Chiral inorganic nanocatalysts for electrochemical and enzyme⁃mimicked biosensing

In recent years,chiral inorganic nanomaterials have become promising candidates for applications in sensing,catalysis,biomedicine,and photonics.Plasmonic nanomaterials with an intrinsic chiral structure exhibit intriguing geometry‑dependent optical chirality,which benefits the combination of plasmonic characteristics with chirality.Recent advances in the biomolecule‑directed geometric control of intrinsically chiral plasmonic nanomaterials have further provided great opportunities for their widespread applications in many emerging technological areas.In this review,we present the recent progress in biosensing using chiral inorganic nanomaterials,with a particular focus on electrochemical and enzyme‑mimicking catalytic approaches.This paper commences with a review of the basic tenets underlying chiral nanocatalysts,incorporating the chiral ligand‑induced mechanism and the architectures of intrinsically chiral nanostructures.Additionally,it methodically expounds upon the applications of chiral nanocatalysts in the realms of electrochemical biosensing and enzyme‑mimicking catalytic biosensing respectively.Conclusively,it proffers a prospective view of the hurdles and prospects that accompany the deployment of chiral nanoprobes for nascent biosensing applications.By rational design of the chiral nanoprobes,it is envisioned that biosensing with increasing sensitivity and resolution toward the single‑molecule level can be achieved,which will substantially promote sensing applications in many emerging interdisciplinary areas.

Effective production of γ-valerolactone from biomass-derived methyl levulinate over CuO_x-CaCO_3 catalyst

The production of?-valerolactone(GVL)from lignocellulosic biomass has become a focus of research owing to its potential applications in fuels and chemicals.In this study,(n)CuOx-CaCO3(where n is the molar ratio of Cu to Ca)compounds were prepared for the first time and shown to function as efficient bifunctional catalysts for the conversion of biomass-derived methyl levulinate(ML)into GVL,using methanol as the in-situ hydrogen source.Among the catalysts with varied Cu/Ca molar ratios,(3/2)CuOx-CaCO3 provided the highest GVL yield of 95.6% from ML.The incorporation of CaCO3 with CuO resulted in the formation of Cu+species in a CuOx-CaCO3 catalyst,which greatly facilitated the hydrogenation of ML.Notably,CuOx-CaCO3 also displayed excellent catalytic performance in the methanolysis products of cellulose,even in the presence of humins.Therefore,a facile two-step strategy for the production of GVL from cellulose could be developed over this robust and inexpensive catalyst,through the integration of cellulose methanolysis catalyzed by sulfuric acid,methanol reforming,and ML hydrogenation in methanol medium.

In situ synthesis of biomass-derived Ni/C catalyst by self-reduction for the hydrogenation of levulinic acid to γ-valerolactone

Herein,we reported in situ synthesis of biomass-derived Ni/C catalyst by self-reduction with pomelo peel.Compared with the conventional method, which includes carbonization, activation, impregnation and reduction, the entire preparation process was simplified to two steps, which was more straightforward. This synthesis method was green as Ni/C can be prepared without any additional chemical and the self-reduction process was realized in N2, which can avoid using H2 thus averting some problems such as storage, transportation and safety of H2. Meanwhile, the size and dispersion of Ni particles can be controlled by changing carbonization temperature.The synthesis mechanism of Ni/C catalyst with selfreduction was investigated, which was mainly attributed to the carbon and reducing gas produced during the carbonization process.For the catalytic performance of GVL synthesis, a high yield (94.5%) can be obtained and it exhibited good stability up to 5 cycles without obvious loss of catalytic activity.

Role of the Cu-ZrO_(2) interface in the hydrogenation of levulinic acid to γ-valerolactone

Here we exquisitely fabricated Cu/ZrO_(2)-dp catalysts with plentiful Cu-ZrO_(2)interfaces by depositing amorphous ZrO_(2)onto Cu nanoparticles for the hydrogenation of levulinic acid(LA)to y-valerolactone(GVL).With the created plentiful CU-ZrO_(2)interfaces,the optimal catalyst 3 Cu/ZrO_(2)-dp exhibited exceptional catalytic performance under mild reaction conditions,and achieved the highest GVL mass productivity of 266.0 mmol GVL·h^(-1)·g^(-1)Cu,which was 12.5 and 2.3 times of CU/ZrO_(2)catalysts with equivalent Cu loadings prepared by traditional impregnation(3 Cu/ZrO_(2)-im)or co-precipitation(3 Cu/ZrO_(2)-cp).As far as we know,this GVL mass productivity stood at the highest level compared with those obtained using non-noble metal catalysts under similar reaction conditions.By systematic investigation with multiple characterizations,density functional theory(DFT)calculations,and kinetic studies,it was found that interfacial active centers were created at Cu-ZrO_(2)interfaces,which contained oxygen vacancies(O_(v)),negatively charged Cu^(δ)-and partially reduced Zr^(3+)The O_(v) favored the adsorption and activation of LA via its ketone group,while negatively charged Cu^(δ)-was able to enhance heterolysis of H2,which resulted in the formation of H^(+)-Cu^(δ)-and Zr^(3+)-H^(-)active species via hydrogen spillover.Also,plentiful acid sites,which derived from coordinatively unsaturated and defective Zr species,generated at Cu-ZrO_(2)interfaces.With the cooperation of interfacial active centers(Cu^(δ-)-O_(v)-Zr^(3+))and acid sites,the fabricated 3 Cu/ZrO_(2)-dp with plentiful Cu-ZrO_(2)interfaces achieved excellent catalytic performance for the hydrogenation of LA to GVL.Hence,the synergistic catalysis of Cu-ZrO_(2)interfaces provided an effective strategy for designing catalysts with a satisfactory performance for the hydrogenation of LA,which also can be expanded to other hydrodeoxygenation reactions.

A New Condensation Reaction of β-Keto-δ-valerolactone with Substituted Aniline

A new condensation reaction of β-keto-δ-valerolactones was developed. The condensation products are composed of a pair of isomers because of the formation ofintramolecular hydrogen bond. Their structures were confirmed by 1HNMR and elemental analysis.

Transformations of biomass-based levulinate ester into γ-valerolactone and pyrrolidones using carbon nanotubes-grafted N-heterocyclic carbene ruthenium complexes

As a renewable biomass-based compound with wide applications in food additives,fine chemical synthesis and fuels,γ-valerolactone(GVL)has attached much attention.While,pyrrolidones are widely used in pharmaceutical,agrochemical,material industrial and other chemical production.In this research,we demonstrated transformations of biomass-based ethyl levulinate(EL)into GVL and pyrrolidones by using heterogeneous catalysts(CNT-Ru-1)with N-heterocyclic carbene ruthenium(NHC-Ru)complex grafted on multi-walled carbon nanotube(CNT).The Ru catalyst showed high efficiency on EL hydrogenation to GVL with both EL conversion and GVL yield exceeding 99%.Moreover,the Ru catalyst readily promoted reductive amination of EL in the presence of various amines for pyrrolidone synthesis.Finally,the Ru catalyst was also applicable to hydrogenation of various carbonyl compounds for the synthesis of the corresponding alcohols with excellent catalytic performance.The research provides insight for heterogenizing the homogeneous noble metal-based catalysts with high catalytic active for biomass-based transformations.

Catalytic transfer hydrogenation of levulinate ester intoγ-valerolactone over ternary Cu/ZnO/Al2O3 catalyst

An effective catalytic transfer hydrogenation (CTH) process of bio-based levulinate esters into γ-valerolactone (GVL) was explored over ternary Cu/ZnO/Al2O3 catalyst which was prepared by coprecipitation method and could be sustainably used. As a result, quantitative conversion of ethyl levulinate (EL) and 99.0% yield of GVL were obtained in the CTH process using i-PrOH as hydrogen donor. The Cu/ZnO/Al2O3 catalyst with high-surface-area could be reused at least four times without the loss of catalytic activity. Furthermore, the structure and properties of Cu/ZnO/Al2O3 catalyst was characterized through XRD, BET, SEM, TEM and H2-TPR. Also, the influence of different support oxides and calcination temperatures was investigated.

Condensation Products from β-Keto-δ-valerolactones

Unexpected condensation products from β-keto-δ-valerolactones were obtained. Theirstructures were confirmed by 'HNMR spectrum and elemental analysis.

Synthesis of ternary magnetic nanoparticles for enhanced catalytic conversion of biomass-derived methyl levulinate into γ-valerolactone

Conversion of levulinic acid and its esters into versatile y-valerolactone(GVL)is a pivotal and challenging step in biorefineries,limited by high catalyst cost,the use of hydrogen atmosphere,or tedious catalyst preparation and recycling process.Here we have successfully synthesized a ternary magnetic nanoparticle catalyst(Al_(2)O_(3)-ZrO_(2)/Fe_(3)O_(4)(5)),over which biomass-derived methyl levulinate(ML)can be quantitively converted to GVL with an extremely high selectivity of>99%and yield of-98%in the absence of molecular hydrogen.Al_(2)O_(3)-ZrO_(2)/Fe_(3)O_(4)(5)incorporates simultaneously inexpensive alumina and zirconia onto magnetite support by a facile coprecipitation method,giving rise to a core-shell structure,welldistributed acid-base sites,and strong magnetism,as evidenced by the X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM),high-angle annular dark-field scanning-TEM(HAADF-STEM),SEM-energy dispersive Xray spectroscopy(SEM-EDX),temperature-programmed desorption of ammonia(NH3-TPD),temperature-programmed desorption of carbon dioxide(CO_(2)-TPD),pyridine-adsorption infrared spectra(Py-IR),and vibrating sample magnetometry(VSM).Such characteristics enable it to be highly active and easily recycled by a magnet for at least five cycles with a slight loss of its catalytic activity,avoiding a time-consuming and energy-intensive reactivation process.It is found that there was a synergistic effect among the metal oxides,and the high efficiency and selectivity originating from such synergism are evidenced by kinetic studies.Furthermore,a reaction mechanism regarding the hydrogenation of ML to GVL is proposed by these findings,coupled with gas chromatography-mass spectrometry(GC-MS)analysis.Accordingly,this readily synthesized and recovered magnetic nanocatalyst for conversion of biomassderived ML into GVL can provide an eco-friendly and safe way for biomass valorization.

The hydrogenation of levulinic acid to γ-valerolactone over Cu–ZrO2 catalysts prepared by a pH-gradient methodology

A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr.All of the catalysts were highly selective to the desired product,γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction.Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability.We consider the active site to be the interface between Cu/CuOxand ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction.This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design.As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.

Effect of <i>γ</i>-Valerolactone Blending on Engine Performance, Combustion Characteristics and Exhaust Emissions in a Diesel Engine

γ-valerolactone (GVL) is a C5-cyclic ester that can be produced from biomass providing a potentially renewable fuel for transportation and feedstock for the chemical industry. Experiments were performed with fossil diesel (D), D + biodiesel (BD) and D + BD + GVL blends. A four-cylinder, turbocharged direct injection diesel engine was used for the tests. The engine was coupled to a dynamometer to vary the load. CO, NOx, THC and smoke emissions were measured by using a multi-channel gas analyzer. Combustion characteristics were assessed by in-cylinder pressure data with respect to crank angle and the derived heat release rates. Compared with D, and D + BD blends, addition of GVL had relatively little effect on engine performance and NOx emission, but reduced the exhaust concentration of CO, unburned fuel and smoke significantly. The smoke reduction is particularly notable in view of the very recent suggestion that black carbon is the second most important greenhouse gas in the atmosphere next to carbon dioxide. No diesel engine study with GVL has been reported so far.

Engineering Nano/Microscale Chiral Self‑Assembly in 3D Printed Constructs

Helical hierarchy found in biomolecules like cellulose,chitin,and collagen underpins the remarkable mechanical strength and vibrant colors observed in living organisms.This study advances the integration of helical/chiral assembly and 3D printing technology,providing precise spatial control over chiral nano/microstructures of rod-shaped colloidal nanoparticles in intricate geometries.We designed reactive chiral inks based on cellulose nanocrystal(CNC)suspensions and acrylamide monomers,enabling the chiral assembly at nano/microscale,beyond the resolution seen in printed materials.We employed a range of complementary techniques including Orthogonal Superposition rheometry and in situ rheo-optic measurements under steady shear rate conditions.These techniques help us to understand the nature of the nonlinear flow behavior of the chiral inks,and directly probe the flow-induced microstructural dynamics and phase transitions at constant shear rates,as well as their post-flow relaxation.Furthermore,we analyzed the photo-curing process to identify key parameters affecting gelation kinetics and structural integrity of the printed object within the supporting bath.These insights into the interplay between the chiral inks self-assembly dynamics,3D printing flow kinematics and photopolymerization kinetics provide a roadmap to direct the out-of-equilibrium arrangement of CNC particles in the 3D printed filaments,ranging from uniform nematic to 3D concentric chiral structures with controlled pitch length,as well as random orientation of chiral domains.Our biomimetic approach can pave the way for the creation of materials with superior mechanical properties or programable photonic responses that arise from 3D nano/microstructure and can be translated into larger scale 3D printed designs.

Reaction mechanism of aqueous-phase conversion of γ-valerolactone(GVL) over a Ru/C catalyst

The present work explores the reaction pathways of γ-valerolactone(GVL) over a supported ruthenium catalyst. The conversion of GVL in aqueous phase over a 5% Ru/C catalyst was investigated in a batch reactor operating at 463 K under 500–1000 psi of H2. The main reaction products obtained under these conditions were 2-butanol(2-BuOH), 1,4-pentanediol(1,4-PDO), 2-methyltetrahydrofuran(2-MTHF) and 2-pentanol(2-PeOH). A complete reaction network was developed, identifying the primary and/or secondary products. In this reaction network, production of 2-BuOH via decarbonylation of a ring-opened surface intermediate CH3CH(O*)–(CH2)2–CO*is clearly the dominant pathway. From the evolution of products as a function of reaction time and theoretical(DFT) calculations, a mechanism for the formation of intermediates and products is proposed. The high sensitivity of 2-BuOH production to the presence of CO, compared to a much lower effect on the production of the other products indicates that the sites responsible for decarbonylation are particularly prone to CO adsorption and poisoning. Also, since the decarbonylation rate is not affected by the H2 pressure it is concluded that the direct decarbonylation path of the CH3CH(O*)–(CH2)2–CO*intermediate does not required a previous dehydrogenation step, as is the case in decarbonylation of short alcohols.

Performance Comparison of Commercial and Home-Made Lipases for Synthesis of Poly(δ-Valerolactone)Homopolymers

Novozyme 435,which is the commercially available immobilized form of Candida antarctica lipase B,has been successfully conducted ring opening polymerization of lactones in organic solvents.In this paper,it was aimed to introduce an alternative biocatalyst for Novozyme 435.Candida antarctica lipase B immobilized onto rice husk ashes via physical adsorption(with a specific activity of 4.4 U/mg)was prepared in previous studies and used as a biocatalyst for poly(δ-valerolactone)synthesis in the present work.Polymerization reactions were proceeded at various reaction temperatures and periods via both two immobilized enzyme preparations.The resulting products were characterized spectroscopically and thermally.The highest molecular weight(Mn=9010 g/mol)was obtained via Novozyme 435 catalysis at 40℃and 24 hours.The performance of home-made lipase,which resulted in a molecular weight of 8040 g/mol,was close to commercial one.

First evidence for chiral wobbling of triaxial nuclei

Chirality(Greek“handiness”)is a property of many com-plex molecules.Chiral molecules exist in two forms,one being the mirror image of the other.Like for our hands,it is impossible to make the images identical by a suitable rota-tion.The two forms are called left-handed and right-handed.They have the same binding energy,because the electro-magnetic interaction,which holds the molecule together,does not change under a reflection.Other properties that are insensitive to the geometry are also the same.The different geometry is the reason why the left-handed form turns the polarization plane of transmitted light in one direction by some angle while the right-handed form turns it in the oppo-site direction by the same angle.However,the geometrical differences between the two species may have other conse-quences.The two species of the carvon molecule shown in Fig.1 taste quite differently.

Chiral Pair Density Waves with Residual Fermi Arcs in RbV_(3)Sb_(5)

The chiral 2×2 charge order has been reported and confirmed in the kagome superconductor RbV_(3)Sb_(5),while its interplay with superconductivity remains elusive owing to its lowest superconducting transition temperature Tc of about 0.85K in the AV_(3)Sb_(5) family(A=K,Rb,Cs)that severely challenges electronic spectroscopic probes.Here,utilizing dilution-refrigerator-based scanning tunneling microscopy down to 30 mK,we observe chiral 2×2 pair density waves with residual Fermi arcs in RbV_(3)Sb_(5).We find a superconducting gap of 150 μeV with substantial residual in-gap states.The spatial distribution of this gap exhibits chiral 2×2 modulations,signaling a chiral pair density wave(PDW).Our quasi-particle interference imaging of the zero-energy residual states further reveals arc-like patterns.We discuss the relation of the gap modulations with the residual Fermi arcs under the space-momentum correspondence between PDW and Bogoliubov Fermi states.

Advancing ophthalmic delivery of flurbiprofen via synergistic chiral resolution and ion-pairing strategies

Flurbiprofen(FB),a nonsteroidal anti-inflammatory drug,is widely employed in treating ocular inflammation owing to its remarkable anti-inflammatory effects.However,the racemic nature of its commercially available formulation(Ocufen^(R))limits the full potential of its therapeutic activity,as the(S)-enantiomer is responsible for the desired antiinflammatory effects.Additionally,the limited corneal permeability of FB significantly restricts its bioavailability.In this study,we successfully separated the chiral isomers of FB to obtain the highly active(S)-FB.Subsequently,utilizing ion-pairing technology,we coupled(S)-FB with various counter-ions,such as sodium,diethylamine,trimethamine(TMA),and l-arginine,to enhance its ocular bioavailability.A comprehensive evaluation encompassed balanced solubility,octanol-water partition coefficient,corneal permeability,ocular pharmacokinetics,tissue distribution,and in vivo ocular anti-inflammatory activity of each chiral isomer salt.Among the various formulations,S-FBTMA exhibited superior water solubility(about 1–12 mg/ml),lipid solubility(1<lgP_(ow)<3)and corneal permeability.In comparison to Ocufen^(R),S-FBTMA demonstrated significantly higher in vivo antiinflammatory activity and lower ocular irritability(such as conjunctival congestion and tingling).The findings from this research highlight the potential of chiral separation and ion-pair enhanced permeation techniques in providing pharmaceutical enterprises focused on drug development with a valuable avenue for improving therapeutic outcomes.

Chiral bound states in a staggered array of coupled resonators

We study the chiral bound states in a coupled-resonator array with staggered hopping strengths,which interacts with a two-level small atom through a single coupling point or two adjacent ones.In addition to the two typical bound states found above and below the energy bands,this system presents an extraordinary chiral bound state located within the energy gap.We use the chirality to quantify the breaking of the mirror symmetry.We find that the chirality value undergoes continuous changes by tuning the coupling strengths.The preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array,but also by the coherence between the two coupling points.In the case with one coupling point,the chirality values varies monotonously with difference between the intracell hopping and the intercell hoppings.While in the case with two coupling points,due to the coherence between the two coupling points the perfect chiral states can be obtained.

Nonreciprocal transport in the superconducting state of the chiral crystal NbGe_(2)

Due to the lack of inversion,mirror or other roto-inversion symmetries,chiral crystals possess a well-defined handedness which,when combined with time-reversal symmetry breaking from the application of magnetic fields,can give rise to directional dichroism of the electrical transport phenomena via the magnetochiral anisotropy.In this study,we investigate the nonreciprocal magneto-transport in microdevices of NbGe_(2),a superconductor with structural chirality.A giant nonreciprocal signal from vortex motions is observed during the superconducting transition,with the ratio of nonreciprocal resistance to the normal resistanceγreaching 6×10^(5)T^(-1)·A^(-1).Interestingly,the intensity can be adjusted and even sign-reversed by varying the current,the temperature,and the crystalline orientation.Our findings illustrate intricate vortex dynamics and offer ways of manipulation on the rectification effect in superconductors with structural chirality.

A Multifunctional Chiral Metasurface with Asymmetric Transmission and Linear-Polarization Conversion

In this paper,a multifunctional chiral metasurface is presented to achieve asymmetric transmission(AT)and linear-polarization conversion(LPC).The designed metasurface consists of a cross swords-like shape and two holes in the lower side of the unit cell.In the frequency band from 8.3 GHz to 10.4 GHz,AT is realized with more than 90%efficiency and the same chiral metasurface transforms linear polarized wave into its orthogonal counterpart with high efficiency.For LPC,the polarization conversion ratio(PCR)is greater than 95%.The proposed metasurface is stable against the incident angles of striking electromagnetic(EM)waves up to 60°for both operations of AT and LPC.