₂ Nanoparticles Formation for Supercapacitor Applications

The SnO₂ nanoparticles formation by hydrothermal method at different experimental conditions such as temperature, pH, reaction time, and capping agent (cetyltrimethylammonium bromide), was studied. X-ray diffraction results confirmed regular rutile crystal structure of SnO₂. The characteristic Raman peak observed at 635 cm^-1 corresponded to A_1g modes of Sn-O vibrations. The study of optical property using photoluminescence confirmed the emissive spectra of SnO₂. The infrared peak observed at 618 cm^-1 corresponded to E_u modes of Sn-O vibrations of TO phonon because of E_⊥ to c-axis. Scanning electron microscope images clearly revealed the formation of complete SnO₂ nanoparticles. The unique SnO₂ nanoparticles stacked together to form microspheres at pH-5 showed high specific capacitance of 274.8 F/g at a current density of 0.5 A/g. The observed results confirmed the feasibility of SnO₂ nanoparticles being used as appropriate positive electrode candidate for supercapacitor applications.

An unusual case of femoral head perforation following fixation with proximal femoral nail antirotation (PFNA-II) for an unstable intertrochanteric fracture: Case report and literature review

The proximal femoral nail antirotation (PFNA-II) is designed for fixation of unstable proximal femoral fractures in Asian patients due to its superior biomechanical properties. The helical blade achieves purchase through bone compaction and requires less removal of bone than a screw. Medial migration of the helical blade with perforation into the hip joint without loss of reduction is a rare problem noted with PFNA. Past literature reporting the migration of the helical blade medially, perforating the femoral head has been addressed as a characteristic complication of the PFNA. A review of literature suggests various reasons for the same such as fresh trauma, fracture settlement and failure of lateralization of the blade. We report a case of postoperative medial migration of the helical blade perforating the femoral head due to loosening of the locking bolt of the helical blade without any signs of rotational or varus displacement of the fracture.

A cholesterol based imidazolium ionic liquid crystal: synthesis, characterisation and its dual application as an electrolyte and electrode material

Dual application of a new cholesterol containing imidazolium ionic liquid crystal as an electrolyte for hybrid flexible supercapacitor and an electrode material in combination with carbon paste.

Structural, Optical and Magnetic Properties of NiO Nanopowders

Nickel oxide (NiO) nanopowders were synthesized without using surfactant by chemical reduction technique. NaBH4 influence on structural, optical and magnetic properties of NiO product was investigated. XRD results revealed the formation of dominant single phase, cubic face centered nickel oxide. Raman peaks depicts the characteristic first-order transverse optical (TO) phonon, two phonon excitation (TO + LO), excitation (2LO) Raman mode vibrations of face centered cubic NiO. PL studies revealed the presence of strong emission band which is in good agreement with the intrinsic NiO product. FTIR studies explored metal oxygen vibrations of the obtained product. TEM results revealed the nanoscale product with spherical shape structures. VSM studies explored weak ferromagnetic behavior of the obtained product. High concentration of NaBH4 increases magnetization value and exhibits the typical weak ferromagnetic curve. Reducing agent played a vital role in the structural, optical and magnetic properties of the obtained NiO product.

Crystal growth and characterization of second- and third-order nonlinear optical chalcone derivative: (2E)-3-(5-bromo-2-thienyl)-1-(4-nitrophenyl)prop-2-en-1-one

Experimental and computational studies of linear and nonlinear optical (NLO) properties of (2E)-3-(5-bromo-2-thienyl)-1-(4-nitrophenyl)prop-2-en-1-one (5B2SNC) single crystals are reported. Good-quality and large-sized single crystals of 5B2SNC were successfully grown and characterized by powder X-ray diffraction and high-resolution X-ray diffractometry techniques. 5B2SNC was found to crystallize in the monoclinic noncentrosymmetric space group Cc and possesses moderately good crystalline perfection. The linear optical properties were investigated using the absorption spectrum, which reveals a direct optical band gap of 3.1 eV. The thermal stability was studied with thermogravimetric analysis/differential thermal analysis. The powder second harmonic generation efficiency was evaluated by the Kurtz and Perry method, and 5B2SNC was found to be 26 times more efficient than urea standard. Third-order NLO properties were studied by the z-scan technique with a femtosecond laser. The second hyperpolarizability was obtained to be ∼1.45 × 10−31 e.s.u. The molecule reveals a strong reverse saturation absorption and negative nonlinear refraction. The molecule exhibited good optical limiting properties, and its limiting threshold was measured to be ∼3.2 mJ cm−2. In addition, static electric dipole moments, linear polarizabilities, and first- and second-order hyperpolarizabilities were calculated by density functional theory (DFT). Highest occupied molecular orbital/lowest unoccupied molecular orbital band gaps were also evaluated by DFT calculations. The experimental and theoretical results showed that 5B2SNC exhibits excellent second- and third-order nonlinear optical properties.

Vertical Alignment of Liquid Crystals Over a Functionalized Flexible Substrate

A simple and effective approach for vertical alignment of liquid crystals (LCs) over a functionalized transparent flexible substrate is described. Surface characterization of this commercially available plastic substrate through X-ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared spectroscopy (ATR-IR) indicated that cellulose acetate is main component of the transparent substrate. This substrate was chemically functionalized with a suitable LC compound. A trimethoxysilane terminated new rod-shaped mesogen is synthesized and covalently attached to the pre-treated film through silane condensation reaction. LC functionalization of the polymer film is confirmed through contact angle (CA), atomic force microscopy (AFM), XPS and ATR-IR spectroscopy studies. Versatility of the LC modified flexible substrates for the alignment of bulk LC sample at substrate-LC interface was assessed for nematic (N) and smectic A (SmA) phases. Remarkably, LC functionalized cellulose acetate films were found to be highly efficient in assisting a perfect homeotropic alignment of LCs (for both, a room temperature N and a high temperature SmA phase) over the entire area of the LC sample under observation indicating their superior aligning ability in comparison to their unmodified and octadecyltrimethoxysilane (OTS) modified counterparts. The demonstrated method of surface modification of flexible polymer film is easy, surface modified substrates are stable for several months, retained their aligning ability intact and more importantly they are reusable with maximum delivery.

Five-year Retrospective Study on Primary Hyperparathyroidism in South India: Emerging Roles of Minimally Invasive Parathyroidectomy and Preoperative Localization with Methionine Positron Emission Tomography-Computed Tomography Scan

BACKGROUND

Primary hyperparathyroidism (PHPT) is a common endocrine disease with a variable clinical presentation. PHPT is usually symptomatic at presentation in majority of the patients, especially in developing countries. As the accessibility to investigations, advanced imaging methods and surgical procedures are improving, the clinical profile of the patients with PHPT has undergone a palpable change compared to the earlier description. Hence we decided to look for a change in clinical, imaging and surgical outcomes of PHPT patients from South India.

METHODS

We collected the data on clinical presentation, biochemistry, radiological features and operative findings of patients with PHPT treated in our hospital from 2011-2015. Cases of PHPT were identified from the laboratory values using the biochemical criteria, after the exclusion of secondary and tertiary hyperparathyroidism cases.

RESULTS

Our study identified 54 patients (19 males and 35 females) with age ranging from 16 to 71 years. A Significant proportion(38.9%) of the patients were asymptomatic. Musculoskeletal symptoms (40.7%), renal manifestations (27.7%) and gastrointestinal system involvement (27.7%) constituted the other common modes of presentation. CNS involvement was seen in 3 patients. A palpable nodule in the neck was detected in 4 patients. Interestingly 4 patients were managed for parathyroid crisis at presentation. Biochemical features included hypercalcaemia (100%) and hypophosphatemia (59%) with a mean intact PTH level of 602.0±721.3 pg/ml. Sensitivity of Ultrasonography and Tc99M Sestamibi was 72% and 70.6% respectively for detecting a parathyroid adenoma. Sensitivity of C11 methionine PET-CT was 71.4% in those patients who were negative for other imaging modalities. Forty three patients (79.6%) underwent minimally invasive parathyroidectomy.

CONCLUSION

In South India we have a notable change in the clinical presentation of PHPT from a symptomatic to an asymptomatic state. C11 Methionine PET - CT is an emerging modality for preoperative localisation especially when other imaging modalities are negative and when a minimally invasive parathyroidectomy is desired.

Treatment Outcomes in Male Breast Cancer: A Retrospective Analysis of 161 Patients

AIMS

Male breast cancer is a rare disease with limited evidence-based guidelines for treatment. This study aimed to identify demographic, pathological and clinical factors associated with its prognosis.

MATERIALS AND METHODS

A retrospective review of 161 male breast cancer patients diagnosed at a single institution from 1987 to June 2017 was conducted. Patient demographics, disease characteristics, treatment and outcome were extracted and included in competing-risk analysis and the univariate Cox proportional hazard model for univariate analysis. Factors with P < 0.10 were included in multivariable analysis.

RESULTS

The mean age at diagnosis was 67 years (standard deviation = 11.2) and the median follow-up duration was 5.3 years (range 0-25 years). There were 48 deaths, including 23 cancer-specific deaths. The actuarial median survival was 19.9 years. In multivariable analysis, factors associated with overall survival were size of tumours (hazard ratio 2.0; 95% confidence interval 1.4-2.7, P < 0.0001) and diagnosis of metastatic disease (hazard ratio 8.7; 95% confidence interval 1.9-40.6; P = 0.006). Of 138 patients without metastases at diagnoses, 11 had local-regional recurrence and 26 had distant metastases. In the multivariable model for local-regional recurrence, a more recent year of diagnosis was associated with reduced risk (hazard ratio 0.9, 95% confidence interval 0.8-1.0, P = 0.008), whereas more positive lymph nodes was associated with higher risk (hazard ratio 2.2, 95% confidence interval 1.2-4.0, P = 0.01). A higher risk of metastases was associated with more positive lymph nodes (hazard ratio 1.9; 95% confidence interval 1.1-3.3; P = 0.03) and tumour size (hazard ratio 1.8; 95% confidence interval 1.1-2.9; P = 0.01). A higher risk of any recurrence or metastases was associated with the number of positive nodes (hazard ratio 1.9; 95% confidence interval 1.2-3.0; P = 0.005) and tumour size (hazard ratio 1.6; 95% confidence interval 1.1-2.2; P = 0.01).

CONCLUSION

In general, tumour size and more positive lymph nodes were associated with worse prognosis. Larger powered studies are needed to identify prognostic factors with smaller effect sizes.

Effect of phenol red dye on monocrystal growth, crystalline perfection, and optical and dielectric properties of zinc (tris) thiourea sulfate

In this work, the growth of large size (∼25 × 29 × 5 mm and ∼25 × 24 × 6 mm) colorful single crystals of zinc (tris) thiourea sulfate (ZTS) in the presence of 0.05–2 wt% phenol red (PR) dye was achieved using a simple and low-cost technique. Powder X-ray diffraction patterns confirm the presence of PR dye, which is indicated by an enhancement of the Raman peak intensities, a shift in their position and the appearance of a few extra peaks. The quality of the grown crystals was assessed by high-resolution X-ray diffraction, which shows that the crystalline perfection of 1 wt% PR-dyed ZTS crystals is better than that of 2 wt% PR-dyed crystals. The measured UV–vis absorbance spectra show two additional, strong absorption bands at ∼430 and 558 nm in the dyed crystals, due to the presence of PR dye, along with a band at ∼276 nm which is present for all crystals but is slightly shifted for the dyed crystals. Photoluminescence spectra were recorded at two excitation wavelengths (λexc= 310 and 385 nm). The luminescence intensity is found to be enriched in dyed crystals, with some extra emission bands. An enhancement in the value of the dielectric constant and a.c. electrical conductivity was also observed in the dyed ZTS crystals.

Controlled Growth of Gold Nanostars: Effect of Spike Length on SERS Signal Enhancement

Two different types of gold nanostars (Au NS), namely, short-spiked nanostars (SSNS) and long-spiked nanostars (LSNS), are prepared by using a hexagonal lyotropic liquid-crystalline (LLC) phase as a template. The formation, size and length of spikes or arms of the resultant Au NS are controlled by preparation in either a hexagonal LLC phase or an isotropic phase. These NS are anchored onto indium tin oxide (ITO) electrodes through a self-assembled monolayer of 3-mercaptopropyltrimethoxysilane, which acts as a linker molecule. Structural and morphological characterisations of SSNS- and LSNS-anchored ITO electrodes are performed by means of microscopic and spectroscopic analyses. Further electrochemical techniques, namely, cyclic voltammetry and electrochemical impedance spectroscopy, are also used to confirm the immobilisation of these Au NS on ITO electrodes and to study the electrochemical characteristics. These studies clearly reveal the formation of star-shaped, branched, anisotropic nanostructures of gold during the template preparation method and these Au NS are successfully anchored onto ITO electrodes through a covalent immobilisation strategy. Furthermore, the SERS activity of these Au NS is analysed by using glutathione and crystal violet as analytes and by employing glass and ITO as substrates. It is interesting to note that SSNS show a significant enhancement in SERS signals relative to those of LSNS.