Shaping ceramic materials at the nanoscale in 3D is a phenomenal engineering challenge, that can offer new opportunities in a number of industrial applications, including metamaterials, nano‐electromechanical systems, photonic crystals, and damage‐tolerant lightweight materials. 3D fabrication of sub‐micrometer ceramic structures can be performed by two‐photon laser writing of a preceramic polymer. However, polymer conversion to a fully ceramic material has proven so far unfeasible, due to lack of suitable precursors, printing complexity, and high shrinkage during ceramic conversion. Here, it is shown that this goal can be achieved through an appropriate engineering of both the material and the printing process, enabling the fabrication of preceramic 3D shapes and their transformation into dense and crack‐free SiOC ceramic components with highly complex, 3D sub‐micrometer architectures. This method allows for the manufacturing of components with any 3D specific geometry with fine details down to 450 nm, rapidly printing structures up to 100 µm in height that can be converted into ceramic objects possessing sub‐micrometer features, offering unprecedented opportunities in different application fields.

Highly doped wide band gap metal oxide nanocrystals have recently been proposed as building blocks for applications as transparent electrodes, electrochromics, plasmonics, and optoelectronics in general. Here we demonstrate the application of gallium-doped zinc oxide (GZO) nanocrystals as novel plasmonic and chemiresistive sensors for the detection of hazardous gases including hydrogen (H) and nitrogen dioxide (NO). GZO nanocrystals with a tunable surface plasmon resonance in the near-infrared are obtained using a colloidal heat-up synthesis. Thanks to the strong sensitivity of the plasmon resonances to chemical and electrical changes occurring at the surface of the nanocrystals, such optical features can be used to detect the presence of toxic gases. By monitoring the changes in the dopant-induced plasmon resonance in the near-infrared, we demonstrate that GZO thin films prepared depositing an assembly of highly doped GZO colloids are able to optically detect both oxidizing and reducing gases at mild (<100 °C) operating temperatures. Combined optical and electrical measurements show that trivalent dopants within ZnO nanocrystals enhance the gas sensing response compared to undoped ZnO. Moreover, improved sub-ppm of NO gas sensitivity is achieved by activating the sensors response through combined purple-blue (λ = 430 nm) light irradiation and mild heating at 75 °C. In addition, these thin films based on degenerately doped semiconductors are highly transparent in the visible range, enabling the fabrication of "invisible" gas sensors. The use of highly doped semiconductive nanocrystals for both IR plasmonic and chemiresistive sensors represent a marked advancement toward the development of highly sensitive and selective devices.

Nowadays nanophotonics aims towards low-cost, chip-scale devices that can tailor electromagnetic properties, one of which is the control of the circular polarization at the nanoscale, important for novel optical devices. Here we show that nanosphere lithography, combined with tilted metal deposition, can provide novel metasurfaces with chiral properties.We apply the photo-acoustic technique to characterize the circular dichroism at 633 nm of polystyrene nanospheres covered by three different metals: Au-and Cr-covered samples show extrinsic chiral behavior, while the Ag-covered sample shows circular dichroism at normal incidence, characteristic for intrinsic chirality. As the experimental data are in good agreement with numerical predictions, we believe that such design can be optimized to get efficient circularly polarized detection at the nanoscale. THE MANUSCRIPTChirality, a lack of the mirror symmetry of an object 1 , is an important property of some of the building blocks of our world: many molecules, amino-acids, DNA, sugars, drugs are chiral. Two mirror images of the same object differently interact with circularly polarized light of the opposite handedness, while having other measurable properties equal. In particular, chirality can affect the absorption and/or phase velocity of circularly polarized light, therefore it is possible to measure a difference in absorption directly related to the molecules' chirality. This measurement is known as Circular Dichroism (CD). At the nanoscale, when the nanostructures are comparable or smaller than the light wavelength, and organized periodically, they form a metasurface; generally, if the symmetry of the metasurface is broken, a chiral behavior is expected 2 . Chiral metasurfaces can manipulate electromagnetic fields and enhance the interaction with chiral molecules, important for chiral sensing 3 . On the other hand, they can control the polarization state of the optical field, or emit circularly polarized light, thus leading to applications in optical and quantum communications 4 . Geometric features of intrinsically chiral metasurfaces (the nanostructure in the unit cell is usually helix or gammadion-like) can be complicated to fabricate and implement at the nanoscale. This problem can be solved by a proper experimental set-up following the rule that the impinging light wavevector, the average surface normal, and the sample direction must be nonplanar. Such chiral behavior is called extrinsic chirality as it is governed by both experimental set-up and the a) Electronic mail:

The control of the spontaneous emission properties of quantum emitters with limited losses by near-field coupling with plasmons-supporting nanostructures is one of the keys for next-generation high-efficiency and high-coherence plasmonic devices. In the present work, gold nanohole arrays are demonstrated to be an effective plasmonic system for controlling radiative rate and quantum efficiency of the 1540 nm emission of Er3+ ions embedded in silica. Finite element method electrodynamic simulations were used to describe the interaction between dipolar Er3+ emitters and the nanohole arrays. The results are in agreement with those of photoluminescence measurements performed in different coupling configurations. Particularly, we demonstrated that owing to the combination of strong emission enhancement and low level of ohmic losses in the metal, nanohole arrays are able to enhance the far-field photon yield up to 74%. This in turn is related to an extremely high far-field quantum efficiency: more than 90% of the emitted photons reach the far-field for the most efficient configurations investigated in which the extraordinary optical transmission peak of the nanohole array is matched with the Er3+ emission.

Silver nanostructures are widely employed for Surface Enhanced Raman Scattering (SERS) characterizations owing to their excellent properties of field confinement in plasmonic resonances. However, the strong tendency to oxidation at room temperature of these substrates may represent a major limitation to their performances. In the present work, we investigated in detail the effects of oxidation on the SERS response of a peculiar kind of Ag nanostructured substrates, i.e., bi-dimensional ordered arrangements of Ag nanoprisms synthesized by nanosphere lithography. Particularly, wavelength-scanned SERS measurements were performed on Ag nanoprism arrays with a different level of oxidation to determine the SERS enhancement curves as a function of the excitation wavelength around the dipolar plasmonic resonance of the arrays. The experimental results were compared with those obtained by finite elements method simulations. With this approach, we were able to decouple the effects of spectral shift and decrease of the maximum value of the SERS enhancement observed for the different oxidation conditions. The results could be interpreted taking into account the inhomogeneities of the electromagnetic field distribution around the Ag nanostructures, as demonstrated by the simulations

Implantable devices need specific tailored surface morphologies and chemistries to interact with the living systems or to actively induce a biological response also by the release of drugs or proteins. These customized requirements foster technologies that can be implemented in additive manufacturing systems. Here, we present a novel approach based on spraying processes that allow to control separately topographic features in the submicron range (∼60 nm to 2 μm), ammine or carboxylic chemistry, and fluorophore release even on temperature-sensitive biodegradable polymers such as polycaprolactone (PCL). We developed a two-steps process with a first deposition of 220 nm silica and poly­(lactic-co-glycolide) (PLGA) fluorescent nanoparticles by aerosol followed by the deposition of a fixing layer by an atmospheric pressure plasma jet (APPJ). The nanoparticles can be used to create the nanoroughness and to include active molecule release, while the capping layer ensures stability and the chemical functionalities. The process is enabled by a novel APPJ which allows deposition rates of 10–20 nm·s–1 at temperatures lower than 50 °C using argon as the process gas. This approach was assessed on titanium alloys for dental implants and on PCL films. The surfaces were characterized by Fourier transform infrared, atomic force microscopy, and scanning electron microscopy (SEM). Titanium alloys were tested with the preosteoblast murine cells line, while the PCL film was tested with fibroblasts. Cell behavior was evaluated by viability and adhesion assays, protein adsorption, cell proliferation, focal adhesion formation, and SEM. The release of a fluorophore molecule was assessed in the cell growing media, simulating a drug release. Osteoblast adhesion on the plasma-treated materials increased by 20% with respect to commercial titanium alloy implants. Fibroblast adhesion increased by a 100% compared to smooth PCL substrates. The release of the fluorophore by the dissolution of the PLGA nanoparticles was verified, and the integrity of the encapsulated drug model was confirmed.

The nonlinear absorption properties of bidimensional arrays of Au-Ag bilayered nanoprisms have been investigated by z-scan measurements as a function of the bimetallic nanoprism composition. A tunable ps laser system was used to excite the ultrafast, electronic nonlinear response matching the laser wavelength with the quadrupolar surface plasmon resonances, in the visible range, of each nanoprism array. Due to the strong electromagnetic field confinement effects at the nanoprism tips, demonstrated by finite element method simulations, these nanosystems proved to have enhanced nonlinear optical properties. Moreover, a tunable changeover from reverse saturable absorption (RSA) to saturable absorption (SA) can be obtained by properly controlling the bimetallic composition of the nanoprisms, without modifying the overall morphology of the nanosystems. This capability makes these nanosystems extremely interesting for the realization of solid-state nanophotonic devices with enhanced ultrafast nonlinear optical properties.

The occurrence of a very efficient non-resonant energy transfer process forming ultrasmall Au-Ag nanoalloy clusters and Er(3+) ions is investigated in silica. The enhancement of the room temperature Er(3+) emission efficiency by an order of magnitude is achieved by coupling rare-earth ions to molecule-like (Au(x)Ag(1-x))N alloy nanoclusters with N = 10-15 atoms and x = 0.6 obtained by optimized sequential ion implantation on Er-implanted silica. For comparison, AuN nanoclusters obtained by the same approach and with the same size and numerical density showed an enhancement by only a factor of 2 with respect to pure Er emission, demonstrating the beneficial effect of using nanoalloyed clusters. The temperature evolution of the energy transfer process is investigated by photoluminescence and exhibits a maximum efficiency at about 600 °C, where the clusters reach the optimal size and the silica matrix completely recovers the implantation damage. The nanoalloy cluster composition and size have been studied by EXAFS analysis, which indicated a stronger Ag-O interaction with respect to the Au-O one and a preferential location of the Ag atoms at the nanoalloy cluster surface.