The performance of tip-enhanced optical microscopy is often limited by inefficient coupling of the excitation field to the plasmonic tip apex, as well as by thermal drift and optical aberrations. Here, we demonstrate that adaptive wavefront shaping based on Zernike mode provides a practical approach to achieving robust near-field optimisation at the tip apex. Using a sequential feedback algorithm, initially using the near-field signal, we narrow the illumination point-spread function and suppress sidelobes. This demonstrates that Zernike-mode control can be used for both aberration correction and field engineering. In tip-enhanced Raman measurements of a Janus MoSSe monolayer, conventional near-field optimisation increases the signal intensity by around 1.4 fold. A second optimisation step based directly on the Raman-band intensity yields a further 5 to 15 fold enhancement, depending on the specific tips used. These results establish a systematic, optics-based strategy for optimising tip fields, providing a transferable framework for improving tip-enhanced and related near-field spectroscopies.

Chalcogenides have recently emerged as an important class of phase-change materials (PCMs) for nanophotonics, owing to their very high refractive index (RI) and low optical loss in the visible to near-infrared range. They exhibit an ultralarge RI change (> 0.7) upon phase transition, which can be triggered by multiple stimuli such as electrical bias, laser illumination or thermal heating. These properties make them highly appealing materials for flat optics and metasurface applications. Current nanophotonic implementations of chalcogenide PCMs mostly rely on two-dimensional (2D) or quasi three-dimensional (3D) thin film patterning based on the coating of chalcogenide materials from a solid-state target. This limits fast prototyping of 3D freeform micro- and nanostructures, thus restricting geometric design freedom and device functionality. Here, we demonstrate a solution-phase direct printing of chalcogenide PCMs into functional structures. The method is based on dip in two photon-induced solidification (DITPS) of a specially synthesized antimony trisulfide (Sb2S3) precursor solution. Direct printing with DITPS is simple, maskless, fast and cost effective, enabling true freeform 3D printing of photonic devices with sub micron resolution. We show direct writing of Sb2S3 helices with different wire cross section profiles on gold and ITO substrates, as well as functional planar Fresnel zone plates (FZPs) and computer generated hologram metasurfaces (CGHMs) in a single printing step. This freeform DITPS approach thus enables rapid 3D prototyping of high index metasurfaces and opens a route to integrating high-index PCMs into existing photonic architectures and device platforms.

Abstract Optical photothermal infrared (OPTIR) spectroscopy and imaging were combined with fluorescence microscopy to track infection progression. Baculovirus infection in Spodoptera frugiperda (Sf) 9 cells with mCherry as a fluorescence imaging reporter was analyzed 3, 6, 12, and 24 h postinfection (hpi). Cells were sandwiched between two CaF2 windows separated by a thin spacer, forming a sealed aqueous chamber that maintained hydration for 4–6 h, enabling IR spectral acquisition and imaging of living cells throughout. Fluorescence microscopy demonstrated a distinct onset of the mCherry reporter signal beginning 12 hpi. Early infection time points 3 and 6 hpi showed increased protein (amide II, 1545 cm–1) and asymmetric phosphate (1241 cm–1) bands, while 12 hpi, the symmetric phosphate (1087 cm–1) band profoundly reversed, consistent with nucleic acid changes associated with infection progression. The amide II to nucleic acid ratio (S1545/1086), obtained from discrete wavenumber imaging, tracked aggregate infection-associated protein changes (of which mCherry is a late-stage contributor), initially increasing 6 hpi, decreasing 12 hpi, and reaching its maximum value 24 hpi. The fluorescence reporter was absent at early stage infection (3 and 6 hpi), where IR spectroscopy and imaging successfully discriminated infected from uninfected cell populations. Fluorescence imaging validated IR measurements for later infection time points (12 and 24 hpi). Infected cells were classified from negative controls with balanced accuracies up to 90%. Overall, this approach identifies spectral signatures consistent with viral infection, providing a label-free method to discriminate infected populations from controls within their natural cellular environment.

The treatment of hydrophilic silicate glass surfaces with alkoxysilanes to produce hydrophobic surfaces is of great importance for many applications. Achieving high hydrophobicity has traditionally relied on fluorinated silanes, which increasingly need to be replaced by alternatives that are less harmful to human health and the environment. Solutions of 3-aminopropyltriethoxysilane (APTES) at millimolar concentrations in a water/isopropanol mixture represent a promising approach for modifying the surface properties of silicate glass. Owing to the low silane consumption, this strategy is advantageous from both resource-efficiency and environmental perspectives. In this study, siloxane films were formed on glass substrates via dip-coating through a self-organizing process using APTES at different degrees of hydrolysis. The morphology, chemical composition, and vibrational properties of the resulting layers were investigated using atomic force microscopy, contact angle measurements, and various vibrational spectroscopic techniques. The film thickness was determined to be on the order of a few nanometers. Although contact angle measurements indicate that the surfaces remain hydrophilic, the resulting films—functionalized with hydroxyl and amino groups—constitute a promising platform for subsequent modification toward hydrophobic glass surfaces.

Like other carbon nanoparticles, diamond nanoparticles, also known as nanodiamonds (NDs), tend to aggregate when they are dispersed in solution or when they are cast on a substrate. This is mainly due to the versatility of functional groups present on their surface. Previous studies have reported the use of several techniques, including chemical modification, surface active compound usage, and mechanical milling using tiny zirconia beads, for destroying the ND aggregates. Herein, we focus on the deposition of hydrogen-terminated NDs (H-NDs) for use as electron transport layer material in inverted organic solar cells and we investigate different approaches to prevent or to eliminate aggregation during the coating of films of H-NDs, including the reduction of the ND concentration in the dispersions and the blending of H-NDs powder with additives or binders such as styrene-butadiene rubber, carboxymethyl cellulose, a combination of both, fluoride-based polyvinylidene fluoride, and the conjugated polyelectrolyte poly(9,9-bis(3 '-(N, N-dimethyl)-N-ethylammonium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br), in dispersions. The film morphology and more specifically the device's performance and stability were improved in several cases and single nanoparticles of diamonds with small sizes (<20 nm) were observed.

The modification of nucleobases in nucleic acids is a naturally occurring process that can affect various positions of the heteroaromatic ring systems. In addition, by the targeted introduction of an artificial substituent, these molecules can be used as markers for detecting specific regions in biomaterials. In the current study, short single- and double-stranded DNA sequences are designed, and selected nucleobases are chemically modified. In a sequence containing all four nucleobases, a single thymine is modified with a side chain comprising internal and terminal carbon-carbon triple bonds. Following hybridization with the unmodified complementary sequence, the strand is examined with tip-enhanced Raman scattering (TERS) under ambient conditions to identify the modified molecular site on the surface. The characteristic vibrational stretching modes of the alkyne groups do not overlap with those of nucleic acids and are therefore suitable for unambiguous identification. A modelling approach to the DNA structure is used to elucidate the observed band shifts and possible influence of the local environment, and the distance to the TERS probe is discussed.A second approach involves a simplified single-stranded DNA sequence with noncomplementary nucleobases, including methylated cytosine, as a naturally occurring modification. TERS spectra are analyzed for the potential identification of the modified cytosine, despite the overlap of its vibrational modes with those of other nucleobases.The results demonstrate that TERS is highly efficacious in detecting individual modified nucleobases in DNA, enabling these markers to be traced on biomaterials with nanometer precision.

Antimony trisulfide (Sb_2S_3), as an emerging material for integrated photonic devices, has attracted significant attention due to its high index, low loss, and phase-changing property in the optical regime. However, conventional lithography-based fabrication methods involve complex, time-consuming, multistep processes, rendering the photonic application of Sb_2S_3 challenging. Here, we demonstrate that positive-tone fabrication of Sb_2S_3 nanostructures using wet-etch femtosecond laser processing, a straightforward technique for the engraving of micro- and nanoscale structures, can address major fabrication challenges. The patterning mechanism and factors influencing resolution of Sb_2S_3 thin film structures deposited on quartz (transmissive) and gold (reflective) substrates are experimentally investigated and supported by theoretical modelling. Using this approach, the smallest linewidth fabricated is measured at 178 nm. Consequently, multiple test patterns are demonstrated showing versatile functionalities. Functional Fresnel Zone Plates (FZPs) with varying focal length are fabricated and characterized. This study provides a significantly simplified approach for realizing Sb_2S_3 based integrated photonic devices.

Fabricating high-index materials with designed three-dimensional (3D) micro optical elements is a challenging yet exciting area of research. Here, we develop an approach to 3D print high-index nanostructures of antimony trisulfide (Sb 2 S 3 ) using grayscale electron beam lithography (g-EBL). A key advantage of our approach is its simplicity compared to the conventional complex EBL-based metalens fabrication process. The refractive index of Sb 2 S 3 films is precisely determined using a computational genetic algorithm and the transfer matrix method. The Sb 2 S 3 structures show high fidelity and reproducibility, with the refractive index being tunable through thermal treatment. We demonstrate the fabrication and performance of 3D Fresnel Zone Plates (FZPs) and metalenses with the same design specification. Theoretical and experimental evaluation confirmed the diffraction-limited capability of as-fabricated 3D optical elements and indicates that the focusing efficiency of FZPs is higher compared to metalenses. This work advances the application of Sb 2 S 3 in micro- and nanoscale photonics, highlighting its potential for dynamic optical devices with precise control over output properties.

The high thermal sensitivity of upconversion nanoparticles (UCNPs) luminescence at the nanoscale enables precise and rapid temperature detection, advancing nano-thermometry applications in quantum optics, catalytic reactions, and nanophotonics. Here, the phonon-assisted upconversion luminescence with a high thermal sensitivity is achieved by rare-earth doped UCNPs (NaYF4 : Yb3+/Er3+) in vacuum optical tweezers. We found that an essential contribution of phonon-assisted luminescence processes leading to high thermal sensitivity is not only from increasing the absorption cross section of Yb3+ but also from facilitating efficient energy transfer from Yb3+ to Er3+ ions. The increase in thermal sensitivity with the number of phonons involved in the progress of phonon-assisted luminescence can be well described by the temperature-dependent phonon population model. The study reveals how phonon-assisted processes influence thermal sensitivity in UCNPs, contributing to a deeper understanding of nanoscale temperature-dependent luminescence.

Surface-enhanced Raman spectroscopy (SERS) has evolved significantly over fifty years into a powerful analytical technique. This review aims to achieve five main goals. (1) Providing a comprehensive history of SERS's discovery, its experimental and theoretical foundations, its connections to advances in nanoscience and plasmonics, and highlighting collective contributions of key pioneers. (2) Classifying four pivotal phases from the view of innovative methodologies in the fifty-year progression: initial development (mid-1970s to mid-1980s), downturn (mid-1980s to mid-1990s), nano-driven transformation (mid-1990s to mid-2010s), and recent boom (mid-2010s onwards). (3) Illuminating the entire journey and framework of SERS and its family members such as tip-enhanced Raman spectroscopy (TERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and highlighting the trajectory. (4) Emphasizing the importance of innovative methods to overcome developmental bottlenecks, thereby expanding the material, morphology, and molecule generalities to leverage SERS as a versatile technique for broad applications. (5) Extracting the invaluable spirit of groundbreaking discovery and perseverant innovations from the pioneers and trailblazers. These key inspirations include proactively embracing and leveraging emerging scientific technologies, fostering interdisciplinary cooperation to transform the impossible into reality, and persistently searching to break bottlenecks even during low-tide periods, as luck is what happens when preparation meets opportunity.

Controlling the nanoscale organization of photosensitizer–catalyst (PS–CAT) assemblies into high-surface-area superstructures holds great promise for enhancing photochemical energy conversion yet remains a formidable challenge. We report the nanoconfined deposition of supramolecular photoactive architectures solely composed of cobaloxime-based catalytic salts (CAT) and an imidazophenanthroline-containing ruthenium photosensitizer (PS) salt using via scanning electrochemical cell microscopy (SECCM). This nanoconfinement strategy enables the controlled formation of PS–CAT supramolecular structures ranging from nanospots to nanowires with a diameter of approx. 80–100 nm that catalyze light-driven hydrogen evolution in the absence of covalent linkers. The supramolecular nanowires, formed solely by tuning the nanopipette retraction speed from the surface, exhibit markedly enhanced photoactivity and stability compared to deposited nanospots using the same PS − CAT ratio. Correlative time-of-flight secondary ion mass spectrometry (ToF-SIMS) and nano-infrared (nano-IR) imaging, supported by molecular dynamics simulations, revealed distinct molecular changes of the different nanostructures, highlighting the crucial role of PF₆⁻ − the counterion of the PS − in stabilizing the supramolecular framework. The presented approach allows designing an optimum arrangement of PS − CAT freestanding supramolecular architectures for improved stability and activity without the need for scaffolds and bridging ligands.

Drug delivery systems have attracted considerable attention due to their potential to increase the bioavailability of certain drugs and mitigating side effects by enabling targeted drug release. Reversibly core-crosslinked block copolymer micelles providing a hydrophilic and potentially non-immunogenic shell and a hydrophobic core suitable for the uptake of hydrophobic drugs, are frequently considered, owing their high stability against environmental changes and dilution. Ultimately, triggering core decrosslinking enables implementing strategies for targeted drug release, which requests insights into the impact of varying nanomechanical properties on the stability of individual micelles. Here, Atomic Force Microscopy nanoindentation in aqueous media is applied to intact α-allyl-PEG80-b-P(tBGE52-co-FGE12) micelles to quantify changes in their nanomechanical properties induced by dithio-bismaleimidoethane meditated Diels-Alder crosslinking of furfuryl moieties, and sequential decrosslinking by reduction of its disulfide bond by tris(2-carboxyethyl) phosphine. Changes to the Young’s modulus can be entirely reversed by decrosslinking. Crosslinked and decrosslinked micelles maintain their structural integrity even in diluted aqueous media below the critical micelle concentration in contrast to the initially non-crosslinked micelles. Understanding the structure-property relations associated to the observed augmented mechanical stability in native environments is crucial for improving the efficiency of drug encapsulation, and introducing refined temporal and spatially controlled drug release mechanisms.

Long-range dipole-dipole interactions (DDIs) are essential for enabling scalable quantum technologies. However, their practical realization is fundamentally limited by spatial rapid decay and environmental noise. In this study, we propose a plasmon-assisted microcavities platform that integrates a photonic cavity with a plasmonic antenna for enhanced energy transfer between donors and acceptors. Benefiting from the resonating of the acceptors within the microcavity after receiving energy, stable long-range DDIs with an interaction distance of ∼13.6 μm and lasing emission can be achieved at ambient temperature. The results of this study suggest the potential for long-range, efficient DDIs in on-chip quantum systems with potential applications in quantum sensing and energy harvesting.

The pre-selection of virus particles based on size and morphology is a crucial step toward rapid and reliable virus identification. Pre-selecting virus particles based on size and morphology represents a critical step toward rapid and reliable identification, which is particulary important in clinical settings when novel virus variants emerge. Although conventional fluorescence imaging enables visualization of specific viral structures via labeling, it does not allow for reliable differentiation of structurally similar particles. In this study, we present a combined imaging approach that integrates atomic force microscopy (AFM) and double-staining fluorescence microscopy to identify SARS-CoV-2 as a model RNA-virus from other sample constituents. Initially, topographical imaging via AFM enables high-resolution visualization of individual virus particles, providing detailed information about particle morphology and height. Subsequently, dual fluorescence labeling of the RNA-containing core and the spike protein-rich surface allows for specific identification of intact viral structures. Correlation of fluorescence signals with AFM-derived height maps offers a comprehensive view of the particles’ morphological and molecular characteristics. This triple-correlation strategy enables the identification of intact SARS-CoV-2 particles and their clear distinction from similarly sized hollow particles, viral fragments, and staining artifacts. The height range of confirmed SARS-CoV-2 particles under the applied conditions was determined to be 60–100 nm. The presented correlative imaging approach is broadly applicable to other RNA viruses, offering a versatile tool for high-specificity virus detection.

Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates with engineered defects have garnered significant research interest due to their comparable enhancement performance to traditional noble metal-based substrates. Among various defect engineering approaches, vacancy creation and elemental doping have emerged as two predominant strategies for optimizing semiconductor-based SERS substrates. Nevertheless, the mechanism and interplay between these two defect types in augmenting SERS enhancement have remained poorly elucidated in previous research. Herein, a type of dual-defect synergistic boosted highly sensitive SERS substrate based on nanostructured CrxTiyO2 with a rational design of Ti vacancies and Cr doping is proposed where Ti vacancies induce electron spin polarization, while Cr doping generates a midgap doping level. The optimal Crx3TiyO2 substrate achieved remarkable detectability of 10-11 M (mol/L) and 10-8 M for methylene blue (MB, 1.86 eV of energy gap) and 4-mercaptobenzoic acid (4-MBA, 4.63 eV of energy gap), respectively, alongside excellent reproducibility and stability. It is proposed that the dual defect Crx3TiyO2 synergistically optimizes the band structure and enhances carrier separation efficiency, thus effectively promoting the photoinduced charge transfer process between the substrate and molecules enabling superior signal amplification, which is confirmed by the density of states using DFT calculations. More importantly, this work offers a novel pathway for designing high-performance semiconductor-based SERS substrates through regulating the multidefect synergy.

Self‐assembly of block copolymers in solution provides access to different nanostructures depending on block composition and processing conditions. However, more complex hierarchical nanostructures as found in nature remain challenging to achieve. In this study, the influence of a β‐sheet forming tetrapeptide sequence (GFFG) is investigated at the interface of an amphiphilic block copolymer based on poly(butyl acrylate) (PBA) and poly(ethylene oxide) (PEO). Using atomic force microscopy (AFM) and tip‐enhanced Raman spectroscopy (TERS), nanoscale insights are provided into the structural organisation and mechanical properties of these hybrid materials. Both the tetrapeptide‐containing block copolymer and a control block copolymer without the peptide linker form wormlike micelles in water. However, the incorporation of the peptide linker alters the micelle morphology by increasing the contour length sixfold compared to the control polymer and by altering the mechanical properties of the wormlike micelles. TERS analysis confirms the presence of ordered β ‐sheet structures at the hydrophilic/hydrophobic interface, which increase the bending stiffness of the micelles. The introduction of additional secondary interactions, such as those induced by the peptide linker, therefore appears as an interesting lever to manipulate the structure formation and mechanical properties block copolymer micelles, opening up interesting design strategies for tailor‐made hierarchically structured nanomaterials.

Drug-delivery systems have attracted considerable attention due to their potential to increase the bioavailability of certain drugs and mitigate side effects by enabling targeted drug release. Reversibly core-cross-linked block copolymer micelles providing a hydrophilic and potentially nonimmunogenic shell and a hydrophobic core suitable for the uptake of hydrophobic drugs are frequently considered because of their high stability against environmental changes and dilution. Ultimately, triggering core-de-cross-linking enables the implementation of strategies for targeted drug release, which requests insights into the impact of varying nanomechanical properties on the stability of individual micelles. Here, atomic force microscopy nanoindentation in aqueous media is applied to intact α-allyl-PEG80-b-P(tBGE52-co-FGE12) micelles to quantify changes in their nanomechanical properties induced by dithiobismaleimidoethane (DTME)-mediated Diels-Alder cross-linking of furfuryl moieties and sequential de-cross-linking by reduction of its disulfide bond by tris(2-carboxyethyl)phosphine. As a result of crosslinking by DTME, the apparent Young's modulus of the micelles roughly doubles to 1.18 GPa. Changes to the Young's modulus can be largely reversed by de-cross-linking. Cross-linked and de-cross-linked micelles maintain their structural integrity even in diluted aqueous media below the critical micelle concentration, in contrast to the micelles prior to crosslinking. Understanding the structure-property relationships associated with the observed augmented mechanical stability in native environments is crucial for improving the efficiency of drug encapsulation and introducing refined temporal and spatially controlled drug-release mechanisms.