Chemisches Abscheiden von NiP‐Nanokomposit‐schichten

Electroless deposition of NiP nanocomposite coatings The electrolytic and electroless deposition of nickel‐based nanocomposites gains increasing interest in worldwide science. Due to the high specific surface of nanoscaled reinforcements, major properties are determined by surface properties. On the other hand, nanoscaled particles offer technological advantages in the production of very thin coatings, e.g. in microsystems technology. But in particular the process parameters in the deposition of electroless microscaled dispersion coatings are not transferable to nanoscaled ones. This article deals with the development and modification of processes for stable electroless deposition of nanoscaled NiP dispersion coatings and their effect on selected coating properties (hardness, photocatalytic activity). The objective to obtain homogeneous and non‐agglomerated incorporation of the particles has been achieved to a large extent. The effect of ultrasound on the incorporation and desagglomeration is discussed.     

Sub‐10‐nm Pd Nanosheets with Renal Clearance for Efficient Near‐Infrared Photothermal Cancer Therapy

Efficient renal clearance is of fundamentally important property of nanoparticles for their in vivo biomedical applications. In this work, we report the successful synthesis of ultra‐small Pd nanosheets (SPNS) with an average diameter of 4.4 nm and their application in photothermal cancer therapy using a near infrared laser. The ultra‐small Pd nanosheets have strong optical absorption in the NIR region and high photothermal conversion efficiency (52.0%) at 808 nm. After being surface‐functionalized with reduced glutathione (GSH), the SPNS‐GSH was administered to mice to investigate the biodistribution, photothermal efficacy and tumor ablation in vivo. The in vivo photothermal therapy studies clearly demonstrate that surface modification with GSH allows the nanosheets to exhibit prolonged blood circulation and thus high accumulation in tumors. Upon 808 nm NIR irradiation, the tumors can be completely ablated. More importantly, with the size below the renal filtration limit (<10 nm), the GSHylated Pd nanosheets can be nicely cleared from body through the renal excretion route and into urine. Together with the high efficacy of NIR photothermal therapy, the unique renal clearance properties make the ultra‐small Pd nanosheets promising for practical use in photothermal cancer therapy.     

Laser treatment of optical Nb2O5‐ and HfO2‐films

Optical thin films have to fulfil high quality requirements, which can be achieved for example by reactive low voltage ion plating (RLVIP). But especially for applications in precision optics, additional treatments are necessary to reduce residual optical absorption and compressive stress arising in the coatings, and to enhance the stability of the coatings – specifically for laser applications. In practice, post deposition heat treatment and backside coatings are mostly used to overcome these problems. In order to provide alternative methods to handle the disadvantages of the RLVIP‐process, the idea was to replace the mentioned steps by a laser treatment. This means that a laser beam is directed onto the sample after deposition or even during the coating process. In this study, the influence of a high power CO²‐laser beam on thin Nb²O⁵‐ and HfO²‐films was investigated. The effects on the refractive index and the film thickness are presented for different energy densities of a TEA‐CO²‐laser beam (10.59μm). For Nb²O⁵‐films a thickness increase up to 12.2nm (6.4 %) and a refractive index decrease of 0.074 (3.1 %) were found. In case of HfO² the values were 2.3nm (1.2 %) in thickness and 0.007 (0.3 %) in refractive index. From the observed changes also distinct impacts on the film stress can be expected. One intention of this research was also to call attention to an alternative technique for enhancement of thin film properties.     

Mitochondria‐Targeting Magnetic Composite Nanoparticles for Enhanced Phototherapy of Cancer

Photothermal therapy (PTT) and photodynamic therapy (PDT) are promising cancer treatment modalities in current days while the high laser power density demand and low tumor accumulation are key obstacles that have greatly restricted their development. Here, magnetic composite nanoparticles for dual‐modal PTT and PDT which have realized enhanced cancer therapeutic effect by mitochondria‐targeting are reported. Integrating PTT agent and photosensitizer together, the composite nanoparticles are able to generate heat and reactive oxygen species (ROS) simultaneously upon near infrared (NIR) laser irradiation. After surface modification of targeting ligands, the composite nanoparticles can be selectively delivered to the mitochondria, which amplify the cancer cell apoptosis induced by hyperthermia and the cytotoxic ROS. In this way, better photo therapeutic effects and much higher cytotoxicity are achieved by utilizing the composite nanoparticles than that treated with the same nanoparticles missing mitochondrial targeting unit at a low laser power density. Guided by NIR fluorescence imaging and magnetic resonance imaging, then these results are confirmed in a humanized orthotropic lung cancer model. The composite nanoparticles demonstrate high tumor accumulation and excellent tumor regression with minimal side effect upon NIR laser exposure. Therefore, the mitochondria‐targeting composite nanoparticles are expected to be an effective phototherapeutic platform in oncotherapy.     

Two‐Photon Up‐Conversion Photoluminescence Realized through Spatially Extended Gap States in Quasi‐2D Perovskite Films

A new approach to generate a two‐photon up‐conversion photoluminescence (PL) by directly exciting the gap states with continuous‐wave (CW) infrared photoexcitation in solution‐processing quasi‐2D perovskite films [(PEA)₂(MA)₄Pb₅Br₁₆ with n = 5] is reported. Specifically, a visible PL peaked at 520 nm is observed with the quadratic power dependence by exciting the gap states with CW 980 nm laser excitation, indicating a two‐photon up‐conversion PL occurring in quasi‐2D perovskite films. Decreasing the gap states by reducing the n value leads to a dramatic decrease in the two‐photon up‐conversion PL signal. This confirms that the gap states are indeed responsible for generating the two‐photon up‐conversion PL in quasi‐2D perovskites. Furthermore, mechanical scratching indicates that the different‐n‐value nanoplates are essentially uniformly formed in the quasi‐2D perovskite films toward generating multi‐photon up‐conversion light emission. More importantly, the two‐photon up‐conversion PL is found to be sensitive to an external magnetic field, indicating that the gap states are essentially formed as spatially extended states ready for multi‐photon excitation. Polarization‐dependent up‐conversion PL studies reveal that the gap states experience the orbit–orbit interaction through Coulomb polarization to form spatially extended states toward developing multi‐photon up‐conversion light emission in quasi‐2D perovskites.     

An Ultrabroadband Mid‐Infrared Pulsed Optical Switch Employing Solution‐Processed Bismuth Oxyselenide

Pulsed lasers operating in the mid‐infrared (3–25 µm) are increasingly becoming the light source of choice for a wide range of industrial and scientific applications such as spectroscopy, biomedical research, sensing, imaging, and communication. Up to now, one of the factors limiting the mid‐infrared pulsed lasers is the lack of optical switch with a capability of pulse generation, especially for those with wideband response. Here, a semiconductor material of bismuth oxyselenide (Bi₂O₂Se) with a facile processibility, constituting an ultrabroadband saturable absorber for the mid‐infrared (actually from the near‐infrared to mid‐infrared: 0.8–5.0 µm) is exhibited. Significantly, it is found that the optical response is associated with a strong nonlinear character, showing picosecond response time and response amplitude up to ≈330.1% at 5.0 µm. Combined with facile processibility and low cost, these solution‐processed Bi₂O₂Se materials may offer a scalable and printable mid‐infrared optical switch to open up the long‐sought parameter space which is crucial for the exploitation of compact and high‐performance mid‐infrared pulsed laser sources.     

Sensitive and Stable Tin–Lead Hybrid Perovskite Photodetectors Enabled by Double‐Sided Surface Passivation for Infrared Upconversion Detection

Tin(Sn)‐based perovskite is currently considered one of the most promising materials due to extending the absorption spectrum and reducing the use of lead (Pb). However, Sn²⁺ is easily oxidized to Sn⁴⁺ in atmosphere, causing more defects and degradation of perovskite materials. Herein, double‐sided interface engineering is proposed, that is, Sn‐Pb perovskite films are sandwiched between the phenethylammonium iodide (PEAI) in both the bottom and top sides. The larger organic cations of PEA+ are arranged into a perovskite surface lattice to form a 2D capping layer, which can effectively prevent the water and oxygen to destroy bulk perovskite. Meanwhile, the PEA+ can also passivate defects of iodide anions at the bottom of perovskite films, which is always present but rarely considered previously. Compared to one sided passivation, Sn‐Pb hybrid perovskite photodetectors contribute a significant enhancement of performance and stability, yielding a broadband response of 300–1050 nm, a low dark current density of 1.25 × 10^–3 mA cm^–2 at –0.1 V, fast response speed of 35 ns, and stability beyond 240 h. Furthermore, the Sn‐Pb broadband photodetectors are integrated in an infrared up‐conversion system, converting near‐infrared light into visible light. It is believed that a double‐sided passivation method can provide new strategies to achieving high‐performance perovskite photodetectors.     

Mixed Lead–Tin Halide Perovskites for Efficient and Wavelength‐Tunable Near‐Infrared Light‐Emitting Diodes

Near‐infrared (NIR) light‐emitting diodes (LEDs), with emission wavelengths between 800 and 950 nm, are useful for various applications, e.g., night‐vision devices, optical communication, and medical treatments. Yet, devices using thin film materials like organic semiconductors and lead based colloidal quantum dots face certain fundamental challenges that limit the improvement of external quantum efficiency (EQE), making the search of alternative NIR emitters important for the community. In this work, efficient NIR LEDs with tunable emission from 850 to 950 nm, using lead–tin (Pb‐Sn) halide perovskite as emitters are demonstrated. The best performing device exhibits an EQE of 5.0% with a peak emission wavelength of 917 nm, a turn‐on voltage of 1.65 V, and a radiance of 2.7 W Sr^?1 m^?2 when driven at 4.5 V. The emission spectra of mixed Pb‐Sn perovskites are tuned either by changing the Pb:Sn ratio or by incorporating bromide, and notably exhibit no phase separation during device operation. The work demonstrates that mixed Pb‐Sn perovskites are promising next generation NIR emitters.     

Laserakustik für Schicht‐ und Oberflächenprüfung

Laser‐acoustics for Testing Coatings and Material Surfaces A laser‐acoustic test method is presented, which can be used for the non‐destructive characterization of coatings and material surfaces. The method measures the dispersion of surface acoustic waves induced by short laser pulses. The technique is based on the fact that the propagation velocity of the wave depends on the frequency in coated and surface modified materials. Measuring the dispersion of the surface acoustic wave enables to determine important properties of the material surface. Three examples demonstrate that the laser‐acoustic method can solve very different problems of surface engineering. The wear resistance of diamond‐like carbon film with a thickness of few nano‐meters was evaluated. The elastic modulus of thermally sprayed coatings which are typically some hundred micro‐meters thick was measured, which allows to conclude on the defect structure of the coatings. The depth of sub‐surface damage layers in semi‐conductor materials was determined, which are created when the wafer is sliced from the ingot.     

Single Pixel Black Phosphorus Photodetector for Near‐Infrared Imaging

Infrared imaging systems have wide range of military or civil applications and 2D nanomaterials have recently emerged as potential sensing materials that may outperform conventional ones such as HgCdTe, InGaAs, and InSb. As an example, 2D black phosphorus (BP) thin film has a thickness‐dependent direct bandgap with low shot noise and noncryogenic operation for visible to mid‐infrared photodetection. In this paper, the use of a single‐pixel photodetector made with few‐layer BP thin film for near‐infrared imaging applications is demonstrated. The imaging is achieved by combining the photodetector with a digital micromirror device to encode and subsequently reconstruct the image based on compressive sensing algorithm. Stationary images of a near‐infrared laser spot (λ = 830 nm) with up to 64 × 64 pixels are captured using this single‐pixel BP camera with 2000 times of measurements, which is only half of the total number of pixels. The imaging platform demonstrated in this work circumvents the grand challenges of scalable BP material growth for photodetector array fabrication and shows the efficacy of utilizing the outstanding performance of BP photodetector for future high‐speed infrared camera applications.     

Inside Front Cover: Experimental Evidence for Superprism Effects in Three‐Dimensional Polymer Photonic Crystals (Adv. Mater. 2/2006)

The inside cover illustrates the highly dispersive propagation of light in a three‐dimensional polymer photonic crystal. White light is coupled into a woodpile structure and split into its wavelength components due to the frequency‐dependent dispersion properties of the structure. This superprism effect is orders of magnitudes higher than in a conventional glass prism and is caused by the strong anisotropy of the dispersion surface at frequencies slightly above the photonic bandgap. In work reported on p. 221, Serbin and Gu fabricated these woodpile structures operating in the near‐infrared wavelength range by means of two‐photon polymerization and give theoretical and experimental evidence for the superprism effect in these low‐index photonic‐crystal structures.     

Investigation of atomization concepts for large‐scale flame spray pyrolysis (FSP)

Flame spray pyrolysis (FSP) is a versatile process for the production of inorganic nanoparticles featuring the advantage that the reagents are directly dissolved in the liquid fuel that is atomized to form the burning flame. A majority of previous studies on flame spray pyrolysis is focused on the formation and growth processes of the nanoparticles but neglect the preceding step of precursor atomization and spray formation. In this work an atomization concept for large‐scale nanoparticle production by flame spray pyrolysis is presented. A pressure swirl nozzle is applied for creating a liquid hollow cone, and in a second step, different dispersion gas nozzles are utilized to enhance the atomization of the liquid phase and to influence the spray cone formation and geometry. The relevant parameters influencing the atomization process (dispersion gas feed rate, liquid feed rate) are investigated (for air, water) in non‐burning (cold) spray conditions in order to access the utilization of the different atomizer concepts for the flame spray pyrolysis‐process. Measurements are conducted by applying high speed camera imaging (HSC), particle image velocimetry (PIV) and laser diffraction spectroscopy (LDS). Computational fluid dynamics (CFD) revealed further insight into the gas entrainment and the trajectory of droplets within the spray. Results show that the liquid volume flow rate (and thus the productivity of the process) may be increased significantly while still maintaining an appropriate droplet size compared to the conventional atomization process conditions in flame spray pyrolysis reactors.     

Ramanspektroskopische Charakterisierung von ultra‐dünnen Kohlenstoff‐Schutzschichten für die Magnetspeichertechnologie

Raman‐spectroscopy is a standard tool for structural characterization of ultra‐thin (<10 nm) amorphous carbon films which are used as protective overcoats in the magnetic storage industry. It provides powerful information on the bonding structure of the films. The Raman‐spectra of amorphous carbons are dominated by the D‐ and G‐bands at around 1350 cm^‐1 – 1600 cm^‐1 whose position and intensity are used for interpreting the carbon bonding. Several carbon films have been investigated using green (λ = 514.5 nm) and ultraviolet (λ = 244 nm) laser‐light. The dispersion of the G‐peak is the most crucial of parameters to describe the internal structure of the films since it distinguishes between graphite‐ and diamond‐like carbon. A high G‐peak‐dispersion corresponds to a high sp³‐fraction. These information are not available by single wavelength investigations due to the so called hysteresis effect causing the Raman‐spectra of different samples accidentally to look similar albeit having a different internal structure. The dual‐method we are here introducing avoids the hysteresis effect and provides good estimations on the sp³‐content and the mass density of different carbon systems. Furthermore, UV‐Raman analysis leads to quantification of the nitrogen content of nitrogen‐doped carbon layers by using the relative intensity of the 2200 cm^‐1 band in the UV‐spectrum. The great advantage of ramanspectroscopic investigations is its celerity. Acquisition times are seldom higher than 1.5 min. Additionally, Raman‐spectroscopy is a non‐destructive tool which leaves the investigated samples undamaged for further processing and makes it an attractive method for insitu‐analysis in the magnetic storage industry.     

Fabrication of Micropatterned Self‐Oscillating Polymer Brush for Direction Control of Chemical Waves

The propagation control of chemical waves via a pentagonal patterned structure in a self‐oscillating polymer brush composed of N‐isopropylacrylamide and a metal catalyst for the Belousov–Zhabotinsky (BZ) reaction is reported. The patterned self‐oscillating polymer brush is prepared by combining surface‐initiated atom transfer radical polymerization and maskless photolithography. Surface modification is confirmed by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, 3D measuring laser microscopy, and fluorescence microscopy. The polymer brush patterns are fabricated with gaps between the pentagonal regions, and investigations on the effect of the gap distance on the BZ reaction reveal that at the appropriate distance, chemical waves propagate across the array from the plane to the corner between the patterns. Unidirectional control is achieved not only in the 1D array, but also in a 2D curved array. This patterned self‐oscillating polymer brush is a novel and advantageous approach for creating an autonomous dynamic soft interface.     

Light‐Triggered Biomimetic Nanoerythrocyte for Tumor‐Targeted Lung Metastatic Combination Therapy of Malignant Melanoma

Red blood cell (RBC) membrane‐cloaked nanoparticles, reserving the intact cell membrane structure and membrane protein, can gain excellent cell‐specific functions such as long blood circulation and immune escape, providing a promising therapy nanoplatform for drug delivery. Herein, a novel RBC membrane biomimetic combination therapeutic system with tumor targeting ability is constructed by embedding bovine serum albumin (BSA) encapsulated with 1,2‐diaminocyclohexane‐platinum (II) (DACHPt) and indocyanine green (ICG) in the targeting peptide‐modified erythrocyte membrane (R‐RBC@BPtI) for enhancing tumor internalization and synergetic chemophototherapy. R‐RBC@BPtI displays excellent stability and high encapsulation efficiency with multiple cores enveloped in the membrane. Benefited from the stealth functionality and targeting modification of erythrocyte membranes, R‐RBC@BPtI can significantly promote tumor targeting and cellular uptake. Under the near‐infrared laser stimuli, R‐RBC@BPtI presents remarkable instability by singlet oxygen and heat‐mediated cleavage so as to trigger effective drug release, thereby achieving deep penetration and accumulation of DACHPt and ROS in the tumor site. Consequently, R‐RBC@BPtI with tumor‐specific targeting ability accomplishes remarkable ablation of tumors and suppressed lung metastasis in vivo by photothermal and chemotherapy combined ablation under phototriggering. This research provides a novel strategy of targeted biomimetic nanoplatforms for combined cancer chemotherapy–phototherapy.     

Parallel Preparation of Densely Packed Arrays of 150‐nm Gold‐Nanocrescent Resonators in Three Dimensions

Metallic nanostructures show interesting optical properties due to their plasmonic resonances, and when arranged in three‐dimensional (3D) arrays hold promise for optical metamaterials with negative refractive index. Towards this goal a simple, cheap, and parallel method to fabricate large‐area, ordered arrays of 150‐nm gold nanocrescents supporting plasmonic resonances in the near‐infrared spectral range is demonstrated. In this process hexagonally ordered monolayers of monodisperse colloids are prepared by a simple floating technique, and subsequently the individual particles are size‐reduced in a plasma process and used as a shadow mask with the initial lattice spacing. The resulting two‐dimensional array of plasmonic resonators is coated with a transparent silica layer, which serves as a support for a second layer prepared by the identical process. The mutual orientation of the nanostructures between the individual layers can be freely adjusted, which determines the polarization‐dependent absorption of the array and opens the possibility to introduce chirality in this type of 3D metamaterial. The iteration of this simple and efficient methodology yields 3D arrays with optical features as sharp as those of the individual nanocrescents, and shows strong potential for large‐scale production of high‐quality optical metamaterials.     

Effect of Laser Shock Peening on the Microstructures and Properties of Oxide‐Dispersion‐Strengthened Austenitic Steels

Oxide‐dispersion‐strengthened (ODS) austenitic steels are promising materials for next‐generation fossil and nuclear energy systems. In this study, laser shock peening (LSP) has been applied to ODS 304 austenitic steels, during which a high density of dislocations, stacking faults, and deformation twins are generated in the near surface of the material due to the interaction of laser‐driven shock waves and the austenitic steel matrix. The dispersion particles impede the propagation of dislocations. The compressive residual stress generated by LSP increases with successive LSP scans and decreases along the depth, with a maximum value of ?369 MPa. The hardness on the surface can be improved by 12% using LSP. In situ transmission electron microscopy (TEM) irradiation studies reveal that dislocations and incoherent twin boundaries induced by LSP serve as effective sinks to annihilate irradiation defects. These findings suggest that LSP can improve the mechanical properties and irradiation resistance of ODS austenitic steels in nuclear reactor environments.

     

Single‐Photomolecular Nanotheranostics for Synergetic Near‐Infrared Fluorescence and Photoacoustic Imaging‐Guided Highly Effective Photothermal Ablation

Multi‐modality imaging‐guided cancer therapy is considered as a powerful theranostic platform enabling simultaneous precise diagnosis and treatment of cancer. However, recently reported multifunctional systems with multiple components and sophisticate structures remain major obstacles for further clinical translation. In this work, a single‐photomolecular theranostic nanoplatform is fabricated via a facile nanoprecipitation strategy. By encapsulating a semiconductor oligomer (IT‐S) into an amphiphilic lipid, water‐dispersible IT‐S nanoparticles (IT‐S NPs) are prepared. The obtained IT‐S NPs have a very simple construction and possess ultra‐stable near‐infrared (NIR) fluorescence (FL)/photoacoustic (PA) dual‐modal imaging and high photothermal conversion efficiency of 72.3%. Accurate spatiotemporal distribution profiles of IT‐S NPs are successfully visualized by NIR FL/PA dual‐modal imaging. With the comprehensive in vivo imaging information provided by IT‐S NPs, tumor photothermal ablation is readily realized under precise manipulation of laser irradiation, which greatly improves the therapeutic efficacy without any obvious side effects. Therefore, the IT‐S NPs allow high tumor therapeutic efficacy under the precise guidance of FL/PA imaging techniques and thus hold great potential as an effective theranostic platform for future clinical applications.     

Controlled,Low‐Temperature Nanogap Propagation in Graphene Using Femtosecond Laser Patterning

Graphene nanogap systems are promising research tools for molecular electronics, memories, and nanodevices. Here, a way to control the propagation of nanogaps in monolayer graphene during electroburning is demonstrated. A tightly focused femtosecond laser beam is used to induce defects in graphene according to selected patterns. It is shown that, contrary to the pristine graphene devices where nanogap position and shape are uncontrolled, the nanogaps in prepatterned devices propagate along the defect line created by the femtosecond laser. Using passive voltage contrast combined with atomic force microscopy, the reproducibility of the process with a 92% success rate over 26 devices is confirmed. Coupling in situ infrared thermography and finite element analysis yields a real‐time estimation of the device temperature during electrical loading. The controlled nanogap formation occurs well below 50 °C when the defect density is high enough. In the perspective of graphene‐based circuit fabrication, the availability of a cold electroburning process is critical to preserve the full circuit from thermal damage.     

Mesoporous‐Silica‐Coated Up‐Conversion Fluorescent Nanoparticles for Photodynamic Therapy

Near‐infrared (NIR)‐to‐visible up‐conversion fluorescent nanoparticles have potential to be used for photodynamic therapy (PDT) in deep tissue because NIR light can penetrate thick tissue due to weak absorption in the optical window. Here a uniform layer of mesoporous silica is coated onto NaYF₄ up‐converting nanocrystals, with a large surface area of ≈770 m² g^?1 and an average pore size of 2 nm. A photosensitizer, zinc phthalocyanine, is incorporated into the mesoporous silica. Upon excitation by a NIR laser, the nanocrystals convert NIR light to visible light, which further activates the photosensitizer to release reactive singlet oxygen to kill cancer cells. The photosensitizer encapsulated in mesoporous silica is protected from degradation in the harsh biological environment. It is demonstrated that the photosensitizers loaded into the porous silica shell of the nanoparticles are not released out of the silica while they continuously produce singlet oxygen upon excitation by a NIR laser. The nanoparticles are reusable as the photosensitizers encapsulated in the silica are removed by soaking in ethanol.