Frontline clinical diagnosis-FTIR on pancreatic cancer.

OBJECTIVE: Accurate, easily accessible and economically viable cancer diagnostic tools are pivotal in improving the abysmal 5% survival rate of pancreatic cancer. METHODS: A novel, affordable, non-invasive diagnostic method has been developed by combining measurement precision of infrared spectroscopy with classification using machine learning tools. RESULTS: Diagnosis accuracy as high as 90% has been achieved. The study investigated urine and blood from pancreas cancer patients and healthy volunteers, and significantly improved accuracy by focusing on sweet-spots within blood plasma fractions containing molecules within a narrow range of molecular weights.

Improving Vibrational Spectroscopy Prospects in Frontline Clinical Diagnosis: Fourier Transform Infrared on Buccal Mucosa Cancer.

We report a novel method with higher than 90% accuracy in diagnosing buccal mucosa cancer. We use Fourier transform infrared spectroscopic analysis of human serum by suppressing confounding high molecular weight signals, thus relatively enhancing the biomarkers' signals. A narrower range molecular weight window of the serum was also investigated that yielded even higher accuracy on diagnosis. The most accurate results were produced in the serum's 10-30 kDa molecular weight region to distinguish between the two hardest to discern classes, i.e., premalignant and cancer patients. This work promises an avenue for earlier diagnosis with high accuracy as well as greater insight into the molecular origins of these signals by identifying a key molecular weight region to focus on.

Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy.

Double-resonance Raman scattering is a sensitive probe to study the electron-phonon scattering pathways in crystals. For semiconducting two-dimensional transition-metal dichalcogenides, the double-resonance Raman process involves different valleys and phonons in the Brillouin zone, and it has not yet been fully understood. Here we present a multiple energy excitation Raman study in conjunction with density functional theory calculations that unveil the double-resonance Raman scattering process in monolayer and bulk MoS2. Results show that the frequency of some Raman features shifts when changing the excitation energy, and first-principle simulations confirm that such bands arise from distinct acoustic phonons, connecting different valley states. The double-resonance Raman process is affected by the indirect-to-direct bandgap transition, and a comparison of results in monolayer and bulk allows the assignment of each Raman feature near the M or K points of the Brillouin zone. Our work highlights the underlying physics of intervalley scattering of electrons by acoustic phonons, which is essential for valley depolarization in MoS2.

Simultaneous topographical, electrical and optical microscopy of optoelectronic devices at the nanoscale.

Novel optoelectronic devices rely on complex nanomaterial systems where the nanoscale morphology and local chemical composition are critical to performance. However, the lack of analytical techniques that can directly probe these structure-property relationships at the nanoscale presents a major obstacle to device development. In this work, we present a novel method for non-destructive, simultaneous mapping of the morphology, chemical composition and photoelectrical properties with <20 nm spatial resolution by combining plasmonic optical signal enhancement with electrical-mode scanning probe microscopy. We demonstrate that this combined approach offers subsurface sensitivity that can be exploited to provide molecular information with a nanoscale resolution in all three spatial dimensions. By applying the technique to an organic solar cell device, we show that the inferred surface and subsurface composition distribution correlates strongly with the local photocurrent generation and explains macroscopic device performance. For instance, the direct measurement of fullerene phase purity can distinguish between high purity aggregates that lead to poor performance and lower purity aggregates (fullerene intercalated with polymer) that result in strong photocurrent generation and collection. We show that the reliable determination of the structure-property relationship at the nanoscale can remove ambiguity from macroscopic device data and support the identification of the best routes for device optimisation. The multi-parameter measurement approach demonstrated herein is expected to play a significant role in guiding the rational design of nanomaterial-based optoelectronic devices, by opening a new realm of possibilities for advanced investigation via the combination of nanoscale optical spectroscopy with a whole range of scanning probe microscopy modes.

Nanoscale mapping of intrinsic defects in single-layer graphene using tip-enhanced Raman spectroscopy.

Non-gap mode tip-enhanced Raman spectroscopy (TERS) is used for the first time to successfully map the intrinsic defects in single-layer graphene with 20 nm spatial resolution. The nanoscale Raman mapping is enabled by an unprecedented near-field to far-field signal contrast of 8.5 at the Ag-coated TERS tip-apex. These results demonstrate the potential of TERS for characterisation of defects in single-layer graphene-based devices at the nanometre length-scale.

Nanoscale mapping of excitonic processes in single-layer MoS2 using tip-enhanced photoluminescence microscopy.

In two-dimensional (2D) semiconductors, photoluminescence originating from recombination processes involving neutral electron-hole pairs (excitons) and charged complexes (trions) is strongly affected by the localized charge transfer due to inhomogeneous interactions with the local environment and surface defects. Herein, we demonstrate the first nanoscale mapping of excitons and trions in single-layer MoS2 using the full spectral information obtained via tip-enhanced photoluminescence (TEPL) microscopy along with tip-enhanced Raman spectroscopy (TERS) imaging of a 2D flake. Finally, we show the mapping of the PL quenching centre in single-layer MoS2 with an unprecedented spatial resolution of 20 nm. In addition, our research shows that unlike in aperture-scanning near field microscopy, preferential exciton emission mapping at the nanoscale using TEPL and Raman mapping using TERS can be obtained simultaneously using this method that can be used to correlate the structural and excitonic properties.

Extending the plasmonic lifetime of tip-enhanced Raman spectroscopy probes.

Tip-enhanced Raman spectroscopy (TERS) is an emerging technique for simultaneous mapping of chemical composition and topography of a surface at the nanoscale. However, rapid degradation of TERS probes, especially those coated with silver, is a major bottleneck to the widespread uptake of this technique and severely prohibits the success of many TERS experiments. In this work, we carry out a systematic time-series study of the plasmonic degradation of Ag-coated TERS probes under different environmental conditions and demonstrate that a low oxygen (<1 ppm) and a low moisture (<1 ppm) environment can significantly improve the plasmonic lifetime of TERS probes from a few hours to a few months. Furthermore, using X-ray photoelectron spectroscopy (XPS) measurements on Ag nanoparticles we show that the rapid plasmonic degradation of Ag-coated TERS probes can be correlated to surface oxide formation. Finally, we present practical guidelines for the effective use and storage of TERS probes to improve their plasmonic lifetime based on the results of this study.

Probing individual point defects in graphene via near-field Raman scattering.

The Raman scattering D-peak in graphene is spatially localised in close proximity to defects. Here, we demonstrate the capability of tip-enhanced Raman spectroscopy (TERS) to probe individual point defects, even for a graphene layer with an extremely low defect density. This is of practical interest for future graphene electronic devices. The measured TERS spectra enable a direct determination of the average inter-defect distance within the graphene sheet. Analysis of the TERS enhancement factor of the graphene Raman peaks highlights the preferential enhancement and symmetry-dependent selectivity of the D-peak intensity caused by zero-dimensional Raman scatterers.

Cognitive self-regulation, social functioning and psychopathology in schizophrenia.

AIM: To explore relation between cognitive self-regulation, social functioning, and psychopathology in schizophrenia. MATERIALS AND METHODS: A total of 100 patients diagnosed with schizophrenia according to International Classification of Diseases (ICD)-10 were taken from Department of Psychiatry of two postgraduate hospitals of Kolkata, India. All subjects gave informed consent. After recording sociodemographic and clinical details, the Positive and Negative Syndrome Scale for Schizophrenia (PANSS), Schizophrenia Research Foundation India-Social Functioning Index (SCARF-SFI), and specially designed questionnaire on cognitive self-regulation was administered. RESULTS: All the four subtests of SCARF-SFI, that is, self-concern, occupational role, social role and family role, and symptoms scale of PANSS were significantly correlated with cognitive self-regulation. Cognitive self-regulation along with positive and negative symptoms was able to predict social functioning. CONCLUSION: Cognitive self-regulation is significantly and positively correlated to social functioning. Cognitive self-regulation along with positive and negative symptoms is a significant predictor of social functioning.

Single-molecule reconstruction of oligonucleotide secondary structure by atomic force microscopy.

Based on soft-touch atomic force microscopy, a method is described to reconstruct the secondary structure of single extended biomolecules, without the need for crystallization. The method is tested by accurately reproducing the dimensions of the B-DNA crystal structure. Importantly, intramolecular variations in groove depth of the DNA double helix are resolved, which would be inaccessible for methods that rely on ensemble-averaging.

State of the art Raman techniques for biological applications.

Raman spectroscopy is a powerful tool for the elucidation of qualitative and quantitative information from biological systems and has huge potential in areas such as biotechnologies, drug discovery, agro-chemical research and clinical diagnostics. This report summarises the principal Raman techniques applied to biomedical systems and discusses the challenges that exist to the wide spread adoption of Raman spectroscopy.

Measurement of the Interaction Between Recombinant I-domain from Integrin alpha 2 beta 1 and a Triple Helical Collagen Peptide with the GFOGER Binding Motif Using Molecular Force Spectroscopy.

The role of the collagen-platelet interaction is of crucial importance to the haemostatic response during both injury and pathogenesis of the blood vessel wall. Of particular interest is the high affinity interaction of the platelet transmembrane receptor, alpha 2 beta 1, responsible for firm attachment of platelets to collagen at and around injury sites. We employ single molecule force spectroscopy (SMFS) using the atomic force microscope (AFM) to study the interaction of the I-domain from integrin alpha 2 beta 1 with a synthetic collagen related triple-helical peptide containing the high-affinity integrin-binding GFOGER motif, and a control peptide lacking this sequence, referred to as GPP. By utilising synthetic peptides in this manner we are able to study at the molecular level subtleties that would otherwise be lost when considering cell-to-collagen matrix interactions using ensemble techniques. We demonstrate for the first time the complexity of this interaction as illustrated by the complex multi-peaked force spectra and confirm specificity using control blocking experiments. In addition we observe specific interaction of the GPP peptide sequence with the I-domain. We propose a model to explain these observations.

A simple bioconjugate attachment protocol for use in single molecule force spectroscopy experiments based on mixed self-assembled monolayers.

Single molecule force spectroscopy is a technique that can be used to probe the interaction force between individual biomolecular species. We focus our attention on the tip and sample coupling chemistry, which is crucial to these experiments. We utilised a novel approach of mixed self-assembled monolayers of alkanethiols in conjunction with a heterobifunctional crosslinker. The effectiveness of the protocol is demonstrated by probing the biotin-avidin interaction. We measured unbinding forces comparable to previously reported values measured at similar loading rates. Specificity tests also demonstrated a significant decrease in recognition after blocking with free avidin.

The European nanometrology landscape.

This review paper summarizes the European nanometrology landscape from a technical perspective. Dimensional and chemical nanometrology are discussed first as they underpin many of the developments in other areas of nanometrology. Applications for the measurement of thin film parameters are followed by two of the most widely relevant families of functional properties: measurement of mechanical and electrical properties at the nanoscale. Nanostructured materials and surfaces, which are seen as key materials areas having specific metrology challenges, are covered next. The final section describes biological nanometrology, which is perhaps the most interdisciplinary applications area, and presents unique challenges. Within each area, a review is provided of current status, the capabilities and limitations of current techniques and instruments, and future directions being driven by emerging industrial measurement requirements. Issues of traceability, standardization, national and international programmes, regulation and skills development will be discussed in a future paper.

Self-assembled lamellar structures with functionalized single wall carbon nanotubes.

Highly ordered self-assembled multi-layer structures with denatured collagen wrapped single wall carbon nanotubes and surfactant systems were obtained through bioinspired methodology.

Nanoscale imaging of carbon nanotubes using tip enhanced Raman spectroscopy in reflection mode.

An apertureless tip enhanced Raman spectrometer in reflection mode geometry is demonstrated. A spatial resolution as small as 30 nm was achieved. This was implemented by placing a sharp gold tip near the single wall carbon nanotubes using an atomic force microscope (AFM). The tip was illuminated from the same side of the sample which eliminated the need for a transparent substrate. The tip was maintained at a distance of a few nanometers using a quartz tuning fork. The Raman signal was collected from the G peak of the single wall carbon nanotubes using a single photon detecting module and topography image was acquired by the AFM.