Post-synthesis Grafting Method Research Articles

Optimization of surface silanol groups in mesoporous SBA-15 and KIT-6 materials: effects on APTES functionalization and CO2 adsorption

Hybrid mesoporous silicas are potentially reusable promising adsorbents for CO2 capture. Here SBA-15 and KIT-6 mesoporous silicas were synthetized by the sol-gel technique using a lower calcination temperature than the conventional one: 300 ºC vs. 550 ºC. This strategy aimed to maximize the surface hydroxyl group density and consequently, to improve functionalizing agent-loading performed by the post-synthesis grafting method. The as-obtained silica-based samples were then characterized and applied to CO2 capture. A correlation between chemical-textural properties and adsorption capacities of pure and modified materials was discussed. The calcined at 300 ºC silica supports, SBA-15-300-1 and KIT-6-300-1, with high silanol group densities showed better adsorption capacities overall pressure range. It is worth highlighting that the KIT-6-300-1: APTES adsorbent had a good stability performance, showing a drop of around 8 % over the aging time of a year. While, the SBA-15-300-1: APTES solid presented an excellent recycled performance after 10 adsorption-desorption cycles, maintaining about 95 % of its initial capacity.

Polystyrene-based hybrid solid acids with tunable hydrophobicity for the synthesis of polyoxymethylene dimethyl ethers from formaldehyde and methanol

In the synthesis of polyoxymethylene dimethyl ethers (PODEn) from formaldehyde (FA) and methanol (MeOH) solution, the methanol conversion and PODEn selectivity are unsatisfactory because the presence of water limits the adsorption of reactants on acid sites and leads to the hydrolysis of some products. Herein, polystyrene-based hybrid solid acids with tunable hydrophobicity and high acid density were synthesized by post-synthesis grafting method in this work. The prepared catalysts were investigated by BET, SEM, TEM, FT-IR, and acid-base titration. The results demonstrated that the surface property of the catalyst could be changed from hydrophilicity to hydrophobicity with the increase of organic group chain length, which effectively improved methanol conversion and PODE3-6 selectivity. The correlation between contact angles and turnover frequency (TOF) was investigated, suggesting that the TOF of polystyrene-based hybrid solid acids treated with octadecyl trichlorosilane was 2.0 times higher than that of untreated ones. Moreover, a supposed reaction pathway for the synthesis of PODEn from formaldehyde and methanol was proposed, indicating that the improvement of hydrophobicity promoted the decrease of local water concentration in the catalyst, thus facilitating the stabilization of carbocations.

Effects of Al introduction methods for Al-SBA-15 on NiMoS active phase morphology and hydrodesulfurization reaction selectivities

A series of Al-SBA-15 were synthesized with three Al introduction methods and different Si/Al molar ratios. The introduction methods included the direct synthesis (DS), post-synthesis grafting (PG) and impregnation synthesis (IM) method. The Si/Al molar ratios of Al-SBA-15 materials were 20, 10 and 5 respectively. The corresponding NiMoS catalysts were performed by hydrodesulfurization (HDS) recations of dibenzothiophene (DBT) to analyze reaction behavior. The characterization results of N2-physisorption, X-ray diffraction and 27Al NMR presented that the Al introduction method has a direct effect on the physical and chemical properties of Al-SBA-15. PG method could introduce most of Al atoms into the framework of parent- material, which was opposed to the IM method. The DS method could better maintain the pore structure advantages of the Al-SBA-15. The PG-NiMo catalyst had the strongest metal-support interaction, and the NiMoS slabs presented the lowest average stacking number over this catalyst. The reaction results showed that DS-NiMo catalyst obtained the highest HDS activity, and PG-NiMo catalyst presented the highest HDS hydrogenolysis selectivity of DBT. It is speculated that the frame-work Al has strong metal interaction with metal oxide precursor, and the morphology of NiMoS Phase has important effect on the selectivity of DBT HDS.

A heterogeneous mesoporous catalyst based on anchored copper: Schiff base complex into SBA-15 for the synthesis of benzimidazoles from orthoesters

In this article, we report the synthesis of 2-substituted benzimidazoles via condensation of 1,2-phenylenediamines and orthoesters using a heterogeneous catalyst based on anchored copper-Schiff base complex into SBA-15 (Cu/SBA-15) as a modified nanoporous material. The catalyst has been prepared via a postsynthesis grafting method and the 2D hexagonal mesoporous structures of this hybrid have been confirmed by small-angle X-ray scattering, transmission electron microscopy, N2 adsorption–desorption isotherms and Fourier transform infrared spectroscopy. Our results show that the benzimidazole heterocycles were obtained in good to excellent yields under solvent-free conditions in the presence of entitled catalyst. The mesoporous silica pore walls of the catalyst create some advantages such as high specific surface area, good to excellent yields of the benzimidazole products, non-toxicity and reusability.

Effect of grafting solvent in the optimisation of Sba-15 acidity for levulinIc acid production

Valorisation of lignocellulosic biomass for chemical production is one of the main challenges of the 21st century. Levulinic acid (LA) has been chosen as the target product due to its potential as an intermediate to produce a wide variety of other chemicals. The attention has been focused on the formulation of an active solid acid catalyst for the hydrolysis of glucose to LA. Therefore, a deep modification of SBA-15 with sulfonic groups was performed using post-synthesis grafting method. In particular, this work focuses on the role of different grafting solvents. Since the traditional solvents such as toluene or hexane, are flammable and toxic, a safer and more environmentally friendly solvent, a mixture of water and NaCl has been investigated. It was found that the nature of the solvent highly affects the morphological and chemical features of the materials. Thus, the best catalytic results were obtained with the catalyst prepared in water and NaCl; indeed 30 % and 16 % of LA yield were obtained from fructose and glucose hydrolysis at 180 °C respectively. Water and NaCl mixture guarantees the best distribution of sulfonic groups over the surface, leading to the most balanced acid catalyst.

The preparation of organophosphorus ligand-modified SBA-15 for effective adsorption of Congo red and Reactive red 2.

P,P-bis (2-oxooxazolidin-3-yl)-N-(3-(triethoxysilyl)propyl)phosphinic amide (APTES-BOP)-modified SBA-15 (SBA-15-BOP) was prepared by a post-synthesis grafting method for the removal of anionic azo dyes from aqueous solutions. The properties of the prepared adsorbent were characterized by PXRD, FT-IR, SEM, TEM, nitrogen sorption, and elemental analysis. Adsorption equilibrium and adsorption kinetic studies demonstrated that the experimental data fitted well with the Langmuir isotherm model and pseudo-second-order model. According to Langmuir fitting, SBA-15-BOP showed high adsorption capacity for CR and RR2 dyes, with the maximum adsorption capacities of 518.1 mg g−1 and 253.8 mg g−1, respectively. The thermodynamic study indicated that the adsorption processes of CR and RR2 dyes on SBA-15-BOP were spontaneous and exothermal. The prepared SBA-15-BOP can be a promising adsorbent for the removal of anionic dyes from aqueous solutions.

Triamine-bearing activated rice husk ash as an advanced functional material for nitrate removal from aqueous solution.

In this study, we proposed a simple method for preparing triamine-bearing activated rice husk ash material (TRI-ARHA) as an advanced functional material with high nitrate adsorption capacity and durability. The novel TRI-ARHA was generated via a post-synthesis grafting method and modified by acidification to form ammonium moiety. TRI-ARHA was then characterized by using thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy and SEM-mapping. The TRI-ARHA had high nitrate adsorption capacity of 163.4 mgNO3 -/g, which was 2.06 times higher than that of a commercial anion exchange resin (Akualite A420) due to strong interactions of Si, C, and N in the material structure. This functional material with good durability after 10 cycles could be very promising for adsorption of other anions (e.g. sulfate and phosphate) in water and wastewater treatment.

Investigation of the mechanism of chromium removal in (3-aminopropyl)trimethoxysilane functionalized mesoporous silica

We are proposed that a possible mechanism for Cr(VI) removal by functionalized mesoporous silica. Mesoporous silica was functionalized with (3-aminopropyl)trimethoxysilane (APTMS) using the post-synthesis grafting method. The synthesized materials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption-desorption analysis, Fourier-transform infrared (FT-IR), thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS) to confirm the pore structure and functionalization of amine groups, and were subsequently used as adsorbents for the removal of Cr(VI) from aqueous solution. As the concentration of APTMS increases from 0.01 M to 0.25 M, the surface area of mesoporous silica decreases from 857.9 m2/g to 402.6 m2/g. In contrast, Cr(VI) uptake increases from 36.95 mg/g to 83.50 mg/g. This indicates that the enhanced Cr(VI) removal was primarily due to the activity of functional groups. It is thought that the optimum concentration of APTMS for functionalization is approximately 0.05 M. According to XPS data, NH3+ and protonated NH2 from APTMS adsorbed anionic Cr(VI) by electrostatic interaction and changed the solution pH. Equilibrium data are well fitted by Temkin and Sips isotherms. This research shows promising results for the application of amino functionalized mesoporous silica as an adsorbent to removal Cr(VI) from aqueous solution.

Interaction between adsorbed molecules and tailor made large chelating ligands grafted on SBA-15 studied by means of thermoporometry

Modified mesoporous silicas were examined as adsorbents for efficient removal of model pollutants from wastewaters. Functionalized SBA-15 materials for capture of cationic pollutants such as metal cations and anionic dyes were obtained using post-synthesis grafting method. Large organic ligands containing acetyloacetone, 2-aminopyridine, 2-aminothiazole and 2-aminobenzothiazole groups were incorporated into the adsorbents' structure. The adsorption capacities reached levels of 38.6, 43.1, 64.3, 68.6 and 88.9 mg g−1 for Cu2+, Rose Bengal, Congo Red, Levafix Amber CA gran and Methyl Orange, respectively. Moreover, the adsorption efficiency depended on a type of the model molecule and a type of the surface chelating group. The pores' size and the pores' volume of the hybrid materials before and after adsorption was determined in hydrated state using thermoporometry. For the first time, by means of this methodology, it was possible to propose a model of interactions between the adsorbed molecules and the grafted organosilanes. Adsorption of organic dyes resulted in most cases in formation of J-aggregates.

Amino- and thiol-modified microporous silicalite-1 and mesoporous MCM-48 materials as potential effective adsorbents for Pb(II) in polluted aquatic systems

Aluminum-free zeolite silicalite-1 and the ordered mesoporous silicates Mobile Crystalline Material No. 48 (MCM-48) were prepared and functionalized with 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) for the enhancement of adsorption capacity. Functionalization via post synthesis grafting method was adopted and the functionalized silicate systems were denoted as silicalite-1-NH2, silcalite-1-SH, MCM-48-NH2and MCM-48-SH. Functionalization, that was confirmed by XRD, FT-IR and surface area measurements, indicated no structural changes on the silicate materials. The adsorption of Pb(II) ions into these modified silicates was investigated in aqueous solutions with optimized pH at 5.5 where adsorption influencing factors including contact time, adsorbent dose and metal ion initial concentration were studied. Adsorption experimental data for silicalite-1-NH2, MCM-48-NH2and MCM-48-SH showed satisfactory correlation with Langmuir and Freundlich models. According to Langmuir isotherm, the maximum capacities for the above three modified silicate systems, for 100 ppm Pb(II) dose, are 43.5, 75.2 and 31.2 mg/g and with Kfconstant values of 16.9, 44.4 and 12.0 L/mg from Freundlich isotherm, respectively. The three modified silicate systems exhibited complete sequestration of Pb(II) ion concentrations in the range 0.48–1.7 ppm from samples collected from Zarqa River in four seasons of the year 2013.

Improved solubility of celecoxib by inclusion in SBA-15 mesoporous silica: Drug loading in different solvents and release

In this study, celecoxib (CLX), a highly hydrophobic nonsteroidal anti-inflammatory drug with relatively low bioavailability, was used as a model drug to determine loading in different solvents and release properties from silica particles. Hydrothermal synthesis method was used to synthesize SBA-15 particles, which were functionalized by post-synthesis grafting method with (3-Aminopropyl) triethoxysilane (APTES). Additionally, boron doped SBA-15 samples were prepared to generate borosilicate samples. After functionalization, drug loading was carried out in three different solvents: ethanol, methanol and hexane and their effect on drug loading and release properties were examined. Particle morphology and solvent effect on drug loading capacity of silica particles, as well as the effect of pH on drug release were analyzed. For this purpose, SBA-15 particles were characterized by using X-ray Diffraction (XRD), Small-Angle X-ray Spectrometry (SAXS), N2 adsorption - desorption, Fourier Transform Infra-red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Ultra-Violet Spectrometry (UV-VIS) and Thermogravimetric Analysis (TGA).Herein we demonstrate a highly improved release rate of CLX by using SBA-15 silica particles as drug carriers compared to the commercial drug, Celebrex. We have observed slow release from SBA-15-A (APTES functionalized SBA-15) particles, while there was burst release from SBA-15-B (boron doped SBA-15) particles and all silica samples prepared in hexane. We also observed greater loss of viability with silica-CLX complexes compared to empty silica particles on colon cancer cell lines HCT-116 and HT-29 in vitro. Our results demonstrate the use of silica supports as potential drug delivery carriers for poorly water soluble drugs.

Amino-functionalized mesoporous MCM-41 silica as an efficient adsorbent for water treatment: batch and fixed-bed column adsorption of the nitrate anion

In the present study, amino-functionalized Mobil Composite Material No. 41 (MCM-41) was used as an adsorbent to remove nitrate anions from aqueous solutions. Mono-, di- and tri-amino functioned silicas (N-MCM-41, NN-MCM-41 and NNN-MCM-41) were prepared by post-synthesis grafting method. The samples were characterized by means of X-ray powder diffraction, FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption–desorption. The effects of pH, initial concentration of anions, and adsorbent loading were examined in batch adsorption system. Results of adsorption experiments showed that the adsorption capacity increased with increasing adsorbent loading and initial anion concentration. It was found that the Langmuir mathematical model indicated better fit to the experimental data than the Freundlich. According to the constants of the Langmuir equation, the maximum adsorption capacity for nitrate anion by N-MCM-41, NN-MCM-41 and NNN-MCM-41 was found to be 31.68, 38.58 and 36.81 mg/g, respectively. The adsorption kinetics were investigated with pseudo-first-order and pseudo-second-order model. Adsorption followed the pseudo-second-order rate kinetics. The coefficients of determination for pseudo-second-order kinetic model are >0.99. For continuous adsorption experiments, NNN-MCM-41 adsorbent was used for the removal of nitrate anion from solutions. Breakthrough curves were investigated at different bed heights, flow rates and initial nitrate anion concentrations. The Thomas and Yan models were utilized to calculate the kinetic parameters and to predict the breakthrough curves of different bed height. Results from this study illustrated the potential utility of these adsorbents for nitrate removal from water solution.

Novel pH-responsive swing gate system for adsorption and controlled release of BTB and MG dyes using amine functionalized mesoporous SBA-15 silica

Adsorption of anionic bromothymol blue (BTB) and cationic malachite green (MG) dyes on mono-, di- and triamine/ammonium functionalized mesoporous SBA-15 silica was investigated. The adsorbents were prepared via a post-synthesis grafting method of SBA-15 material using 3-aminopropyltrimethoxysilane, [1-(2-aminoethyl)-3aminopropyl]trimethoxysilane and 1-[3-(trimethoxysilyl)-propyl]-diethylenetriamine, followed by acidification in HCl solution to convert the attached surface amine groups to positively charged ammonium moieties. The release of BTB and MG species from free amine or ammonium functionalized adsorbents was controlled by adjusting the pH of solution. This system is proposed to be used as delivery modulation design system in which an ionically controlled molecular gate is created by using free amine/ammonium functionalized mesoporous materials with pH-responsive groups at the pore outlets. Results showed that the functionalized amine/ammonium SBA-15 materials act as a swing gate system and allow controlled selective adsorption–release of BTB and MG adsorbents and resulted in clean separation between them.

Complexes of N,N-bis (salicylidene)4,5-dimethyl-1,2-phenylenediamine immobilized on porous nanomaterials: Synthesis, characterization and study of their antimicrobial activity

A new hybrid antibacterial material was developed by post synthesis grafting method. 3-aminopropyl triethoxysilane (3-APTES) was first anchored over MCM-41 and NaY Zeolite upon reaction with transition metal (M = Mn(II), Co(II) and Cu(II)) complexes of tetradentate Schiff base ligand L: (C22H20N2O2). The prepared materials were characterized by several techniques: chemical analysis, diffuse reflectance spectroscopy (DRS), Fourier transfer infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Burner–Emmet–Taller(BET). The in vitro antibacterial activity of these compounds was evaluated against Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis), as Gram-positive bacteria, and further against Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), as Gram-negative bacteria. Then, the results were compared with standard drugs. The analysis revealed that hybrid materials that prepared by immobilization Schiff base in porous materials show fine inhibition on bacterial growth till 24 h.

The cooperative adsorption properties of cetyl/amino-SBA-15 for 4-nonylphenol.

In this study, mesoporous SBA-15 bifunctionalized with cetyl and amino groups (cetyl/amino-SBA-15) was successfully prepared by a post-synthesis grafting method. Detailed characterization by XRD, FT-IR, N2 adsorption-desorption and elemental analysis confirmed that cetyl/amino-SBA-15 still retained a long-range ordered hexagonal mesostructure. Cetyl and aminopropyl groups were simultaneously functionalized on the surface of SBA-15. The adsorption capacity of cetyl/amino-SBA-15 was much higher than the arithmetic sum of those of cetyl-SBA-15 and amino-SBA-15 due to the cooperative effect of hydrogen bonding/electrostatic interaction between 4-nonylphenol (4-NP) and aminopropyl groups and hydrophobic interactions between 4-NP and cetyl groups. The effects of the dosage and mole ratio of cetyl and amino groups on the adsorption properties of cetyl/amino-SBA-15 for 4-NP were also investigated. Cetyl/amino-SBA-15 exhibited excellent adsorption capacity over a wide range of pH values and cetyl/amino-SBA-15(3.2/0.8) displayed the highest adsorption capacity up to 120 mg g(-1). Furthermore, cetyl/amino-SBA-15 exhibited high adsorption selectivity for 4-NP against phenol as well as high reusability, showing great potential for applications in wastewater treatment.

Polymerizable Ligands as Stabilizers for Nanoparticles

Monomers bearing functional groups that can get chemisorbed on nanoparticles to form polymerizable monolayers have emerged as an interesting class of stabilizer ligands for various nanoparticles. High-surface coverage, their ability to modify the properties of underlying nanoparticles, capability to form polymers of different molecular weights and possibility to make structural modifications make them attractive for their use as stabilizer ligands for nanoparticles. Both in situ and post-synthesis grafting methods for attaching polymerizable ligands to nanoparticles are frequently used. The advantage of grafting polymerizable stabilizer on the surface of nanoparticles is that initially the polymerizable molecule acts as a proper stabilizer for the nanoparticles and later their surface polymerization or co-polymerization with another suitable monomer can be carried out to generate the desired polymer scaffold around the nanoparticles, which ensures the increased stability of the resulting core-polymerized shell nanoparticles. This review discusses interesting reports from recent literature on grafting of polymerizable ligands and their polymerization on gold, silver, silica, and iron oxide nanoparticles.

Surface functionalized TiO2 supported Pd catalysts for solvent-free selective oxidation of benzyl alcohol

Pd catalysts supported on TiO2 functionalized with various amounts of 3-aminopropyltriethoxysilane (APTES) were prepared using a post-synthesis grafting method combined with electroless deposition of Pd. As revealed by the Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results, monolayer APTES grafting was obtained using 0.005mmol APTES on 1.5g TiO2 support. Excess amounts of APTES resulted in both multilayer and reversed attachment, which NH2 attached to the TiO2 surface rather than giving free NH2 termination. The catalytic activity in the solvent-free selective oxidation of benzyl alcohol was correlated well with the highest amount of Pd deposited as well as the formation of small and uniform Pd nanoclusters with narrow particle size distribution (average diameter 3.4nm) on the 1%Pd/TiO2-0.005APTES. Increasing of surface basicity via the hydrolysis of amino groups (NH2) is suggested to enhance the dehydrogenation of benzyl alcohol, and as a consequence the selectivity toward benzaldehyde increased for all the APTES-modified TiO2 supported Pd catalysts. In addition, the combination of metallic Pd0 and PdOx (Pd2+/Pd4+) species gave high catalytic activity in the benzyl alcohol oxidation, emphasizing that the reduction of PdOx species by the adsorbed benzyl alcohol is an essential step to form highly active metallic Pd0 sites.

Palladium nanoparticles supported on organosilane-functionalized carbon nanotube for solvent-free aerobic oxidation of benzyl alcohol

Palladium nanoparticles supported on carbon nanotubes (CNT) functionalized with various organosilane modifiers have been prepared through a post-synthesis grafting method followed by a metal adsorption–reduction approach. The surface property, catalyst structure, electrochemical activity, and catalytic performance were tested in the selective aerobic oxidation of benzyl alcohol. The variation in type and amount of surface-functional groups played a key role in controlling catalytic behavior through fine tuning the surface basicity, metal nanoparticle size and size distribution, metal–support electronic interaction. In all these tested organosilane modifiers, 3-aminopropyl triethoxysilane exhibited the largest improvement in catalytic performance, with a remarkably high quasi-turnover frequency of 288,755h−1 based on the electrochemical active surface area.

4,4′-Diaminodiphenyl Sulfone Functionalized SBA-15: Toluene Sensing Properties and Improved Proton Conductivity

4,4′-Diaminodiphenyl sulfone functionalized SBA-15 (DDS/SBA-15) with various loading amounts of DDS has been prepared via a postsynthesis grafting method. The 2D hexagonal mesoporous structures of these hybrids have been confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N2 adsorption–desorption isotherms. The covalent grafting of DDS onto the SBA-15 was further confirmed by Fourier transform infrared spectroscopy (FT-IR). DDS/SBA-15 based quartz crystal microbalance (QCM) sensor shows good selectivity and quick response toward toluene vapor, and the detection limit is down to 20 ppb. Impedance spectroscopy measurements showed that the proton conductivity properties of DDS/SBA-15 depended on the loading amount of DDS. These hybrids demonstrated improved proton conductivities compared with pristine SBA-15, and a highest value of 2.26 × 10–4 S cm–1 has been observed when the DDS loading amount is 0.37 mmol g–1. Therefore, DDS/SBA-15 could serve as a promising candi...

Fluorescent hybrid assembled with Rhodamine B entrapped in hierarchical vesicular mesoporous silica

Vesicular mesoporous silica (VMS) was synthesized using cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulfate (SDS) as co-surfactant templates and then functionalized with (3-aminopropyl)triethoxysilane (APTES) as the silylation reagent through a post-synthesis grafting method. The results showed that the particle size and hierarchical structure of VMS could be modified by adjusting the anionic–cationic surfactant molar ratio and 1,3,5-triisopropylbenzene (TIPB) concentration. Changes in the molar ratio of SDS/CTAB generated a regular VMS comprising a hierarchical structure and two unique inter-cores. Fluorescent hybrid materials assembled with Rhodamine B (Rh B) on VMS or aminopropyl-functionalized VMS (NH2-VMS) were prepared. The hybrid materials were well characterized by Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectra, N2 adsorption–desorption experiments, elemental analysis, 29Si and 13C cross-polarization and magic angle spinning nuclear magnetic resonance, and fluorescence spectra. Rh B was used as a fluorescence unit to study the effect of aminopropyl functionalization on the fluorescence intensity of hybrid materials. We found that the fluorescence intensity of VMS-Rh B was significantly weaker than that of NH2-VMS-Rh B. In addition, compared to VMS2-Rh B and VMS4-Rh B, NH2-VMS2-Rh B and NH2-VMS4-Rh B exhibited blue shifts of fluorescence emission spectra from 588nm to 565nm and 578nm, respectively.