Surface-enhanced Raman spectroscopy (SERS) in cotton fabrics analysis

Assessment of Cellulose Nanofiber-Based Elastase Biosensors to Inflammatory Disease as a Function of Spacer Length and Fluorescence Response

Inflammatory disease biomarker detection has become a high priority in point-of-care diagnostic research in relation to chronic wounds, with a variety of sensor-based designs becoming available. Herein, two primary aspects of biosensor design are examined: (1) assessment of a cellulose nanofiber (CNF) matrix derived from cotton ginning byproducts as a sensor transducer surface; and (2) assessment of the relation of spacer length and morphology between the CNF cellulose backbone and peptide fluorophore as a function of sensor activity for porcine pancreatic and human neutrophil elastases. X-ray crystallography, specific surface area, and pore size analyses confirmed the suitability of CNF as a matrix for wound care diagnostics. Based upon the normalized degree of substitution, a pegylated-linker connecting CNF transducer substrate to peptide fluorophore showed the greatest fluorescence response, compared to short- and long-chain alkylated linkers.

Planting gold nanoflower for harvesting reproducible SERS substrate

Surface-enhanced Raman scattering (SERS) is an ultrasensitive analytical method which has been applied in many fields, and the reproducibility of the substrate is important for reliable SERS analysis. In present work, an innovative method inspired by the flower planting process is put forward to acquire gold nanoflower (AuNF) SERS substrate. Three steps (digging holes, sowing the gold nanoseeds and seeds grow into gold nanoflowers) are included in the substrate fabrication process, and the influence of preparing conditions (like reacting time and Na3Au(SO3)2 concentration) on the substrate morphology and SERS performance are investigated. The acquired AuNF substrate not only exhibits good SERS performance but also possesses excellent reproducibility while being used to detect the rhodamine 6G (R6G) molecular. The relative standard deviation (RSD) of Raman signals among substrates acquired in distinct batches (substrate-to-substrate) is as low as 6.67 %. Since the AuNF substrate is prepared by the wet chemistry route based on seed-mediated growth and there are no expensive reagents or complicated process used, the new process to obtain AuNF substrate is cost-effective and easy to scale up.

Chemical-Physical Characterization of PET-G-Based Material for Orthodontic Use: Preliminary Evaluation of micro-Raman Analysis

OBJECTIVES

 Orthodontic treatment with clear thermoplastic aligners is in great demand by patients especially for aesthetics. Any alterations in the chemical composition of the thermoplastic material for aligners, subjected to the oral environment and exposure to various commonly used substances, could influence the desired orthodontic movement decreasing the predictability of the treatment. The objective of this study was to determine the chemical-physical characterization by micro-Raman spectroscopy of a thermoplastic material based on polyethylene terephthalate glycol (PET-G) used for the manufacture of Lineo aligners (Micerium Lab, Avegno, Italy) subjected to different staining beverages and cleaning agents.

MATERIALS AND METHODS

 Twenty-two thermoformed PET-G samples were immersed to various substances of daily use for 10 and 15 days (coffee, tea, Coca-Cola, red wine, colloidal silver disinfectant, nicotine, artificial saliva, cigarette smoke, and different combinations of saliva with some of the previous solutions). Subsequently, the chemical-physical characterization was investigated by micro-Raman spectroscopy.

RESULTS

 The analysis of the spectra acquired for all the specimens showed no difference in the exposure to the different solvents at 10 and 15 days. Furthermore, having ascertained the heterogeneous surface morphology of the PET-G material due to thermoforming, various deposits were present on all the samples whose consistency and concentration depended on the substance used.

CONCLUSION

 The spectroscopic investigations have provided a precise and detailed analysis of the qualitative and structural data of the PET-G material under examination. No significant structural modifications of the thermoplastic polymer were found after immersion in different solutions in the exposure times adopted.

Applications of Raman spectroscopy in the analysis of biological evidence

During the past few decades, Raman spectroscopy has progressed and captivated added attention in the field of science. However, the application of Raman spectroscopy is not limited to the field of forensic science and analytical chemistry; it is one of the emerging spectroscopic techniques, utilized in the field of forensic science which in turn could be a supporting tool in the law and justice system. The advantage of Raman spectroscopy over the other conventional techniques is that it is rapid, reliable, and non-destructive in nature with minimal or no sample preparation. The quantitative and qualitative analysis of evidence from biological and non-biological origins could easily be performed by using Raman spectroscopy. The forensic domain is highly complex with multidisciplinary branches, and therefore a plethora of techniques are utilized for the detection, identification, and differentiation of innumerable pieces of evidence for the purpose of law and justice. Herein, a systematic review is carried out on the application of Raman spectroscopy in the realm of forensic biology and serology considering its usefulness in practical perspectives. This review paper highlights the significance of modern techniques, including micro-Raman spectroscopy, confocal Raman spectroscopy, surface-enhanced Raman spectroscopy, and paper-based surface-enhanced Raman spectroscopy, in the field of Raman spectroscopy. These techniques have demonstrated notable advancements in terms of their applications and capabilities. Furthermore, to comprehensively capture the progress in the development of Raman spectroscopy, all the published papers which could be retrieved from the available databases from the year 2007 to 2022 were incorporated.

Assessment of detection limits for dyed and mounted textile fibers using Raman spectroscopy

Trace evidence in the form of textile fibers can be used to link objects and places during an investigation. Raman spectroscopy is a well-established technique that has been used for the examination of various pigments, paints, inks, and dyes. The objective of this study was to determine the capability of Raman spectroscopy to detect several different dye classes and colors on a variety of textile fibers. To test this, four categories of dyes, reactive, disperse, acid, and direct were examined with Raman microscopy while applied to one of five fiber types (cotton, polyester, nylon, wool, and rayon). Each dye category was tested using four colors, black, blue, red, and yellow, while at four concentrations of dye (w/w), 4% (black only), 1%, 0.5%, and 0.05% (blue, red, and yellow). Finally, each dye, fiber, color, and dye concentration combination were examined with Raman using one of two laser excitation sources (532 nm and 780 nm) while mounted in one of two mounting media, Permount™ and Entellan® new, as well as unmounted. Raman spectroscopy could detect some dyes at low concentrations (0.5% and 0.05%) even when mounted in mounting media and covered with a glass coverslip. Excitation source, dye category, dye concentration, fiber type, and mounting method all influence the ability to detect any given dye. These results support the continued study of Raman as a tool for the examination of fiber dyes as it has shown the potential to be effective even under constraints experienced by forensic examiners.

Airborne and marine microplastics from an oceanographic survey at the Baltic Sea: An emerging role of air-sea interaction?

Microplastics (MPs) pollution is one of the most important problems of the Earth. They have been found in all the natural environments, including oceans and the atmosphere. In this study, the concentrations of both atmospheric and marine MPs were measured over the Baltic along a research cruise that started in the Gdansk harbour, till the Gotland island, and the way back. A deposition box (based on a combination of active/passive sampling) was used to collect airborne MPs while, marine MPs concentrations were investigated during the cruise using a dedicated net. Ancillary data were obtained using a combination of particle counters (OPC, LAS and CPC), Aethalometer (AE33 Magee Scientific), spectrofluorometer (sea surface samples, Varian Cary Eclipse), and meteorological sensors. Results showed airborne microplastics average concentrations higher in the Gdansk harbour (161 ± 75 m^-3) compared to the open Baltic Sea and to the Gotland island (24 ± 9 and 45 ± 20 m^-3). These latter values are closer to the ones measured in the sea (79 ± 18 m^-3). The MPs composition was investigated using μ-Raman (for the airborne ones) and FTIR (for marine ones); similar results (e.g. polyethylene, polyethylene terephthalates, polyurethane) were found in the two environmental compartments. The concentrations and similar composition in air and sea suggested a linkage between the two compartments. For this purpose, the atmospheric MPs' equivalent aerodynamic diameter was calculated (28 ± 3 μm) first showing the capability of atmospheric MPs to remain suspended in the air. At the same time, the computed turnover times (0.3-90 h; depending on MPs size) limited the transport distance range. The estimated MPs sea emission fluxes (4-18 ∗ 10⁶ μm³ m^-2 s^-1 range) finally showed the contemporary presence of atmospheric transport together with a continuous emission from the sea surface enabling a grasshopper long-range transport of microplastics across the sea.

Forensic examination of textile fibres using Raman imaging and multivariate analysis

Vibrational spectroscopic techniques have shown to be highly suitable for the identification and comparison of textile fibres and clothing fabrics. On the other hand, new chemical imaging modes based on these spectroscopic techniques are becoming useful in multiple fields. This is particularly important to, for instance, chemically visualize and screen different samples including forensic evidence (crime scene investigation), chemical and food products (quality control), biological tissues and living beings (medical imaging), among others. This study explores the forensic examination and selective chemical visualization of textile fibres and clothing fabrics using Raman imaging. Four experiments were performed, which were focused on the screening of (i) white different materials made of 100 % cotton (gauze, cotton wool, t-shirt, and swab), (ii) polyester and cotton fabrics evidence of the same colour, (iii) five different coloured cotton fabrics, and (iv) textile fibres of different materials (acrylic, cotton, nylon, polyester, and silk). Several methods of multivariate chemometric analysis including principal component analysis (PCA), multivariate analysis of variance (MANOVA), and multivariate curve resolution (MCR) were applied to enhance the limited visual comparison of the spectra accomplished with the unaided eye. The results evidenced the suitability of Raman imaging to statistically discriminate textile fibres and fabrics due to the chemical composition of both the clothing material and the dyestuff.

Lightweight TiO2@C/Carbon Fiber Aerogels Prepared from Ti3C2Tx/Cotton for High-Efficiency Microwave Absorption

Carbon fiber aerogel (CFA) derived from cotton wool as a potential microwave absorbing material has received intensive attention owing to the low density, high conductivity, large surface area, and low cost, but its applications are limited by the relatively high complex permittivity. To solve this problem, TiO₂@C (derived from Ti₃C₂T_x) is introduced into CFA to prepare lightweight TiO₂@C/CFA composites based on electromagnetic (EM) parameter optimization and enhanced EM wave attenuation performance. The microwave absorption capacity of TiO₂@C/CFA-2 composite is obviously better than that of CFA. It is confirmed that good impedance matching derived from the combination of TiO₂@C and CFA is the main factor to achieve excellent microwave absorption. Moreover, the improved microwave absorption capabilities are closely related to multiple EM wave absorbing mechanisms including multiple reflections and scattering, dipolar and interfacial polarization, and conductivity loss. TiO₂@C/CFA-2 possesses a maximum reflection loss (RL) of -43.18 dB at a low response frequency of 6.0 GHz. As the matching thickness is less than 2.0 mm, the maximum RL values can still exceed -20 dB, and at the same time, the wide effective absorption bandwidth (EAB) below -10 dB achieves 4.36 GHz at only 1.9 mm thickness. Our work confirms that the lightweight and high-performance TiO₂@C/CFA composites are promising choices and offer a new approach to design and construct carbon-based microwave absorbents derived from biomass.

Effect of Reactive Dyeing on Fabrics Modification with Silver Nanowires (AgNWs)

This paper presents the characterization of cotton and wool fabrics modified by silver nanowires (AgNWs). The effect of reactive dyeing of wool and cotton fabrics on their modification with AgNWs was analyzed. Both fabrics were dyed using reactive dyes (yellow, red, blue) at four color intensities (0.5, 1, 2, and 5%). Dyed fabrics were characterized by the determined Kubelka-Munk's coefficient (K/S) ratio and vibrational spectra (Fourier transform infrared (FTIR) and Raman). Analysis of the amount of AgNWs applied on cotton and wool fabrics indicates that the presence of dye affects the surface modification with AgNWs depending on the type of fibers. While for cotton no significant differences were noted in relation to the color intensity, in the case of wool, the higher the dye contents, the more nanowires were deposited on the surface. Surface-enhanced Raman spectroscopy (SERS) effect accompanying AgNW modification was also observed on wool, similar to the previous study on cotton.

New superhydrophobic and self-cleaning zirconia/polydimethylsiloxane nanocomposite coated cotton fabrics

Zirconia/polydimethylsiloxane nanocomposite coated fabric demonstrates unique stability with tendencies toward self-cleaning and oil–water separations due to its nanopatterned morphologies and adhering superhydrophobic polysiloxane chemical groups.

The Identification of Cotton Fibers Dyed with Reactive Dyes for Forensic Purposes

Some of the most common microtraces that are currently collected at crime scenes are fragments of single fibers. The perpetrator leaves them at a crime scene or takes them away, for example, on their clothing or body. In turn, the microscopic dimensions of such traces mean that the perpetrator does not notice them and therefore usually does not take action to remove them. Cotton and polyester fibers dyed by reactive and dispersion dyes, respectively, are very popular within clothing products, and they are hidden among microtraces at the scene of a crime. In our recently published review paper, we summarized the possibilities for the identification of disperse dyes of polyester fibers for forensic purposes. In this review, we are concerned with cotton fibers dyed with reactive dyes. Cotton fibers are natural ones that cannot easily be distinguished on the basis of morphological features. Consequently, their color and consequently the dye composition are often their only characteristics. The presented methods for the identification of reactive dyes could be very interesting not only for forensic laboratories, but also for scientists working in food, cosmetics or pharmaceutical/medical sciences.

Au Sputtered Paper Chromatography Tandem Raman Platform for Sensitive Detection of Heavy Metal Ions

Surface-enhanced Raman scattering (SERS) is a powerful technique for sensitive detection, but it normally has difficulty in multicomponent detection in a complex system, especially for simultaneous analysis of mixture of heavy metal ions. In this work, a simple paper chromatography tandem SERS (PC-SERS) separation/detection platform is proposed by ion-sputtering gold on a filter paper. Based on SEM results, the great electromagnetic field inside nanogaps of Au nanoislands on the paper surface is evaluated with FDTD simulation. It is found that the PC-SERS platform has good uniformity (RSD = 10.12%) and long-time stability. The as-prepared PC-SERS platform was applied to efficiently separate and detect a mixture of pesticides (MG, MB, and CV) in pond water without any pretreatment process, and the limits of detection (LODs) were down to 10 nM. As a crucial application for food safety, several heavy metal ions such as Cd²⁺, Cu²⁺, and Ni²⁺ in grinded rice were successfully detected by the PC-SERS method taking advantage of the sandwich structure based on 4-mercaptobenzoic acid (4-MBA) molecules, which were modified onto sputtering the Au filter paper and gold nanoparticles (Au NPs) to link metal ions and acted as Raman signal molecules. All the LODs for metal ions were down to 1 μM. Due to the easiness of fabrication, good reproducibility, and simple pretreatment step, the PC-SERS platform holds promise in multicomponent detection in a real sample.

Synthesis of corrugated surface AgNWs and their applications in surface enhanced Raman spectroscopy

Among metals, AgNWs are considered to be excellent materials for use in surface enhancement Raman spectroscopic (SERS) sensing due to their superior electrical properties, strong electromagnetic field generation and strong enhancement intensity.