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Multiphoton 3D lithography is becoming a tool of choice in a wide variety of fields. Regenerative medicine is one of them. Its true 3D structuring capabilities beyond diffraction can be exploited to produce structures with diverse functionality. Furthermore, these objects can be produced from unique materials allowing expanded performance. Here, we review current trends in this research area. We pay particular attention to the interplay between the technology and materials used. Thus, we extensively discuss undergoing light-matter interactions and peculiarities of setups needed to induce it. Then, we continue with the most popular resins, photoinitiators, and general material functionalization, with emphasis on their potential usage in regenerative medicine. Furthermore, we provide extensive discussion of current advances in the field as well as prospects showing how the correct choice of the polymer can play a vital role in the structure’s functionality. Overall, this review highlights the interplay between the structure’s architecture and material choice when trying to achieve the maximum result in the field of regenerative medicine.

In the present study the single phase polycrystalline GdB5O9:Sm3+ target materials were prepared by aqueous sol–gel method. The powder X-ray diffraction was used to monitor the crystal phase formation. Samples doped with 1 and 2.5% Sm3+ showed bright orange–red emission upon excitation with near-UV radiation. The emission possessed excellent colour saturation and good colour coordinate stability. Emission spectra recorded at different temperatures showed that the thermal quenching activation energy is around 35 meV. Moreover, the temperature dependent photoluminescence (PL) decay measurements revealed that PL lifetime values barely change in the temperature range of 77–500 K showing that the external quantum yield decreases much faster than the internal one. The highest quantum yield of ca. 60% was obtained for the sample doped with 1% Sm3+ ions. Further increase of Sm3+ content resulted in concentration quenching as a consequence of increased probability of cross-relaxation. Rather high quantum yield and well resolved sharp emission lines makes these phosphors suitable for application as an orange–red component in near-UV LEDs, on the one hand, and the luminescent security pigments, on the other hand.

Polycrystalline powders of K2LaNb5O15 doped with Eu3+ ions were prepared by high temperature solid state reaction. The phase formation of these compounds was monitored by X-ray diffraction measurements. Excitation of the prepared phosphors with near-UV or blue radiation resulted in a bright red luminescence, dominated by 5D0 → 7F2 transition at ca. 613 nm, with excellent colour saturation. The colour coordinates were relatively stable regardless the Eu3+ concentration and temperature. Furthermore, sample doped with 75% Eu3+ showed high 66% quantum efficiency if excited at 394 nm. Temperature dependent photoluminescence and decay measurements showed that internal quantum efficiency of the phosphors decreases slower than the external quantum efficiency at elevated temperatures. Moreover, synthesized K2LaNb5O15:Eu3+ phosphors possess rather unique emission spectra with strong and finely split emission lines originating from the 5D0 → 7F4 transition (ca. 700 nm) what makes these materials very attractive for application in luminescent security pigments.

Fabrication of a true-3D inorganic ceramic with resolution down to the nanoscale (∼100 nm) using a sol–gel resist precursor is demonstrated. This method has an unrestricted free-form capability, control of the fill-factor, and high fabrication throughput. A systematic study of the proposed approach based on ultrafast laser 3D lithography of organic–inorganic hybrid sol–gel resin followed by a heat treatment enabled the formation of inorganic amorphous and crystalline composites guided by the composition of the initial resin. The achieved resolution of 100 nm was obtained for 3D patterns of complex free-form architectures. Fabrication throughput of 50 × 103 voxels per second is achieved; voxel – a single volume element recorded by a single pulse exposure. A post-exposure thermal treatment was used to form a ceramic phase, the composition and structure of which were dependent on the temperature and duration of the heat treatment as revealed by Raman micro-spectroscopy. The X-ray diffraction (XRD) showed a gradual emergence of the crystalline phases at higher temperatures with a signature of cristobalite SiO2, a high-temperature polymorph. Also, a tetragonal ZrO2 phase known for its high fracture strength was observed. This 3D nano-sintering technique is scalable from nanoscale to millimeter dimensions and opens a conceptually novel route for optical 3D nano-printing of various crystalline inorganic materials defined by an initial composition for diverse applications for microdevices designed to function in harsh physical and chemical environments and at high temperatures.

The current paper is focused on the rapidly developing field of nano-/micro three-dimensional production of inorganic materials. The fabrication method includes laserlithography of hybrid organic-inorganic materials with subsequent heat treatment lead-ing to a variety of crystalline phases in 3D structures. In this work, it was examineda series of organometallic polymer precursors with different silicon (Si) and zirconium (Zr) molar ratios, ranging from 9:1 to 5:5, prepared via sol-gel method. All mixtureswere examined for perspective used in 3D laser by manufacturing by fabricating nano-and micro-feature sized structures. Their deformation and surface morphology wereevaluated depending on chemical composition and crystallographic phase. The appear-ance of a crystalline phase was proven using single-crystal X-ray diffraction analysis,which revealed a lower crystallization temperature for microstructures compared tobulk materials. Fabricated 3D objects retain a complex geometry without any distortion after heat treatment up to 1400oC. Under the proper conditions, a zircon phase (ZrSiO4 - a highly stable material) can be observed. In addition, the highest newrecord of achieved resolution below 60 nm has been reached. The proposed prepara-tion protocol can be used to manufacture micro/nano-devices with high precision andresistance to high temperature and aggressive environment.

Yttrium aluminium garnet substituted by samarium Y3−xSm x Al5O12, (YSmAG, x = 0.1, 0.15, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5 and 3.0) was prepared by an aqueous sol–gel processing using etane-1,2-diol as complexing agent. The end products obtained at 1000°C in air were characterized by x-ray diffraction analysis, infrared spectroscopy (FT-IR) and scanning electron microscopy. It was demonstrated, however, that the total substitution of yttrium by samarium does not proceed in the YSmAG. The single cubic garnet phase was formed only at a low concentration of samarium (x = 0.1, 0.15, 0.25, 0.5, 0.75, 1.0). With further substitutional levels, if the amount of samarium was x = 1.5, 2.0, 2.5 and 3, respectively, the formation a of minor amount of side perovskite samarium aluminate SmAlO3 (SmAP) phase was observed. Surprisingly, when yttrium was totally replaced by the samarium (x = 3.0) the main synthesis product was SmAP. The possible formation of Sm3Al5O12 (SmAG) garnet was also investigated for the first time by variation of the temperature in the range of 780–835°C.

Upconverting nanoparticles (UCNPs) are promising, new imaging probes capable of serving as multimodal contrast agents. In this study, monodisperse and ultrasmall core and core–shell UCNPs were synthesized via a thermal decomposition method. Furthermore, it was shown that the epitaxial growth of a NaGdF4 optical inert layer covering the NaGdF4:Yb,Er core effectively minimizes surface quenching due to the spatial isolation of the core from the surroundings. The mean diameter of the synthesized core and core–shell nanoparticles was ≈8 and ≈16 nm, respectively. Hydrophobic UCNPs were converted into hydrophilic ones using a nonionic surfactant Tween 80. The successful coating of the UCNPs by Tween 80 has been confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), photoluminescence (PL) spectra and magnetic resonance (MR) T1 relaxation measurements were used to characterize the size, crystal structure, optical and magnetic properties of the core and core–shell nanoparticles. Moreover, Tween 80-coated core–shell nanoparticles presented enhanced optical and MR signal intensity, good colloidal stability, low cytotoxicity and nonspecific internalization into two different breast cancer cell lines, which indicates that these nanoparticles could be applied as an efficient, dual-modal contrast probe for in vivo bioimaging.

A polycrystalline Eu 2 Mo 4 O 15 phosphor sample was prepared by high temperature solid state reaction. Phase purity and morphological features of the phosphor were investigated by X-ray diffraction and scanning electron microscopy, respectively. Reflectance spectra showed that the optical band gap of Eu 2 Mo 4 O 15 is 2.95 eV. Phosphor emits intensive red light when excited with 394 and 465 nm radiation. Temperature dependent emission and luminescence lifetime measurements revealed that external and internal quantum yields decrease at the same rate and that luminescence quenches due to photoionization. The calculated external quantum yields for 394 and 465 nm excitation were 7.8% and 53.5%, respectively.

Aqueous sol–gel chemistry route based on ammonium–hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as source of calcium ions, and 1,2-ethylendiaminetetraacetic acid (EDTA), or 1,2-diaminocyclohexanetetracetic acid (DCTA), or tartaric acid (TA), or ethylene glycol (EG), or glycerol (GL) as complexing agents have been used to prepare calcium hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , CHAp). The phase transformations, composition, and structural changes in the polycrystalline samples were studied by infrared spectroscopy (FTIR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). The local short-range (nano- and mezo-) scale effects in CHAp were studied using solid-state NMR spectroscopy. The spatial 3D data from the SEM images of CHAp samples obtained by TA, EG and GL sol–gel routes were recovered for the first time to our knowledge.

A novel and simple method for CeO2 nanoscale particle synthesis in aqueous solutions via a photochemical route is reported in this paper. To this end, CeCl3·7H2O or Ce(NO3)3·6H2O was used as a Ce precursor, while NaN3 was chosen as the photoactive compound. Synthesis was carried out without any surfactants or by using polyvinylpyrrolidone (PVP). The synthesized samples were subsequently thermally treated at different temperatures between 100 and 900 °C. XRD patterns and Raman spectra indicated that CeO2 samples possess the fluorite structure. TEM analysis revealed that synthesis without surfactants leads to formation of highly agglomerated particles, while adding PVP to the primary solution resulted in decreased agglomeration and reduced particle size. The particle size was calculated from XRD and Raman line broadening and confirmed by TEM analysis. The average crystallite size for the unheated samples prepared without surfactant was hardly radiation exposure dependent and varied from 6.5 to 8.9 nm. Even smaller particles (3.3–7.0 nm) were formed by using PVP. It turned out that an increase of the calcination temperature causes significant crystallite growth. A strong interaction between CeO2 nanoparticles and PVP was revealed by TG analysis. The UV/VIS absorption spectra showed a strong absorption below 400 nm (3.10 eV) with a well-defined absorption peak at around 295–320 nm. The estimated band gap (Eg) of the obtained nanoscale particles was in the range of 2.90–3.57 eV, i.e. the values are higher than that of a bulk CeO2 powder (Eg = 3.19 eV), except for the sample calcined at 900 °C.

Sm2+ and Sm3+ co-doped SrB4O7 could be utilized in several high-level optical devices and fundamental knowledge about the optical behavior of these materials benefits the development of luminescent applications. Herein, we report luminescence and its vacuum ultraviolet (VUV) excitation spectra in samarium doped SrB4O7. Both, Sm2+ and Sm3+ luminescence centers have been examined and distinguished in the emission and the excitation spectra investigated under synchrotron radiation. The contribution of either Sm2+ or Sm3+ emission lines into the emission spectra heavily depended on the excitation energy, and strong f-f transitions of both Sm2+ and Sm3+ were detected. At 10 K, a broad intrinsic luminescence in the UV range was detected and attributed to the radiative transition of either bound or self-trapped exciton in SrB4O7. The optical behavior, including e.g. inter-configurational f-d transitions of Sm(n+) were elucidated with first-principles calculations. Partial density of states well represents the changes of the electronic states that are related to the samarium doping, which in turn explains the emerging features in excitation spectra. In summary, the obtained results clarify the excitation and emission behavior of samarium doped SrB4O7.

A number of different morphologies of rhabdophane-type GdPO4·nH2O particles were synthesized via hydrothermal route with presence of tartaric acid as a coordinating/capping agent. Nanorods, hexagonal nanoprisms and nanospheres of different sizes were obtained. An impact of P O 4 3 − /Gd3+ molar ratio, Gd3+ absolute concentration, pH and duration of synthesis on the phase composition, particle morphology and colloidal stability in water was investigated. These synthesis parameters greatly influenced the particle size and morphology. It turned out that the best way to control the particle shape and size is to change the P O 4 3 − /Gd3+ ratio in the reaction mixture. The measured zeta potential values showed that the stability range of GdPO4·nH2O nanoparticles in aqueous solutions are influenced by the shape of particles; therefore, the appropriate GdPO4·nH2O nanoparticles could be synthesized for the desired applications.

Ceramics as advanced materials play an important role in science and technology as they are mechanically robust, can withstand immense heat, are chemically inert. Consequently, there is a direct end-user driven need to find ways for efficiently acquiring free-form 3D ceramic structures. Recently, stereo-lithographic 3D printing of hybrid organic-inorganic photo-polymer and subsequent heating was demonstrated to be capable of providing true 3D ceramic and glass structures. Up to now, this was limited to (sub-)millimeter scale and naturally the next step is to acquire functional glass-/ceramic-like 3D structures in micro-/nano-dimensions. In this paper, we explore a possibility to apply ultrafast 3D laser nanolithography followed by heating to acquire ceramic 3D structures down to micro-/nano-dimension. Laser fabrication is employed for the production of initial 3D structures with varying (ranging within hundreds of nm) feature sizes out of hybrid organic-inorganic material SZ2080. Then, a post-fabrication heating at different temperatures up to 1500 °C in an air atmosphere facilitates metal-organic framework decomposition, which results in the glass-ceramic hybrid material. Additionally, annealing procedure densifies the obtained objects providing an extra route for size control. As we show, this can be applied to bulk and free-form objects. We uncover that the geometric downscaling can reach up to 40%, while the aspect ratio of single features, as well as filling ratio of the whole object, remains the same regardless of volume/surface-area ratio. The structures proved to be qualitatively resistant to dry etching, hinting at significantly increased resiliency. Finally, Raman spectrum and X-ray diffraction (XRD) analysis were performed in order to uncover undergoing chemical processes during heat-treatment in order to determine the composition of material obtained. Revealed physical and chemical properties prove the proposed approach paving a route towards 3D opto-structuring of ceramics at the nanoscale for diverse photonic, microfluidic and biomedical applications.

Glass-ceramics play an important role in todays science and industry as it can withstand immense heat, mechanical and other hazards. Consequently, there is a need to find ever-new ways to acquire more sophisticated free-form 3D ceramic and glass structures. Recently, stereo-lithographic 3D printing of hybrid organic-inorganic photopolymer and subsequent pyrolysis was demonstrated to be capable of providing true 3D ceramic and glass structures. However, such approach was limited to (sub-)millimeter scale, while one of the aims in the field is to acquire functional 3D glass-like structures in micro- or even nano-dimensions. In this paper, we explore a possibility to apply ultrafast 3D laser nanolithography in conjunction with pyrolysis to acquire glass-ceramic 3D structures in micro- and nano-scale. Laser fabrication allows production of initial 3D structures with relatively small (hundreds of nm) feature sizes out of hybrid organic-inorganic material SZ2080. Then, a post-fabrication heating at different temperatures up to 1000°C in Ar , air or O2 atmospheres decomposes organic part of the material leaving only the glass-ceramic component of the hybrid. As we show, this can be done to 3D woodpiles and bulk objects. We uncover that the shrinkage during sintering can reach up to 40%, while the aspect ratio of single features as well as filling ratio of the whole object remains the same. This hints at homogeneous reduction in size that can be easily accounted for and pre-compensated before manufacturing. Additionally, the structures prove to be relatively resilient to focused ion beam (FIB) milling, hinting at increased rigidity. Finally, thermal gravimetric analysis (TGA) and Fourier transform infrared micro-spectroscopy measurements are performed in order to uncover undergoing chemical and physical phenomena during pyrolysis and composition of the remnant material. The proposed post-processing approach offers a straightforward way to downscale true 3D micro-/nanostructures for applications in nanophotonics, microoptics and mechanic devices with improved performance while being highly resilient to harsh surrounding conditions.

Luminescence measurements of upconverting nanocrystals (UCNCs) dispersed in SZ2080 prepolymer being pro- cessed by direct laser writing (DLW) nanopolymerization technique are presented. Er3+ ions doped β-NaYbF4 and Er3+,Yb3+ co-doped β-NaGdF4 core and core-shell UCNCs were prepared by a thermal decomposition method. The ratio of the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 emission intensities under λ = 975 nm excitation was confirmed to follow Boltzmann-type distribution in the temperature range from 20 °C to 200 °C and enabled a self-referenced optical readout of the sample temperature changes. Variation of thermally-coupled spectral bands fluorescence intensity ratio (FIR) was observed while prepolymer being processed under typical DLW conditions (1030 nm, 300 fs, 200 kHz, NA = 0.8) and Epulse varying from below modification threshold to the optical breakdown. Average fitted temperature changes around polymerized voxel measured ∆T1 < 30 °C within polymerization window and increases up to ∆T2~100 °C in overexposing regime.

In this work we explore a possibility to apply ultrafast 3D laser nanolithography in conjunction with pyrolysis to acquire glass-ceramic 3D structures in micro- and nano-scale. Laser fabrication allows for production of initial 3D structures with relatively small (hundreds nm - μm) feature sizes out of SZ2080 hybrid material. Then, postfabrication heating at 600°C in Ar atmosphere decomposes organic part of the material leaving the glass-ceramic component of the hybrid. Resulting structures are uniformly shrunk by 40%. This brings us one step closer to fabricating highly efficient slow-light absorbers.

We introduce optically clear and resilient free-form micro-optical components of pure (non-photosensitized) organic-inorganic SZ2080 material made by femtosecond 3D laser lithography (3DLL). This is advantageous for rapid printing of 3D micro-/nano-optics, including their integration directly onto optical fibers. A systematic study of the fabrication peculiarities and quality of resultant structures is performed. Comparison of microlens resiliency to continuous wave (CW) and femtosecond pulsed exposure is determined. Experimental results prove that pure SZ2080 is ∼20 fold more resistant to high irradiance as compared with standard lithographic material (SU8) and can sustain up to 1.91 GW/cm2 intensity. 3DLL is a promising manufacturing approach for high-intensity micro-optics for emerging fields in astro-photonics and atto-second pulse generation. Additionally, pyrolysis is employed to homogeneously shrink structures up to 40% by removing organic SZ2080 constituents. This opens a promising route towards downscaling photonic lattices and the creation of mechanically robust glass-ceramic microstructures.

The Er3+-activated NaYbF4 microparticles were synthesized by a thermal decomposition method and their temperature-dependent upconversion luminescence dynamics were studied. The fluorescence intensity ratio change and optical temperature sensing have been evaluated by analyzing emission data obtained under 980 nm laser excitation. Maximum relative sensitivity of 3.46%·K−1 was achieved at the temperature of 175 K, providing encouraging results for temperature sensor application. It is necessary to mention that besides the promising temperature sensing capabilities, synthesized microparticles have potential for application as anti-counterfeiting pigments.

There are several key requirements that a very good LED phosphor should meet, i.e., strong absorption, high quantum efficiency, high colour purity, and high luminescence quenching temperature. The reported Rb2Bi(PO4)(MoO4):Eu3+ phosphors have all these properties. The Rb2Bi(PO4)(MoO4):Eu3+ phosphors emit bright red light if excited with near-UV radiation. The calculated colour coordinates show good stability in the 77&ndash, 500 K temperature range. Moreover, sample doped with 50% Eu3+ possesses quantum efficiency close to unity. Besides the powder samples, ceramic disks of Rb2Eu(PO4)(MoO4) specimen were also prepared, and the red light sources from these disks in combination with near-UV emitting LED were fabricated. The obtained results indicated that ceramic disks efficiently absorb the emission of 375 and 400 nm LED and could be applied as a red component in phosphor-converted white LEDs.

A good LED phosphor must possess strong enough absorption, high quantum yields, colour purity and quenching temperatures. Our synthesized Y2Mo4O15:Eu3+ phosphors possess all of these properties. Excitation of these materials with near-UV or blue radiation yields bright red emission and the colour coordinates are relatively stable upon temperature increase. Furthermore, samples doped with 50% Eu3+ showed quantum yields up to 85%, what is suitable for commercial application. Temperature dependent emission spectra revealed that heavily Eu3+ doped phosphors possess stable emission up to 400 K and lose half of the efficiency only at 515 K. In addition, ceramic disks of Y2Mo4O15:75%Eu3+ phosphor with thickness of 0.71 and 0.98 mm were prepared and it turned out that they efficiently convert radiation of 375 and 400 nm LEDs to the red light, whereas combination with 455 nm LED yields purple colour.

The characteristics of CO2 reacting with CaO in a molten eutectic mixture of CaF2 and NaF has been investigated. Calculations of the Gibbs free energy, temperature analysis of the decomposition of the formed carbonates, and XRD analyses of quenched samples taken during CO2 absorption or desorption were employed to identify the phases present in the melt. Efficient CO2 absorption from a simulated flue gas was observed, due to a combined reaction where CaO initially reacts with CO2 and forms CaCO3. Subsequently, Na2CO3 is formed by an ion exchange reaction between CaCO3 and NaF. It was found that the CaO activity is highest in the temperature range 826–834°C. Increasing the CaO concentration from 5 to 20 wt% in the molten salt resulted in reduced CO2 reactivity efficiency, probably because of precipitation and agglomeration of the sorbent. The total carbonation conversion was independent of the CO2 concentration in the inlet gas, and the sorbent carrying capacity was in the range 0.722–0.743 g CO2/g CaO corresponding to 0.037–0.144 g CO2/g total liquid. Decarbonation was conducted by raising the temperature. 40% conversion back to CaO was recorded at 1160°C. The recorded curves for the CO2 concentration in the outlet gas exhibited a rapid desorption step followed by a slow step.