State of arts on the bio-synthesis of noble metal nanoparticles and their biological application

Nanomaterials are materials in which at least one of the dimensions of the particles is 100 nm and below.There are many types of nanomaterials,but noble metal nanoparticles are of interest due to their uniquely large surface-to-volume ratio,high surface area,optical and electronic properties,high stability,easy synthesis,and tunable surface functionalization.More importantly,noble metal nanoparticles are known to have excellent compatibility with bio-materials,which is why they are widely used in biological applications.The synthesis method of noble metal nanoparticles conventionally involves the reduction of the noble metal salt precursor by toxic reaction agents such as NaBH4,hydrazine,and formaldehyde.This is a major drawback for researchers involved in biological application researches.Hence,the bio-synthesis of noble metal nanoparticles(NPs)by bio-materials via bio-reduction provides an alternative method to synthesize noble metal nanoparticles which are potentially non-toxic and safer for biological application.In this review,the bio-synthesis of noble metal nanoparticle including gold nanoparticle(AuNPs),silver nanoparticle(AgNPs),platinum nanoparticle(PtNPs),and palladium nanoparticle(PdNPs)are first discussed.This is followed by a discussion of these biosynthesized noble metal in biological applications including antimicrobial,wound healing,anticancer drug,and bioimaging.Based on these,it can be concluded that the study on bio-synthesized noble metal nanoparticles will expand further involving bio-reduction by unexplored bio-materials.However,many questions remain on the feasibility of bio-synthesized noble metal nanoparticles to replace existing methods on various biological applications.Nevertheless,the current development of the biological application by bio-synthesized noble metal NPs is still intensively ongoing,and will eventually reach the goal of full commercialization.

STUDY ON THE INTERACTION BETWEEN POLYVINYLPYRROLIDONE AND PLATINUM METALS DURING THE FORMATION OF THE COLLOIDAL METAL NANOPARTICLES

Several PVP-stabilized colloidal platinum metals nanoparticles have been synthesized and characterized by FTIR and TEM.Comparing with the pure PVP,carbonyl groups of PVP in the mixture of PVP and the metal precursors or in the PVP-stabilized metal nanoparticles have obvious peak shifts in FTIR spectra.The peak shifts reveal the interaction between PVP and the metal species.The interaction between PVP and metal precursors has effect on the formation of the colloidal metal nanoparticles.Strength of the intera...

Second harmonic generation of metal nanoparticles under tightly focused illumination

The near-field and far-field second harmonic （SH） responses of a metal spherical nanoparticle placed in the focal region of a highly focused beam are investigated by using the calculation model based on three-dimensional finite-difference time-domain （FDTD） method. The results show that off-axis backward-propagating SH response can be reinforced by tightly focusing, due to the increase of the relative magnitude of the longitudinal field component and the phase shift along the propagation direction.

CATALYTIC PROPERTIES OF POLYMER-STABILIZED COLLOIDAL METAL NANOPARTICLES SYNTHESIZED BY MICROWAVE IRRADIATION

Catalytic properties of polymer-stabilized colloidal metal nanoparticles synthesized by microwave irradiationwere studied in the selective hydrogenation of unsaturated aldehydes,o-chloronitrobenzene and the hydrogenationof alkenes.The results show that nanosized metal particles synthesized by microwave irradiation have similar catalyticperformance in selective hydrogenation of unsaturated aldehydes,better selectivity to o-chloroaniline in hydrogenation ofo-chloronitrobenzene and higher catalytic activities in hydrogenation of alkenes,compared with metal clusters prepared byconventional heating.The same apparent activation energy(E_a=29 kJ mol^(-(?)) for hydrogenation of (?)-heptene catalyzed withplatinum nanoparticles prepared by both heating modes implied that the reaction followed the same mechanism.

Thermodynamic analysis and modification of Gibbs–Thomson equation for melting point depression of metal nanoparticles

Abnormal melting point depression of metal nanoparticles often occurs in heterogeneous catalytic reactions,which leads to a reduction in the stability of reactive nanoclusters.To study this abnormal phenomenon,the original and surface-energy modified Gibbs-Thomson equations were analyzed in this work and further modified by considering the effect of the substrate.The results revealed that the original Gibbs-Thomson equation was not suitable for the particles with radii smaller than 10 nm.Moreover,the performance of the surface-energy modified Gibbs-Thomson equation was improved,and the deviation was reduced to(-350-100)K,although further modification of the equation by considering the interfacial effect was necessary for the small particles(r<5 nm).The new model with the interfacial effect improved the model performance with a deviation of approximately-50 to 20 K,where the interfacial effect can be predicted quantitatively from the thermodynamic properties of the metal and substrate.Additionally,the micro-wetting parameterα_W can be used to qualitatively study the overall impact of the substrate on the melting point depression.

Metal nanoparticles for cancer therapy:Precision targeting of DNA damage

Cancer,a complex and heterogeneous disease,arises from genomic instability.Currently,DNA damage-based cancer treatments,including radiotherapy and chemotherapy,are employed in clinical practice.However,the efficacy and safety of these therapies are constrained by various factors,limiting their ability to meet current clinical demands.Metal nanoparticles present promising avenues for enhancing each critical aspect of DNA damage-based cancer therapy.Their customizable physicochemical properties enable the development of targeted and personalized treatment platforms.In this review,we delve into the design principles and optimization strategies of metal nanoparticles.We shed light on the limitations of DNA damage-based therapy while highlighting the diverse strategies made possible by metal nanoparticles.These encompass targeted drug delivery,inhibition of DNA repair mechanisms,induction of cell death,and the cascading immune response.Moreover,we explore the pivotal role of physicochemical factors such as nanoparticle size,stimuli-responsiveness,and surface modification in shaping metal nanoparticle platforms.Finally,we present insights into the challenges and future directions of metal nanoparticles in advancing DNA damage-based cancer therapy,paving the way for novel treatment paradigms.

Quasi-MOF-immobilized metal nanoparticles for synergistic catalysis

Through partial deligandation of metal-organic frameworks(MOFs),quasi-MOFs with a transition structure between MOFs and metal compounds(such as metal oxides,nitrides,sulfides,and phosphides)can be fabricated.Quasi-MOFs can not only retain the porous structure of MOFs to a certain extent,but also expose the inorganic nodes to the guest species(e.g.,metal nanoparticles)to show enhanced metal-support interaction for synergistic catalysis.This concept was first demonstrated by our group through calcining Au/MIL-101 at different temperatures under Ar flow to adjust the interface between Au nanoparticles and the inorganic Cr–O nodes.The obtained Au/quasi-MIL-101 showed superior enhanced catalytic activity in the oxidation of carbon monoxide.This study has inspired further research interest to fabricate other quasi-MOFs through controlled deligandation of mono-and bimetallic MOFs and their composites for the design of efficient catalysts.

Rapid room-temperature synthesis of a porphyrinic MOF for encapsulating metal nanoparticles

While metal nanoparticles(NPs)have shown great promising applications as heterogeneous catalysts,their agglomeration caused by thermodynamic instability is detrimental to the catalytic performance.To tackle this hurdle,we successfully prepared a functional and stable porphyrinic metal-organic framework(MOF),PCN-224-RT,as a host for encapsulating metal nanoparticles by direct stirring at room temperature.As a result,Pt@PCN-224-RT composites with well-dispersed Pt NPs can be constructed by introducing pre-synthesized Pt NPs into the precursor solution of PCN-224-RT.Of note,the rapid and simple stirring method in this work is more in line with the requirements of environmental friendly and industrialization compared with traditional solvothermal methods.

Investigation of multiple metal nanoparticles near-field coupling on the surface by discrete dipole approximation method

We use the method of discrete dipole approximation with surface interaction to construct a model in which a plurality of nanoparticles is arranged on the surface of BK7 glass. Nanoparticles are in air medium illuminated by evanescent wave generated from total internal reflection. The effects of the wavelength, the polarization of the incident wave, the number of nanoparticles and the spacing of multiple nanoparticles on the field enhancement and extinction efficiency are calculated by our model. Our work could pave the way to improve the field enhancement of multiple nanoparticles systems.

Spatial compartmentalization of metal nanoparticles within metal-organic frameworks for tandem reaction

Fabrication of multifunctional catalysts has always been the pursuit of synthetic chemists due to their efficiency,cost-effectiveness,and environmental friendliness.However,it is difficult to control multi-step reactions in one-pot,especially the spatial compartmentalization of incompatible active sites.Herein,we constructed metal-organic framework(MOF)composites which regulate the location distribution of metal nanoparticles according to the reaction path and coupled with the diffusion of substrates to achieve tandem reaction.The designed UiO-66-Pt-Au catalyst showed good activity and selectivity in hydrosilylation-hydrogenation tandem reaction,because the uniform microporous structures can control the diffusion path of reactants and intermediates,and Pt and Au nanoparticles were arranged in core-shell spatial distribution in UiO-66.By contrast,the low selectivity of catalysts with random deposition and physical mixture demonstrated the significance of artificial control to the spatial compartmentalization of active sites in tandem catalytic reactions,which provides a powerful approach for designing high-performance and multifunctional heterogeneous catalysts.

Catalytic activity of noble metal nanoparticles toward hydrodechlorination： influence of catalyst electronic structure and nature of adsorption

In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose （CMC） as a capping agent. These metal nanoparticles were then tested for catalytic hydrodechlorination toward two classes of organochlorinated compounds （vinyl polychlorides includ- ing trichloroethylene （TCE）, tetrachloroethylene （PCE）, and alkyl polychlorides including 1,1,1-trichloroethane （1,1,1-TCA）, and 1,1,1,2-tetrachloroethane （1,1,1,2- TeCA）） to determine the rate-limiting steps and to explore the reaction mechanisms. The surface area normalized reaction rate constant, ksA, showed a systematic depen- dence on the electronic structure （the density of states at the Fermi level） of the metals, suggesting that adsorption of organochlorinated reactants on the metal catalyst surfaces is the rate-limiting step for catalytic hydrodechlorination. Hydrodechlorination rates of 1,1,1-TCA and 1,1,1,2-TeCA agreed with the bond strength of the first （weakest） dissociated C-C1 bond, suggesting that C-C1 bond cleavage, which is the first step for dissociative adsorption of the alkyl polychlorides, controlled the catalytic hydro- dechlorination rate. However, hydrodechlorination rates of TCE and PCE correlated with the adsorption energies of their molecular （non-dissociative） adsorption on the noble metals rather than with the first C-C1 bond strength, suggesting that molecular adsorption governs the reaction rate for hydrodechlorination of the vinyl polychlorides.

Numerical Simulation on Thermal Response of Laser-Irradiated Biological Tissues Embedded with Liquid Metal Nanoparticles

Photothermal therapy is emerging as a very promising way for minimally invasive cancer treatment.To enhance thermal energy deposition of laser in target malignant tissues,liquid metal nanoparticles(LMNPs)have been recently identified as completely unprecedented photothermal sensitizers due to their unique physicochemical properties and superior photothermal conversion rate under near-infrared(NIR)laser irradiation.However,there is currently a strong lack of understanding of the laser energy distribution and the transient temperature field within the biological tissues,which would seriously hinder the development of LMNPs assisted photothermal therapy.Therefore,this paper focused on the distinctive photothermal effect of LMNPs embedded in biological tissues under NIR laser irradiation.The mathematical model coupling the Monte-Carlo photon transport model with Penne's bioheat transfer model has been established.Simulation studies have shown that LMNPs play an important role in enhancing the absorption of NIR laser,which contributes to local temperature rise and improves the temperature distribution.Comparing with the control case without LMNPs,the maximum temperature increases by nearly 1.0 time,the local temperature rise reaches 30℃ in 1.0 second.When the diameter and concentration of LMNPs are 40 nm and 1012/mm3,the resulting temperature variation and distribution is best for the effective killing of tumors without damaging normal tissues.In addition,the simulation results are meaningful for guiding the selection of laser irradiation time in conjunction with the cooling time,ensuring the controllable accuracy of treatment.To the best of our knowledge,the present study is one of the first attempts to quantify the influence of transformable LMNPs on the temperature distributions inside the biological tissues,showing important academic significance for guiding LMNPs assisted photothermal treatment.

Finned Zn-MFI zeolite encapsulated noble metal nanoparticle catalysts for the oxidative dehydrogenation of propane with carbon dioxide

Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.

Effect of the orientation of non-spherical metal nanoparticle with respect to light polarization on its transient optical response

Nanoparticles with non-spherical shapes are now being widely used for various photonic applications.We observe experimentally that the magnitude as well as the time dependence of the transient absorption of a colloid of silver nanoplatelets depends on the relative polarization of the pump and probe pulses.There have been a few reports about the dependence of the transient signal magnitude on polarization,but little information is available on its temporal dependence.Using a theoretical model,we show that this observed behavior arises from the fact that the energy absorption by a non-spherical nanoparticle depends on,among other factors,the nanoparticle orientation with respect to the pump and probe polarization directions.It is essential to consider this when estimating nanoparticle characteristics such as carrier thermalization time,carrier–phonon scattering time,and complex polarizability from transient absorption measurements.

Inorganic shell nanostructures to enhance performance and stability of metal nanoparticles in catalytic applications

In this article,we review the recent progress and our research activity on the synthesis of inorganic shell nanostructures to enhance the catalytic performance and stability of metal nanoparticles in catalytic applications.First,we introduce general synthetic strategies for the fabrication of inorganic nanoscale shell layers,including template-assisted sol-gel coating,hydrothermal(or solvothermal)synthesis and the self-templating process.We also discuss recent examples of metal nanoparticles(NPs)with nanoscale shell layers,namely core-shell,yolk-shell and multiple NPs-embedded nanoscale shell.We then discuss the performance and stability of metal particles in practical catalytic applications.Finally,we conclude with a summary and perspective on the further progress of inorganic nanostructure with nanoscale shell layers for catalytic applications.

Recent Advances on Confining Noble Metal Nanoparticles Inside Metal-Organic Frameworks for Hydrogenation Reactions

Hydrogenation reaction is one of the pillars of the chemical industry for the synthesis of drugs and fine chemicals.To achieve high catalytic performance,it is still highly desirable for constructing novel supported metal catalysts.Different from conventional supports like metal oxides,zeolites and carbon materials,metal-organic frameworks(MOFs)as the emerging porous materials have exhibited great potential to host metal nanoparticles(NPs)for achieving hydrogenation reactions with high catalytic efficiency,due to their unique porous structures.Recently,many progresses have been made,and thus,it is necessary to summarize the recent progresses on confining metal NPs inside MOFs for hydrogenation reactions.In this review,we first introduced the general synthesis methods for confining noble metal NPs inside MOFs.Then,the applications of noble metal NPs/MOFs catalysts in hydrogenation reactions were summarized,and the synergistic catalytic performances among noble metal NPs,metal nodes,functional groups,and pore channels in MOFs were illustrated.Subsequently,the hydrogen spillover effect involved in the hydrogenation reactions was discussed.Finally,we provide an outlook on the future research directions and challenges of confining noble metal NPs inside MOFs for hydrogenation reactions.

Biosynthesized metallic nanoparticles as fertilizers:An emerging precision agriculture strategy

Nanofertilizers increase efficiency and sustainability of agricultural crop production.Due to their nanosize properties,they have been shown to increase productivity through target delivery or slow release of nutrients,thereby limiting the rate of fertilizer application required.Nanofertilizers can be synthesized via different approaches ranging from physical and chemical to green(biological)synthesis.The green approach is preferable because it makes use of less chemicals,thereby producing less chemical contamination and it is safer in comparison to physicochemical approaches.Hence,discussion on the use of green synthesized nanoparticles as nanofertilizers is pertinent for a sustainable approach in agriculture.This review discusses recent developments and applications of biologically synthesized metallic nanoparticles that can also be used as nanofertilizers,as well as their uptake mechanisms for plant growth.Toxicity concerns of nanoparticle applications in agriculture are also discussed.

Monodisperse magnetic metallic nanoparticles: synthesis,performance enhancement, and advanced applications

Monodisperse Fe-based and Co-based nanopar-ticles exhibit unique magnetic properties. They play important roles in magnetic storage and biomedical application. Their chemical synthesis and performance enhancement draw a lot of study interest. Investigations of magnetic metallic nano-particles are very active in many scientific fields. This paper reviews the present advances in chemical synthesis, perfor-mance enhancement, and potential applications of monodis-perse Fe-based and Co-based nanoparticles.

Fabrication of metal nanoparticles on highly dispersed pristine carbon nanotubes

A convenient approach to fabricate metal(i.e.gold,platinum,and palladium)nanoparticles on highly dispersed pristine carbon nanotubes(CNTs)was developed using a conjugated block copolymer of poly(3-hexylthiophene)-b-poly(vinylpyrrolidone)(P3HT-b-PVP).P3HT-b-PVP not only provides a stable dispersion of pristine CNTs through theπ–πinteractions between P3HT block and CNTs,but also introduces PVP groups on CNT surfaces to induce the heterogeneous nucleation of metal nanoparticles and protect them from aggregating.The density of metal nanoparticles on CNT surfaces was controlled by the metal salt/CNT feed ratio.The simple processing procedure,versatility in synthesizing various metal nanoparticles,high metal nanoparticle loading capacity,and excellent dispersibility and processability of the product make this approach a promising method to fabricate metal nanoparticles on CNTs.

Onion-structured transition metal dichalcogenide nanoparticles by laser fabrication in liquids and atmospheres

Since the discovery of transition metal dichalcogenide(TMDC)nanoparticles(NPs)with the onion-like structure,many efforts have been made to develop their fabrication methods.Laser fabrication(LF)is one of the most promising methods to prepare onion-structured TMDC(or OS-TMDC)NPs due to its green,flexible,and scalable syntheses.In this mini-review article,we systematically introduce various laser-induced OS-TMDC(especially the OS-MoS_(2))NPs,their formation mechanism,properties,and applications.The preparation routes mainly include laser ablation in liquids and atmospheres,and laser irradiation in liquids.The various formation mechanisms are then introduced based on the different preparation routes,to describe the formations of the corresponding OS-NPs.Finally,some interesting properties and novel applications of these NPs are briefly demonstrated,and a short outlook is also given.This review could help to understand the progress of the laser-induced OS-TMDC NPs and their applications.