One-Step In Situ Patternable Reduction of a Ag–rGO Hybrid Using Temporally Shaped Femtosecond Pulses

In recent years, metallic nanoparticle (NP)–two-dimensional material hybrids have been widely used for photocatalysis and photoreduction. Here, we introduce a femtosecond laser reduction approach that relies on the repetitive ablation of recast layers by usi–ng temporally shaped pulses to achieve the fast fabrication of metallic NP–two-dimensional material hybrids. We selectively deposited silver-reduced graphene oxide (Ag–rGO) hybrids on different substrates under various fabrication conditions. The deposition of the hybrids was attributed to the redistribution of the cooling ejected plume after multiple radiation pulses and the exchange of carriers with ejected plume ions containing activated species such as small carbon clusters and H2O. The proposed one-step in situ fabrication method is a competitive fabrication process that eliminates the additive separation process and exhibits morphological controllability. The Ag–rGO hybrids demonstrate considerable potential for chemomolecular and biomolecular detection because the surface-enhanced Raman scattering signal of the enhancement factor reached 4.04 × 108.

Pyrophosphate-Enhanced Oxidase Activity of Cerium Oxide Nanoparticles for Colorimetric Detection of Nucleic Acids

In recent years, cerium oxide (CeO2) nanoparticles (NPs) have drawn significant attention owing to their intrinsic enzyme mimetic properties, which make them powerful tools for biomolecular detection. In this work, we evaluated the effect of pyrophosphate (PPi) on the oxidase activity of CeO2 NPs. The presence of PPi was found to enhance the oxidase activity of CeO2 NPs, with enhanced colorimetric signals. This particular effect was then used for the colorimetric detection of target nucleic acids. Overall, the PPi-enhanced colorimetric signals of CeO2 NPs oxidase activity were suppressed by the presence of the target nucleic acids. Compared with previous studies using CeO2 NPs only, our proposed system significantly improved the signal change (ca. 200%), leading to more sensitive and reproducible colorimetric analysis of target nucleic acids. As a proof-of-concept study, the proposed system was successfully applied to the highly selective and sensitive detection of polymerase chain reaction products derived from Klebsiella pneumoniae. Our findings will benefit the rapid detection of nucleic acid biomarkers (e.g., pathogenic bacterial DNA or RNA) in point-of-care settings.

Liquid crystal-amplified optofluidic biosensor for ultra-highly sensitive and stable protein assay

Protein assays show great importance in medical research and disease diagnoses. Liquid crystals (LCs), as a branch of sensitive materials, offer promising applicability in the field of biosensing. Herein, we developed an ultrasensitive biosensor for the detection of low-concentration protein molecules, employing LC-amplified optofluidic resonators. In this design, the orientation of LCs was disturbed by immobilized protein molecules through the reduction of the vertical anchoring force from the alignment layer. A biosensing platform based on the whispering-gallery mode (WGM) from the LC-amplified optofluidic resonator was developed and explored, in which the spectral wavelength shift was monitored as the sensing parameter. The microbubble structure provided a stable and reliable WGM resonator with a high Q factor for LCs. It is demonstrated that the wall thickness of the microbubble played a key role in enhancing the sensitivity of the LC-amplified WGM microcavity. It is also found that protein molecules coated on the internal surface of microbubble led to their interactions with laser beams and the orientation transition of LCs. Both effects amplified the target information and triggered a sensitive wavelength shift in WGM spectra. A detection limit of 1 fM for bovine serum albumin (BSA) was achieved to demonstrate the high-sensitivity of our sensing platform in protein assays. Compared to the detection using a conventional polarized optical microscope (POM), the sensitivity was improved by seven orders of magnitude. Furthermore, multiple types of proteins and specific biosensing were also investigated to verify the potential of LC-amplified optofluidic resonators in the biomolecular detection. Our studies indicate that LC-amplified optofluidic resonators offer a new solution for the ultrasensitive real-time biosensing and the characterization of biomolecular interactions.

Recent advances in biomedical, biosensor and clinical measurement devices for use in humans and the potential application of these technologies for the study of physiology and disease in wild animals

The goal of achieving enhanced diagnosis and continuous monitoring of human health has led to a vibrant, dynamic and well-funded field of research in medical sensing and biosensor technologies. The field has many sub-disciplines which focus on different aspects of sensor science; engaging engineers, chemists, biochemists and clinicians, often in interdisciplinary teams. The trends which dominate include the efforts to develop effective point of care tests and implantable/wearable technologies for early diagnosis and continuous monitoring. This review will outline the current state of the art in a number of relevant fields, including device engineering, chemistry, nanoscience and biomolecular detection, and suggest how these advances might be employed to develop effective systems for measuring physiology, detecting infection and monitoring biomarker status in wild animals. Special consideration is also given to the emerging threat of antimicrobial resistance and in the light of the current SARS-CoV-2 outbreak, zoonotic infections. Both of these areas involve significant crossover between animal and human health and are therefore well placed to seed technological developments with applicability to both human and animal health and, more generally, the reviewed technologies have significant potential to find use in the measurement of physiology in wild animals. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part II)’.

Platinum Layers Sandwiched between Black Phosphorous and Graphene for Enhanced SPR Sensor Performance

Highly sensitivity Surface Plasmon resonance (SPR) sensor consisting of Ag-Pt bimetallic films sandwiched with 2D materials Black Phosphorus (BP) and Graphene over Pt layer in Kretschmann configuration is analyzed theoretically using the Transfer Matrix Method. Numerical results shows that upon suitable optimization of thickness of Ag-Pt and number of layers of BP & graphene, sensitivity as high as 412º/RIU can be achieved for p-polarized light of wavelength 633 nm. This performance can be tuned and controlled by changing the number of layers of BP and graphene. Further, the addition of graphene and heterostructures of black phosphorus not only improved the sensitivity of the sensor but keep the FWHM of the resonance curve much smaller than the conventional sensor utilizing Au as plasmon metal and hence improved the resolution to a significant extent. We expect that this new proposed design will be useful for medical diagnosis, biomolecular detection and chemical examination.

3-D Fibrous Network of TiO2 Nanoparticles: Raman Sensor Development

A 3-D nano-fiber particle network of TiO2 nanoparticles is synthesized by pulsed femtosecond laser irradiation of a pure Ti substrate. This study investigated the properties of the resulting nanostructure for chemical and biomolecular detection by Raman spectroscopy. Controlled tuning of surface roughness, porosity and depth of the 3-D network were found to directly influence Raman detection. The presented findings support a previously unrealized detection capacity by TiO2. Crystal violet was used to test the Surface-Enhanced Raman Spectroscopy (SERS) performance of the developed TiO2 sensor pads. The corresponding Raman enhancement factor was determined to be 1.3x106 which is directly comparable to commercial Ag and Au based Raman substrates. Bisphenol-A and diclofenac sodium salt were introduced into drinking water and tested with various sensor pads to develop a Raman detection map. The results suggest an affinity towards uniform TiO2 3-D nanofibrous networks.

3-D Fibrous Network of TiO2 Nanoparticles: Raman Sensor Development

A 3-D nano-fiber particle network of TiO2 nanoparticles is synthesized by pulsed femtosecond laser irradiation of a pure Ti substrate. This study investigated the properties of the resulting nanostructure for chemical and biomolecular detection by Raman spectroscopy. Controlled tuning of surface roughness, porosity and depth of the 3-D network were found to directly influence Raman detection. The presented findings support a previously unrealized detection capacity by TiO2. Crystal violet was used to test the Surface-Enhanced Raman Spectroscopy (SERS) performance of the developed TiO2 sensor pads. The corresponding Raman enhancement factor was determined to be 1.3x106 which is directly comparable to commercial Ag and Au based Raman substrates. Bisphenol-A and diclofenac sodium salt were introduced into drinking water and tested with various sensor pads to develop a Raman detection map. The results suggest an affinity towards uniform TiO2 3-D nanofibrous networks.