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Precise manipulation of liquid metal (LM) droplets possesses the potential to enable a wide range of applications in reconfigurable electronics, robotics, and microelectromechanical systems. Although a variety of methods have been explored to actuate LM droplets on a 2D plane, versatile 3D manipulation remains a challenge due to the difficulty in overcoming their heavy weight. Here, foam-core liquid metal (FCLM) droplets that can maintain the surface properties of LM while significantly reducing the density are developed, enabling 3D manipulation in an electrolyte. The FCLM droplet is fabricated by coating LM on the surface of a copper-grafted foam sphere. The actuation of the FCLM droplet is realized by electrically inducing Marangoni flow on the LM surface. Two motion modes of the FCLM droplet are observed and studied and the actuation performance is characterized. Multiple FCLM droplets can be readily controlled to form 3D structures, demonstrating their potential to be further developed to form collaborative robots for enabling wider applications.

Copper peroxide coated upconversion nanoparticle was modified with glucose oxidase to obtain the efficient nanocomposite UCN@CuO2–GOx that was successfully applied for H2O2 self-supplying starvation-enhanced chemodynamic therapy in vitro.

A single-light irradiated multifunctional PdAu-based nanotheranostic agent was developed for MR/CT/PA triple-modal imaging guided photothermal therapy and oxygen-independent photodynamic therapy.

Photothermal therapy has been considered a powerful means of cancer therapy due to its minimal invasiveness, effectiveness, and convenience. Although promising, the therapeutic effects are greatly limited as they rely on the photothermal agent (PTA). It is urgent to develop new PTAs with high photothermal conversion performance, especially under irradiation in the long-wavelength biowindows. Herein, a dual-biowindow-responsive PTA made of NbS2-PVP nanosheets was fabricated to be used both in the first near-infrared (NIR-I) and the second near-infrared (NIR-II) biowindows. With excellent hydrophilicity and biocompatibility, the nanosheets could effectively convert the near-infrared (NIR) light into heat, showing prominent photothermal stability. The calculated photothermal conversion efficiencies reached 59.2% (under NIR-I excitation) and 69.1% (under NIR-II excitation), respectively, which are comparable to those of metallic PTAs. The NbS2-PVP nanosheets had low cytotoxicity and could trigger strong photothermal treatment and cause cancer cell death upon irradiation by NIR-I or NIR-II light in vitro. Moreover, we have also demonstrated the highly efficient tissue ablation and tumor inhibition capability of NbS2-PVP nanosheets in vivo. This work explores an effective PTA of two-dimensional nanomaterials in NIR-I and NIR-II biowindows and offers a reference for the design of new kinds of PTAs.

Carbon monoxide (CO) can cause mitochondrial dysfunction, inducing apoptosis of cancer cells, which sheds light on a potential alternative for cancer treatment. However, the existing CO-based compounds are inherently limited by their chemical nature, such as high biological toxicity and uncontrolled CO release. Therefore, a nanoplatform - UmPF - that addresses such pain points is urgently in demand. In this study, we have proposed a nanoplatform irradiated by near-infrared (NIR) light to release CO. Iron pentacarbonyl (Fe(CO)5) was loaded in the mesoporous polydopamine layer that was coated on rare-earth upconverting nanoparticles (UCNPs). The absorption wavelength of Fe(CO)5 overlaps with the emission bands of the UCNPs in the UV-visible light range, and therefore the emissions from the UCNPs can be used to incite Fe(CO)5 to control the release of CO. Besides, the catechol groups, which are abundant in the polydopamine structure, serve as an ideal locating spot to chelate with Fe(CO)5; in the meantime, the mesoporous structure of the polydopamine layer improves the loading efficiency of Fe(CO)5 and reduces its biological toxicity. The photothermal effect (PTT) of the polydopamine layer is highly controllable by adjusting the external laser intensity, irradiation time and the thickness of the polydopamine layer. The results illustrate that the combination of CO gas therapy (GT) and polydopamine PTT brought by the final nanoplatform can be synergistic in killing cancer cells in vitro. More importantly, the possible toxic side effects can be effectively prevented from affecting the organism, since CO will not be released in this system without near-infrared light radiation.

Developing multifunctional nanocomposites for a pH-responsive controlled dual-drug delivery is still a huge challenge. Herein, we report a gentle and simple method for growing metal-organic frameworks (MOFs) that can load two anticancer drugs, namely DOX and 5-FU (doxorubicin and 5-fluorouracil), on the surface of upconversion nanoparticles (UCNPs) by the reactions of Schiff bases and electrostatic adsorption. The resulting pH-responsive UCMOFs@D@5 nanosystem showed effective dual-drug release by the cleavage of chemical bonds and the disruption of the MOF structure under acidic conditions. Moreover, the final nanosystem UCMOFs@D@5 showed much higher cytotoxicity in comparison with UCMOFs@D and UCMOFs@5, which loaded only one kind of drug, respectively, after being incubated with human cervical cancer (HeLa) cells, indicating that Dox and 5-FU released from the final nanosystem had synergistic effects on cytotoxicity. Cellular uptake studies showed that UCMOFs@D@5 was well uptaken by HeLa cells and has potential for bioimaging applications in intracellular fluorescence imaging with high-contrast, and is beneficial for the intracellular localization of anti-cancer drugs. In addition, the nanosystem can be successfully applied in T1-weighted magnetic resonance imaging. Therefore, we developed a visualized tracking agent combined with MOFs to load two anticancer drugs to form a nanosystem for diagnosis and synergistic treatment, thus achieving the bioimaging and stimulation-responsive dual-drug release.

Microrobots have attracted considerable attention due to their immense potential for biomedical and engineering applications in recent years. Inspired by human walks, a bipedal microwalker capable of standing and walking like humans regulated by external weak magnetic fields was reported in this paper. The walker has a submillimeter size and a simple arrowhead shape. Its standing and walking locomotion is controlled by external oscillating magnetic fields generated by orthogonal electromagnetic coil pairs. The walking speeds of the microwalker are controlled using magnetic fields with varying parameters. The walking speeds on a glass substrate immersed in water could reach up to 2.2 mm s−1. Designed walking paths of the microwalker on a horizontal substrate are also demonstrated. Besides walking on horizontal flat surfaces, the microwalker can climb up slopes and walk freely in circular microtubes. The microwalker is of interest in fundamental robotic gait research and for micromanipulation applications.

Nanocomposites have been playing an increasingly significant role in the bioimaging-guided visualization of cancer physiotherapy. However, it has been a challenge to explore new diagnosis and treatment reagents with small size, good stability, and high photothermal conversion efficiency. Herein, we report a novel preparation of nanocomposites based on the heterogeneous growth of nano-palladium on the surface of upconversion nanoparticles (UCNPs). The final poly vinylpyrrolidone (PVP) modified UCNPs@Pd nanocomposites possess a small size and exhibit good monodispersity, biocompatibility and high photothermal conversion efficiency. In addition, relevant cellular assays show that based on the growth of palladium, the UCNPs@Pd-PVP nanocomposites can effectively kill HeLa cells under 808 nm laser irradiation. The nanocomposites also present effective upconversion luminescence imaging and T1 signal enhancement capability based on Er3+ and Gd3+ ions, respectively. Therefore, the nanocomposites successfully integrate upconversion luminescence imaging, magnetic resonance imaging, and photothermal therapy. This work provides new insights for the future development of multi-application materials based on the multicomponent heterogeneous growth of nanocomposites.

Recent progress of untethered mobile micromotors has shown immense potential for targeted drug delivery in vivo. However, designing a wireless micromotor with high maneuverability and biocompatibility and achieving controlled drug release with high efficiency at a specific position remains a great challenge. Herein, we present a pine pollen-based micromotor (PPBM) and demonstrate its potential application as a cargo carrier for targeted drug delivery. These multifunctional biohybrid micromotors were massively and inexpensively fabricated by the encapsulation of magnetic particles (Fe3O4) and medicine into the two hollow air sacs of pine pollen, via vacuum loading. PPBMs successfully inherit the intrinsic functionalities of pine pollen: structural uniformity, morphological stability, biocompatibility, autofluorescence (AF) and physicochemical robustness. Under an external magnetic field, the loaded Fe3O4 enables individual and swarm PPBMs to propel precisely in complex biological fluids. Capitalizing on the magnetic nanoparticle aggregation phenomenon under a powerful magnetic field, controlled release of the therapeutic cargo is achieved using a fluid field generated by the rotating magnetic agglomerate. The biohybrid micromotors reported here turn natural pine pollen into active and controllable cargo carriers for biomedical applications.

Flexible piezoresistive sensors with high sensitivity and repeatability are highly desirable for monitoring human activity and human–machine interactions. However, it is still a great challenge to fabricate high-performance sensors due to the limits of multifunctional sensing platforms. In this work, hierarchical framework-structured PVDF/PU/MWCNT (PPM) aerogels fabricated by a facile thermo-assembly method were suggested as sensitive sensing platform to detect pressure and strain. The pressure-sensing platform based on optimized PPM aerogels exhibited high sensitivity of 62.4 kPa−1 and fast response of 35 ms, which enabled the detection of minute static pressure of 3 Pa. The sensing platform was also able to detect wide-range compression from 0.5% to 90% and dynamic piezoresistive response behaviour from 1 Hz to 3 kHz, showing excellent repeatability over 50 000 compression cycles and ultrahigh strain sensitivity of 156.4, which was the highest reported gauge factor. Moreover, the sensing platform with ultrahigh sensitivity and excellent repeatability enabled the monitoring of human activities, human health, human–machine interactions and non-contact actions such as music intensity. The facile fabrication and versatile capabilities of the sensing platform make it a promising candidate for wearable sensors.

A new kind of carbon dots with an average diameter of approximately 3–5 nm were synthesized using L-lysine. Subsequently, a series of lanthanide complex-functionalized carbon dots were designed and synthesized, denoted as Ln-CDs (Ln = Eu, Sm, Er, Yb, Nd). In addition, by changing the ratio of Eu complexes and carbon dots, four kinds of Eu complex-functionalized carbon dots were also obtained (Eu-CDs-1, Eu-CDs-2, Eu-CDs-3, Eu-CDs-4). The derived nanomaterials were characterized by Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. Upon visible-light excitation, these lanthanide complex-functionalized carbon dots show multicolor visible (Eu; with red, orange, grey and blue colors, respectively) and near-infrared (Sm, Er, Nd, Yb) luminescence (emission covered from 400 nm to 1700 nm spectral region).

A novel fluorescent chemosensor containing two rhodamine B moieties per molecule was synthesized and characterized as an “off–on” fluorescent probe for the detection of copper ions (Cu2+). The crystal structure of the chemosensor was confirmed by X-ray analysis and the recognition mechanism of detecting Cu2+ was proposed with absorption and fluorescence characterization. The chemosensor showed high selectivity and sensitivity and good repetition in sensing Cu2+, and the detection limit is as low as 38.00 nM. In addition, the chemosensor displayed low cytotoxicity as revealed by methyl thiazolyl tetrazolium (MTT) assays and was successfully applied to fluorescence test paper and living cell imaging for detecting Cu2+. Therefore, based on its environmental friendliness and good biocompatibility, the results offered the advantages including the detection of Cu2+ in the environment and bioimaging of intracellular Cu2+.

A new 2,2′-bipyridine-4,4′-dicarboxylic acid-functionalized polyhedral oligomeric silsesquioxane (named as bpdc-POSS) was successfully synthesized. Subsequently, six new Ln-bpdc-POSS (Ln = Eu, Tb, Sm, Nd, Yb, Er) hybrid materials covalently linked with lanthanide complexes were prepared, based on the bpdc-POSS material acting as a matrix. The Ln-bpdc-POSS hybrid materials retain the structure of POSS and size distribution approximately 50 nm, and display visible as well as near-infrared luminescence (covered from 450 to 1700 nm wavelength region) under UV/visible light excitation. The Ln-bpdc-POSS materials (Ln = Eu, Tb, Sm, Er, Nd, Yb) were characterized by using wide-angle X-ray powder diffraction, Fourier-transform infrared (FT-IR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), fluorescent spectroscopy and thermogravimetric analysis. The method offers advantages including the ease of synthesis and handling, as well as extending the use of POSS and expanding the field of luminescent inorganic–organic hybrid materials based on lanthanides.

Two kinds of luminescent nanoprobes were developed for Pb2+ detection based on luminescence resonance energy transfer (LRET) by using sodium citrate functionalized upconversion nanoparticles (Cit-UCNPs) as the energy donor and single-walled carbon nanohorns (SWCNHs) or graphene oxide (GO) as the energy acceptor. A Pb2+ aptamer 5′-NH2-(CH2)6-GGGTGGGTGGGTGGGT-3′ (denoted as pDNA) sequence was assembled with Cit-UCNPs to form the Cit-UCNPs–pDNA. By using the SWCNHs (or GO) as matrix, the final Cit-UCNPs–pDNA–SWCNHs (or Cit-UCNPs–pDNA–GO) nanoprobe can be obtained, in which the LRET process happened and the upconversion luminescence of the probe was quenched. With the addition of Pb2+, a stable G-quadruplex–Pb2+ complex was formed, which results in the separation between Cit-UCNPs–pDNA nanoparticles and SWCNHs (or GO) and the recovery of the upconversion luminescence. The two turn-on luminescence probes could detect Pb2+ ions from amongst other ions with high sensitivity and selectivity in aqueous solution. To the best of our knowledge, a nanoprobe for the detection of Pb2+ ions based on LRET between UCNPs and SWCNHs (or GO) has not been reported in the literature to date. This work demonstrates a simple yet powerful sensing strategy, which may open up potential perspectives for environmental monitoring applications.

A new luminescence “Turn-On” nanoplatform based on luminescence resonance energy transfer (LRET) from sodium citrate functionalized upconversion nanoparticles (Cit-UCNPs, energy donor) to single-walled carbon nanohorns (SWCNHs, energy acceptor) was prepared for sensitive detection of acute promyelocytic leukemia (APL). In the presence of the target DNA, a PML/RARα fusion gene of APL, the π–π stacking interaction between the energy donor Cit-UCNPs and energy acceptor SWCNHs weakened and their distance enlarged. Therefore, the luminescence of Cit-UCNPs would be recovered (turn on) due to the inhibition of the LRET process. Based on this fact, a sensitive method was developed for the fluorescence turn on detection of ALP with a detection limit as low as 0.28 nM. To the best of our knowledge, this is the first time that upconversion nanoparticles and single-walled carbon nanohorns were used as a donor–acceptor pair to detect PML/RARα fusion gene sequences through a LRET process.

It is greatly important to seek a fast and sensitive method for the detection of Cu2+ ions because of their vital role in the human body. Fluorescent probes, especially the rhodamine derivatives, have been considered as promising candidates for detection of Cu2+ ions due to their attractive features. However, one problem frequently encountered in rhodamine-based fluorescent probes is that some of them could not distinguish Cu2+ from Hg2+ and these drawbacks limit their application in biological samples. In this paper, a rhodamine B derivative (RBH) was grafted to mesoporous silica coated upconversion nanoparticles (CS-UCNP) to fabricate a new organic–inorganic hybrid nanoprobe. On addition of Cu2+ ions, an emission band at about 580 nm appeared while the intensity of the green emission at about 545 nm of the nanoprobe decreased upon excitation of a 980 nm laser, implying that a luminescence resonance energy transfer (LRET) happened from the CS-UCNP to the RBH–Cu2+ complex. The obtained LRET nanoprobe could detect Cu2+ exclusively even in the presence of Hg2+ with a detection limit of 0.82 μM in absolute ethanol solution. Most importantly, this nanoprobe can be used for monitoring subcellular distribution of Cu2+ in living cells based on upconversion luminescence and downconversion fluorescence.

A novel mesoporous nanosphere functionalized with 3-(aminopropyl)triethoxysilane (APTES) and 2-(5-bromothiophen)imidazo[4,5-f][1,10]phenanthroline (5-Br-Tip) was synthesized (denoted as Tip-MSS). With the coordinating function of the 5-Br-Tip to lanthanide (Ln) ions, for the first time, LnL3(5-Br-Tip) complexes were linked to the mesoporous nanospheres. The derived materials, named Ln-Tip-MSS (Ln = Eu, Tb, Sm, Nd, Yb), were characterized by Fourier-transform infrared (FT-IR) spectroscopy, TEM, XRD (wide-angle and small-angle), N2 adsorption/desorption analysis, and fluorescence spectroscopy. Upon excitation in the ligand absorption, the Ln-Tip-MSS nanomaterials show characteristic visible (Eu, Tb, Sm) and NIR (Sm, Nd, Yb) luminescence (multicolor emission covered from 450 nm to 1400 nm spectral region). Of importance is that, with low cytotoxicity and good biocompatibility given by the methyl thiazolyl tetrazolium (MTT) assay, the Eu-Tip-MSS was successfully applied to cell imaging in vitro based on the Eu(3+) luminescence (under 405 nm excitation).

We designed an easy-to-fabricate multi-luminescent nanopaper with high transparency, for the first time, by grafting lanthanide complexes [Eu(dbm)3(H2O)2, Sm(dbm)3(H2O)2, Tb(tfacac)3(H2O)2] on TEMPO mediated oxidized nanofibrillated cellulose (ONFC). The lanthanide complex functionalized ONFC nanopaper (Ln–ONFC nanopaper, Ln = Eu, Sm, Tb) with uniform luminescence was rapidly fabricated after solvent exchange using a press-controlled extrusion papermaking method. The new TEMPO-induced carboxyl groups on the surface of ONFC provided the possibility to participate in the coordination with lanthanide ions and then to construct heterogeneous network architectures. The fluorescent properties of the Ln–ONFC hybrid nanopaper were significantly influenced by the amount of lanthanide complexes and the solvent medium during the extrusion. Based on simple manipulation and mild conditions, a highly transparent NFC template provided a soft matrix and afforded the high thermal stability and excellent luminescent properties of the Ln–ONFC nanopaper, which yields ever increasing potential to supersede petroleum-based materials for diverse applications.

A series of new multifunctional nanomesoporous materials based on upconversion nanophosphors NaYF4:Yb,Tm@NaGdF4 (UCNPs) and lanthanide complexes were designed and synthesized through mesoporous capping UCNPs nanophosphors and linking lanthanide (Ln) complexes. The obtained UCNPs@mSiO2-Ln(dbm)4 (Ln = Eu, Sm, Er, Nd, Yb) materials can achieve downconversion and upconversion luminescence to show multicolor emission (covering the spectral region from 450 nm to 1700 nm) under visible-light excitation and 980 nm excitation, respectively. In addition, low cytotoxicity and good biocompatibility was found as determined by methyl thiazolyl tetrazolium assay, and the nanomesoporous materials were successfully applied to cell imaging in vitro based on Eu(3+) luminescence (under 405 nm excitation) and small animal imaging based on Tm(3+) luminescence (under 980 nm excitation). The doped Gd(3+) ion endows the nanomesoporous materials UCNPs@mSiO2-Ln(dbm)4 with effective T1 signal enhancement, which affords them as potential magnetic resonance imaging (MRI) contrast agents. Therefore, our results may provide more exciting opportunities for multimodal bioimaging and multifunctional applications.

Folate receptors (FRs) are overexpressed on a variety of human cancer cells and tissues, including cancers of the breast, ovaries, endometrium, and brain. This over-expression of FRs can be used to target folate-linked imaging specifically to FR-expressing tumors. Fluorescence is emerging as a powerful new modality for molecular imaging in both the diagnosis and treatment of disease. Combining innovative molecular biology and chemistry, we prepared three kinds of folate-targeted up-conversion nanoparticles as imaging agents (UCNC-FA: UCNC-Er-FA, UCNC-Tm-FA, and UCNC-Er,Tm-FA). In vivo and in vitro toxicity studies showed that these nanoparticles have both good biocompatibility and low toxicity. Moreover, the up-conversion luminescence imaging indicated that they have good targeting to HeLa cells and can therefore serve as potential fluorescent contrast agents.

Correction for ‘Folic acid-functionalized up-conversion nanoparticles: toxicity studies in vivo and in vitro and targeted imaging applications’ by Lining Sun et al., Nanoscale, 2014, 6, 8878–8883.

A new type of monodisperse mesoporous titania microspheres possessing visible (Eu3+, Sm3+) and near-infrared (Sm3+, Yb3+, Nd3+) luminescence were synthesized with covalent linking to Ln(dbm)3bpdc complexes (Ln = Eu, Sm, Yb, Nd, dbm = dibenzoylmethanate, bpdc = 2,2′-bipyridine-4,4′-dicarboxylic acid). These lanthanide complex-functionalized titania microspheres can be excited with visible light to extend the practical application in lighting devices and biomedical analysis. The materials were characterized using Fourier-transform infrared (FT-IR) spectroscopy, wide-angle X-ray powder diffraction (WAXD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), nitrogen adsorption/desorption, diffuse reflectance (DR) spectroscopy, fluorescence spectroscopy, and thermogravimetric analysis. The results show that the microsphere morphology composed of single anatase crystallites and mesoporous structure is retained after linking to the lanthanide complexes. To the best of our knowledge, this is the first successful attempt to graft lanthanide complexes onto mesoporous anatase titania microspheres with high crystallinity. The novel combination of lanthanide complexes with NIR luminescence under visible light excitation and mesoporous titania microspheres with high thermal and chemical stabilities as well as anatase crystallinity affords potential applications in the fields of energy conversion, photocatalysis, and biomaterials.

The homogeneously transparent hybrid gels (Ln–N–P-gel, Ln = Sm, Yb, Nd, Er, Pr, Ho, Tm) containing lanthanide complexes (by using dinaphthoylmethane (dnm) as the primary ligand and 1,10-phenanthroline (phen) as the synergic ligand) via the in situ approach have been prepared. The dnm ligand was synthesized and adopted with the aim to sensitize the lanthanide ions with visible light. The properties of Ln–N–P-gels were investigated by Fourier-transform infrared (FT-IR), diffuse reflectance (DR), scanning electron micrographs (SEM), fluorescence spectra and thermogravimetric analyses. The results reveal that the lanthanide complexes are successfully in situ synthesized in the corresponding Ln–N–P-gels. Under the excitation of visible-light, the Ln–N–P-gels showed the respective visible (Sm3+) and near-infrared (Sm3+, Yb3+, Nd3+, Er3+, Pr3+, Ho3+, Tm3+) luminescence. The near-infrared (NIR) luminescence of Sm3+, Pr3+, Ho3+, and Tm3+ complexes sensitized by visible-light had been rarely reported previously, which is highly desired for biomedical and photonics applications. Based on the relevant energy levels, a model was proposed to explain the visible-NIR luminescence of the Ln–N–P-gels based on the visible-light excitation.

A new periodic mesoporous organosilica material (named as bpd-PMO) was synthesized through co-condensation of bis(triethoxysilyl)ethane (BTEE) and a synthesized silsesquioxane precursor 4,4′-bis[Si(OEt)3(CH2)4]-2,2′-bipyridine (bpd-Si) in the presence of cetyltrimethylammonium bromide (CTAB) surfactant as template. Subsequently, three near-infrared (NIR) luminescent PMO hybrid materials (named as Ln(dbm)3bpd-PMO, Ln = Er, Nd, Yb) covalently linked with lanthanide complexes were successfully prepared via a ligand exchange reaction. The materials were characterized by XRD, N2 adsorption–desorption isotherms, SEM, and fluorescence spectra, and the corresponding luminescent decay analyses were recorded. Of importance here is that the excitation spectra of the Ln(dbm)3bpd-PMO extend to the visible-light range. Following the visible-light excitation, the Ln(dbm)3bpd-PMO materials show the characteristic NIR-luminescence of the corresponding Ln3+ ions. The good NIR-luminescence properties of the Ln(dbm)3bpd-PMO with the visible-light excitation would extend the potential applications of the PMO matrix to the NIR optical field.

A simple and versatile method was proposed for self-assembling magnetic nanoparticles and hydrophobic upconversion nanoparticles on to a mesoporous nanoprobe by the means of an electrostatic interaction and binding scheme. The hybrid nanoprobes showed good magnetic and near-infrared luminescent properties, and could be explored as biosensors.

A series of dysprosium complex doped xerogels with the same first ligand (acac = acetylacetone) and different neutral ligands were synthesized in situ via a sol-gel process. The Fourier transform infrared (FTIR) spectra, diffuse reflectance (DR) spectra, and near-infrared (NIR) luminescent properties of dysprosium complexes and dysprosium complex doped xerogels are described in detail. The results reveal that the dysprosium complex is successfully synthesized in situ in the corresponding xerogel. Excitation at the maximum absorption wavelength of the ligands resulted in the characteristic NIR luminescence of the Dy3+ ion, which contributes to the energy transfer from the ligands to the central Dy3+ ion in both the dysprosium complexes and xerogels via an antenna effect. The NIR luminescent properties of the dysprosium complexes and xerogels were compared, respectively. The evidence showed that the neutral ligand triphenyl phosphine oxide (TPPO) could increase the emission intensity of the dysprosium complex while 1,10-phenanthroline (phen) gave the negative effect. In addition, the coordinated water molecules affect the emission intensity of the dysprosium complex doped xerogel without the neutral ligand.

Luminescent lanthanide complex, Eu(phen)2Cl3·2H2O (Euphen, phen = 1,10-phenanthroline) has been incorporated inside the channels of mesoporous silica MCM-41 with its external surface modified by phenyltriethoxysilane (Ph-Si(OEt)3) via a simple template-ion exchange method. The passivation of active groups such as silanols in the external surface ensures that the ion exchange reaction occurs between the surfactant cations and the lanthanide complex ions inside the channels of the modified MCM-41. The passivation result is confirmed by 29Si MAS NMR spectroscopy. FT-IR demonstrates that the cationic surfactants are completely removed. XRD and N2 adsorption–desorption measurements are employed to characterize the mesostructure of Euphen-Ph-MCM-41. Luminescence and stability studies on the materials of Euphen and Euphen-Ph-MCM-41 show that the resultant hybrid material Euphen-Ph-MCM-41 exhibits the characteristic emission of Eu3+ ions under UV irradiation with higher 5D0 luminescence quantum efficiency, longer lifetime and better thermal stability than the corresponding pure complex Euphen. Moreover, the characterization results show that the local symmetry and the first coordination shell of Eu3+ ions are changed after the complex ions become incorporated into the MCM-41 channels and that a more symmetric environment is occupied by the Eu3+ ions in Euphen-Ph-MCM-41 than in Euphen. There is also a more efficient ligand-to-Eu(III) intramolecular energy transfer process in Euphen-Ph-MCM-41.