Co-MOF-74 rod like crystals with a length of several hundred micrometers are synthesized by a solvothermal procedure and their interaction with different gases is evaluated for selective gas sensing. We show strongly anisotropic absorption behavior of the Co-MOF-74 crystals when illuminated with polarized light. The interactions of guests (CO , propane, propene, Ar, MeOH, H O) with Co-MOF-74, is studied by various spectroscopic techniques. Vis/NIR shows peak shifts of Co-MOF-74 depending on the interaction with the guest. In the visible and the NIR the maximum absorbance is shifted selectively corresponding to the intensity of the Co -guest interaction. Even propene and propane could be distinguished at room temperature by their different interactions with Co-MOF-74. Raman spectroscopy was used to detect a modified vibrational behavior of Co-MOF-74 upon gas adsorption. We show that the adsorption of H O leads to a characteristic shift of the peak maxima in the Raman spectra.

In this work, we investigate the occurrence of localized surface plasmon resonances (LSPRs) in different nickel sulfide nanostructures. Therefore, spherical and anisotropic nickel sulfide nanoparticles (NPs) are synthesized and analyzed regarding their optical properties by UV/vis/NIR and transient absorption spectroscopy. Furthermore, new pathways for the synthesis of spherical Ni3S2 nanodots with an extremely narrow size distribution, as well as Au–Ni3S2 core–shell NPs with controllable shell thickness, are presented. Our results show that NPs of different metallic nickel sulfide phases like Ni3S2 and Ni3S4 exhibit LSPR bands in the visible regime of the electromagnetic spectrum, which possibly makes them a comparably cheaper alternative to NPs consisting of noble metals like Au and Ag. In case of the presented plasmonic core–shell particles, the resonance frequency of the plasmon can be tuned between those of pure gold and pure Ni3S2 NPs by varying the Ni3S2 shell thickness.

Stäbchenförmige Co‐MOF‐74‐Kristalle wurden über ein Solvothermalverfahren synthetisiert, um die Wechselwirkungen mit Gasen zu untersuchen. Bei der Bestrahlung von Co‐MOF‐74 mit polarisiertem Licht weisen die Kristalle ein stark anisotropes Absorptionsverhalten auf. Des Weiteren wurden die Wechselwirkungen von Co‐MOF‐74 mit den Gastmolekülen CO2, Propan, Propen, Ar, MeOH und H2O mithilfe verschiedener spektroskopischer Methoden untersucht. Wechselwirkungs‐abhängige Peak‐Verschiebungen der Co‐MOF‐74‐Banden im Vis/NIR‐Bereich wurden beobachtet. Sowohl im sichtbaren als auch im Nah‐IR‐Bereich wird die maximale Absorption selektiv, entsprechend der Intensität der CoII‐Gastmolekül‐Wechselwirkung, verschoben. Aufgrund ihrer unterschiedlichen Wechselwirkungen mit Co‐MOF‐74 war es möglich, Propan und Propen bei Raumtemperatur zu unterscheiden. Raman‐Spektroskopisch konnte eine Änderung des Schwingungsverhaltens von Co‐MOF‐74 bei Gasadsorption nachgewiesen werden. Außerdem wurde eine charakteristische Verschiebung der Peak‐Maxima durch die Adsorption von H2O gezeigt.

Due to their unique optical properties, nanoparticles are well suited for heating by laser irradiation. In this context, colloidally dispersed particles are of particular interest because in conventional ways of heating, the maximum attainable temperature is limited by the boiling point of the solvent. With the right choice of the used laser wavelength, it is possible to selectively heat these particles above the melting point of the material whereas the surrounding and laser-transparent medium remains comparatively cold. This type of laser process is called laser melting in liquids (LML). To further investigate the possibilities of laser-induced heating processes, colloidally dispersed copper(II) oxide (CuO) nanoparticles were synthesized, dispersed in ethanol, and irradiated with a nanosecond-pulsed Nd:YAG laser. In this way, a laser-induced phase transition into the copper richer copper(I) oxide (Cu 2 O) phase and into elemental copper can be observed. The conversion process is followed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED), and UV−vis spectroscopy. It is shown that in the initial LML process a minimum particle size of 23−29 nm is required for a successful phase transition likely due to the size dependent heating efficiency, cooling effects, and the formation of nanobubbles.

In this article, we study the size-dependent interactions of quasi-spherical nanocrystals with voids of concave nanoparticles of complementary sizes and shapes. Experimental insights into a system with key and lock particles with smaller dimensions than 15 nm are presented, which provide evidence for key-lock specific interaction on this length scale. Using depletion attraction as a driving force, the key-lock interaction is shown to be reversible and independent of the material composition of the key particles. Poly(ethylene glycol) methacrylate was utilized as a depletion agent in toluene, the solvent of the studied key-lock system. For this work, a model system of specifically developed concave manganese oxide nanocrystals, synthesized via a cast-mold approach, in combination with highly monodisperse quasi-spherical gold nanocrystals, was investigated with transmission electron microscopy, optical UV/vis/NIR spectroscopy and powder X-ray diffraction. Size-dependent key-lock interactions are clearly identified to occur. For geometrical reasons, only key particles with smaller particle diameters than the voids of the complementary lock particles are able to enter the void. So the void diameter of the lock particles sets a diameter threshold for the key-lock interaction. Additionally, other key particles like silver, iron oxide and even core-shell structured gold-nickel sulfide nanocrystals show key-in-lock assemblies with concave manganese oxide nanocrystals. This behaviour might open up new routes for size-selective particle sensing.