Surface-enhanced Raman scattering (SERS) enables trace-detection for biosensing and environmental monitoring. Optimized enhancement of SERS can be achieved when the energy of the localized surface plasmon resonance (LSPR) is close to the energy of the Raman excitation wavelength. The LSPR can be tuned using a plasmonic superstructure array with controlled periods. In this paper, we develop a new technique based on laser near-field reduction to fabricate a superstructure array, which provides distinct features in the formation of periodic structures with hollow nanoclusters and flexible control of the LSPR in fewer steps than current techniques. Fabrication involves irradiation of a continuous wave laser or femtosecond laser onto a monolayer of self-assembled silica microspheres to grow silver nanoparticles along the silica microsphere surfaces by laser near-field reduction. The LSPR of superstructure array can be flexibly tuned to match the Raman excitation wavelengths from the visible to the infrared regions using different diameters of silica microspheres. The unique nanostructure formed can contribute to an increase in the sensitivity of SERS sensing. The fabricated superstructure array thus offers superior characteristics for the quantitative analysis of fluorescent perfluorooctanoic acid with a wide detection range from 11 ppb to 400 ppm.
Surface-enhanced Raman scattering (SERS) has provided new pathways for the development of biomedical devices over the last ten years. This critical review aims to introduce several emerging strategies based on SERS that have achieved ultrahigh sensitivity for biomedical applications. These include liquid interface-assisted SERS, photo-induced SERS, dynamic SERS, optical-trapping SERS, and some other attractive approaches. The mechanisms involved are discussed to demonstrate the capability of an enhancement factor that exceeds 1014. In addition, we present some novel applications in biomedicine to illustrate the versatility of the SERS strategies. In the Outlook section, we highlight barriers and possibilities of next-generation SERS analyzers for biomedical applications.
The authors have investigated various photonic processing for various energy devices on flexible substrates with nanoinks. For printable electronics, different conducting nanoinks are developed, including silver nanowires, silver nanoplates, Cu-Ag core-shell nanoparticles, graphene oxide, and graphene. The authors showed that these inks are enabling for direct writing of antenna on paper for radio frequency (RF) energy harvesting, potentially for wireless charging application. For curing printed nanoinks and nanopastes, the authors compared four kinds of methods: chemical activated self-sintering, thermal sintering, photonic sintering with flash light, and athermal sintering with ultrafast fiber laser irradiation. The authors also developed an innovative and facile approach to fabricate supercapacitors on flexible substrates with femtosecond laser writing and photonic reduction. Au-reduced graphene oxide nanocomposite is used for electrical electrodes and collectors. Unlike previous studies, collectors are fabricated through conventional photolithography gold electrodes is directly written by femtosecond laser reduction of Au ions. The authors found that gold nanoparticles can be well sintered on the surface of reduced graphene. The reduced graphene also work as glues to bridge the electrical interconnection. The measured conductivity of Au/reduced graphene reaches 10% of that of bulk gold. By optimizing an interdigital structure, the areal capacitor is achieved as 1.5 mF/cm2.
In recent years, nanotechnology has made significant advancements in the medical field, particularly in the diagnosis and treatment of tumors. This special issue showcases the latest research achievements in the field of nanomaterials and tumor therapy, focusing on two main areas: the development of anticancer drugs based on organic nanomaterials and the application of magnetic nanomaterials in imaging diagnosis and treatment.In the realm of organic nanomaterials, Rongyi Wang et al. have developed ROS-responsive organic nanomaterials that, through laser-triggered mitochondrial targeting, combine photodynamic therapy with chemotherapy to effectively promote mitochondrial apoptosis. Additionally, Masataka Takahashi et al.have developed DDS-type NIR absorbers that enhance therapeutic effects in laser photothermal therapy, treating deep-seated lesions while minimizing damage to surrounding healthy tissues.These studies have achieved significant progress in the development of antitumor drugs and the realm of multimodal combination therapies, enhancing therapeutic precision and diminishing drug-related side effects through the use of organic nanomaterials, thus offering valuable insights for their future clinical application.In the domain of magnetic nanomaterials, research is divided into two subfields: nanomaterials for tumor medical imaging such as magnetic particle imaging (MPI), and tumor-targeted therapy based on magnetic drug delivery systems. Lingke Gai et al.have developed a dynamic imaging device for superficial and deep tumors using magnetic nanomaterials as tracers, namely a handheld MPI device. This technology has been approved by the Chinese Clinical Trial Registration Center to conduct the world's first intraoperative detection clinical trial for breast cancer based on MPI technology (registration number: ChiCTR2300077785), marking a significant breakthrough in the clinical application of magnetic nanomaterials in MPI technology. Xiaodan Zhang et al.have clarified the inducing magnetic field strength and gradient required for various magnetic nanomaterials to achieve pace-controlled induction and synchronized visualization under MPI or MRI through mathematical and physical analysis, as well as biological experiments. This study provides ample references and basis for subsequent drug delivery based on visualizable magnetic nanomaterials targeting the human body.Yixuan Zhou et al. have developed composite nanomaterials for magnetic targeted drug delivery and sonodynamic combined therapy, using magnetic nanomaterials as carriers. These materials can be controlled by an induced magnetic field to move within the body, achieving precise targeting of tumor areas and delivery of sonosensitizer drugs, enhancing the targeting and efficacy of sonodynamic therapy in ovarian cancer treatment and demonstrating the value of magnetic nanomaterials in multimodal treatment strategies.Researchers such as Chao Guan et al.and Lin Miao et al. have provided a review and commentary on the application of nanomaterials in tumor therapy and diagnosis, highlighting the immense potential of nanomaterials in targeted drug delivery, imaging analysis, immunotherapy, gene therapy, and multimodal combined therapies. This provides new strategies and theoretical frameworks for tumor diagnosis and treatment.As a summary, with the rapid development of nano-processing and characterization technologies, as well as the advances of supporting instruments, nanomaterials have shown significant scientific and clinical potentials for cancer diagnosis and treatment. Based on the paper collation of the special issue and the understanding by the editorial team, we strongly recommend further researchers should pay their attention on in-depth consideration of the integration of medicine and engineering technologies. The key to the success of clinical-grade tumor diagnosis and treatment technology using nanomaterials is to understand the whole-cycle of biological and physical characteristics of nanomaterials in physiological states, as well as the limits of supporting instruments at the current stage. We also suggest that researchers may focus on functional nanomaterials which provide additional clinical values, such as the imaging tracer, drug delivery, and hyperthermia ability of magnetic nanoparticles. These new nanoscale capabilities rely more on the physical properties of nanomaterials, which provide innovative complementary support for traditional cancer treatment options based on chemical or biological principles.
Laser-induced near-field effect concentrates the laser energy to be enhanced on a localized area much smaller than the wavelength for nanoprocessing. Owing to the superhigh fabrication resolution, the laser near-field processing has been used for the surface nanostructuring to create photonic devices. The near-field processing is typically performed by using scanning optical microscope or scanning probe microscope combined with laser, while nano/microspheres provide the unique advantages of maskless, time-saving schemes. In this paper, laser near-field reduction of metal ions assisted by silica spheres is presented for fabrication of plasmonic superlattices on silicon substrate, which can tune localized surface plasmonic resonance wavelengths from the visible to the near-infrared region by adjustment of the lattice periods. In the laser near-field reduction, the incident laser is tightly focused at the bottom side of the silica sphere to confine the reaction the in near-field.
Surface-enhanced Raman scattering (SERS) is a multidisciplinary trace analysis technique based on plasmonic effects. The development of SERS microfluidic chips has been exploited extensively in recent times impacting on applications in diverse fields. However, despite much progress, the excitation of label-free molecules is extremely challenging when analyte concentrations are lower than 1 nM because of the blinking SERS effect. In this paper, a novel analytical strategy which can achieve detection limits at an attomolar level is proposed. This performance improvement is due to the use of a glass microfluidic chip that features an analyte air–solution interface which forms on the SERS substrate in the microfluidic channel, whereby the analyte molecules aggregate locally at the interface during the measurement, hence the term liquid interface-assisted SERS (LI-SERS). The microfluidic chips are fabricated using hybrid femtosecond (fs) laser processing consisting of fs laser-assisted chemical etching, selective metallization, and metal surface nanostructuring. The novel LI-SERS technique can achieve an analytical enhancement factor of 1.5 × 1014, providing a detection limit below 10–17 M (<10 aM). The mechanism for the extraordinary enhancement afforded by LI-SERS is attributed to Marangoni convection induced by the photothermal effect.
Direct laser-reduction of graphene oxide (GO), as a lithography-free approach, has been proven effective in manufacturing in-plane micro-supercapacitors (MSCs) with fast ion diffusion.
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