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The crystal structure of a polymorph of Glycyl-L-alanine HI.H2O was synthesized from chiral cyclic Glycyl-L-alanine dipeptide, known to show molecular flexibility in different environments. The space group is polar (P21) and therefore pyroelectricity and optical second harmonic generation properties are allowed by symmetry. We report a pyroelectric coefficient as high as 45 µC/m2K occurring at 345 K, one order of magnitude smaller than the semi-organic ferroelectric Triglycine Sulphate (TGS) crystal. Furthermore, the polymorph displays a nonlinear optical effective coefficient of 0.14 pm/V, around 14 times smaller than the value from a phase-matched inorganic Barium Borate (BBO) single crystal.

Dual self-assembly of dipeptides into microspheres and microtapes. Quantum confinement in self-assembled structures of dipeptides. Self-assembly of dipeptides as nanospheres and nanotubes into blue luminescent electrospun fibers.

Lead-free ferroelectric perovskite N-methyl-N'-diazabicyclo[2.2.2]octonium)–ammonium triio-dide, MDABCO-NH4I3, nanocrystals are embedded in three different polymer fibers fabricated by the electrospinning technique. The nanofibers, which are very flexible and have a high Young modulus, behave as active piezoelectric energy harvesting sources that produce a piezoelectric voltage coefficient up to geff = 3.6 VmN-1 and show a blue intense luminescence band at 325 nm. In this work, the pyroelectric coefficient is reported for the MDABCO-NH4I3 perovskite inserted in electrospun fibers. At the ferroelectric-paraelectric phase transition, the embedded nanocrystals display a pyroelectric coefficient as high as 194×10-6 Cm-2k-1, within the same order of magnitude as that reported for the state-of-the-art bulk ferroelectric triglycine sulfate (TGS). The perovskite nanocrystals embedded into the polymer fibers remain stable, and no degradation is caused by oxidation.

Dipeptide biomaterials are strong piezoelectric materials that can convert applied mechanical forces into electricity. We have developed large-scale hybrid electrospun arrays containing N-tert-butoxycarbonyl (Boc) diphenylalanine in the form of nanotubes embedded in biocompatible polymers. These nanofibers exhibit strong piezoelectric properties when a periodic mechanical force is applied. The nanostructured hybrid materials were produced by the electrospinning technique. Optical absorption measurements show four bands in the spectral region 240-280 nm indicating quantum confinement due to nanotube formation of Boc-diphenylalanine in dichloromethane solutions. A strong blue photoluminescence emission was observed from nanotubes crystallized inside the fiber arrays during the electrospinning process. These two dimensional hybrid biomaterial structures are able to generate voltage, current and density power of up to 30 V, 300 nA and 2.3 mu W cm(-2), respectively, when a periodical force of 1.5 N is applied. The dipeptide-polymer electrospun arrays can power several liquid-crystal display panels and may be used for biomedical applications and as bio-energy sources., We are grateful to the FUNDACAO PARA A CIENCIA E TECNOLOGIA (FCT) for a post-doctoral grant to R.M.F. Batista (SFRH/BPD/79333/2011), and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support through the Physics Centers of the Universities of Minho and Porto (Ref. UID/FIS/04650/2013) and the Chemistry Research Centre of the University of Minho (Ref. UID/QUI/00686/2013 and UID/QUI/0686/2016). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT.

This study reports on the synthesis of highly oriented chromium triiodide (CrI3) magnetic inclusions inside nano/microfibres with a polyethylene oxide matrix, prepared by the electrospinning technique. The structural, microstructural and spectroscopic analysis shows uniformly dispersed CrI3 nanosized inclusions inside the fibres, presenting a C2/m monoclinic structure at room temperature, where their c-axis is perpendicular to the fibre mat plane and the ab layers are in-plane. Analysis of the magnetic properties show that the samples have a ferromagnetic-paramagnetic phase transition at ∼55-56 K, lower than that of bulk CrI3. Noticeably, a field-driven metamagnetic transition is observed below ∼45 K, from M versus H curves, when the applied magnetic field is perpendicular to the fibre mat plane, while it is strongly reduced when the field is in-plane. This anisotropic behaviour is attributed to the field-induced changes from antiferromagnetic to ferromagnetic interlayer magnetic moment alignment along the CrI3 c-axis stacked layers. These CrI3 electrospun fibres then show an efficient cost-effective route to synthesize magnetic composite fibres with highly oriented van der Walls inclusions, for spintronic applications, taking advantage of their anisotropic 2D layered materials properties., We are grateful to the Fundacao Para a Ciencia e a Tecnologia (FCT) for the financial support through the Physics Centers of the Universities of Minho and Porto (Ref. UIDB/04650/2020) and projects UTAPEXPL/NTec/0046/2017, NORTE-01-0145-FEDER-028538 and PTDC/FIS-MAC/29454/2017. J H Belo thanks FCT for the Grant SFRH/BD/88440/2012, the project PTDC/FIS-MAC/31302/2017 and his contract DL57/2016 reference SFRH-BPD-87430/2012. J P Araujo and J H Belo thank the funding from the project, with reference POCI-01-0145-FEDER-032527. V B Isfahani acknowledges a Post-Doc grant from the project NORTE-01-0145-FEDER-028538. L Boddapati acknowledges the Nano TRAIN for Growth II program by the European Commission through the Horizon 2020 Marie Sklodowska-Curie COFUND Programme and support provided by the International Iberian Nanotechnology Laboratory. We are gratefull to Professor Michael Belsley, of the Physics Department at Minho University, for the fruitfull discussions on the manuscript.

This study reports on the synthesis of highly oriented chromium triiodide (CrI

Using the electrospinning technique nanofibers consisting of organic nonlinear optical 3-nitroaniline (3NA, C6H6N2O2) nanocrystals embedded in poly-epsilon-caprolactone (PCL) polymer, 3NA@PCL nanofibers, were produced. Polarimetry optical second harmonic generation and X-ray diffraction studies show that 3NA push-pull molecules crystallize inside the polymer fibers with a strong preferential orientation giving rise to an alignment of the molecular dipole moments along the nanofibers longitudinal axis. This alignment strongly enhances the second order nonlinear optical response of the fibers. Intense second harmonic generation emission was observed from a single nanofiber, corresponding to an effective second order susceptibility of 80 pm V-1, four times greater than the largest second order susceptibility tensor element (21 pm V-1) associated with a macroscopic 3NA crystal. Moreover, when subjected to a modest periodically applied force of 3 N, a piezoelectric current of 70 nA generated by a 4 cm(2) electrospun nanofiber mat amounted to 122 nW cm(-2) of instantaneous density power, sufficient to power a LCD display. The results show that the electrospinning technique is a powerful technique to fabricate organic functional materials with oriented nanocrystals made of highly polarizable molecules, embedded in a polymer matrix., The authors acknowledge funding from the FUNDACAO PARA A CIENCIA E TECNOLOGIA (FCT) for a post-doctoral grant to Rosa M. F. Batista (SFRH/BPD/79333/2011), a PhD grant to Cesar R. Bernardo (SHFR/BD/102616/2014) funding in the framework of the project PTDC/NAN-OPT/29265/2017, and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support through the Physics Center of the Universities of Minho and Porto (Ref. UID/FIS/04650/2013 and UID/FIS/04650/2019) and the Chemistry Research Centre of the University of Minho (Ref. UID/QUI/00686/2013 and UID/QUI/0686/2016). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT.

Poly(methyl methacrylate) electro-spun fibers with embedded nanocrystals of the paradigmatic donor–acceptor nonlinear chromophore para-nitroaniline have been recently demonstrated to be efficient generators of second harmonic light. To understand the influence of the size and local strain experienced by the embedded para-nitroaniline nanocrystals, a Williamson−Hall analysis was carried out on the X-ray diffraction intensity. Both the mean crystal size and strain can be tuned by simple changes in the deposition parameters of flow rate and applied voltage. The observed second harmonic signal is well correlated with the ratio of the fiber diameter to the mean para-nitroaniline crystal size suggesting that surface effects are the main source of the strong nonlinear optical response. Adjusting the electro-spinning deposition parameters when producing polymeric fibers doped with strong nonlinear organic chromophores with high dipole moments has the potential to provide a versatile and efficient method for developing second-order nonlinear optical materials.

The piezoelectric and pyroelectric properties of electrospun polyethylene oxide nanofibres embedded with polar amino acids DL-alanine and L-lysine hemihydrate are reported. Ahigh pyroelectric coefficient of 150 mu Cm-2 K-1 was measured for L-lysine hemihydrate and piezoelectric current densities up to 7 mu Am-2 were obtained for the nanofibres. The study reveals a potential for polymer amino-acid nanofibres to be used as biocompatible energy harvesters for autonomous circuit applications like in implantable electronics., This work was supported by Portuguese funds through Foundation for Science and Technology (FCT) under the Strategic Financing UID/FIS/04650/2013., info:eu-repo/semantics/publishedVersion

Intense well polarized second harmonic light was generated by poly(methyl methacrylate) nanofibres with embedded para-nitroaniline nanocrystals. Subwavelength diameter fibres were electro-spun using a 1.2 weight ratio of chromophore to polymer. Analysis of the generated second harmonic light indicates that the para-nitroaniline molecules, which nominally crystalize in the centrosymmetric space group, were organized into noncentrosymmetric structures leading to a second order susceptibility dominated by a single tensor element. Under the best deposition conditions, the nanofibrers display an effective nonlinear optical susceptibility approximately two orders of magnitude greater than that of potassium dihydrogen phosphate. Generalizing this approach to a broad range of organic molecules with strong individual molecular second order nonlinear responses, but which nominally form centrosymmetric organic crystals, could open a new pathway for the fabrication of efficient sub-micron sized second harmonic light generators., Hugo Goncalves thanks the Portuguese Foundation for Science and Technology (FCT) for the support under grant PD/BD/111873/2015. The equipment used to characterize the second harmonic response of the electro-spun fibres was acquired within the framework of the Portuguese National Program for Scientific Re-equipment, contract REEQ-25/FIS/2005 with funds from POCI 2010 (FEDER) and FCT. The Raman microscope was acquired through the project nSTeP Nanostructured Systems for Tailored Performance, NORTE-07-0124-FEDER-000039, ON. 2. This work was in part developed in the scope of the projects CICECO-Aveiro Institute of Materials (UID/CTM/50011/2013), financed by national funds through the Fundacao para a Ciencia e a Tecnologia/Ministerio da Educacao e Ciencia (FCT/MEC) and co-financed by FEDER under the PT2020 Partnership Agreement. The authors are grateful to A M P Botas (University of Aveiro) for help in acquiring the hyperspectral microscopy data., info:eu-repo/semantics/acceptedVersion

The use of crystal vibrational modes and frequencies calculated for the periodic system to complement a Translation Libration Screw (TLS) fit in the estimation of anisotropic displacement parameters (ADPs) of hydrogen atoms in molecular crystals is proposed. As a test case we have used the para-nitroaniline crystal, for which a reference set of ADPs has been obtained by performing a single crystal neutron diffraction study at 100 K. Although the largest difference between estimated and experimental reference values amounts to 0.06 Å2, this value being about six times the experimental uncertainty, the agreement is betterthan three experimental uncertainties for 33 out of the total of 36 ADPs. The performance of the suggested method, particularly for the amino atoms, is thoroughly analyzed. Fil: Pozzi, Carlos Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Fantoni, Adolfo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Goeta, Andrés E.. University Of Durham. Dep.of Chemistry; Reino Unido Fil: De Matos Gomes, Etelvina. Universidade do Minho; Portugal Fil: McIntyre, Garry J.. Institut Laue Langevin; Francia Fil: Punte, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

Potential ferroelectricity in charge-transfer organic materials is often masked by the intrinsic conductivity. Here, we report the compelling evidence of ferroelectricity in organic p-conjugated meta-nitroaniline (m-NA) crystals as shown by the local electromechanical measurements using the piezoresponse force microscopy (PFM) technique. m-NA is a charge-transfer molecular material with the exceptional optical non-linearity and perceptible conductivity along the crystallographic polar axis. While standard Sawyer-Tower measurements revealed an apparently lossydielectric hysteresis, The PFM switching spectroscopy indicated clear ferroelectric behaviour in this technologically important multifunctional material. Further study of the pyroelectric properties in m-NA crystals confirmed their high spontaneous polarization of 18 microC/cm2 at room temperature, comparable to the best known organic ferroelectrics., This work was supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124FEDER-014628, FCOMP-01-0124-FEDER-009457)and FCT Grant No. PTDC/CTMNAN/114269/2009), Pest-C/CTM/ LA0011/013, and by RFBR Grant No. 13-02-90925. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials (POCI-01-0145FEDER-007679, FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement, and by Government of the RF (Act 211, Agreement 02.A03.21.0006).

A series of complexes trans-[FMo(N=NCHL)(dppe) 2 ][BF 4 ] {L = (bi)thienyl or arylthienyl}, were synthesized and fully characterized by 1 H, 13 C, 31 P NMR, IR and UV/Vis spectroscopy. The electronic spectra and electrochemical behavior of the complexes were investigated. The electronic absorption spectra of these complexes display a broad low-energy band in the visible region attributable to metal-to-ligand charge-transfer (MLCT) transitions. The electron-conjugated effect with the heterocyclic nucleus led to a notable improvement of visible light absorption and marked changes in the electrochemical behavior. The hyperpolarizabilities β of the synthesized compounds were evaluated using the hyper-Rayleigh scattering technique.

Several novel compounds with protonated 2,2′-biquinoline (biqui) and Keggin polyoxoanions (α-isomers), having the general formula (Hbiqui) m [XM 12 O 40 ]· n solv, X=P ( m =3), Si ( m =4); M=Mo, W; n =0, 3; solv=H 2 O, N , N -dimethylformamide (dmf), were synthesized and characterized by analytical, spectroscopic and X-ray diffraction techniques. Electronic spectroscopy (visible/UV) indicated the presence of intermolecular charge transfer between the organic and inorganic moieties in the solid state. Evidence for the existence of intermolecular electronic interaction in solution was found for compounds with the [SiW 12 O 40 ] 4− anion, a fact quite uncommon for charge transfer compounds based on Keggin anions. A single crystal X-ray diffraction study could be performed on (Hbiqui) 4 [SiW 12 O 40 ]·3dmf crystals, but the refinements revealed the presence of highly disordered 2,2′-biquinoline molecules and α-[SiW 12 O 40 ] 4− anions. Photosensitivity to sunlight and to W-lamp visible light was assessed for all compounds. Photochromic properties were found for solids with [XMo 12 O 40 ] m − Keggin anions. Reduction of these anions upon irradiation was observed by diffuse reflectance and EPR spectroscopy. After a minimum of 5 h under sunlight, the extent of anion reduction followed the order (Hbiqui) 3 [PMo 12 O 40 ]·3dmf>(Hbiqui) 4 [SiMo 12 O 40 ]·3dmf>(Hbiqui) 3 [PMo 12 O 40 ]>(Hbiqui) 4 [SiMo 12 O 40 ]·4H 2 O. The Kurtz powder test was used to evaluate the second-order non-linear optical properties of the prepared compounds. (Hbiqui) 4 [SiW 12 O 40 ]·3H 2 O originated a second harmonic generation signal with intensity about 15% that of urea for 1064 nm radiation.

"Published in SPIE Proceedings Vol. 9286", We present a flexible fluorescence lifetime imaging device which can be employed to scan large sample areas with a spatial resolution adjustable from many micrometers down to sub-micrometers and a temporal resolution of 20 picoseconds. Several different applications of the system will be presented including protein microarrays analysis, the scanning of historical samples, evaluation of solar cell surfaces and nanocrystalline organic crystals embedded in electrospun polymeric nanofibers. Energy transfer processes within semiconductor quantum dot superstructures as well as between dye probes and graphene layers were also investigated., This work was financially supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124-FEDER-014628) and the Portuguese Fundacao para a Ciencia e Tecnologia (FCT) through the projects "Functional structuring, inter-particle interaction and energy transfer in ensembles of nanocrystal dots" (PTDC/FIS/113199/2009), Ultra-fast spectroscopy on the dynamics and relaxation of Dirac electrons in graphene" (PTDC/FIS/101434/ 2008) and "Low dimensional nanostructures for nonlinear optical applications" PTDC/CTmNAN/114269/2009.

We demonstrate an approach that uses normally centrosymmetric, but highly polarizable organic molecules of para-nitroaniline (p-NA) as very efficient second harmonic generator (SHG) for near infra-red light. The approach is based on an effective manipulation of the nanocrystalline size and their assembly into a highly orientated mesocrystalline structures. The resulting mesocrystalline form of p-NA consists of multiple nanocrystals with common orientation, providing a set of surfaces with highly aligned molecules forming a head-to-tail polar arrangement. The second harmonic generation efficiency from this arrangement of mesocrystalline nanostructures is comparable to that from the conventional non-centrosymmetric organic crystals. The experimental results indicate that a very strong second-order nonlinear response can be obtained from small D-p-A organic molecules with elevated molecular hyperpolarizabilities even if these molecules tend to crystallize in centrosymmetric structures. (C) 2014 AIP Publishing LLC., This work was financially supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124-FEDER-014628) and the Portuguese Fundacao para a Ciencia e Tecnologia (PTDC/CT-NAN/114269/2009 and PTDC/CTM/105597/2008)., info:eu-repo/semantics/publishedVersion

We report measurements of the molecular first hyperpolarizability, thermal stability, photophysical, piezoelectric and ferroelectric properties of a benzothiazole derivative bearing an arylthiophene π-conjugated bridge both in solution and when embedded into a poly (L-lactic acid) (PLLA) matrix in the form of electrospun fibers with an average diameter of roughly 500 nm. The embedded nanocrystalline phenylthienyl-benzothiazole derivative, with crystal sizes of about 1.4 nm resulted in a good piezoelectric response from these functionalized electrospun fibers, indicative of a polar crystalline structure., Fundação para a Ciência e a Tecnologia (FCT)

Crystals of 2-methyl-4-nitroaniline were grown from solution while subjected to a dc electric field of 9.8×104 V m−1. This resulted in an alteration of the unit cell lattice parameters while the space group was modified from Cc to one of its subgroups Pc. The modified crystals display an increased second harmonic generation efficiency accompanied by a decrease in the dielectric permittivity as well as changes in the internal and external vibrational modes.

We report the synthesis, structural and ferroelectric characterization of continuous well-aligned nanofibres of barium titanate produced by the electrospinning technique. The fibres with average diameter of 150-400 nm consist of connected nanoparticles of BaTiO3 stacked together to form the shape of a long filament. The tetragonal phase in the obtained nanofibres was revealed by the x-ray diffraction and Raman spectroscopy and has been also confirmed by the second harmonic generation (SHG) and piezoresponse force microscopy (PFM). The temperature dependence of the SHG in the vicinity of the paraelectric-ferroelectric phase transition suggests that barium titanate nanofibres are indeed ferroelectric with an apparent glass-like state caused by metastable polar nanoregions. The existence of domain structure and local switching studied by PFM present clear evidence of the polar phase at room temperature., This work has been done in the framework of the CIENCIA-2007 programme (reference UMINHO-CF-06) and was financially supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124-FEDER-014628), by the Portuguese Foundation for Science and Technology (FCT) (PTDC/CTM-NAN/114269/2009, PTDC/CTM-NAN/115125/2009, PTDC/CTM-CER/115085/2009, PTDC/CTM/105597/2008, PTDC/CTM/099415/2008) and by the strategic project PEST-C/FIS/UI607/2011., info:eu-repo/semantics/publishedVersion

We show that the normally centro-symmetric crystalline structure of para-nitroaniline is altered by recrystallization under the influence of an intense continuous electric field. This electric field induced symmetry breaking is confirmed by the generation of an optical second harmonic signal.

A new hybrid organic–inorganic non-linear optical crystalline material, L-argininium perrhenate has been synthesized. The crystal belongs to P212121 space group, has a good optical quality and high transmission in the visible and near infra-red spectral regions. L-argininium perrhenate has high birefringence and is more than four times as efficient as KDP in second harmonic generation, making it a potentially attractive material for non-linear optical applications, This work was financially supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124-FEDER-014628) and the Portugal Fundacao para a Ciencia e Tecnologia (PTDC/CTM-NAN/114269/2009, PTDC/CTM/105597/2008 and Pest-C/FIS/UI0036/2011).

Electrospinning of an aqueous poly(vinyl alcohol) and glycine solution has been used to produce nanofibers with an embedded crystalline glycine exclusively in the form of the β polymorph. The β-glycine nanocrystals are highly oriented within the polymer fibers and present good polar properties. Piezoelectric and nonlinear optical responses have been quantitatively examined showing piezoelectric coefficient deff = 12.5 pm/V and an effective nonlinear optical susceptibility two times greater than that of potassium dihydrogen phosphate (KDP). Additionally, although bulk β-glycine is metastable at room temperature, when confined inside the polymeric nanofibers, it is shown to be remarkably stable., Fundação para a Ciência e a Tecnologia (FCT) - CIÊNCIA-2007 (ref UMINHO-CF-06), CIÊNCIA-2008, bolsa PTDC/CTM-NAN/114269/2009, PTDC/CTM/ CTM/105597/2008

In-plane aligned nanofibers of organic 2-methyl-4-nitroaniline (MNA) were produced by the electrospinning technique using a 1:1 weight ratio with poly(L-lactic acid). The fibers are capable of enormous efficient optical second harmonic generation as strong as pure MNA crystals in powder form. Structural, spectroscopic, and second harmonic generation polarimetry studies show that the MNA crystallizes within the fibers in an orientation in which the aromatic rings of MNA are predominantly orientated edge-on with respect to the plane of the fiber array and with their dipole moments aligned with the fiber axis. The results show that the electrospinning technique is an effective method to fabricate all-organic molecular functional devices based on polymer nanofibers with guest molecules possessing strong nonlinear optical and/or polar properties., Fundação para a Ciência e a Tecnologia (FCT) - CIÈNCIA-2007UMINHO-CF-06

In this work we present the synthesis and characterization of polyethylene oxide (PEO) based triglycine sulfate (NH2(CH2OOH)3H2S04, TGS) nanofibres obtained by electrospinning. The fibres, with typical diameters of about 190–750 nm and above several hundred micrometres in length, present the nanocrystals of TGS embedded in a polymer matrix. The obtained nanofibres were characterized by FT-IR spectroscopy and the domain structure was examined by piezoforce microscopy. Dielectric permittivity measurements on the TGS–PEO nanofibres exhibit the characteristic ferroelectric–paraelectric phase transition at around 50 ºC., This work was financially supported by Fundacao para a Ciencia e Tecnologia (reference CIENCIA-2007 UMINHOCF-06). The authors would like to acknowledge Luis Vieira for help in FT-IR measurements.

Cesium hydrogen L-malate monohydrate, CsH(C 4 H 4 O 5 ).H 2 O, is a new non-linear optical semi-organic crystalline material with a second harmonic generation efficiency roughly 2.5 times greater than KDP. Its crystal structure, space group P2 1 , shows that the malate anions, are interconnected through directional O-H•••O hydrogen bonding, in a head-to-tail arrangement, creating extended anionic layers. The water molecules provide a cross-link, through hydrogen bonding, between adjacent layers. Especially noteworthy is that the Cesium cations and the COO- group from the malate anions, form a sequence of nearly perfectly aligned dipoles oriented along the b crystallographic axis giving a permanent dipole moment of 38 Debye per unit cell. As the crystals are non hygroscopic and easy to grow, they are potential new material for nonlinear optical and pyroelectric applications.

Crystals of para-nitroaniline were grown from solution while subjected to a strong dc electric field of 2 X 105 V/m. This resulted in a modification of the unit cell lattice parameters and space group with respect to crystal grown in the absence of an electric field. The modified crystal are capable of generating a second harmonic signal and poses a significantly lower dielectric permittivity.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.