Crystals

14 pages, 3374 KiB

Open AccessArticle

Spectroscopic and Structural Properties of β-Tricalcium Phosphates Ca₉RE(PO₄)₇ (RE = Nd, Gd, Dy)

by Veronica Paterlini, Asmaa El Khouri, Marco Bettinelli, Daniele Maria Trucchi and Francesco Capitelli

Crystals 2021, 11(10), 1269; https://doi.org/10.3390/cryst11101269 - 19 Oct 2021

Cited by 2 | Viewed by 1686

Abstract

Rare-earth-based Ca₉RE(PO₄)₇ (RE = Nd, Gd, Dy) materials were synthesized by solid-state reaction at T = 1200 °C. The obtained tricalcium phosphate (TCP) materials are efficient light emitters due to the presence of RE³⁺ ions, [...] Read more.

Rare-earth-based Ca₉RE(PO₄)₇ (RE = Nd, Gd, Dy) materials were synthesized by solid-state reaction at T = 1200 °C. The obtained tricalcium phosphate (TCP) materials are efficient light emitters due to the presence of RE³⁺ ions, although these ions are present at high concentrations. Moreover, in these host structures, these ions can be used as optical probes to study their local environments. Thus, photoluminescence (PL) emission spectra of the powder samples clearly indicated, for Dy³⁺ and Gd³⁺ ions, the presence of the RE³⁺ ion in low-symmetry sites with some local structural disorder, and the spectra show the presence of vibrational features (in the case of Gd³⁺). For the Nd³⁺ phase, emission bands are present around 900, 1050, and 1330 nm, originating from the ⁴F_3/2 level. In general, these RE-TCP samples are interesting luminescent materials in the visible (Dy), UV (Gd), and NIR (Nd) regions, due to weak concentration quenching even for high concentrations of the emitting ion. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Online Conference on Crystals)

► Show Figures

Figure 1

19 pages, 54589 KiB

Open AccessArticle

One-Step Multi-Doping Process for Producing Effective Zinc Oxide Nanofibers to Remove Industrial Pollutants Using Sunlight

by Osama Saber, Nagih M. Shaalan, Faheem Ahmed, Shalendra Kumar and Adil Alshoaibi

Crystals 2021, 11(10), 1268; https://doi.org/10.3390/cryst11101268 - 19 Oct 2021

Cited by 8 | Viewed by 1486

Abstract

Doping processes for optical materials are one of the driving forces for developing efficient and clean technologies for decontamination of aquatic effluents through lowering their band gap energy to become effective in sunlight. The current study has used a non-conventional technique for doping [...] Read more.

Doping processes for optical materials are one of the driving forces for developing efficient and clean technologies for decontamination of aquatic effluents through lowering their band gap energy to become effective in sunlight. The current study has used a non-conventional technique for doping zinc oxide by multi metals, non-metals and organic dyes through a one-step process. In this trend, Zn-Al nanolayered structures have been used as hosts for building host–guest interactions. Organic dyes that have inorganic species of iron, nitrogen and sulfur have been used as guests in the intercalation reactions of Zn-Al layered double hydroxides. By intercalating green dyes, organic–inorganic nanohybrids were formed as nanolayered structures with expanding interlayered spacing to 2.1 nm. By changing the concentration of green dyes and thermal treatment, series of nanofibers and nanoplates of zinc oxides were formed and doped by aluminum, iron and sulfur in addition to colored species. The optical properties of the multi-doped zinc oxide indicated that it became suitable for solar applications because its band gap energy decreased from 3.30 eV to 2.80 eV. The experimental and kinetic results of the multi-doped zinc oxide concluded that the colored pollutants were effectively removed during 50 min of sunlight irradiation. Full article

(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)

► Show Figures

Figure 1

9 pages, 1696 KiB

Open AccessArticle

The Effect of Red Mud on Sintering Processes and Minerals of Portland Cement for Roads

by Xiao Wang, Ke Sun, Xin Li, Juntao Ma and Zhongtao Luo

Crystals 2021, 11(10), 1267; https://doi.org/10.3390/cryst11101267 - 19 Oct 2021

Cited by 4 | Viewed by 1753

Abstract

As a solid waste generated in the alumina industry, red mud poses a significant environmental hazard and a storage problem. In this study, red mud was added to road cement clinker in order to utilize it. The sintering red mud was first de-alkalized, [...] Read more.

As a solid waste generated in the alumina industry, red mud poses a significant environmental hazard and a storage problem. In this study, red mud was added to road cement clinker in order to utilize it. The sintering red mud was first de-alkalized, and then mixed with fly ash, clay, limestone, and sandstone, among other materials, to make Portland cement for road clinker. The effect of the addition of red mud on the thermal decomposition characteristics of Portland cement for roads was studied. The existent states of alkali and radioactive elements in Portland cement for road clinker were investigated by XRD and SEM analysis. The research results showed that the addition of red mud in Portland cement for road raw material significantly promoted the decomposition of carbonates in raw material. The major mineral phases of Portland cement for road clinker were C₃S with a polyhedral morphology, quasi-spherical C₂S, and tubular C₄AF. A small part of the alkali combined with the silicate phase to form a solid solution, and most of the alkali combined with S to form vermiform sulfate in the intermediate phase. The radionuclide ²²⁶Ra was mainly distributed in the silicate phase. ²³²Th was mainly distributed in interstitial phases and then silicate phases, while ⁴⁰K was mainly distributed in the interstitial phases. Full article

(This article belongs to the Special Issue Advances in Green Building Materials and Structural Performances)

► Show Figures

Figure 1

10 pages, 38284 KiB

Open AccessArticle

Impact of Thermal Treatment on the Surface of Na_0.5Bi_0.5TiO₃-Based Ceramics

by Liga Bikse, Marija Dunce, Eriks Birks, Karlis Kundzins, Otto Freimanis, Maris Livins, Jevgenijs Gabrusenoks and Andris Sternberg

Crystals 2021, 11(10), 1266; https://doi.org/10.3390/cryst11101266 - 19 Oct 2021

Cited by 3 | Viewed by 1728

Abstract

Thermal etching is a widely accepted surface treatment method for studying microstructure in Na_0.5Bi_0.5TiO₃-based compositions. Surprisingly, besides the flat pattern of grains (suitable for evaluating ceramics’ microstructure), images illustrating well-expressed relief and even microstructure consisting of partly [...] Read more.

Thermal etching is a widely accepted surface treatment method for studying microstructure in Na_0.5Bi_0.5TiO₃-based compositions. Surprisingly, besides the flat pattern of grains (suitable for evaluating ceramics’ microstructure), images illustrating well-expressed relief and even microstructure consisting of partly bonded cubic-shaped grains are also found among the micrographs presented in various publications. The present paper shows that this different surface character in Eu-modified Na_0.5Bi_0.5TiO₃ can be obtained through thermal treatment across a wide range of temperatures. At higher temperatures, remarkable growth of cubic-shaped grains on the surface is observed. This growth affects the grain size distribution on the surface more than it does within the bulk of a sample. Such micrographs cannot be used to characterise the microstructure of dense ceramics. Intensive growth of TiO₂ inclusions at high thermal treatment temperatures is also observed, revealing substantial evaporation of Bi and Na from the surface of a ceramic sample, but not from its core part. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

► Show Figures

Graphical abstract

14 pages, 3843 KiB

Open AccessEditor’s ChoiceArticle

Photosensitive Bent-Core Liquid Crystals with Laterally Substituted Azobenzene Unit

by Diana Jágerová, Michal Šmahel, Anna Poryvai, Jan Macháček, Vladimíra Novotná and Michal Kohout

Crystals 2021, 11(10), 1265; https://doi.org/10.3390/cryst11101265 - 18 Oct 2021

Cited by 4 | Viewed by 2383

Abstract

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables [...] Read more.

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables fast (E)-to-(Z)-isomerization upon irradiation with UV-light and visible light, while the substitution facilitates the high stability of the photochemically formed (Z)-isomer. The effectiveness of the irradiation and the composition of photostationary states was determined by UV/Vis and ¹H NMR spectroscopy. A nematic phase formed by the materials was characterized by differential scanning calorimetry and optical polarizing microscopy. We show that the materials easily change their relative configuration of the N=N double bond not only in solution, but also in the mesophase, which leads to fast isothermal phase transition from the nematic phase to isotropic liquid. Full article

(This article belongs to the Special Issue Photosensitive Liquid Crystals)

► Show Figures

Graphical abstract

10 pages, 2578 KiB

Open AccessArticle

Stepwise Current Increment Sintering of Silver Nanoparticle Structures

by Dongkeun Kim, Arif Hussain, Hee-Lak Lee, Yoon-Jae Moon, Junyoung Hwang and Seung-Jae Moon

Crystals 2021, 11(10), 1264; https://doi.org/10.3390/cryst11101264 - 18 Oct 2021

Cited by 8 | Viewed by 1499

Abstract

Owing to its unique properties, silver (Ag) in the form of nanoparticle (NP) ink promises to play a vital role in the development of printed and flexible electronics. Once printed, metal NP inks require a thermal treatment process called sintering to render them [...] Read more.

Owing to its unique properties, silver (Ag) in the form of nanoparticle (NP) ink promises to play a vital role in the development of printed and flexible electronics. Once printed, metal NP inks require a thermal treatment process called sintering to render them conductive. Among the various methods, electrical sintering is a highly selective and rapid sintering method. Here, we studied the electrical sintering of inkjet-printed Ag NP lines via a stepwise current increment sintering (SCIS) technique. In the SCIS technique, the supplied electric current was gradually increased in multiple steps from low electric currents to higher electric currents to avoid thermal damage to the printed Ag NP ink lines. In less than 0.15 s, a line resistivity as low as 6.8 μΩcm was obtained which was comparable with furnace sintered line resistivity of 6.13 μΩcm obtained at 250 °C in 600 s. Furthermore, a numerical model was developed for the SCIS process temperature estimation. The results enabled us to elaborate on the relationship between the Ag NP line resistivity and the process temperature under various electric currents. Under the applied SCIS technique, a stable sintering process was carried out avoiding the conductive ink line and substrate damage. Full article

► Show Figures

Figure 1

18 pages, 5075 KiB

Open AccessArticle

Impediment of Iron Corrosion by N,N′-Bis[2-hydroxynaphthylidene]amino]oxamide in 3.5% NaCl Solution

by El-Sayed M. Sherif, Ayman H. Ahmed, Hany S. Abdo and Monerah N. DefAllah

Crystals 2021, 11(10), 1263; https://doi.org/10.3390/cryst11101263 - 18 Oct 2021

Cited by 8 | Viewed by 1799

Abstract

Hydrazone [N,N′-bis[2-hydroxynaphthylidene]amino]oxamide] derived from the condensation of ethanedihydrazide with 2-hydroxynaphthalene-1-carbaldehyde was synthesized and assessed on the basis of elemental analysis (CHN) and spectral (IR, mass, ¹³C/¹H NMR and UV-Vis) measurements. The influence of N,N [...] Read more.

Hydrazone [N,N′-bis[2-hydroxynaphthylidene]amino]oxamide] derived from the condensation of ethanedihydrazide with 2-hydroxynaphthalene-1-carbaldehyde was synthesized and assessed on the basis of elemental analysis (CHN) and spectral (IR, mass, ¹³C/¹H NMR and UV-Vis) measurements. The influence of N,N-bis([2-hydroxynaphthylidene]amino)oxamide (HAO) in terms of the inhibition of iron corrosion in concentrated sodium chloride solution (3.5 wt.% NaCl) after various exposure periods was assessed. Numerous electrochemical and spectroscopic assessment techniques were performed. Cyclic potentiodynamic polarization experiments indicated that the presence of HAO and its increased concentration decreased the corrosion of iron in NaCl solution by decreasing the corrosion values, anodic and cathodic currents, and corrosion rate. The electrochemical impedance spectroscopy results showed that HAO molecules greatly increased the corrosion resistance. The chronoamperometric experiments performed at −475 mV (Ag/AgCl) revealed that the HAO molecules decreased the absolute currents and reduced the probability of the occurrence of pitting corrosion. The effect of HAO on the inhibition of iron corrosion was also confirmed through scanning electron microscopy micrographs and energy-dispersive X-ray profile analyses, which proved that the surface of the iron sample exposed to chloride solution alone was pitted, while the presence of HAO molecules reduced the severity of the pitting corrosion. The results confirmed that the presence of HAO molecules inhibits the corrosion of iron and this impact increased when the exposure time was increased to 48 h. Full article

(This article belongs to the Topic Electrolyte Design and Interface Engineering toward Safer Energy Storage)

► Show Figures

Graphical abstract

8 pages, 2187 KiB

Open AccessCommunication

Structural and Biochemical Studies of Bacillus subtilis MobB

by Dajeong Kim, Sarah Choi, Hyunjin Kim and Jungwoo Choe

Crystals 2021, 11(10), 1262; https://doi.org/10.3390/cryst11101262 - 18 Oct 2021

Cited by 1 | Viewed by 1469

Abstract

The biosynthesis of molybdenum cofactor for redox enzymes is carried out by multiple enzymes in bacteria including MobA and MobB. MobA is known to catalyze the attachment of GMP to molybdopterin to form molybdopterin guanine dinucleotide. MobB is a GTP binding protein that [...] Read more.

The biosynthesis of molybdenum cofactor for redox enzymes is carried out by multiple enzymes in bacteria including MobA and MobB. MobA is known to catalyze the attachment of GMP to molybdopterin to form molybdopterin guanine dinucleotide. MobB is a GTP binding protein that enhances the activity of MobA by forming the MobA:MobB complex. However, the mechanism of activity enhancement by MobB is not well understood. The structure of Bacillus subtilis MobB was determined to 2.4 Å resolution and it showed an elongated homodimer with an extended β-sheet. Bound sulfate ions were observed in the Walker A motifs, indicating a possible phosphate-binding site for GTP molecules. The binding assay showed that the affinity between B. subtilis MobA and MobB increased in the presence of GTP, suggesting a possible role of MobB as an enhancer of MobA activity. Full article

(This article belongs to the Special Issue Crystallographic Studies of Enzymes (Volume II))

► Show Figures

Figure 1

11 pages, 13150 KiB

Open AccessArticle

Kappa Carbide Precipitation in Duplex Fe-Al-Mn-Ni-C Low-Density Steel

by Jaka Burja, Barbara Šetina Batič and Tilen Balaško

Crystals 2021, 11(10), 1261; https://doi.org/10.3390/cryst11101261 - 18 Oct 2021

Cited by 2 | Viewed by 2156

Abstract

The microstructural evolution of a Fe-Mn-Al-Ni-C low-density steel was studied. The lightweight low-density steels are a promising material for the transportation industry, due to their good mechanical properties and low density. The base microstructure of the investigated steel consists of ferrite and austenite. [...] Read more.

The microstructural evolution of a Fe-Mn-Al-Ni-C low-density steel was studied. The lightweight low-density steels are a promising material for the transportation industry, due to their good mechanical properties and low density. The base microstructure of the investigated steel consists of ferrite and austenite. Thermo-Calc calculations showed the formation of an ordered BCC (body-centred cubic) B2 phase below 1181 °C and kappa carbides below 864 °C. The steel was produced in a vacuum induction furnace, cast into ingots and hot forged into bars. The forged bars were solution annealed and then isothermally annealed at 350, 450, 550, 650, 750, and 850 °C. The microstructure of the as-cast state, the hot forged state, solution annealed, and isothermally annealed were investigated by optical microscopy and scanning electron microscopy. The results showed the formation of kappa carbides and the ordered B2 phase. The kappa carbides appeared in the as-cast sample and at the grain boundaries of the isothermally annealed samples. At 550 °C, the kappa carbides began to form in the austenite phase and coarsened with increasing temperature. Full article

(This article belongs to the Special Issue Advance in Alloy Materials)

► Show Figures

Figure 1

12 pages, 2580 KiB

Open AccessArticle

Crystallization Behaviors of Composites Comprising Biodegradable Polyester and Functional Nucleation Agent

by Li-Ting Lee, Hsiang-Yun Tseng and Tzi-Yi Wu

Crystals 2021, 11(10), 1260; https://doi.org/10.3390/cryst11101260 - 18 Oct 2021

Cited by 5 | Viewed by 1557

Abstract

In this study, a thorough study of the crystallization behaviors of the biodegradable polymer composites of poly(ethylene succinate) (PESu) and hexagonal boron nitride (h-BN) was carried out. We found that h-BN had a significant nucleation effect on crystallization behaviors. DSC isothermal crystallization results [...] Read more.

In this study, a thorough study of the crystallization behaviors of the biodegradable polymer composites of poly(ethylene succinate) (PESu) and hexagonal boron nitride (h-BN) was carried out. We found that h-BN had a significant nucleation effect on crystallization behaviors. DSC isothermal crystallization results demonstrated that the crystallization time of the PESu/h-BN composites became shorter after adding h-BN. The rate constant k values calculated from the Avrami equation were larger for the composites, demonstrating that PESu’s crystallization rate was increased by adding h-BN. TEM and SEM images showed the well-dispersed h-BN in the PESu matrix. Optical microscopy revealed that the PESu/h-BN composites formed more and smaller spherulites than neat PESu did, which confirmed that h-BN caused the nucleation effect. H-BN also accelerated non-isothermal crystallization kinetics. We discussed the behaviors of the Mo model, which demonstrated that h-BN promoted the kinetics of non-isothermal crystallization. The XRD diffraction patterns showed that h-BN in the composites would not obviously change the crystalline structure of PESu. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

► Show Figures

Graphical abstract

5 pages, 2424 KiB

Open AccessArticle

A Method to Improve the Lifetime of Microcapsule Electrophoretic Display Modules

by Xidu Wang, Guoyuan Li, Xi Zeng, Yu Chen and Dianlu Hu

Crystals 2021, 11(10), 1259; https://doi.org/10.3390/cryst11101259 - 18 Oct 2021

Viewed by 1746

Abstract

Microcapsule electrophoretic display (MED) is a kind of display with the properties of reflectivity and low power consumption. It is widely used in electronic book readers, but some new applications have appeared in the Internet of Things (IoT) products. Long working time is [...] Read more.

Microcapsule electrophoretic display (MED) is a kind of display with the properties of reflectivity and low power consumption. It is widely used in electronic book readers, but some new applications have appeared in the Internet of Things (IoT) products. Long working time is required in IoT products because it is not easy to replace or install such displays. The main failure phenomenon is the mura that will appear after about 1 to 2 years of use. The root cause of the failure is analyzed, and the lifetime prediction models for MED are introduced. The high temperature and high humidity (HTHH) test is used to evaluate the protective effect of the packaging structure. The HTHH test result is reported for the new MED structure; it shows that the MED with the new structure involves a longer working time. Full article

(This article belongs to the Special Issue Liquid Crystals in China)

► Show Figures

Figure 1

10 pages, 1901 KiB

Open AccessArticle

X-ray Spectrum Reconstruction by Diamond Detectors with Linear Response to Dose Rate

by Daniele Maria Trucchi and Paolo Ascarelli

Crystals 2021, 11(10), 1258; https://doi.org/10.3390/cryst11101258 - 18 Oct 2021

Cited by 1 | Viewed by 1757

Abstract

The absorbers method is here applied by interposing filters of variable thickness between the X-ray source and a detector so to attenuate the radiation intensity by using the attenuation coefficient as a selective photon energy operator. The analysis of the signal provided by [...] Read more.

The absorbers method is here applied by interposing filters of variable thickness between the X-ray source and a detector so to attenuate the radiation intensity by using the attenuation coefficient as a selective photon energy operator. The analysis of the signal provided by a polycrystalline diamond thin film detector exposed to the energy-selectively-attenuated X-ray beam was used for the reconstruction of the radiation spectrum. The 50 μm thick diamond detector achieves conditions of linear response to the dose rate of the incident radiation (linearity coefficient of 0.997 ± 0.003) for a bias voltage ≥90 V, corresponding to an electric field ≥1.8 × 10⁴ V/cm. Once the absorbers method is applied, only the detector signal linearity to dose rate allows reconstructing the source X-ray bremsstrahlung spectrum with sufficiently high accuracy. Full article

► Show Figures

Graphical abstract

7 pages, 930 KiB

Open AccessArticle

Ab initio Investigation of Impurity Ferromagnetism in the Pd_1−xFe_x Alloys: Concentration and Position Dependences

by Irina Piyanzina, Amir Gumarov, Rustam Khaibullin and Lenar Tagirov

Crystals 2021, 11(10), 1257; https://doi.org/10.3390/cryst11101257 - 18 Oct 2021

Cited by 1 | Viewed by 1693

Abstract

We present the results of ab initio studies of the structural and magnetic properties of the Pd host matrix doped by Fe atoms at various concentrations. By means of the density functional theory, we deduce that iron impurities are able to initialize significant [...] Read more.

We present the results of ab initio studies of the structural and magnetic properties of the Pd host matrix doped by Fe atoms at various concentrations. By means of the density functional theory, we deduce that iron impurities are able to initialize significant magnetization of the Pd atoms, when the impurity concentration exceeds 3 at.%. We also demonstrate that the induced magnetization depends on impurity positions in the host matrix, in particular, there is a maximum of magnetization for a uniform distribution of the iron solute. Full article

(This article belongs to the Topic First-Principles Simulation—Nano-Theory)

► Show Figures

Graphical abstract

13 pages, 3478 KiB

Open AccessArticle

Oxidative Thermal Conversion of Hydrothermal Derived Precursors toward the Mixed-Metal Cobaltite Spinel Oxides (ZnCo₂O₄ and NiCo₂O₄): In-Situ Investigation by Synchrotron-Radiation XRD and XAS Techniques

by Wanchai Deeloed, Yuranan Hanlumyuang, Wanwisa Limphirat, Songwut Suramitr, Kantapat Chansaenpak, Pongsakorn Kanjanaboos, Suttipong Wannapaiboon and Worawat Wattanathana

Crystals 2021, 11(10), 1256; https://doi.org/10.3390/cryst11101256 - 17 Oct 2021

Cited by 3 | Viewed by 2322

Abstract

In-situ investigations of structural transitions during the thermal-oxidative event of mixed-metal spinel oxide precursors, the so-called nickel- (NCO) and zinc-containing (ZCO) cobaltite spinel precursors, were investigated to understand the formations of the derived NiCo₂O₄ and ZnCo₂O₄ spinel [...] Read more.

In-situ investigations of structural transitions during the thermal-oxidative event of mixed-metal spinel oxide precursors, the so-called nickel- (NCO) and zinc-containing (ZCO) cobaltite spinel precursors, were investigated to understand the formations of the derived NiCo₂O₄ and ZnCo₂O₄ spinel oxides, respectively. In-situ XRD investigation revealed that emerged temperatures for spinel oxide phase were between 325 and 400 °C, depending on the cationic substituent. It indicated that the emerged temperature correlated with the absolute octahedral site preference energy (OSPE) of those cations that participated in the development of the spinel framework. Moreover, the incorporated nickel and zinc in the precursors was beneficial for inhibiting the occurrence of the undesired CoO phase. Time-resolved X-ray absorption spectroscopic (TRXAS) data suggested the local structure rearrangement of nickel and zinc throughout the calcination process, which differed from the behavior of single-metal cobalt system. The essential information reported herein provides a benefit to control the cationic distribution within spinel materials, leading to the tunable physical and chemical properties. Full article

(This article belongs to the Special Issue Solid State Chemistry: Memorial Issue for Professor Emilio Morán)

► Show Figures

Graphical abstract

13 pages, 1236 KiB

Open AccessPerspective

A Short Review on the Utilization of Incense Sticks Ash as an Emerging and Overlooked Material for the Synthesis of Zeolites

by Virendra Kumar Yadav, Nisha Choudhary, Vineet Tirth, Haresh Kalasariya, Govindhan Gnanamoorthy, Ali Algahtani, Krishna Kumar Yadav, Sunil Soni, Saiful Islam, Shalini Yadav and Byong-Hun Jeon

Crystals 2021, 11(10), 1255; https://doi.org/10.3390/cryst11101255 - 15 Oct 2021

Cited by 13 | Viewed by 2658

Abstract

The traditional hydrothermal synthesis methods are mainly performed under batch operation, which generally takes few days to weeks to yield a zeolite with the desired properties and structure. The zeolites are the backbone of the petrochemical and wastewater industries due to their importance. [...] Read more.

The traditional hydrothermal synthesis methods are mainly performed under batch operation, which generally takes few days to weeks to yield a zeolite with the desired properties and structure. The zeolites are the backbone of the petrochemical and wastewater industries due to their importance. The commercial methods for zeolite synthesis are expensive, laborious and energy intensive. Among waste products, incense sticks ash is a compound of aluminosilicates and could act as a potential candidate for the synthesis of zeolites for daily needs in these industries. Incense sticks ash is the byproduct of religious places and houses and is rich in Ca, Mg, Al and Si. As a result, incense sticks ash can be proven to be a potential candidate for the formation of calcium-rich zeolites. The formation of zeolites from incense sticks ash is an economical, reliable and eco-friendly method. The application of incense sticks ash for zeolite synthesis can also minimize the problem related to its disposal in the water bodies, which will also minimize the solid waste in countries where it is considered sacred and generated in tons every day. Full article

(This article belongs to the Special Issue Zeolites: Synthesis and Applications)

► Show Figures

Figure 1

11 pages, 4355 KiB

Open AccessArticle

Characterization, X-ray Absorption Spectroscopic Analysis and Photocatalytic Activity of Co/Zn Co-Doped TiO₂ Nanoparticles Synthesized by One-Step Sonochemical Process

by Wanichaya Mekprasart, Sorapong Pavasupree, C. K. Jayasankar, Balaji Rao Ravuri, Chakkaphan Wattanawikkam and Wisanu Pecharapa

Crystals 2021, 11(10), 1254; https://doi.org/10.3390/cryst11101254 - 15 Oct 2021

Cited by 5 | Viewed by 2005

Abstract

A novel one-step preparation of sonochemical method was applied to synthesize Co/Zn co-doped TiO₂ nanoparticles using a sonicator of 750 W, 20 kHz for 30 min at room temperature. The formation of the anatase TiO₂ phase for all as-prepared samples was [...] Read more.

A novel one-step preparation of sonochemical method was applied to synthesize Co/Zn co-doped TiO₂ nanoparticles using a sonicator of 750 W, 20 kHz for 30 min at room temperature. The formation of the anatase TiO₂ phase for all as-prepared samples was observed from XRD results with a crystalline size in nanoscale. The use of ultrasound allowed for the successful doping of both Co and Zn into the TiO₂ lattice, which was confirmed by Synchrotron light including X-ray near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) spectroscopy. Ti K-edge, Co K-edge, and Zn K-edge XANES spectra exhibited the dominating +4, +2, and +2 valence state of Ti, Co, and Zn in as-prepared samples, respectively. A detailed XANES and EXAFS data analysis give strong evidence that the Co/Zn dopants partially replace the Ti atom of the TiO₂ host. The Co/Zn co-doping extends the light absorption of the host to the visible region and restricts the e⁺/h⁺ recombination. The photocatalytic activity of samples was tested for degradation of Rhodamine B dye solution under visible light irradiation. The as-synthesized of the co-doped catalyst was presented as highly efficient, with 2.5 and 5 times dye degradation compared with single-doped and bare TiO₂. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

► Show Figures

Figure 1

15 pages, 3260 KiB

Open AccessArticle

Shape Memory Properties and Microstructure of New Iron-Based FeNiCoAlTiNb Shape Memory Alloys

by Li-Wei Tseng, Chih-Hsuan Chen, Wei-Cheng Chen, Yu Cheng and Nian-Hu Lu

Crystals 2021, 11(10), 1253; https://doi.org/10.3390/cryst11101253 - 15 Oct 2021

Cited by 7 | Viewed by 1878

Abstract

The shape memory properties and microstructure of Fe₄₁Ni₂₈Co₁₇Al_11.5(Ti+Nb)_2.5 (at.%) cold-rolled alloys were studied at the first time using the values reported in constant stress thermal cycling experiments in a three-point bending test. Thermo-magnetization curves [...] Read more.

The shape memory properties and microstructure of Fe₄₁Ni₂₈Co₁₇Al_11.5(Ti+Nb)_2.5 (at.%) cold-rolled alloys were studied at the first time using the values reported in constant stress thermal cycling experiments in a three-point bending test. Thermo-magnetization curves of 97% cold-rolled and solution-treated sample aged at 600 °C for 24, 48 and 72 h showed evidence of the martensitic transformation, and the transformation temperatures increased their values from 24 to 72 h. The alloy cold-rolled to 97% and then solution-treated at 1277 °C for 1 h showed that most grains were aligned near <100> in the rolling direction in the recrystallization texture. The intensity of texture was 13.54, and an average grain size was around 400 μm. The sample aged at 600 °C for 48 h showed fully recoverable strain up to 1.6% at 200 MPa stress level in the three-point bending test. However, the experimental recoverable strain values were lower than the theoretical values, possibly due to the small volume fraction of low angle grain boundary, the formation of brittle grain boundary precipitates, and a grain boundary constraint lower than the expected intensity of texture in the samples. Full article

(This article belongs to the Special Issue Crystal Plasticity (Volume II))

► Show Figures

Figure 1

16 pages, 4095 KiB

Open AccessArticle

Relationship between Structural Stiffness and Viscous Damping Coefficient in Reinforced Carbon Structure under Varying Carbon Fiber Angles

by Chan-Jung Kim

Crystals 2021, 11(10), 1252; https://doi.org/10.3390/cryst11101252 - 15 Oct 2021

Cited by 2 | Viewed by 1401

Abstract

A linearized dynamic model of a carbon-fiber-reinforced plastic (CFRP) structure can be formulated using the structural stiffness and viscous damping coefficient. The carbon fiber angle is an influential factor in determining the structural stiffness of CFRP structures by serially combining the stiffness of [...] Read more.

A linearized dynamic model of a carbon-fiber-reinforced plastic (CFRP) structure can be formulated using the structural stiffness and viscous damping coefficient. The carbon fiber angle is an influential factor in determining the structural stiffness of CFRP structures by serially combining the stiffness of a binding matrix and that of a carbon fiber. The viscous damping coefficient of the CFRP structure is also highly sensitive to the carbon fiber angle; that is, it assumes a parallel series between the damping coefficient of the binding matrix and that of the carbon fiber. In this study, a sensitivity formula was derived to obtain the ratio of two parameters—the structural stiffness, and the viscous damping coefficient—by dividing all parameters by the value of the reference angle. The CFRP structure was chosen for a simple rectangular specimen with five carbon fiber angles, ranging from 0° (reference) to 90°. The identified modal parameters were used from the impact modal test conducted in a previous study. Sensitivity analysis was conducted for both the structural stiffness and the viscous damping coefficient. The sensitivity results revealed that the sensitivity index of the viscous damping coefficient was proportional to that of the structural stiffness. Even a small value of the viscous damping coefficient of the carbon fiber was sensitive to the CFRP structure because the carbon-fiber damping coefficient was parallel to the large damping coefficient of the binding matrix. Full article

(This article belongs to the Section Crystal Engineering)

► Show Figures

Figure 1

8 pages, 2301 KiB

Open AccessArticle

Low-Threshold and Wavelength-Tunable InGaN Tubular WGM Laser Embedded in a Flexible Substrate

by Peng Hu, Yufeng Li, Shengnan Zhang, Ye Zhang, Zhenhuan Tian and Feng Yun

Crystals 2021, 11(10), 1251; https://doi.org/10.3390/cryst11101251 - 15 Oct 2021

Cited by 4 | Viewed by 1436

Abstract

We have fabricated a tubular whispering gallery mode laser based on InGaN/GaN quantum wells and transferred it onto a flexible substrate. Compared with those without the transferring processes, the threshold energy density was reduced by 60%, at about 25.55 µJ/cm², while [...] Read more.

We have fabricated a tubular whispering gallery mode laser based on InGaN/GaN quantum wells and transferred it onto a flexible substrate. Compared with those without the transferring processes, the threshold energy density was reduced by 60%, at about 25.55 µJ/cm², while a high-quality factor of >15,000 was obtained. Finite-difference time-domain simulation demonstrated that such a low threshold energy density can be attributed to the decreased mode volume, from 1.32 × 10⁻³ μm³ to 6.92 × 10⁻⁴ μm³. The wavelength dependences on strain were found to be 5.83 nm, 1.38 nm, and 2.39 nm per stretching unit ε in the X, Y, and Z directions, respectively. Such strain sensitivity was attributed to the deformation of the GaN microtube and the change in the refractive index of the PDMS. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor Materials and Devices)

► Show Figures

Graphical abstract

19 pages, 14514 KiB

Open AccessArticle

Crystalline Phase Transitions and Reactivity of Ammonium Nitrate in Systems Containing Selected Carbonate Salts

by Maciej Kaniewski, Marta Huculak-Mączka, Jakub Zieliński, Marcin Biegun, Krystyna Hoffmann and Józef Hoffmann

Crystals 2021, 11(10), 1250; https://doi.org/10.3390/cryst11101250 - 15 Oct 2021

Cited by 5 | Viewed by 3760

Abstract

Samples of pure ammonium nitrate (AN) and its mixtures with calcium carbonate, potassium hydrogen carbonate and potassium carbonate were investigated with the use of differential thermal analysis with mass spectrometry, powder X-ray diffraction and scanning electron microscopy. The main objective of the study [...] Read more.

Samples of pure ammonium nitrate (AN) and its mixtures with calcium carbonate, potassium hydrogen carbonate and potassium carbonate were investigated with the use of differential thermal analysis with mass spectrometry, powder X-ray diffraction and scanning electron microscopy. The main objective of the study was to determine the influence of selected carbonate materials on phase transitions of ammonium nitrate and to consider a possibility to use such potassium salts as fillers in fertilizer production. It was proven that all carbonate salts caused the absence of a phase transition that normally would occur at around 84–86 °C. Potassium carbonates were too reactive in systems containing AN. Based on the performed study, it was concluded that even though potassium carbonates are not fit to replace mineral fillers in the production process of fertilizers containing ammonium nitrate, they could be used in lesser amounts to remove the presence of low-temperature phase transitions of AN. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Graphical abstract

10 pages, 1978 KiB

Open AccessArticle

Producing Iron Endohedral Fullerene on Electron Cyclotron Resonance Ion Source

by Yushi Kato, Takayuki Omori, Issei Owada, Wataru Kubo, Shuhei Harisaki, Koichi Sato, Kazuki Tsuda, Takumu Maenaka, Masahiro Anan, Masayuki Muramatsu, Atsushi Kitagawa and Yoshikazu Yoshida

Crystals 2021, 11(10), 1249; https://doi.org/10.3390/cryst11101249 - 15 Oct 2021

Viewed by 1463

Abstract

An electron cyclotron resonance (ECR) ion source (ECRIS) can generate an available amount of multicharged ions, thus it is not limited for use in the field of accelerator science, but also in medical/biological fields, such as for heavy ion beam cancer treatment and [...] Read more.

An electron cyclotron resonance (ECR) ion source (ECRIS) can generate an available amount of multicharged ions, thus it is not limited for use in the field of accelerator science, but also in medical/biological fields, such as for heavy ion beam cancer treatment and ion engines. The processes of generating multicharged ions are mainly sequential collisions of a direct ionization process by electrons, and have good ion confinement characteristics. By utilizing this confinement property, we have synthesized iron-encapsulated fullerenes, which are supramolecular and can be expected to have various high functions. Fullerenes and iron ions are vaporized from pure solid materials and introduced into the ECRIS together with the support gas. We investigated conditions under which fullerene ions do not dissociate and iron ions are generated so that both can coexist. Generated ions are extracted from the ECRIS and separated by mass/charge with a dipole magnet, and detected with a Faraday cup. This measurement system is characterized by a wide dynamic range. The charge-state distribution (CSD) of ion currents was measured to investigate the optimum conditions for supramolecular synthesis. As a result, a significant spectrum suggesting the possibility of iron-encapsulated fullerenes was obtained. This paper describes the details of these experimental results. Full article

(This article belongs to the Special Issue Applications of Fullerene Material)

► Show Figures

Figure 1

11 pages, 19345 KiB

Open AccessArticle

Performance Improvement of Amorphous Ga₂O₃/P-Si Deep Ultraviolet Photodetector by Oxygen Plasma Treatment

by Jin Cao, Liang Chen, Xin Chen, Yu Zhu, Jianqi Dong, Baoyu Wang, Miao He and Xingfu Wang

Crystals 2021, 11(10), 1248; https://doi.org/10.3390/cryst11101248 - 15 Oct 2021

Cited by 8 | Viewed by 2669

Abstract

Gallium oxide (Ga₂O₃) is an attractive semiconductor that is very suitable for deep ultraviolet (DUV) inspection. However, due to the existence of many types of oxygen vacancies in the amorphous Ga₂O₃ (a-Ga₂O₃) [...] Read more.

Gallium oxide (Ga₂O₃) is an attractive semiconductor that is very suitable for deep ultraviolet (DUV) inspection. However, due to the existence of many types of oxygen vacancies in the amorphous Ga₂O₃ (a-Ga₂O₃) film, it greatly limits the performance of the a-Ga₂O₃-based photodetector. Here, we perform oxygen plasma treatment on the a-Ga₂O₃/p-Si photodetector to reduce the concentration of oxygen vacancies in the a-Ga₂O₃ film, so that the dark current is reduced by an order of magnitude (from 1.01 × 10⁻³ A to 1.04 × 10⁻⁴ A), and the responsivity is increased from 3.7 mA/W to 9.97 mA/W. In addition, oxygen plasma processing makes the photodetector operate well at 0 V bias. The response speed is that the rise time is 2.45 ms and the decay time is 1.83 ms, while it does not respond to the DUV illumination without oxygen plasma treating at a zero bias. These results are attributed to the fact that oxygen plasma treatment can reduce the Schottky barrier between a-Ga₂O₃ and the electrode indium tin oxide (ITO), which promotes the separation and collection efficiency of photo-generated carriers. Therefore, this work proposes a low-cost method to improve the performance of Ga₂O₃ film-based DUV photodetectors. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor Materials and Devices)

► Show Figures

Graphical abstract

10 pages, 9307 KiB

Open AccessArticle

Efficient Synthesis of Mesoporous Nano ZSM-5 Zeolite Crystals without a Mesoscale Template

by Changsheng Zhang, Kai Fan, Ge Ma, Chi Lei, Wei Xu, Jie Jiang, Bing Sun, Hongxing Zhang, Yunfeng Zhu and Song Wen

Crystals 2021, 11(10), 1247; https://doi.org/10.3390/cryst11101247 - 15 Oct 2021

Cited by 4 | Viewed by 2324

Abstract

Hierarchical zeolites attract people’s attention due to their enhanced mass transfer properties in catalytic reactions. The research over obtaining these zeolites in green and efficient methods is of great significance for the current post-treatments and templating strategies tend to be costly for hierarchical [...] Read more.

Hierarchical zeolites attract people’s attention due to their enhanced mass transfer properties in catalytic reactions. The research over obtaining these zeolites in green and efficient methods is of great significance for the current post-treatments and templating strategies tend to be costly for hierarchical zeolite synthesis. In this research, nanosized mesoporous ZSM-5 (SN-ZSM-5) zeolites have been synthesized without the addition of mesoscale templates under highly concentrated conditions. The physicochemical characteristics were systematically investigated by XRD, SEM, N2 sorption, TEM, and NMR. The SEM images showed ZSM-5 crystals with sizes between 50–110 nm were obtained. N₂ sorption and high-resolution TEM images gave direct evidence for the hierarchical structure of SN-ZSM-5. The forming mechanism for the hierarchical structure was proposed that the etching effect of the highly alkaline environment for the starting gels played a critical role in the formation of hierarchical structure. Catalytic tests in methanol-to-olefins (MTO) showed the SN-ZSM-5 performed a longer catalyst lifetime and higher propylene selectivity than the conventional ZSM-5 zeolites (C-ZSM-5) obtained from a traditional hydrothermal method. The features of hierarchical structure in the SN-ZSM-5 crystals and the sustainability for synthesis method could show a promising choice for wide applications of these SN-ZSM-5 zeolites in the future. Full article

► Show Figures

Figure 1

9 pages, 3564 KiB

Open AccessArticle

The Use of Hirshfeld Surface Analysis Tools to Study the Intermolecular Interactions in Single Molecule Magnets

by Vassilis Psycharis, Despina Dermitzaki and Catherine P. Raptopoulou

Crystals 2021, 11(10), 1246; https://doi.org/10.3390/cryst11101246 - 14 Oct 2021

Cited by 8 | Viewed by 2461

Abstract

Intermolecular interactions have proved to play an important role in properties of SMMs such as quantum tunneling of magnetization (QTM), and they also reduce the rate of magnetic relaxation, as through the influence they have on QTM, they quicken the reverse of magnetization. [...] Read more.

Intermolecular interactions have proved to play an important role in properties of SMMs such as quantum tunneling of magnetization (QTM), and they also reduce the rate of magnetic relaxation, as through the influence they have on QTM, they quicken the reverse of magnetization. In addition, they are considered as the generative cause of the exchange-biased phenomenon. Using the Hirshfeld analysis tools, all the intermolecular interactions of a molecule and its neighbors are revealed, and this leads to a systematic study of the observed interactions, which could probably be helpful in other studies, such as theoretical calculations. In addition, they could be helpful to design new systems because intermolecular interactions in SMMs have been proposed as a probable tool to monitor their properties. The observation of characteristic patterns on the Hirshfeld Surfaces (HS) decorated with different properties makes easier the recognition of possible structural pathways for the different types of interactions of a molecule with its surrounding. Full article

(This article belongs to the Special Issue Synthesis and Characterization of Molecular Magnetic Materials Based on Coordination Chemistry)

► Show Figures

Figure 1

11 pages, 45710 KiB

Open AccessArticle

Thermal Deformation Behavior of Ti-6Mo-5V-3Al-2Fe Alloy

by Lin Han, Haoyu Zhang, Jun Cheng, Ge Zhou, Chuan Wang and Lijia Chen

Crystals 2021, 11(10), 1245; https://doi.org/10.3390/cryst11101245 - 14 Oct 2021

Cited by 2 | Viewed by 1246

Abstract

The Gleeble-3800 thermal simulation machine was used to perform hot compression experiments on a new type of β alloy, Ti-6Mo-5V-3Al-2Fe (wt.%), at temperatures of 700–900 °C, strain rates of 5 × 10⁻¹ to 5 × 10⁻⁴ s⁻¹, and total [...] Read more.

The Gleeble-3800 thermal simulation machine was used to perform hot compression experiments on a new type of β alloy, Ti-6Mo-5V-3Al-2Fe (wt.%), at temperatures of 700–900 °C, strain rates of 5 × 10⁻¹ to 5 × 10⁻⁴ s⁻¹, and total strain of 0.7. Transmission and EBSD techniques were used to observe the microstructure. The results show that the deformation activation energy of the alloy was 356.719 KJ/mol, and dynamic recrystallization occurred during the hot deformation. The higher the deformation temperature was, the more obvious the dislocations that occurred and the more sufficient the dynamic recrystallization that occurred, but the effect of strain rate was the opposite. When the deformation temperature was higher than the phase transition point, the recrystallized grains clearly grew up. The calculated strain rate sensitivity index of the alloy was 0.14–0.29. The constitutive equation of hot deformation of Ti-6Mo-5V-3Al-2Fe alloy was established by using the Arrhenius hyperbolic sine equation. The dynamic DMM hot working diagram with the strain of 0.7 was constructed. The relatively good hot working area of the alloy was determined to be the deformation temperature of 700–720 °C and 0.0041–0.0005 s⁻¹. Full article

► Show Figures

Graphical abstract

19 pages, 11232 KiB

Open AccessArticle

Structural and Spectroscopic Characteristics of Ni^II and Cu^II Complexes with Poly (Vinyl Alcohol-Nicotinic Acid) Copolymers for Photocatalytic Degradation of Indigo Carmine Dye

by Ibraheem O. Ali, Hisham S. Nassar, Ahmed M. Naglah, Laila M. Al-Harbi and Ahmed A. Elhenawy

Crystals 2021, 11(10), 1244; https://doi.org/10.3390/cryst11101244 - 14 Oct 2021

Cited by 2 | Viewed by 1633

Abstract

Poly-vinyl-alcohol (PVA) has been cross-linked chemically with nicotinic-acid (NA) in an aqueous medium. The copolymers were complexed with Ni^II and Cu^II ions. The complexes and copolymers were analyzed using FT-IR and UV–Visible spectroscopy, XRD and TGA, but copolymers were extra analyzed [...] Read more.

Poly-vinyl-alcohol (PVA) has been cross-linked chemically with nicotinic-acid (NA) in an aqueous medium. The copolymers were complexed with Ni^II and Cu^II ions. The complexes and copolymers were analyzed using FT-IR and UV–Visible spectroscopy, XRD and TGA, but copolymers were extra analyzed with nuclear magnetic resonance (¹H NMR). FT-IR spectra of copolymer revealed the presence of C=O & C–N groups due to the esterification of PVA-NA. The Cu/NA-PVA formed via bidentate interaction of the pyridinyl and carboxyl of NA. EPR/UV-vis data shows the square-planar geometry for Ni^II and Cu^II complexes. The adsorption of IC dye onto Cu^II/NA-PVA complex was noticeably greater (90%) in 35 min than Ni^II/NA-PVA. The DFT\B3LYP with 6- 311G* quantum chemical calculations were carried out for tested compounds. The DFT was conducted to examine an interaction mode of the target compounds with the reaction system. The QSPR was calculated as: optimization geometries, (FMOs), chemical-reactivities and NLO for the copolymers. The (MEPs) were figured to predict the interaction behavior of the ligand and its complexes. Full article

(This article belongs to the Special Issue Research about Vital Organic Chelates and Metal Ion Complexes)

► Show Figures

Figure 1

3 pages, 192 KiB

Open AccessEditorial

Green Approach in Synthesis of Bio-Inspired Materials

by Anamarija Stanković, Martina Medvidović-Kosanović, Jasminka Kontrec and Branka Njegić Džakula

Crystals 2021, 11(10), 1243; https://doi.org/10.3390/cryst11101243 - 14 Oct 2021

Viewed by 1193

Abstract

In this Special Issue, we focus on biomineralization/pathological biomineralization systems and the synthesis of bioinspired materials [...] Full article

(This article belongs to the Special Issue Green Approach in Synthesis of Bio-Inspired Materials)

6 pages, 1571 KiB

Open AccessArticle

Timing Fluctuation Correction of A Femtosecond Regenerative Amplifier

by Keyang Liu, Hongyang Li, Xinliang Wang, Yanqi Liu, Liwei Song and Yuxin Leng

Crystals 2021, 11(10), 1242; https://doi.org/10.3390/cryst11101242 - 14 Oct 2021

Cited by 1 | Viewed by 1603

Abstract

We report on the long-term correction of a timing fluctuation between the femtosecond regenerative amplifier and the reference oscillator for the seed 100 PW laser system in the Station of Extreme Light (SEL). The timing fluctuation was characterized by a noncollinear balanced optical [...] Read more.

We report on the long-term correction of a timing fluctuation between the femtosecond regenerative amplifier and the reference oscillator for the seed 100 PW laser system in the Station of Extreme Light (SEL). The timing fluctuation was characterized by a noncollinear balanced optical cross-correlator that maps the time difference to the sum frequency intensity of the amplifier and oscillator laser pulses. A feedback loop was employed to correct the timing jitter by adjusting the time delay line in the amplifier beam path. The timing fluctuation was reduced to 1.26 fs root-mean-square from hundreds of fs over 10 hours. Benefitting from excellent performance and long-term stability, this timing jitter correction scheme, as a component of optical synchronization in the 100 PW laser facility, will be integrated into SEL. Full article

(This article belongs to the Section Crystal Engineering)

► Show Figures

Figure 1

13 pages, 962 KiB

Open AccessReview

A Literature Review on High-Performance Photocatalysts for Sustainable Cancer Therapy

by Hanxi Yi and Zeneng Cheng

Crystals 2021, 11(10), 1241; https://doi.org/10.3390/cryst11101241 - 14 Oct 2021

Cited by 5 | Viewed by 2372

Abstract

Since cancer is a serious threat to public health worldwide, the development of novel methods and materials for treating cancer rapidly and thoroughly is of great significance. This review summarizes the mechanism and application of photocatalytic materials used to kill cancer cells. The [...] Read more.

Since cancer is a serious threat to public health worldwide, the development of novel methods and materials for treating cancer rapidly and thoroughly is of great significance. This review summarizes the mechanism and application of photocatalytic materials used to kill cancer cells. The photosensitivity and toxicological properties of several common photcatalysts used in anti-cancer treatment are discussed in detail. The ideal photocatalyst must possess the following characteristics: a highly stable production of active oxygen species and high selectivity to cancer cells without causing any damage to healthy tissues. This work concluded the existing photocatalytic materials used to treat cancer, as well as the current challenges in the application of cancer therapy. We aim to provide a basis for the development of new photocatalytic anti-cancer materials with high stability and selectivity while maintaining high photodynamic reaction performance. Full article

(This article belongs to the Special Issue Crystalline Micro- and Nano-Materials for Medical and Other Biochemical Applications)

► Show Figures

Figure 1

17 pages, 4678 KiB

Open AccessArticle

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

by Luka Fotović and Vladimir Stilinović

Crystals 2021, 11(10), 1240; https://doi.org/10.3390/cryst11101240 - 14 Oct 2021

Cited by 7 | Viewed by 2509

Abstract

We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared [...] Read more.

We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared them with their N-methyl-3-halopyridinium analogues. Structural analysis revealed that N-ethylated halogenopyridinium cations form slightly shorter C−X⋯I⁻ halogen bonds with iodide anion. We have also attempted synthesis of ditopic symmetric bis-(3-iodopyridinium) dications. Although successful in only one case, the syntheses have afforded two novel ditopic asymmetric monocations with an iodine atom bonded to the pyridine ring and another on the aliphatic N-substituent. Here, the C−I⋯I⁻ halogen bond lengths involving pyridine iodine atom were notably shorter than those involving an aliphatic iodine atom as a halogen bond donor. This trend in halogen bond lengths is in line with the charge distribution on the Hirshfeld surfaces of the cations—the positive charge is predominantly located in the pyridine ring making the pyridine iodine atom σ-hole more positive than the one on the alkyl chan. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Crystals, Volume 11, Issue 10 (October 2021) – 119 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI